Foam Concrete Lifting Crystal Lake

Foam Concrete Lifting Crystal Lake

Concrete Floor Leveling Contractors

As we look toward the horizon, it's clear that the future of concrete raising holds exciting advancements and possibilities for our community. First off, they use a unique polyurethane injection method that lifts and stabilizes sinking concrete slabs. Learn more about Expert Concrete Lifting Services in Crystal Lake, Illinois here. Learn more about Foam Concrete Lifting Crystal Lake here You'll be amazed at how quickly and efficiently we can restore your concrete, minimizing disruption to your daily life.

Settled Concrete Solutions

  1. Polyurethane Concrete Lifting
  2. Sidewalk Leveling Experts
  3. Concrete Resurfacing
  4. Polyurethane Foam Injection
  5. Concrete Settling
  6. Trip Hazard Removal
  7. Driveway Void Repair
  8. Commercial Concrete Services
  9. Porch Leveling
  10. Local Concrete Repair Crystal Lake
  11. Concrete Surface Repair
  12. Crystal Lake IL Contractors
  13. Crystal Lake Home Services
  14. Sidewalk Leveling
  15. Residential Concrete Services
Cement production is a significant source of CO2 emissions globally. Our team is punctual and respectful of your time, so we'll make sure to start and finish as promised.
Over time, concrete structures can develop cracks and damage, leading to safety concerns and costly repairs if not addressed promptly.

Concrete Support Injection

  1. Trip Hazard Removal
  2. Driveway Void Repair
  3. Commercial Concrete Services
  4. Porch Leveling
  5. Local Concrete Repair Crystal Lake
  6. Concrete Surface Repair
  7. Crystal Lake IL Contractors
  8. Crystal Lake Home Services
  9. Sidewalk Leveling
  10. Residential Concrete Services
  11. Concrete Pressure Injection
  12. Basement Floor Lifting
  13. Local Concrete Leveling Services
  14. Interior Floor Lifting
  15. Concrete Leveling
  16. Garage Slab Settlement
  17. Helical Piers
  18. Sunken Step Repair
  19. Slabjacking
  20. Uneven Concrete Repair
But with Acme's Smart Lift System, that's not your reality.

This step is crucial because it helps us tailor our approach to your specific situation. This collective effort can significantly raise property values, making your neighborhood a more desirable place to live. Their commitment to excellence and customer satisfaction sets them apart, making them the go-to for concrete repairs in Crystal Lake. The journey through these revelations will leave you questioning the status quo and curious about the innovative solutions that are setting new standards in concrete repair.

Acme Concrete Raising & Repair provides cost-effective solutions that not only fix the issue at hand but also prevent future problems. Typically, smaller repair jobs might cost less, while larger areas requiring extensive work will see a higher price tag. Unlike traditional mudjacking materials, polyurethane foam is less invasive and requires smaller holes to be drilled into your concrete, making it a more aesthetically pleasing solution.

Now, picture a smooth, level surface that not only looks inviting but also ensures everyone's safety as they step on it. In the world of concrete, Acme Concrete Raising & Repair is paving a new path in Crystal Lake, much like the way stars illuminate the night sky, guiding travelers to their destination. This means you'll save money in the long run by avoiding repeated repairs.

This innovative approach combines the latest in concrete technology with proven techniques to ensure a durable and long-lasting repair. The longer you wait, the more complicated and expensive the repairs can become. Their team isn't just skilled; they're innovators, constantly refining their techniques to ensure the best possible outcomes.

Foam Jacking

  1. Concrete Settling
  2. Trip Hazard Removal
  3. Driveway Void Repair
  4. Commercial Concrete Services
  5. Porch Leveling
  6. Local Concrete Repair Crystal Lake
  7. Concrete Surface Repair
  8. Crystal Lake IL Contractors
  9. Crystal Lake Home Services
  10. Sidewalk Leveling
  11. Residential Concrete Services
  12. Concrete Pressure Injection
  13. Basement Floor Lifting
  14. Local Concrete Leveling Services
  15. Interior Floor Lifting
  16. Concrete Leveling
  17. Garage Slab Settlement
  18. Helical Piers
  19. Sunken Step Repair
  20. Slabjacking


Citations and other links

Concrete Leveling and Raising Crystal Lake

Don't let aging concrete defeat you; there are affordable ways to bring it back to life. These aren't just eyesores; they pose real hazards. Moreover, the process eliminates the need for disruptive replacement work, preserving the original look of your concrete surfaces. Acme's system means your property is back to normal, faster than you'd expect, minimizing inconvenience for you and your family. In essence, the Smart Lift difference is clear: it's about providing you with a reliable, efficient, and lasting solution to your concrete problems.
Water often undermines concrete by washing away the soil underneath or causing freeze-thaw cycles that lead to cracks and sinking. You're not just getting a temporary fix but a long-term solution. The process is precise, allowing for targeted lifting that repairs your concrete without the need for replacement. By unveiling their approach, the benefits become clear, from reduced downtime and less disruption to the surrounding area, to a lesser environmental footprint compared to older methods.
Acme Concrete Raising & Repair makes it incredibly easy for you to get started on this journey towards smoother, more reliable paths. This attention to detail means you're less likely to notice the repairs themselves and more likely to enjoy the uninterrupted beauty of Crystal Lake's walkways. It's a smart, seamless solution to a common problem. Sunken Concrete Concrete raising, also known as slab jacking, is a cost-effective method to repair uneven concrete surfaces by lifting the slab back to its original position. Read more about Foam Concrete Lifting Crystal Lake here
This innovative approach is quicker, cleaner, and more environmentally friendly than traditional methods. Expect to encounter smart monitoring technologies as well. They don't just repair concrete; they restore your peace of mind, proving time and again why they're the top choice in Crystal Lake.

Precision Concrete Leveling

  1. Subgrade Stabilization
  2. Concrete Raising Contractors
  3. Concrete Driveway Maintenance
  4. Concrete Foundation Settlement
  5. Eco-Friendly Concrete Lifting
  6. Garage Floor Lifting
  7. Crystal Lake Foundation Contractors
  8. Garage Apron Repair
  9. Foundation Leveling Services
  10. Concrete Grinding
  11. No-Dig Concrete Repair
  12. Sunken Walkway Fix
  13. Cracked Driveway Repair
  14. Concrete Floor Repair
  15. Concrete Void Filling
  16. Concrete Slab Stabilization
  17. Concrete Leveling Companies
  18. Patio Leveling
It's a problem that doesn't fix itself and can worsen if ignored.

Residential Driveway Leveling
Concrete Leveling and Raising Crystal Lake
Concrete Jacking Near Me Crystal Lake

Concrete Jacking Near Me Crystal Lake

However, our after shots reveal the true potential of what expert raising and repair can accomplish. This means we're always a step ahead, utilizing innovative methods that ensure efficiency and effectiveness in our work. Well, several factors contribute to soil instability. Their innovative approach to concrete lifting not only promises a return to level surfaces but also introduces a sustainable alternative to the traditional, often more invasive, methods of repair.

You'll appreciate its efficiency, and the peace of mind it brings, knowing you've chosen a durable, environmentally friendly solution. Our collection of testimonials doesn't just end with words. Knowing Crystal Lake's climate and ground conditions allows them to tailor their services perfectly, ensuring the best possible outcome.

Slab Leveling Solutions

  • Concrete Foundation Settlement
  • Eco-Friendly Concrete Lifting
  • Garage Floor Lifting
  • Crystal Lake Foundation Contractors
  • Garage Apron Repair
  • Foundation Leveling Services
  • Concrete Grinding
  • No-Dig Concrete Repair
  • Sunken Walkway Fix
  • Cracked Driveway Repair
  • Concrete Floor Repair
  • Concrete Void Filling
  • Concrete Slab Stabilization
  • Concrete Leveling Companies
  • Patio Leveling
  • Polyurethane Concrete Lifting
  • Sidewalk Leveling Experts
  • Concrete Resurfacing
  • Polyurethane Foam Injection
  • Concrete Settling


This mixture can introduce new materials to the site, potentially disrupting local soil composition and water runoff patterns.

Concrete Crack Injection

  • Driveway Settling Solutions
  • Concrete Contractors Crystal Lake
  • Fix Uneven Driveway Crystal Lake
  • Subgrade Stabilization
  • Concrete Raising Contractors
  • Concrete Driveway Maintenance
  • Concrete Foundation Settlement
  • Eco-Friendly Concrete Lifting
  • Garage Floor Lifting
  • Crystal Lake Foundation Contractors
  • Garage Apron Repair
  • Foundation Leveling Services
  • Concrete Grinding
  • No-Dig Concrete Repair
  • Sunken Walkway Fix
  • Cracked Driveway Repair
  • Concrete Floor Repair
  • Concrete Void Filling
Addressing these common repair needs not only enhances safety but also improves the overall look and value of your property. Addressing sinking concrete sooner rather than later is crucial.

It's a two-part compound that, when mixed, expands rapidly to fill voids and raise concrete with precision. Acme's Smart Lift System uses advanced materials and techniques that ensure a long-lasting fix, so you're not dealing with the same problem a few years down the line. Plus, the drilled holes are then filled and sealed, leaving your concrete looking as good as new.

Local Concrete Contractors Crystal Lake

The repairs made with the Smart Lift System are designed to last, offering you peace of mind that you won't need to revisit the same issue year after year. You'll notice the difference immediately and over time. As we explore how Crystal Lake's landscapes are being transformed and hear firsthand from satisfied clients, you'll see why Acme's method is not just the future of concrete raising-it's the present. Additionally, ensure the contractor is fully licensed and insured. Just like a well-oiled machine needs periodic maintenance to run smoothly, the sidewalks and driveways of Crystal Lake are about to receive a much-needed overhaul thanks to Acme Concrete's advanced repair system.

First off, a team of experts comes to your place to thoroughly inspect the concrete damage.

Precision Concrete Leveling

  1. Concrete Floor Leveling Contractors
  2. Sunken Concrete
  3. Precision Concrete Leveling
  4. Illinois Concrete Repair
  5. Foundation Repair
  6. Foam Jacking
  7. Backyard Patio Repair
  8. Concrete Support Injection
  9. Settled Concrete Solutions
  10. Slab Leveling Solutions
  11. Residential Driveway Leveling
  12. Concrete Crack Repair
  13. Concrete Crack Injection
  14. Sidewalk Trip Hazard Fix
  15. Leveling Concrete Slabs
  16. Driveway Settling Solutions
  17. Concrete Contractors Crystal Lake
  18. Fix Uneven Driveway Crystal Lake
  19. Subgrade Stabilization
  20. Concrete Raising Contractors
You might wonder how this happens. In most cases, the job can be completed in just a few hours, and the area is immediately ready for use. By choosing Acme's system, you're not just repairing the concrete; you're investing in the safety and well-being of your employees and customers.

Foam Jacking

  • Commercial Concrete Services
  • Porch Leveling
  • Local Concrete Repair Crystal Lake
  • Concrete Surface Repair
  • Crystal Lake IL Contractors
  • Crystal Lake Home Services
  • Sidewalk Leveling
  • Residential Concrete Services
  • Concrete Pressure Injection
  • Basement Floor Lifting
  • Local Concrete Leveling Services
  • Interior Floor Lifting
  • Concrete Leveling
  • Garage Slab Settlement
  • Helical Piers
  • Sunken Step Repair
  • Slabjacking
  • Uneven Concrete Repair
  • Fix Uneven Driveway Crystal Lake


This precision not only preserves the integrity of your landscape but also reduces the risk of further damage. We were amazed at how quickly Acme's team lifted it back to its original level. With our state-of-the-art techniques, we lift and stabilize your concrete to eliminate hazards, creating a smooth, level surface. This can be done through their website or by giving them a call.

So, why should you keep an eye on this development? Even the initial soil compaction during construction isn't always perfect, leaving room for future settling. They've streamlined their process to be quick and non-invasive, meaning you won't be dealing with lengthy disruptions or mess. Tripping on an uneven surface can result in injuries, and water seeping through cracks can undermine the foundation of structures, making them unsafe.

Local Concrete Contractors Crystal Lake
Cement Repair Crystal Lake
Cement Repair Crystal Lake

They're in and out before you know it, leaving behind nothing but excellent results.

Concrete Contractors Crystal Lake

  1. Crystal Lake IL Contractors
  2. Crystal Lake Home Services
  3. Sidewalk Leveling
  4. Residential Concrete Services
  5. Concrete Pressure Injection
  6. Basement Floor Lifting
  7. Local Concrete Leveling Services
  8. Interior Floor Lifting
  9. Concrete Leveling
  10. Garage Slab Settlement
  11. Helical Piers
  12. Sunken Step Repair
  13. Slabjacking
  14. Uneven Concrete Repair
  15. Slab Leveling Solutions
  16. Residential Driveway Leveling
  17. Concrete Crack Repair
  18. Concrete Crack Injection
  19. Sidewalk Trip Hazard Fix
  20. Leveling Concrete Slabs
With its blend of cutting-edge technology and user-friendly features, Acme's system not only promises to raise the bar but also to redefine it. This step is vital for ensuring the longevity of our repair work.

Driveway Settling Solutions

  1. Concrete Support Injection
  2. Settled Concrete Solutions
  3. Slab Leveling Solutions
  4. Residential Driveway Leveling
  5. Concrete Crack Repair
  6. Concrete Crack Injection
  7. Sidewalk Trip Hazard Fix
  8. Leveling Concrete Slabs
  9. Driveway Settling Solutions
  10. Concrete Contractors Crystal Lake
  11. Fix Uneven Driveway Crystal Lake
  12. Subgrade Stabilization
  13. Concrete Raising Contractors
  14. Concrete Driveway Maintenance
  15. Concrete Foundation Settlement
  16. Eco-Friendly Concrete Lifting
  17. Garage Floor Lifting
  18. Crystal Lake Foundation Contractors
  19. Garage Apron Repair
  20. Foundation Leveling Services
That's the reality for many in your community.

Sweep off debris and wash the surface gently to prevent dirt accumulation that can cause wear over time. Once you decide to move forward, we'll set a date to begin the work. As Acme Concrete paves the way in this niche, they're not only setting a new standard but also challenging the status quo of traditional concrete repair methods.

Across the globe, homeowners and businesses alike have witnessed the transformative power of the Smart Lift system through numerous real-life success stories. You're actively choosing a greener alternative to traditional concrete replacement methods. Initially, technicians carefully assess your sunken concrete to determine the best approach.

As you confront the challenge of aging concrete and weigh the costs of replacement against the benefits of repair, Acme Concrete emerges as a beacon of hope for Crystal Lake residents. These case studies highlight not just the immediate improvements in appearance and safety but also the long-term benefits of choosing modern concrete raising methods. That's what we achieve at Acme Concrete Raising & Repair. Concrete Crack Repair

Concrete Lifting Contractor Near Me Crystal Lake

Not only does it ruin your moment, but it also poses a serious safety risk. You might think mudjacking has stood the test of time as a reliable method for concrete raising, but a leading company in Crystal Lake urges you to reconsider.

Illinois Concrete Repair

  1. Concrete Pressure Injection
  2. Basement Floor Lifting
  3. Local Concrete Leveling Services
  4. Interior Floor Lifting
  5. Concrete Leveling
  6. Garage Slab Settlement
  7. Helical Piers
  8. Sunken Step Repair
  9. Slabjacking
  10. Uneven Concrete Repair
  11. Driveway Settling Solutions
  12. Concrete Contractors Crystal Lake
  13. Fix Uneven Driveway Crystal Lake
  14. Subgrade Stabilization
  15. Concrete Raising Contractors
  16. Concrete Driveway Maintenance
  17. Concrete Foundation Settlement
  18. Eco-Friendly Concrete Lifting
  19. Garage Floor Lifting
  20. Crystal Lake Foundation Contractors
Acme provides clear, upfront estimates without hidden fees, ensuring you know exactly what your project will cost before any work begins. That's where Acme's Smart Lift System comes in, offering a cutting-edge solution to this pervasive problem. This means you're not just getting a facelift for your walkways; you're investing in the longevity and safety of your property.
Initially, a professional team assesses your concrete's condition to determine the best approach. Driveway Settling Solutions This foam expands beneath the concrete, filling voids and lifting the slab back to its original level. Concrete Support Injection Moreover, Acme Concrete values your time and property. They use a polyurethane foam that expands beneath the concrete, gently lifting it back into place.
The system starts with a thorough evaluation of your concrete's condition. Imagine you've noticed your driveway, patio, or sidewalk starting to sink. Illinois Concrete Repair In Crystal Lake, where appearances matter, this could be a deciding factor for someone considering your home. You won't be waiting days for the area to be usable again.
Another standout feature is its minimal environmental impact. You're left with a stabilized, level concrete surface, ready to withstand the test of time without the hassle of a complete overhaul. Choosing Acme means you're opting for durability, sustainability, and reliability. You'll notice cracks, uneven surfaces, and even potholes forming, which not only diminish your property's appeal but can also pose safety risks.

Explore Foam Concrete Lifting Crystal Lake here
Concrete Lifting Contractor Near Me Crystal Lake
Polyurethane synthesis: the urethane groups −NH−(C=O)−O− link the molecular units, resulting in a polymer consisting of an alternating chain of two monomers.
A kitchen sponge made of polyurethane foam

Polyurethane (/ËŒpÉ’liˈjÊŠÉ™rəˌθeɪn, -jʊəˈrÉ›θeɪn/;[1] often abbreviated PUR and PU) is a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane does not refer to a single type of polymer but a group of polymers. Unlike polyethylene and polystyrene, polyurethanes can be produced from a wide range of starting materials, resulting in various polymers within the same group. This chemical variety produces polyurethanes with different chemical structures leading to many different applications. These include rigid and flexible foams, and coatings, adhesives, electrical potting compounds, and fibers such as spandex and polyurethane laminate (PUL). Foams are the largest application accounting for 67% of all polyurethane produced in 2016.[2]

A polyurethane is typically produced by reacting a polymeric isocyanate with a polyol.[3] Since a polyurethane contains two types of monomers, which polymerize one after the other, they are classed as alternating copolymers. Both the isocyanates and polyols used to make a polyurethane contain two or more functional groups per molecule.

Global production in 2019 was 25 million metric tonnes,[4] accounting for about 6% of all polymers produced in that year.

History

[edit]
Otto Bayer in 1952 demonstrating his creation

Otto Bayer and his coworkers at IG Farben in Leverkusen, Germany, first made polyurethanes in 1937.[5][6] The new polymers had some advantages over existing plastics that were made by polymerizing olefins or by polycondensation, and were not covered by patents obtained by Wallace Carothers on polyesters.[7] Early work focused on the production of fibers and flexible foams and PUs were applied on a limited scale as aircraft coating during World War II.[7] Polyisocyanates became commercially available in 1952, and production of flexible polyurethane foam began in 1954 by combining toluene diisocyanate (TDI) and polyester polyols. These materials were also used to produce rigid foams, gum rubber, and elastomers. Linear fibers were produced from hexamethylene diisocyanate (HDI) and 1,4-Butanediol (BDO).

DuPont introduced polyethers, specifically poly(tetramethylene ether) glycol, in 1956. BASF and Dow Chemical introduced polyalkylene glycols in 1957. Polyether polyols were cheaper, easier to handle and more water-resistant than polyester polyols. Union Carbide and Mobay, a U.S. Monsanto/Bayer joint venture, also began making polyurethane chemicals.[7] In 1960 more than 45,000 metric tons of flexible polyurethane foams were produced. The availability of chlorofluoroalkane blowing agents, inexpensive polyether polyols, and methylene diphenyl diisocyanate (MDI) allowed polyurethane rigid foams to be used as high-performance insulation materials. In 1967, urethane-modified polyisocyanurate rigid foams were introduced, offering even better thermal stability and flammability resistance. During the 1960s, automotive interior safety components, such as instrument and door panels, were produced by back-filling thermoplastic skins with semi-rigid foam.

In 1969, Bayer exhibited an all-plastic car in Düsseldorf, Germany. Parts of this car, such as the fascia and body panels, were manufactured using a new process called reaction injection molding (RIM), in which the reactants were mixed and then injected into a mold. The addition of fillers, such as milled glass, mica, and processed mineral fibers, gave rise to reinforced RIM (RRIM), which provided improvements in flexural modulus (stiffness), reduction in coefficient of thermal expansion and better thermal stability. This technology was used to make the first plastic-body automobile in the United States, the Pontiac Fiero, in 1983. Further increases in stiffness were obtained by incorporating pre-placed glass mats into the RIM mold cavity, also known broadly as resin injection molding, or structural RIM.

Starting in the early 1980s, water-blown microcellular flexible foams were used to mold gaskets for automotive panels and air-filter seals, replacing PVC polymers. Polyurethane foams are used in many automotive applications including seating, head and arm rests, and headliners.

Polyurethane foam (including foam rubber) is sometimes made using small amounts of blowing agents to give less dense foam, better cushioning/energy absorption or thermal insulation. In the early 1990s, because of their impact on ozone depletion, the Montreal Protocol restricted the use of many chlorine-containing blowing agents, such as trichlorofluoromethane (CFC-11). By the late 1990s, blowing agents such as carbon dioxide, pentane, 1,1,1,2-tetrafluoroethane (HFC-134a) and 1,1,1,3,3-pentafluoropropane (HFC-245fa) were widely used in North America and the EU, although chlorinated blowing agents remained in use in many developing countries. Later, HFC-134a was also banned due to high ODP and GWP readings, and HFC-141B was introduced in early 2000s as an alternate blowing agent in developing nations.[8]

Chemistry

[edit]

Polyurethanes are produced by reacting diisocyanates with polyols,[9][10][11][12][13][14] often in the presence of a catalyst, or upon exposure to ultraviolet radiation.[15] Common catalysts include tertiary amines, such as DABCO, DMDEE, or metallic soaps, such as dibutyltin dilaurate. The stoichiometry of the starting materials must be carefully controlled as excess isocyanate can trimerise, leading to the formation of rigid polyisocyanurates. The polymer usually has a highly crosslinked molecular structure, resulting in a thermosetting material which does not melt on heating; although some thermoplastic polyurethanes are also produced.

 
Carbon dioxide gas and urea links formed by reacting water and isocyanate

The most common application of polyurethane is as solid foams, which requires the presence of a gas, or blowing agent, during the polymerization step. This is commonly achieved by adding small amounts of water, which reacts with isocyanates to form CO2 gas and an amine, via an unstable carbamic acid group. The amine produced can also react with isocyanates to form urea groups, and as such the polymer will contain both these and urethane linkers. The urea is not very soluble in the reaction mixture and tends to form separate "hard segment" phases consisting mostly of polyurea. The concentration and organization of these polyurea phases can have a significant impact on the properties of the foam.[16]

The type of foam produced can be controlled by regulating the amount of blowing agent and also by the addition of various surfactants which change the rheology of the polymerising mixture. Foams can be either "closed-cell", where most of the original bubbles or cells remain intact, or "open-cell", where the bubbles have broken but the edges of the bubbles are stiff enough to retain their shape, in extreme cases reticulated foams can be formed. Open-cell foams feel soft and allow air to flow through, so they are comfortable when used in seat cushions or mattresses. Closed-cell foams are used as rigid thermal insulation. High-density microcellular foams can be formed without the addition of blowing agents by mechanically frothing the polyol prior to use. These are tough elastomeric materials used in covering car steering wheels or shoe soles.

The properties of a polyurethane are greatly influenced by the types of isocyanates and polyols used to make it. Long, flexible segments, contributed by the polyol, give soft, elastic polymer. High amounts of crosslinking give tough or rigid polymers. Long chains and low crosslinking give a polymer that is very stretchy, short chains with many crosslinks produce a hard polymer while long chains and intermediate crosslinking give a polymer useful for making foam. The choices available for the isocyanates and polyols, in addition to other additives and processing conditions allow polyurethanes to have the very wide range of properties that make them such widely used polymers.

Raw materials

[edit]

The main ingredients to make a polyurethane are di- and tri-isocyanates and polyols. Other materials are added to aid processing the polymer or to modify the properties of the polymer. PU foam formulation sometimes have water added too.

Isocyanates

[edit]

Isocyanates used to make polyurethane have two or more isocyanate groups on each molecule. The most commonly used isocyanates are the aromatic diisocyanates, toluene diisocyanate (TDI) and methylene diphenyl diisocyanate, (MDI). These aromatic isocyanates are more reactive than aliphatic isocyanates.

TDI and MDI are generally less expensive and more reactive than other isocyanates. Industrial grade TDI and MDI are mixtures of isomers and MDI often contains polymeric materials. They are used to make flexible foam (for example slabstock foam for mattresses or molded foams for car seats),[17] rigid foam (for example insulating foam in refrigerators) elastomers (shoe soles, for example), and so on. The isocyanates may be modified by partially reacting them with polyols or introducing some other materials to reduce volatility (and hence toxicity) of the isocyanates, decrease their freezing points to make handling easier or to improve the properties of the final polymers.

MDI isomers and polymer
MDI isomers and polymer

Aliphatic and cycloaliphatic isocyanates are used in smaller quantities, most often in coatings and other applications where color and transparency are important since polyurethanes made with aromatic isocyanates tend to darken on exposure to light.[page needed][18] The most important aliphatic and cycloaliphatic isocyanates are 1,6-hexamethylene diisocyanate (HDI), 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (isophorone diisocyanate, IPDI), and 4,4′-diisocyanato dicyclohexylmethane (H12MDI or hydrogenated MDI). Other more specialized isocyanates include Tetramethylxylylene diisocyanate (TMXDI).

Polyols

[edit]

Polyols are polymers in their own right and have on average two or more hydroxyl groups per molecule. They can be converted to polyether polyols by co-polymerizing ethylene oxide and propylene oxide with a suitable polyol precursor.[19] Polyester polyols are made by the polycondensation of multifunctional carboxylic acids and polyhydroxyl compounds. They can be further classified according to their end use. Higher molecular weight polyols (molecular weights from 2,000 to 10,000) are used to make more flexible polyurethanes while lower molecular weight polyols make more rigid products.

Polyols for flexible applications use low functionality initiators such as dipropylene glycol (f = 2), glycerine (f = 3), or a sorbitol/water solution (f = 2.75).[20] Polyols for rigid applications use higher functionality initiators such as sucrose (f = 8), sorbitol (f = 6), toluenediamine (f = 4), and Mannich bases (f = 4). Propylene oxide and/or ethylene oxide is added to the initiators until the desired molecular weight is achieved. The order of addition and the amounts of each oxide affect many polyol properties, such as compatibility, water-solubility, and reactivity. Polyols made with only propylene oxide are terminated with secondary hydroxyl groups and are less reactive than polyols capped with ethylene oxide, which contain primary hydroxyl groups. Incorporating carbon dioxide into the polyol structure is being researched by multiple companies.

Graft polyols (also called filled polyols or polymer polyols) contain finely dispersed styrene–acrylonitrile, acrylonitrile, or polyurea (PHD) polymer solids chemically grafted to a high molecular weight polyether backbone. They are used to increase the load-bearing properties of low-density high-resiliency (HR) foam, as well as add toughness to microcellular foams and cast elastomers. Initiators such as ethylenediamine and triethanolamine are used to make low molecular weight rigid foam polyols that have built-in catalytic activity due to the presence of nitrogen atoms in the backbone. A special class of polyether polyols, poly(tetramethylene ether) glycols, which are made by polymerizing tetrahydrofuran, are used in high performance coating, wetting and elastomer applications.

Conventional polyester polyols are based on virgin raw materials and are manufactured by the direct polyesterification of high-purity diacids and glycols, such as adipic acid and 1,4-butanediol. Polyester polyols are usually more expensive and more viscous than polyether polyols, but they make polyurethanes with better solvent, abrasion, and cut resistance. Other polyester polyols are based on reclaimed raw materials. They are manufactured by transesterification (glycolysis) of recycled poly(ethyleneterephthalate) (PET) or dimethylterephthalate (DMT) distillation bottoms with glycols such as diethylene glycol. These low molecular weight, aromatic polyester polyols are used in rigid foam, and bring low cost and excellent flammability characteristics to polyisocyanurate (PIR) boardstock and polyurethane spray foam insulation.

Specialty polyols include polycarbonate polyols, polycaprolactone polyols, polybutadiene polyols, and polysulfide polyols. The materials are used in elastomer, sealant, and adhesive applications that require superior weatherability, and resistance to chemical and environmental attack. Natural oil polyols derived from castor oil and other vegetable oils are used to make elastomers, flexible bunstock, and flexible molded foam.

Co-polymerizing chlorotrifluoroethylene or tetrafluoroethylene with vinyl ethers containing hydroxyalkyl vinyl ether produces fluorinated (FEVE) polyols. Two-component fluorinated polyurethanes prepared by reacting FEVE fluorinated polyols with polyisocyanate have been used to make ambient cure paints and coatings. Since fluorinated polyurethanes contain a high percentage of fluorine–carbon bonds, which are the strongest bonds among all chemical bonds, fluorinated polyurethanes exhibit resistance to UV, acids, alkali, salts, chemicals, solvents, weathering, corrosion, fungi and microbial attack. These have been used for high performance coatings and paints.[21]

Phosphorus-containing polyols are available that become chemically bonded to the polyurethane matrix for the use as flame retardants. This covalent linkage prevents migration and leaching of the organophosphorus compound.

Bio-derived materials

[edit]

Interest in sustainable "green" products raised interest in polyols derived from vegetable oils,[22][23][24] fatty acids,[25] lignin, sorbitol,[26] etc. These are mostly contributing to polyol part. There are attempts made to prepare isocyanate part using bio-derived material. However, as far as commercialization is concern, polyol part is more targeted being easy and required in more quantity than isocyanate part. Various oils used in the preparation polyols for polyurethanes include soybean oil, cottonseed oil, neem seed oil, algae oil,[27][28] and castor oil. Vegetable oils are functionalized in various ways and modified to polyetheramides, polyethers, alkyds, etc. Renewable sources used to prepare polyols may be fatty acids or dimer fatty acids.[29] Some biobased and isocyanate-free polyurethanes exploit the reaction between polyamines and cyclic carbonates to produce polyhydroxyurethanes.[30]

Chain extenders and cross linkers

[edit]

Chain extenders (f = 2) and cross linkers (f ≥ 3) are low molecular weight hydroxyl and amine terminated compounds that play an important role in the polymer morphology of polyurethane fibers, elastomers, adhesives, and certain integral skin and microcellular foams.

The elastomeric properties of these materials are derived from the phase separation of the hard and soft copolymer segments of the polymer, such that the urethane hard segment domains serve as cross-links between the amorphous polyether (or polyester) soft segment domains. This phase separation occurs because the mainly nonpolar, low melting soft segments are incompatible with the polar, high melting hard segments. The soft segments, which are formed from high molecular weight polyols, are mobile and are normally present in coiled formation, while the hard segments, which are formed from the isocyanate and chain extenders, are stiff and immobile. As the hard segments are covalently coupled to the soft segments, they inhibit plastic flow of the polymer chains, thus creating elastomeric resiliency. Upon mechanical deformation, a portion of the soft segments are stressed by uncoiling, and the hard segments become aligned in the stress direction. This reorientation of the hard segments and consequent powerful hydrogen bonding contributes to high tensile strength, elongation, and tear resistance values.[12][31][32][33][34] The choice of chain extender also determines flexural, heat, and chemical resistance properties.

The most important chain extenders are ethylene glycol, 1,4-butanediol (1,4-BDO or BDO), 1,6-hexanediol, cyclohexane dimethanol and hydroquinone bis(2-hydroxyethyl) ether (HQEE). All of these glycols form polyurethanes that phase separate well and form well defined hard segment domains, and are melt processable. They are all suitable for thermoplastic polyurethanes with the exception of ethylene glycol, since its derived bis-phenyl urethane undergoes unfavorable degradation at high hard segment levels.[10] Diethanolamine and triethanolamine are used in flex molded foams to build firmness and add catalytic activity. Diethyltoluenediamine is used extensively in RIM, and in polyurethane and polyurea elastomer formulations.

Table of chain extenders and cross linkers[35]
Compound type Molecule Mol.
mass
Density
(g/cm3)
Melting
pt (°C)
Boiling
pt (°C)
Hydroxyl compounds – difunctional molecules Ethylene glycol 62.1 1.110 −13.4 197.4
Diethylene glycol 106.1 1.111 −8.7 245.5
Triethylene glycol 150.2 1.120 −7.2 287.8
Tetraethylene glycol 194.2 1.123 −9.4 325.6
Propylene glycol 76.1 1.032 Supercools 187.4
Dipropylene glycol 134.2 1.022 Supercools 232.2
Tripropylene glycol 192.3 1.110 Supercools 265.1
1,3-Propanediol 76.1 1.060 −28 210
1,3-Butanediol 92.1 1.005 207.5
1,4-Butanediol 92.1 1.017 20.1 235
Neopentyl glycol 104.2 130 206
1,6-Hexanediol 118.2 1.017 43 250
1,4-Cyclohexanedimethanol
HQEE
Ethanolamine 61.1 1.018 10.3 170
Diethanolamine 105.1 1.097 28 271
Methyldiethanolamine 119.1 1.043 −21 242
Phenyldiethanolamine 181.2 58 228
Hydroxyl compounds – trifunctional molecules Glycerol 92.1 1.261 18.0 290
Trimethylolpropane
1,2,6-Hexanetriol
Triethanolamine 149.2 1.124 21
Hydroxyl compounds – tetrafunctional molecules Pentaerythritol 136.2 260.5
N,N,N′,N′-Tetrakis
(2-hydroxypropyl)
ethylenediamine
Amine compounds – difunctional molecules Diethyltoluenediamine 178.3 1.022 308
Dimethylthiotoluenediamine 214.0 1.208

Catalysts

[edit]

Polyurethane catalysts can be classified into two broad categories, basic and acidic amine. Tertiary amine catalysts function by enhancing the nucleophilicity of the diol component. Alkyl tin carboxylates, oxides and mercaptides oxides function as mild Lewis acids in accelerating the formation of polyurethane. As bases, traditional amine catalysts include triethylenediamine (TEDA, also called DABCO, 1,4-diazabicyclo[2.2.2]octane), dimethylcyclohexylamine (DMCHA), dimethylethanolamine (DMEA), Dimethylaminoethoxyethanol and bis-(2-dimethylaminoethyl)ether, a blowing catalyst also called A-99. A typical Lewis acidic catalyst is dibutyltin dilaurate. The process is highly sensitive to the nature of the catalyst and is also known to be autocatalytic.[36]

Another class of catalysts was published in a study in May 2024. In this study, polyurethane synthesis was investigated in the presence of acid catalysts, namely dimethylphosphite (DMHP), methanesulfonic acid (MSA), and trifluoromethanesulfonic acid (TFMSA). The thermodynamic profile was examined and described in detail through computational tools, showing that TFMSA had the best catalytic properties. The study aimed to open the door to a new class of catalysts.[37]

Factors affecting catalyst selection include balancing three reactions: urethane (polyol+isocyanate, or gel) formation, the urea (water+isocyanate, or "blow") formation, or the isocyanate trimerization reaction (e.g., using potassium acetate, to form isocyanurate rings). A variety of specialized catalysts have been developed.[38][39][40]

Surfactants

[edit]

Surfactants are used to modify the characteristics of both foam and non-foam polyurethane polymers. They take the form of polydimethylsiloxane-polyoxyalkylene block copolymers, silicone oils, nonylphenol ethoxylates, and other organic compounds. In foams, they are used to emulsify the liquid components, regulate cell size, and stabilize the cell structure to prevent collapse and sub-surface voids.[41] In non-foam applications they are used as air release and antifoaming agents, as wetting agents, and are used to eliminate surface defects such as pin holes, orange peel, and sink marks.

Production

[edit]

Polyurethanes are produced by mixing two or more liquid streams. The polyol stream contains catalysts, surfactants, blowing agents (when making polyurethane foam insulation) and so on. The two components are referred to as a polyurethane system, or simply a system. The isocyanate is commonly referred to in North America as the 'A-side' or just the 'iso'. The blend of polyols and other additives is commonly referred to as the 'B-side' or as the 'poly'.[citation needed] This mixture might also be called a 'resin' or 'resin blend'. In Europe the meanings for 'A-side' and 'B-side' are reversed.[citation needed] Resin blend additives may include chain extenders, cross linkers, surfactants, flame retardants, blowing agents, pigments, and fillers. Polyurethane can be made in a variety of densities and hardnesses by varying the isocyanate, polyol or additives.

Health and safety

[edit]

Fully reacted polyurethane polymer is chemically inert.[42] No exposure limits have been established in the U.S. by OSHA (Occupational Safety and Health Administration) or ACGIH (American Conference of Governmental Industrial Hygienists). It is not regulated by OSHA for carcinogenicity.

Open-flame test. Top: untreated polyurethane foam burns vigorously. Bottom: with fire-retardant treatment.

Polyurethanes are combustible.[43] Decomposition from fire can produce significant amounts of carbon monoxide and hydrogen cyanide, in addition to nitrogen oxides, isocyanates, and other toxic products.[44] Due to the flammability of the material, it has to be treated with flame retardants (at least in case of furniture), almost all of which are considered harmful.[45][46] California later issued Technical Bulletin 117 2013 which allowed most polyurethane foam to pass flammability tests without the use of flame retardants. Green Science Policy Institute states: "Although the new standard can be met without flame retardants, it does NOT ban their use. Consumers who wish to reduce household exposure to flame retardants can look for a TB117-2013 tag on furniture, and verify with retailers that products do not contain flame retardants."[47]

Liquid resin blends and isocyanates may contain hazardous or regulated components. Isocyanates are known skin and respiratory sensitizers. Additionally, amines, glycols, and phosphate present in spray polyurethane foams present risks.[48]

Exposure to chemicals that may be emitted during or after application of polyurethane spray foam (such as isocyanates) are harmful to human health and therefore special precautions are required during and after this process.[49]

In the United States, additional health and safety information can be found through organizations such as the Polyurethane Manufacturers Association (PMA) and the Center for the Polyurethanes Industry (CPI), as well as from polyurethane system and raw material manufacturers. Regulatory information can be found in the Code of Federal Regulations Title 21 (Food and Drugs) and Title 40 (Protection of the Environment). In Europe, health and safety information is available from ISOPA,[50] the European Diisocyanate and Polyol Producers Association.

Manufacturing

[edit]

The methods of manufacturing polyurethane finished goods range from small, hand pour piece-part operations to large, high-volume bunstock and boardstock production lines. Regardless of the end-product, the manufacturing principle is the same: to meter the liquid isocyanate and resin blend at a specified stoichiometric ratio, mix them together until a homogeneous blend is obtained, dispense the reacting liquid into a mold or on to a surface, wait until it cures, then demold the finished part.

Dispensing equipment

[edit]

Although the capital outlay can be high, it is desirable to use a meter-mix or dispense unit for even low-volume production operations that require a steady output of finished parts. Dispense equipment consists of material holding (day) tanks, metering pumps, a mix head, and a control unit. Often, a conditioning or heater–chiller unit is added to control material temperature in order to improve mix efficiency, cure rate, and to reduce process variability. Choice of dispense equipment components depends on shot size, throughput, material characteristics such as viscosity and filler content, and process control. Material day tanks may be single to hundreds of gallons in size and may be supplied directly from drums, IBCs (intermediate bulk containers, such as caged IBC totes), or bulk storage tanks. They may incorporate level sensors, conditioning jackets, and mixers. Pumps can be sized to meter in single grams per second up to hundreds of pounds per minute. They can be rotary, gear, or piston pumps, or can be specially hardened lance pumps to meter liquids containing highly abrasive fillers such as chopped or hammer-milled glass fiber and wollastonite.[citation needed]

The pumps can drive low-pressure (10 to 30 bar, 1 to 3 MPa) or high-pressure (125 to 250 bar, 12.5 to 25.0 MPa) dispense systems. Mix heads can be simple static mix tubes, rotary-element mixers, low-pressure dynamic mixers, or high-pressure hydraulically actuated direct impingement mixers. Control units may have basic on/off and dispense/stop switches, and analogue pressure and temperature gauges, or may be computer-controlled with flow meters to electronically calibrate mix ratio, digital temperature and level sensors, and a full suite of statistical process control software. Add-ons to dispense equipment include nucleation or gas injection units, and third or fourth stream capability for adding pigments or metering in supplemental additive packages.

Tooling

[edit]

Distinct from pour-in-place, bun and boardstock, and coating applications, the production of piece parts requires tooling to contain and form the reacting liquid. The choice of mold-making material is dependent on the expected number of uses to end-of-life (EOL), molding pressure, flexibility, and heat transfer characteristics.

RTV silicone is used for tooling that has an EOL in the thousands of parts. It is typically used for molding rigid foam parts, where the ability to stretch and peel the mold around undercuts is needed. The heat transfer characteristic of RTV silicone tooling is poor. High-performance, flexible polyurethane elastomers are also used in this way.

Epoxy, metal-filled epoxy, and metal-coated epoxy is used for tooling that has an EOL in the tens of thousands of parts. It is typically used for molding flexible foam cushions and seating, integral skin and microcellular foam padding, and shallow-draft RIM bezels and fascia. The heat transfer characteristic of epoxy tooling is fair; the heat transfer characteristic of metal-filled and metal-coated epoxy is good. Copper tubing can be incorporated into the body of the tool, allowing hot water to circulate and heat the mold surface.

Aluminum is used for tooling that has an EOL in the hundreds of thousands of parts. It is typically used for molding microcellular foam gasketing and cast elastomer parts, and is milled or extruded into shape.

Mirror-finish stainless steel is used for tooling that imparts a glossy appearance to the finished part. The heat transfer characteristic of metal tooling is excellent.

Finally, molded or milled polypropylene is used to create low-volume tooling for molded gasket applications. Instead of many expensive metal molds, low-cost plastic tooling can be formed from a single metal master, which also allows greater design flexibility. The heat transfer characteristic of polypropylene tooling is poor, which must be taken into consideration during the formulation process.

Applications

[edit]

In 2007, the global consumption of polyurethane raw materials was above 12 million metric tons, and the average annual growth rate was about 5%.[51] Revenues generated with PUR on the global market are expected to rise to approximately US$75 billion by 2022.[52] As they are such an important class of materials, research is constantly taking place and papers published.[53]

Degradation and environmental fate

[edit]

Effects of visible light

[edit]
Polyurethane foam made with an aromatic isocyanate, which has been exposed to UV light. Readily apparent is the discoloration that occurs over time.

Polyurethanes, especially those made using aromatic isocyanates, contain chromophores that interact with light. This is of particular interest in the area of polyurethane coatings, where light stability is a critical factor and is the main reason that aliphatic isocyanates are used in making polyurethane coatings. When PU foam, which is made using aromatic isocyanates, is exposed to visible light, it discolors, turning from off-white to yellow to reddish brown. It has been generally accepted that apart from yellowing, visible light has little effect on foam properties.[54][55] This is especially the case if the yellowing happens on the outer portions of a large foam, as the deterioration of properties in the outer portion has little effect on the overall bulk properties of the foam itself.

It has been reported that exposure to visible light can affect the variability of some physical property test results.[56]

Higher-energy UV radiation promotes chemical reactions in foam, some of which are detrimental to the foam structure.[57]

Hydrolysis and biodegradation

[edit]

Polyurethanes may degrade due to hydrolysis. This is a common problem with shoes left in a closet, and reacting with moisture in the air.[58]

Microbial degradation of polyurethane is believed to be due to the action of esterase, urethanase, hydrolase and protease enzymes.[59] The process is slow as most microbes have difficulty moving beyond the surface of the polymer. Susceptibility to fungi is higher due to their release of extracellular enzymes, which are better able to permeate the polymer matrix. Two species of the Ecuadorian fungus Pestalotiopsis are capable of biodegrading polyurethane in aerobic and anaerobic conditions such as found at the bottom of landfills.[60][61] Degradation of polyurethane items at museums has been reported.[62] Polyester-type polyurethanes are more easily biodegraded by fungus than polyether-type.[63]

See also

[edit]
  • Botanol, a material with higher plant-based content
  • Passive fire protection
  • Penetrant (mechanical, electrical, or structural)
  • Polyaspartic
  • Polyurethane dispersion
  • Thermoplastic polyurethanes
  • Thermoset polymer matrix

References

[edit]
  1. ^ "polyurethane". Dictionary.com Unabridged (Online). n.d.
  2. ^ Gama, Nuno; Ferreira, Artur; Barros-Timmons, Ana (27 September 2018). "Polyurethane Foams: Past, Present, and Future". Materials. 11 (10): 1841. Bibcode:2018Mate...11.1841G. doi:10.3390/ma11101841. PMC 6213201. PMID 30262722.
  3. ^ "Polyurethane". American Chemistry Council. Retrieved 2022-09-19.
  4. ^ "Polyurethane global market volume 2015-2026". Statista. Retrieved 23 July 2021.
  5. ^ Bayer, Otto (1947). "Das Di-Isocyanat-Polyadditionsverfahren (Polyurethane)". Angewandte Chemie. 59 (9): 257–72. Bibcode:1947AngCh..59..257B. doi:10.1002/ange.19470590901.
  6. ^ DE 728981, I.G. Farbenindustrie A.G., "Verfahren zur Herstellung von Polyurethanen bzw. Polyharnstoffen [Process for the production of polyurethanes or polyurea]", published 1942-12-07 
  7. ^ a b c Seymour, Raymond B.; Kauffman, George B. (1992). "Polyurethanes: A class of modern versatile materials". Journal of Chemical Education. 69 (11): 909. Bibcode:1992JChEd..69..909S. doi:10.1021/ed069p909.
  8. ^ Feske, Bert (October 2004). "The Use of Saytex RB-9130/9170 Low Viscosity Brominated Flame Retardant Polyols in HFC-245fa and High Water Formulations" (PDF). Polyurethanes Expo 2004. Las Vegas, NV: Alliance for the Polyurethane Industry Technical Conference. p. 309. Retrieved 2007-08-01.
  9. ^ n ≥ 2
  10. ^ a b Gum, Wilson; Riese, Wolfram; Ulrich, Henri (1992). Reaction Polymers. New York: Oxford University Press. ISBN 978-0-19-520933-4.
  11. ^ Harrington, Ron; Hock, Kathy (1991). Flexible Polyurethane Foams. Midland: The Dow Chemical Company.
  12. ^ a b Oertel, Gunter (1985). Polyurethane Handbook. New York: Macmillen Publishing Co., Inc. ISBN 978-0-02-948920-8.[page needed]
  13. ^ Ulrich, Henri (1996). Chemistry and Technology of Isocyanates. New York: John Wiley & Sons, Inc. ISBN 978-0-471-96371-4.[page needed]
  14. ^ Woods, George (1990). The ICI Polyurethanes Book. New York: John Wiley & Sons, Inc. ISBN 978-0-471-92658-0.[page needed]
  15. ^ Soto, Marc; Sebastián, Rosa María; Marquet, Jordi (2014). "Photochemical Activation of Extremely Weak Nucleophiles: Highly Fluorinated Urethanes and Polyurethanes from Polyfluoro Alcohols". The Journal of Organic Chemistry. 79 (11): 5019–27. doi:10.1021/jo5005789. PMID 24820955.
  16. ^ Kaushiva, Byran D. (August 15, 1999). Structure-Property Relationships of Flexible Polyurethane Foams (Ph.D.). Virginia Polytechnic Institute.
  17. ^ "Technical data sheet from Dow Chemical". Archived from the original on 2007-10-13. Retrieved 2007-09-15.
  18. ^ Randall, David; Lee, Steve (2002). The Polyurethanes Book. New York: Wiley. ISBN 978-0-470-85041-1.
  19. ^ Petrović, Zoran S. (2008). "Polyurethanes from Vegetable Oils". Polymer Reviews. 48 (1): 109–155. doi:10.1080/15583720701834224. S2CID 95466690.
  20. ^ EP 0755955, Hager, Stanley L.; Knight, James E. & Helma, Gregory F. et al., "Polyether polyols suitable for flexible polyurethane foam prepared by co-initiation of aqueous solutions of solid polyhydroxyl initiators", published 1997-01-29, assigned to ARCO Chemical Technology 
  21. ^ Bob Parker. "FEVE Technology for Higher Performance Coating Systems on Bridges" (PDF). Paintsquare.com. Archived from the original (PDF) on 15 August 2021. Retrieved 5 March 2022.
  22. ^ Khanderay, Jitendra C., and Vikas V. Gite. "Vegetable oil-based polyurethane coatings: recent developments in India." Green Materials 5.3 (2017): 109-122.
  23. ^ Niemeyer, Timothy; Patel, Munjal; Geiger, Eric (September 2006). A Further Examination of Soy-Based Polyols in Polyurethane Systems. Salt Lake City, UT: Alliance for the Polyurethane Industry Technical Conference.
  24. ^ "New Twist on Green: 2008 Ford Mustang Seats Will Be Soy-Based Foam". Edmunds inside line. July 12, 2007. Archived from the original on 2008-05-31. Retrieved 2010-06-15.
  25. ^ SD Rajput, PP Mahulikar, VV Gite, Biobased dimer fatty acid containing two pack polyurethane for wood finished coatings, Progress in Organic Coatings 77 (1), 38-46 https://doi.org/10.1016/j.porgcoat.2014.04.030
  26. ^ A Anand, RD Kulkarni, VV Gite, Preparation and properties of eco-friendly two pack PU coatings based on renewable source (sorbitol) and its property improvement by nano ZnO, Progress in Organic Coatings 74 (4), 764-767, https://doi.org/10.1016/j.porgcoat.2011.09.031
  27. ^ Chandrashekhar K Patil, Harishchandra D Jirimali, Jayasinh S Paradeshi, Bhushan L Chaudhari, Prakash K Alagi, Pramod P Mahulikar, Sung Chul Hong, Vikas V Gite, Chemical transformation of renewable algae oil to polyetheramide polyols for polyurethane coatings, Progress in Organic Coatings 151, 106084, https://doi.org/10.1016/j.porgcoat.2020.106084
  28. ^ CK Patil, HD Jirimali, JS Paradeshi, BL Chaudhari, VV Gite, Functional antimicrobial and anticorrosive polyurethane composite coatings from algae oil and silver doped egg shell hydroxyapatite for sustainable development, Progress in Organic Coatings 128, 127-136, https://doi.org/10.1016/j.porgcoat.2018.11.002
  29. ^ Biobased dimer fatty acid containing two pack polyurethane for wood finished coatings, SD Rajput, PP Mahulikar, VV Gite, Progress in Organic Coatings 77 (1), 38-46
  30. ^ Nohra, Bassam; Candy, Laure; Blanco, Jean-François; Guerin, Celine; Raoul, Yann; Mouloungui, Zephirin (2013). "From Petrochemical Polyurethanes to Biobased Polyhydroxyurethanes" (PDF). Macromolecules. 46 (10): 3771–92. Bibcode:2013MaMol..46.3771N. doi:10.1021/ma400197c. Archived (PDF) from the original on 2017-09-22.
  31. ^ Blackwell, J.; Nagarajan, M. R.; Hoitink, T. B. (1981). "The Structure of the Hard Segments in MDI/diol/PTMA Polyurethane Elastomers". ACS Symposium Series. 172. Washington, D.C.: American Chemical Society: 179–196. doi:10.1021/bk-1981-0172.ch014. ISBN 978-0-8412-0664-9. ISSN 0097-6156.
  32. ^ Blackwell, John; Gardner, Kenncorwin H. (1979). "Structure of the hard segments in polyurethane elastomers". Polymer. 20 (1): 13–17. doi:10.1016/0032-3861(79)90035-1. ISSN 0032-3861.
  33. ^ Grillo, D. J.; Housel, T. L. (1992). "Physical Properties of Polyurethanes from Polyesters and Other Polyols". Polyurethanes '92 Conference Proceedings. New Orleans, LA: The Society of the Plastics Industry, Inc.
  34. ^ Musselman, S. G.; Santosusso, T. M.; Sperling, L. H. (1998). "Structure Versus Performance Properties of Cast Elastomers". Polyurethanes '98 Conference Proceedings. Dallas, TX: The Society of the Plastics Industry, Inc.
  35. ^ A Guide to Glycols. Midland, Mich.: The Dow Chemical Co., Chemicals and Metals Department. 1992. Brochure 117-00991-92Hyc.
  36. ^ Adam, Norbert; Avar, Geza; Blankenheim, Herbert; Friederichs, Wolfgang; Giersig, Manfred; Weigand, Eckehard; Halfmann, Michael; Wittbecker, Friedrich-Wilhelm; Larimer, Donald-Richard; Maier, Udo; Meyer-Ahrens, Sven; Noble, Karl-Ludwig; Wussow, Hans-Georg (2005). "Polyurethanes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a21_665.pub2. ISBN 978-3-527-30673-2.
  37. ^ Waleed, H. Q.; Viskolcz, B.; Fiser, B. (2024). "Urethane Synthesis in the Presence of Organic Acid Catalysts—A Computational Study". Molecules (Basel, Switzerland). 29 (10): 2375. doi:10.3390/molecules29102375. PMC 11123846. PMID 38792235.
  38. ^ "Jeffcat Amine Catalysts for the Polyurethane Industry" (PDF). 2006. Archived from the original (PDF) on 2007-11-29. Retrieved 2007-10-23.
  39. ^ "Building quality with Air Products trimerisation catalysts" (PDF). 2003. Archived from the original (PDF) on 2007-11-29. Retrieved 2007-10-23.
  40. ^ "FOMREZ Specialty Tin Catalysts for Polyurethane Applications". 120-074-10. January 2001.
  41. ^ Randall, David; Lee, Steve, eds. (2002). "10". The Polyurethanes Book. The United Kingdom: Huntsman International LLC, Polyurethanes business. pp. 156–159. ISBN 978-0470850411. Archived from the original on 2018-05-24. Retrieved 2018-05-23.
  42. ^ Dernehl, C. U. (1966). "Health hazards associated with polyurethane foams". Journal of Occupational Medicine. 8 (2): 59–62. PMID 5903304.
  43. ^ "Health Alert: Polyurethane exposure" (PDF). Archived from the original (PDF) on 2004-10-19. Retrieved 2009-12-19.
  44. ^ McKenna, Sean Thomas; Hull, Terence Richard (2016). "The fire toxicity of polyurethane foams". Fire Science Reviews. 5 (1): 3. doi:10.1186/s40038-016-0012-3.
  45. ^ "Environmental Profiles of Chemical Flame-Retardant Alternatives for Low-Density Polyurethane Foam". United States Environmental Protection Agency. September 2005.
  46. ^ "Flame Retardants Used in Flexible Polyurethane Foam – Draft Update to a 2005 Alternatives Assessment". United States Environmental Protection Agency. June 2014. Archived from the original on November 21, 2014.
  47. ^ "Manufacturers" (PDF). greensciencepolicy.org. 2015. Archived (PDF) from the original on 2015-12-19.
  48. ^ "Help Wanted: Spray Polyurethane Foam Insulation Research". NIOSH Science Blog. CDC. 21 March 2012.
  49. ^ "Quick Safety Tips for Spray Polyurethane Foam Users". United States Environmental Protection Agency. 4 August 2015.
  50. ^ "Home : ISOPA". www.isopa.org.
  51. ^ Avar, G. (October 2008). "Polyurethanes (PU)". Kunststoffe International (10/2008): 123–7.
  52. ^ "Market Study: Polyurethanes and Isocyanates". Ceresana. July 2013.
  53. ^ Jakhmola, Swati; Das, Sonalee; Dutta, Kingshuk (2023-10-31). "Emerging research trends in the field of polyurethane and its nanocomposites: Chemistry, Synthesis, Characterization, Application in coatings and Future perspectives". Journal of Coatings Technology and Research. 21 (1): 137–172. doi:10.1007/s11998-023-00841-z. ISSN 1935-3804. S2CID 264908475.
  54. ^ "Discoloration of polyurethane foam" (PDF). Foamex Information sheet. Archived from the original (PDF) on 2010-09-24. Retrieved 2010-09-26.
  55. ^ Valentine, C.; Craig, T.A.; Hager, S.L. (1993). "Inhibition of the Discoloration of Polyurethane Foam Caused by Ultraviolet Light". Journal of Cellular Plastics. 29 (6): 569–88. doi:10.1177/0021955X9302900605. S2CID 208363195.
  56. ^ Blair, G. Ron; Dawe, Bob; McEvoy, Jim; Pask, Roy; de Priamus, Marcela Rusan; Wright, Carol (2007). The Effect of Visible Light on the Variability of Flexible Foam Compression Sets (PDF). Orlando, FL: Center for the Polyurethane Industry. Retrieved 2008-01-26.
  57. ^ Newman, Christopher R.; Forciniti, Daniel (2001). "Modeling the Ultraviolet Photodegradation of Rigid Polyurethane Foams". Industrial & Engineering Chemistry Research. 40 (15): 3346–52. doi:10.1021/ie0009738.
  58. ^ "Hydrolysis, The Crumbling of Shoe Soles explained | Safety Shoes and Gloves". www.safetyjogger.com.
  59. ^ Toward, Gary T. (June 2002). "Biodegradation of polyurethane: a review". International Biodeterioration & Biodegradation. 49 (4): 245–252. Bibcode:2002IBiBi..49..245H. doi:10.1016/S0964-8305(02)00051-3.
  60. ^ Russell, J. R.; Huang, J.; Anand, P.; Kucera, K.; Sandoval, A. G.; Dantzler, K. W.; Hickman, D.; Jee, J.; Kimovec, F. M.; Koppstein, D.; Marks, D. H.; Mittermiller, P. A.; Nunez, S. J.; Santiago, M.; Townes, M. A.; Vishnevetsky, M.; Williams, N. E.; Vargas, M. P. N.; Boulanger, L.-A.; Bascom-Slack, C.; Strobel, S. A. (2011). "Biodegradation of Polyester Polyurethane by Endophytic Fungi". Applied and Environmental Microbiology. 77 (17): 6076–84. Bibcode:2011ApEnM..77.6076R. doi:10.1128/AEM.00521-11. PMC 3165411. PMID 21764951.
  61. ^ "Could Plastic-Eating Mushrooms Solve mankind's Plastic Problem?". Sciencemint. 2021-04-14. Archived from the original on 2021-07-09. Retrieved 2021-07-02.
  62. ^ Cappitelli, F.; Sorlini, C. (2007). "Microorganisms Attack Synthetic Polymers in Items Representing Our Cultural Heritage". Applied and Environmental Microbiology. 74 (3): 564–9. Bibcode:2008ApEnM..74..564C. doi:10.1128/AEM.01768-07. PMC 2227722. PMID 18065627.
  63. ^ Tokiwa, Yutaka; Calabia, Buenaventurada P.; Ugwu, Charles U.; Aiba, Seiichi (2009). "Biodegradability of Plastics". International Journal of Molecular Sciences. 10 (9): 3722–42. doi:10.3390/ijms10093722. PMC 2769161. PMID 19865515.
[edit]
  • Center for the Polyurethanes Industry: information for EH&S issues related to polyurethanes developments
  • Polyurethane synthesis, Polymer Science Learning Center, University of Southern Mississippi
  • Polyurethane Foam Association: Industry information, educational materials and resources related to flexible polyurethane foam
  • PU Europe: European PU insulation industry association (formerly BING): European voice for the national trade associations representing the polyurethane insulation industry
  • ISOPA: European Diisocyanate & Polyol Producers Association: ISOPA represents the manufacturers in Europe of aromatic diisocyanates and polyols

 

Polyurethane synthesis: the urethane groups −NH−(C=O)−O− link the molecular units, resulting in a polymer consisting of an alternating chain of two monomers.
A kitchen sponge made of polyurethane foam

Polyurethane (/ËŒpÉ’liˈjÊŠÉ™rəˌθeɪn, -jʊəˈrÉ›θeɪn/;[1] often abbreviated PUR and PU) is a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane does not refer to a single type of polymer but a group of polymers. Unlike polyethylene and polystyrene, polyurethanes can be produced from a wide range of starting materials, resulting in various polymers within the same group. This chemical variety produces polyurethanes with different chemical structures leading to many different applications. These include rigid and flexible foams, and coatings, adhesives, electrical potting compounds, and fibers such as spandex and polyurethane laminate (PUL). Foams are the largest application accounting for 67% of all polyurethane produced in 2016.[2]

A polyurethane is typically produced by reacting a polymeric isocyanate with a polyol.[3] Since a polyurethane contains two types of monomers, which polymerize one after the other, they are classed as alternating copolymers. Both the isocyanates and polyols used to make a polyurethane contain two or more functional groups per molecule.

Global production in 2019 was 25 million metric tonnes,[4] accounting for about 6% of all polymers produced in that year.

History

[edit]
Otto Bayer in 1952 demonstrating his creation

Otto Bayer and his coworkers at IG Farben in Leverkusen, Germany, first made polyurethanes in 1937.[5][6] The new polymers had some advantages over existing plastics that were made by polymerizing olefins or by polycondensation, and were not covered by patents obtained by Wallace Carothers on polyesters.[7] Early work focused on the production of fibers and flexible foams and PUs were applied on a limited scale as aircraft coating during World War II.[7] Polyisocyanates became commercially available in 1952, and production of flexible polyurethane foam began in 1954 by combining toluene diisocyanate (TDI) and polyester polyols. These materials were also used to produce rigid foams, gum rubber, and elastomers. Linear fibers were produced from hexamethylene diisocyanate (HDI) and 1,4-Butanediol (BDO).

DuPont introduced polyethers, specifically poly(tetramethylene ether) glycol, in 1956. BASF and Dow Chemical introduced polyalkylene glycols in 1957. Polyether polyols were cheaper, easier to handle and more water-resistant than polyester polyols. Union Carbide and Mobay, a U.S. Monsanto/Bayer joint venture, also began making polyurethane chemicals.[7] In 1960 more than 45,000 metric tons of flexible polyurethane foams were produced. The availability of chlorofluoroalkane blowing agents, inexpensive polyether polyols, and methylene diphenyl diisocyanate (MDI) allowed polyurethane rigid foams to be used as high-performance insulation materials. In 1967, urethane-modified polyisocyanurate rigid foams were introduced, offering even better thermal stability and flammability resistance. During the 1960s, automotive interior safety components, such as instrument and door panels, were produced by back-filling thermoplastic skins with semi-rigid foam.

In 1969, Bayer exhibited an all-plastic car in Düsseldorf, Germany. Parts of this car, such as the fascia and body panels, were manufactured using a new process called reaction injection molding (RIM), in which the reactants were mixed and then injected into a mold. The addition of fillers, such as milled glass, mica, and processed mineral fibers, gave rise to reinforced RIM (RRIM), which provided improvements in flexural modulus (stiffness), reduction in coefficient of thermal expansion and better thermal stability. This technology was used to make the first plastic-body automobile in the United States, the Pontiac Fiero, in 1983. Further increases in stiffness were obtained by incorporating pre-placed glass mats into the RIM mold cavity, also known broadly as resin injection molding, or structural RIM.

Starting in the early 1980s, water-blown microcellular flexible foams were used to mold gaskets for automotive panels and air-filter seals, replacing PVC polymers. Polyurethane foams are used in many automotive applications including seating, head and arm rests, and headliners.

Polyurethane foam (including foam rubber) is sometimes made using small amounts of blowing agents to give less dense foam, better cushioning/energy absorption or thermal insulation. In the early 1990s, because of their impact on ozone depletion, the Montreal Protocol restricted the use of many chlorine-containing blowing agents, such as trichlorofluoromethane (CFC-11). By the late 1990s, blowing agents such as carbon dioxide, pentane, 1,1,1,2-tetrafluoroethane (HFC-134a) and 1,1,1,3,3-pentafluoropropane (HFC-245fa) were widely used in North America and the EU, although chlorinated blowing agents remained in use in many developing countries. Later, HFC-134a was also banned due to high ODP and GWP readings, and HFC-141B was introduced in early 2000s as an alternate blowing agent in developing nations.[8]

Chemistry

[edit]

Polyurethanes are produced by reacting diisocyanates with polyols,[9][10][11][12][13][14] often in the presence of a catalyst, or upon exposure to ultraviolet radiation.[15] Common catalysts include tertiary amines, such as DABCO, DMDEE, or metallic soaps, such as dibutyltin dilaurate. The stoichiometry of the starting materials must be carefully controlled as excess isocyanate can trimerise, leading to the formation of rigid polyisocyanurates. The polymer usually has a highly crosslinked molecular structure, resulting in a thermosetting material which does not melt on heating; although some thermoplastic polyurethanes are also produced.

 
Carbon dioxide gas and urea links formed by reacting water and isocyanate

The most common application of polyurethane is as solid foams, which requires the presence of a gas, or blowing agent, during the polymerization step. This is commonly achieved by adding small amounts of water, which reacts with isocyanates to form CO2 gas and an amine, via an unstable carbamic acid group. The amine produced can also react with isocyanates to form urea groups, and as such the polymer will contain both these and urethane linkers. The urea is not very soluble in the reaction mixture and tends to form separate "hard segment" phases consisting mostly of polyurea. The concentration and organization of these polyurea phases can have a significant impact on the properties of the foam.[16]

The type of foam produced can be controlled by regulating the amount of blowing agent and also by the addition of various surfactants which change the rheology of the polymerising mixture. Foams can be either "closed-cell", where most of the original bubbles or cells remain intact, or "open-cell", where the bubbles have broken but the edges of the bubbles are stiff enough to retain their shape, in extreme cases reticulated foams can be formed. Open-cell foams feel soft and allow air to flow through, so they are comfortable when used in seat cushions or mattresses. Closed-cell foams are used as rigid thermal insulation. High-density microcellular foams can be formed without the addition of blowing agents by mechanically frothing the polyol prior to use. These are tough elastomeric materials used in covering car steering wheels or shoe soles.

The properties of a polyurethane are greatly influenced by the types of isocyanates and polyols used to make it. Long, flexible segments, contributed by the polyol, give soft, elastic polymer. High amounts of crosslinking give tough or rigid polymers. Long chains and low crosslinking give a polymer that is very stretchy, short chains with many crosslinks produce a hard polymer while long chains and intermediate crosslinking give a polymer useful for making foam. The choices available for the isocyanates and polyols, in addition to other additives and processing conditions allow polyurethanes to have the very wide range of properties that make them such widely used polymers.

Raw materials

[edit]

The main ingredients to make a polyurethane are di- and tri-isocyanates and polyols. Other materials are added to aid processing the polymer or to modify the properties of the polymer. PU foam formulation sometimes have water added too.

Isocyanates

[edit]

Isocyanates used to make polyurethane have two or more isocyanate groups on each molecule. The most commonly used isocyanates are the aromatic diisocyanates, toluene diisocyanate (TDI) and methylene diphenyl diisocyanate, (MDI). These aromatic isocyanates are more reactive than aliphatic isocyanates.

TDI and MDI are generally less expensive and more reactive than other isocyanates. Industrial grade TDI and MDI are mixtures of isomers and MDI often contains polymeric materials. They are used to make flexible foam (for example slabstock foam for mattresses or molded foams for car seats),[17] rigid foam (for example insulating foam in refrigerators) elastomers (shoe soles, for example), and so on. The isocyanates may be modified by partially reacting them with polyols or introducing some other materials to reduce volatility (and hence toxicity) of the isocyanates, decrease their freezing points to make handling easier or to improve the properties of the final polymers.

MDI isomers and polymer
MDI isomers and polymer

Aliphatic and cycloaliphatic isocyanates are used in smaller quantities, most often in coatings and other applications where color and transparency are important since polyurethanes made with aromatic isocyanates tend to darken on exposure to light.[page needed][18] The most important aliphatic and cycloaliphatic isocyanates are 1,6-hexamethylene diisocyanate (HDI), 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (isophorone diisocyanate, IPDI), and 4,4′-diisocyanato dicyclohexylmethane (H12MDI or hydrogenated MDI). Other more specialized isocyanates include Tetramethylxylylene diisocyanate (TMXDI).

Polyols

[edit]

Polyols are polymers in their own right and have on average two or more hydroxyl groups per molecule. They can be converted to polyether polyols by co-polymerizing ethylene oxide and propylene oxide with a suitable polyol precursor.[19] Polyester polyols are made by the polycondensation of multifunctional carboxylic acids and polyhydroxyl compounds. They can be further classified according to their end use. Higher molecular weight polyols (molecular weights from 2,000 to 10,000) are used to make more flexible polyurethanes while lower molecular weight polyols make more rigid products.

Polyols for flexible applications use low functionality initiators such as dipropylene glycol (f = 2), glycerine (f = 3), or a sorbitol/water solution (f = 2.75).[20] Polyols for rigid applications use higher functionality initiators such as sucrose (f = 8), sorbitol (f = 6), toluenediamine (f = 4), and Mannich bases (f = 4). Propylene oxide and/or ethylene oxide is added to the initiators until the desired molecular weight is achieved. The order of addition and the amounts of each oxide affect many polyol properties, such as compatibility, water-solubility, and reactivity. Polyols made with only propylene oxide are terminated with secondary hydroxyl groups and are less reactive than polyols capped with ethylene oxide, which contain primary hydroxyl groups. Incorporating carbon dioxide into the polyol structure is being researched by multiple companies.

Graft polyols (also called filled polyols or polymer polyols) contain finely dispersed styrene–acrylonitrile, acrylonitrile, or polyurea (PHD) polymer solids chemically grafted to a high molecular weight polyether backbone. They are used to increase the load-bearing properties of low-density high-resiliency (HR) foam, as well as add toughness to microcellular foams and cast elastomers. Initiators such as ethylenediamine and triethanolamine are used to make low molecular weight rigid foam polyols that have built-in catalytic activity due to the presence of nitrogen atoms in the backbone. A special class of polyether polyols, poly(tetramethylene ether) glycols, which are made by polymerizing tetrahydrofuran, are used in high performance coating, wetting and elastomer applications.

Conventional polyester polyols are based on virgin raw materials and are manufactured by the direct polyesterification of high-purity diacids and glycols, such as adipic acid and 1,4-butanediol. Polyester polyols are usually more expensive and more viscous than polyether polyols, but they make polyurethanes with better solvent, abrasion, and cut resistance. Other polyester polyols are based on reclaimed raw materials. They are manufactured by transesterification (glycolysis) of recycled poly(ethyleneterephthalate) (PET) or dimethylterephthalate (DMT) distillation bottoms with glycols such as diethylene glycol. These low molecular weight, aromatic polyester polyols are used in rigid foam, and bring low cost and excellent flammability characteristics to polyisocyanurate (PIR) boardstock and polyurethane spray foam insulation.

Specialty polyols include polycarbonate polyols, polycaprolactone polyols, polybutadiene polyols, and polysulfide polyols. The materials are used in elastomer, sealant, and adhesive applications that require superior weatherability, and resistance to chemical and environmental attack. Natural oil polyols derived from castor oil and other vegetable oils are used to make elastomers, flexible bunstock, and flexible molded foam.

Co-polymerizing chlorotrifluoroethylene or tetrafluoroethylene with vinyl ethers containing hydroxyalkyl vinyl ether produces fluorinated (FEVE) polyols. Two-component fluorinated polyurethanes prepared by reacting FEVE fluorinated polyols with polyisocyanate have been used to make ambient cure paints and coatings. Since fluorinated polyurethanes contain a high percentage of fluorine–carbon bonds, which are the strongest bonds among all chemical bonds, fluorinated polyurethanes exhibit resistance to UV, acids, alkali, salts, chemicals, solvents, weathering, corrosion, fungi and microbial attack. These have been used for high performance coatings and paints.[21]

Phosphorus-containing polyols are available that become chemically bonded to the polyurethane matrix for the use as flame retardants. This covalent linkage prevents migration and leaching of the organophosphorus compound.

Bio-derived materials

[edit]

Interest in sustainable "green" products raised interest in polyols derived from vegetable oils,[22][23][24] fatty acids,[25] lignin, sorbitol,[26] etc. These are mostly contributing to polyol part. There are attempts made to prepare isocyanate part using bio-derived material. However, as far as commercialization is concern, polyol part is more targeted being easy and required in more quantity than isocyanate part. Various oils used in the preparation polyols for polyurethanes include soybean oil, cottonseed oil, neem seed oil, algae oil,[27][28] and castor oil. Vegetable oils are functionalized in various ways and modified to polyetheramides, polyethers, alkyds, etc. Renewable sources used to prepare polyols may be fatty acids or dimer fatty acids.[29] Some biobased and isocyanate-free polyurethanes exploit the reaction between polyamines and cyclic carbonates to produce polyhydroxyurethanes.[30]

Chain extenders and cross linkers

[edit]

Chain extenders (f = 2) and cross linkers (f ≥ 3) are low molecular weight hydroxyl and amine terminated compounds that play an important role in the polymer morphology of polyurethane fibers, elastomers, adhesives, and certain integral skin and microcellular foams.

The elastomeric properties of these materials are derived from the phase separation of the hard and soft copolymer segments of the polymer, such that the urethane hard segment domains serve as cross-links between the amorphous polyether (or polyester) soft segment domains. This phase separation occurs because the mainly nonpolar, low melting soft segments are incompatible with the polar, high melting hard segments. The soft segments, which are formed from high molecular weight polyols, are mobile and are normally present in coiled formation, while the hard segments, which are formed from the isocyanate and chain extenders, are stiff and immobile. As the hard segments are covalently coupled to the soft segments, they inhibit plastic flow of the polymer chains, thus creating elastomeric resiliency. Upon mechanical deformation, a portion of the soft segments are stressed by uncoiling, and the hard segments become aligned in the stress direction. This reorientation of the hard segments and consequent powerful hydrogen bonding contributes to high tensile strength, elongation, and tear resistance values.[12][31][32][33][34] The choice of chain extender also determines flexural, heat, and chemical resistance properties.

The most important chain extenders are ethylene glycol, 1,4-butanediol (1,4-BDO or BDO), 1,6-hexanediol, cyclohexane dimethanol and hydroquinone bis(2-hydroxyethyl) ether (HQEE). All of these glycols form polyurethanes that phase separate well and form well defined hard segment domains, and are melt processable. They are all suitable for thermoplastic polyurethanes with the exception of ethylene glycol, since its derived bis-phenyl urethane undergoes unfavorable degradation at high hard segment levels.[10] Diethanolamine and triethanolamine are used in flex molded foams to build firmness and add catalytic activity. Diethyltoluenediamine is used extensively in RIM, and in polyurethane and polyurea elastomer formulations.

Table of chain extenders and cross linkers[35]
Compound type Molecule Mol.
mass
Density
(g/cm3)
Melting
pt (°C)
Boiling
pt (°C)
Hydroxyl compounds – difunctional molecules Ethylene glycol 62.1 1.110 −13.4 197.4
Diethylene glycol 106.1 1.111 −8.7 245.5
Triethylene glycol 150.2 1.120 −7.2 287.8
Tetraethylene glycol 194.2 1.123 −9.4 325.6
Propylene glycol 76.1 1.032 Supercools 187.4
Dipropylene glycol 134.2 1.022 Supercools 232.2
Tripropylene glycol 192.3 1.110 Supercools 265.1
1,3-Propanediol 76.1 1.060 −28 210
1,3-Butanediol 92.1 1.005 207.5
1,4-Butanediol 92.1 1.017 20.1 235
Neopentyl glycol 104.2 130 206
1,6-Hexanediol 118.2 1.017 43 250
1,4-Cyclohexanedimethanol
HQEE
Ethanolamine 61.1 1.018 10.3 170
Diethanolamine 105.1 1.097 28 271
Methyldiethanolamine 119.1 1.043 −21 242
Phenyldiethanolamine 181.2 58 228
Hydroxyl compounds – trifunctional molecules Glycerol 92.1 1.261 18.0 290
Trimethylolpropane
1,2,6-Hexanetriol
Triethanolamine 149.2 1.124 21
Hydroxyl compounds – tetrafunctional molecules Pentaerythritol 136.2 260.5
N,N,N′,N′-Tetrakis
(2-hydroxypropyl)
ethylenediamine
Amine compounds – difunctional molecules Diethyltoluenediamine 178.3 1.022 308
Dimethylthiotoluenediamine 214.0 1.208

Catalysts

[edit]

Polyurethane catalysts can be classified into two broad categories, basic and acidic amine. Tertiary amine catalysts function by enhancing the nucleophilicity of the diol component. Alkyl tin carboxylates, oxides and mercaptides oxides function as mild Lewis acids in accelerating the formation of polyurethane. As bases, traditional amine catalysts include triethylenediamine (TEDA, also called DABCO, 1,4-diazabicyclo[2.2.2]octane), dimethylcyclohexylamine (DMCHA), dimethylethanolamine (DMEA), Dimethylaminoethoxyethanol and bis-(2-dimethylaminoethyl)ether, a blowing catalyst also called A-99. A typical Lewis acidic catalyst is dibutyltin dilaurate. The process is highly sensitive to the nature of the catalyst and is also known to be autocatalytic.[36]

Another class of catalysts was published in a study in May 2024. In this study, polyurethane synthesis was investigated in the presence of acid catalysts, namely dimethylphosphite (DMHP), methanesulfonic acid (MSA), and trifluoromethanesulfonic acid (TFMSA). The thermodynamic profile was examined and described in detail through computational tools, showing that TFMSA had the best catalytic properties. The study aimed to open the door to a new class of catalysts.[37]

Factors affecting catalyst selection include balancing three reactions: urethane (polyol+isocyanate, or gel) formation, the urea (water+isocyanate, or "blow") formation, or the isocyanate trimerization reaction (e.g., using potassium acetate, to form isocyanurate rings). A variety of specialized catalysts have been developed.[38][39][40]

Surfactants

[edit]

Surfactants are used to modify the characteristics of both foam and non-foam polyurethane polymers. They take the form of polydimethylsiloxane-polyoxyalkylene block copolymers, silicone oils, nonylphenol ethoxylates, and other organic compounds. In foams, they are used to emulsify the liquid components, regulate cell size, and stabilize the cell structure to prevent collapse and sub-surface voids.[41] In non-foam applications they are used as air release and antifoaming agents, as wetting agents, and are used to eliminate surface defects such as pin holes, orange peel, and sink marks.

Production

[edit]

Polyurethanes are produced by mixing two or more liquid streams. The polyol stream contains catalysts, surfactants, blowing agents (when making polyurethane foam insulation) and so on. The two components are referred to as a polyurethane system, or simply a system. The isocyanate is commonly referred to in North America as the 'A-side' or just the 'iso'. The blend of polyols and other additives is commonly referred to as the 'B-side' or as the 'poly'.[citation needed] This mixture might also be called a 'resin' or 'resin blend'. In Europe the meanings for 'A-side' and 'B-side' are reversed.[citation needed] Resin blend additives may include chain extenders, cross linkers, surfactants, flame retardants, blowing agents, pigments, and fillers. Polyurethane can be made in a variety of densities and hardnesses by varying the isocyanate, polyol or additives.

Health and safety

[edit]

Fully reacted polyurethane polymer is chemically inert.[42] No exposure limits have been established in the U.S. by OSHA (Occupational Safety and Health Administration) or ACGIH (American Conference of Governmental Industrial Hygienists). It is not regulated by OSHA for carcinogenicity.

Open-flame test. Top: untreated polyurethane foam burns vigorously. Bottom: with fire-retardant treatment.

Polyurethanes are combustible.[43] Decomposition from fire can produce significant amounts of carbon monoxide and hydrogen cyanide, in addition to nitrogen oxides, isocyanates, and other toxic products.[44] Due to the flammability of the material, it has to be treated with flame retardants (at least in case of furniture), almost all of which are considered harmful.[45][46] California later issued Technical Bulletin 117 2013 which allowed most polyurethane foam to pass flammability tests without the use of flame retardants. Green Science Policy Institute states: "Although the new standard can be met without flame retardants, it does NOT ban their use. Consumers who wish to reduce household exposure to flame retardants can look for a TB117-2013 tag on furniture, and verify with retailers that products do not contain flame retardants."[47]

Liquid resin blends and isocyanates may contain hazardous or regulated components. Isocyanates are known skin and respiratory sensitizers. Additionally, amines, glycols, and phosphate present in spray polyurethane foams present risks.[48]

Exposure to chemicals that may be emitted during or after application of polyurethane spray foam (such as isocyanates) are harmful to human health and therefore special precautions are required during and after this process.[49]

In the United States, additional health and safety information can be found through organizations such as the Polyurethane Manufacturers Association (PMA) and the Center for the Polyurethanes Industry (CPI), as well as from polyurethane system and raw material manufacturers. Regulatory information can be found in the Code of Federal Regulations Title 21 (Food and Drugs) and Title 40 (Protection of the Environment). In Europe, health and safety information is available from ISOPA,[50] the European Diisocyanate and Polyol Producers Association.

Manufacturing

[edit]

The methods of manufacturing polyurethane finished goods range from small, hand pour piece-part operations to large, high-volume bunstock and boardstock production lines. Regardless of the end-product, the manufacturing principle is the same: to meter the liquid isocyanate and resin blend at a specified stoichiometric ratio, mix them together until a homogeneous blend is obtained, dispense the reacting liquid into a mold or on to a surface, wait until it cures, then demold the finished part.

Dispensing equipment

[edit]

Although the capital outlay can be high, it is desirable to use a meter-mix or dispense unit for even low-volume production operations that require a steady output of finished parts. Dispense equipment consists of material holding (day) tanks, metering pumps, a mix head, and a control unit. Often, a conditioning or heater–chiller unit is added to control material temperature in order to improve mix efficiency, cure rate, and to reduce process variability. Choice of dispense equipment components depends on shot size, throughput, material characteristics such as viscosity and filler content, and process control. Material day tanks may be single to hundreds of gallons in size and may be supplied directly from drums, IBCs (intermediate bulk containers, such as caged IBC totes), or bulk storage tanks. They may incorporate level sensors, conditioning jackets, and mixers. Pumps can be sized to meter in single grams per second up to hundreds of pounds per minute. They can be rotary, gear, or piston pumps, or can be specially hardened lance pumps to meter liquids containing highly abrasive fillers such as chopped or hammer-milled glass fiber and wollastonite.[citation needed]

The pumps can drive low-pressure (10 to 30 bar, 1 to 3 MPa) or high-pressure (125 to 250 bar, 12.5 to 25.0 MPa) dispense systems. Mix heads can be simple static mix tubes, rotary-element mixers, low-pressure dynamic mixers, or high-pressure hydraulically actuated direct impingement mixers. Control units may have basic on/off and dispense/stop switches, and analogue pressure and temperature gauges, or may be computer-controlled with flow meters to electronically calibrate mix ratio, digital temperature and level sensors, and a full suite of statistical process control software. Add-ons to dispense equipment include nucleation or gas injection units, and third or fourth stream capability for adding pigments or metering in supplemental additive packages.

Tooling

[edit]

Distinct from pour-in-place, bun and boardstock, and coating applications, the production of piece parts requires tooling to contain and form the reacting liquid. The choice of mold-making material is dependent on the expected number of uses to end-of-life (EOL), molding pressure, flexibility, and heat transfer characteristics.

RTV silicone is used for tooling that has an EOL in the thousands of parts. It is typically used for molding rigid foam parts, where the ability to stretch and peel the mold around undercuts is needed. The heat transfer characteristic of RTV silicone tooling is poor. High-performance, flexible polyurethane elastomers are also used in this way.

Epoxy, metal-filled epoxy, and metal-coated epoxy is used for tooling that has an EOL in the tens of thousands of parts. It is typically used for molding flexible foam cushions and seating, integral skin and microcellular foam padding, and shallow-draft RIM bezels and fascia. The heat transfer characteristic of epoxy tooling is fair; the heat transfer characteristic of metal-filled and metal-coated epoxy is good. Copper tubing can be incorporated into the body of the tool, allowing hot water to circulate and heat the mold surface.

Aluminum is used for tooling that has an EOL in the hundreds of thousands of parts. It is typically used for molding microcellular foam gasketing and cast elastomer parts, and is milled or extruded into shape.

Mirror-finish stainless steel is used for tooling that imparts a glossy appearance to the finished part. The heat transfer characteristic of metal tooling is excellent.

Finally, molded or milled polypropylene is used to create low-volume tooling for molded gasket applications. Instead of many expensive metal molds, low-cost plastic tooling can be formed from a single metal master, which also allows greater design flexibility. The heat transfer characteristic of polypropylene tooling is poor, which must be taken into consideration during the formulation process.

Applications

[edit]

In 2007, the global consumption of polyurethane raw materials was above 12 million metric tons, and the average annual growth rate was about 5%.[51] Revenues generated with PUR on the global market are expected to rise to approximately US$75 billion by 2022.[52] As they are such an important class of materials, research is constantly taking place and papers published.[53]

Degradation and environmental fate

[edit]

Effects of visible light

[edit]
Polyurethane foam made with an aromatic isocyanate, which has been exposed to UV light. Readily apparent is the discoloration that occurs over time.

Polyurethanes, especially those made using aromatic isocyanates, contain chromophores that interact with light. This is of particular interest in the area of polyurethane coatings, where light stability is a critical factor and is the main reason that aliphatic isocyanates are used in making polyurethane coatings. When PU foam, which is made using aromatic isocyanates, is exposed to visible light, it discolors, turning from off-white to yellow to reddish brown. It has been generally accepted that apart from yellowing, visible light has little effect on foam properties.[54][55] This is especially the case if the yellowing happens on the outer portions of a large foam, as the deterioration of properties in the outer portion has little effect on the overall bulk properties of the foam itself.

It has been reported that exposure to visible light can affect the variability of some physical property test results.[56]

Higher-energy UV radiation promotes chemical reactions in foam, some of which are detrimental to the foam structure.[57]

Hydrolysis and biodegradation

[edit]

Polyurethanes may degrade due to hydrolysis. This is a common problem with shoes left in a closet, and reacting with moisture in the air.[58]

Microbial degradation of polyurethane is believed to be due to the action of esterase, urethanase, hydrolase and protease enzymes.[59] The process is slow as most microbes have difficulty moving beyond the surface of the polymer. Susceptibility to fungi is higher due to their release of extracellular enzymes, which are better able to permeate the polymer matrix. Two species of the Ecuadorian fungus Pestalotiopsis are capable of biodegrading polyurethane in aerobic and anaerobic conditions such as found at the bottom of landfills.[60][61] Degradation of polyurethane items at museums has been reported.[62] Polyester-type polyurethanes are more easily biodegraded by fungus than polyether-type.[63]

See also

[edit]
  • Botanol, a material with higher plant-based content
  • Passive fire protection
  • Penetrant (mechanical, electrical, or structural)
  • Polyaspartic
  • Polyurethane dispersion
  • Thermoplastic polyurethanes
  • Thermoset polymer matrix

References

[edit]
  1. ^ "polyurethane". Dictionary.com Unabridged (Online). n.d.
  2. ^ Gama, Nuno; Ferreira, Artur; Barros-Timmons, Ana (27 September 2018). "Polyurethane Foams: Past, Present, and Future". Materials. 11 (10): 1841. Bibcode:2018Mate...11.1841G. doi:10.3390/ma11101841. PMC 6213201. PMID 30262722.
  3. ^ "Polyurethane". American Chemistry Council. Retrieved 2022-09-19.
  4. ^ "Polyurethane global market volume 2015-2026". Statista. Retrieved 23 July 2021.
  5. ^ Bayer, Otto (1947). "Das Di-Isocyanat-Polyadditionsverfahren (Polyurethane)". Angewandte Chemie. 59 (9): 257–72. Bibcode:1947AngCh..59..257B. doi:10.1002/ange.19470590901.
  6. ^ DE 728981, I.G. Farbenindustrie A.G., "Verfahren zur Herstellung von Polyurethanen bzw. Polyharnstoffen [Process for the production of polyurethanes or polyurea]", published 1942-12-07 
  7. ^ a b c Seymour, Raymond B.; Kauffman, George B. (1992). "Polyurethanes: A class of modern versatile materials". Journal of Chemical Education. 69 (11): 909. Bibcode:1992JChEd..69..909S. doi:10.1021/ed069p909.
  8. ^ Feske, Bert (October 2004). "The Use of Saytex RB-9130/9170 Low Viscosity Brominated Flame Retardant Polyols in HFC-245fa and High Water Formulations" (PDF). Polyurethanes Expo 2004. Las Vegas, NV: Alliance for the Polyurethane Industry Technical Conference. p. 309. Retrieved 2007-08-01.
  9. ^ n ≥ 2
  10. ^ a b Gum, Wilson; Riese, Wolfram; Ulrich, Henri (1992). Reaction Polymers. New York: Oxford University Press. ISBN 978-0-19-520933-4.
  11. ^ Harrington, Ron; Hock, Kathy (1991). Flexible Polyurethane Foams. Midland: The Dow Chemical Company.
  12. ^ a b Oertel, Gunter (1985). Polyurethane Handbook. New York: Macmillen Publishing Co., Inc. ISBN 978-0-02-948920-8.[page needed]
  13. ^ Ulrich, Henri (1996). Chemistry and Technology of Isocyanates. New York: John Wiley & Sons, Inc. ISBN 978-0-471-96371-4.[page needed]
  14. ^ Woods, George (1990). The ICI Polyurethanes Book. New York: John Wiley & Sons, Inc. ISBN 978-0-471-92658-0.[page needed]
  15. ^ Soto, Marc; Sebastián, Rosa María; Marquet, Jordi (2014). "Photochemical Activation of Extremely Weak Nucleophiles: Highly Fluorinated Urethanes and Polyurethanes from Polyfluoro Alcohols". The Journal of Organic Chemistry. 79 (11): 5019–27. doi:10.1021/jo5005789. PMID 24820955.
  16. ^ Kaushiva, Byran D. (August 15, 1999). Structure-Property Relationships of Flexible Polyurethane Foams (Ph.D.). Virginia Polytechnic Institute.
  17. ^ "Technical data sheet from Dow Chemical". Archived from the original on 2007-10-13. Retrieved 2007-09-15.
  18. ^ Randall, David; Lee, Steve (2002). The Polyurethanes Book. New York: Wiley. ISBN 978-0-470-85041-1.
  19. ^ Petrović, Zoran S. (2008). "Polyurethanes from Vegetable Oils". Polymer Reviews. 48 (1): 109–155. doi:10.1080/15583720701834224. S2CID 95466690.
  20. ^ EP 0755955, Hager, Stanley L.; Knight, James E. & Helma, Gregory F. et al., "Polyether polyols suitable for flexible polyurethane foam prepared by co-initiation of aqueous solutions of solid polyhydroxyl initiators", published 1997-01-29, assigned to ARCO Chemical Technology 
  21. ^ Bob Parker. "FEVE Technology for Higher Performance Coating Systems on Bridges" (PDF). Paintsquare.com. Archived from the original (PDF) on 15 August 2021. Retrieved 5 March 2022.
  22. ^ Khanderay, Jitendra C., and Vikas V. Gite. "Vegetable oil-based polyurethane coatings: recent developments in India." Green Materials 5.3 (2017): 109-122.
  23. ^ Niemeyer, Timothy; Patel, Munjal; Geiger, Eric (September 2006). A Further Examination of Soy-Based Polyols in Polyurethane Systems. Salt Lake City, UT: Alliance for the Polyurethane Industry Technical Conference.
  24. ^ "New Twist on Green: 2008 Ford Mustang Seats Will Be Soy-Based Foam". Edmunds inside line. July 12, 2007. Archived from the original on 2008-05-31. Retrieved 2010-06-15.
  25. ^ SD Rajput, PP Mahulikar, VV Gite, Biobased dimer fatty acid containing two pack polyurethane for wood finished coatings, Progress in Organic Coatings 77 (1), 38-46 https://doi.org/10.1016/j.porgcoat.2014.04.030
  26. ^ A Anand, RD Kulkarni, VV Gite, Preparation and properties of eco-friendly two pack PU coatings based on renewable source (sorbitol) and its property improvement by nano ZnO, Progress in Organic Coatings 74 (4), 764-767, https://doi.org/10.1016/j.porgcoat.2011.09.031
  27. ^ Chandrashekhar K Patil, Harishchandra D Jirimali, Jayasinh S Paradeshi, Bhushan L Chaudhari, Prakash K Alagi, Pramod P Mahulikar, Sung Chul Hong, Vikas V Gite, Chemical transformation of renewable algae oil to polyetheramide polyols for polyurethane coatings, Progress in Organic Coatings 151, 106084, https://doi.org/10.1016/j.porgcoat.2020.106084
  28. ^ CK Patil, HD Jirimali, JS Paradeshi, BL Chaudhari, VV Gite, Functional antimicrobial and anticorrosive polyurethane composite coatings from algae oil and silver doped egg shell hydroxyapatite for sustainable development, Progress in Organic Coatings 128, 127-136, https://doi.org/10.1016/j.porgcoat.2018.11.002
  29. ^ Biobased dimer fatty acid containing two pack polyurethane for wood finished coatings, SD Rajput, PP Mahulikar, VV Gite, Progress in Organic Coatings 77 (1), 38-46
  30. ^ Nohra, Bassam; Candy, Laure; Blanco, Jean-François; Guerin, Celine; Raoul, Yann; Mouloungui, Zephirin (2013). "From Petrochemical Polyurethanes to Biobased Polyhydroxyurethanes" (PDF). Macromolecules. 46 (10): 3771–92. Bibcode:2013MaMol..46.3771N. doi:10.1021/ma400197c. Archived (PDF) from the original on 2017-09-22.
  31. ^ Blackwell, J.; Nagarajan, M. R.; Hoitink, T. B. (1981). "The Structure of the Hard Segments in MDI/diol/PTMA Polyurethane Elastomers". ACS Symposium Series. 172. Washington, D.C.: American Chemical Society: 179–196. doi:10.1021/bk-1981-0172.ch014. ISBN 978-0-8412-0664-9. ISSN 0097-6156.
  32. ^ Blackwell, John; Gardner, Kenncorwin H. (1979). "Structure of the hard segments in polyurethane elastomers". Polymer. 20 (1): 13–17. doi:10.1016/0032-3861(79)90035-1. ISSN 0032-3861.
  33. ^ Grillo, D. J.; Housel, T. L. (1992). "Physical Properties of Polyurethanes from Polyesters and Other Polyols". Polyurethanes '92 Conference Proceedings. New Orleans, LA: The Society of the Plastics Industry, Inc.
  34. ^ Musselman, S. G.; Santosusso, T. M.; Sperling, L. H. (1998). "Structure Versus Performance Properties of Cast Elastomers". Polyurethanes '98 Conference Proceedings. Dallas, TX: The Society of the Plastics Industry, Inc.
  35. ^ A Guide to Glycols. Midland, Mich.: The Dow Chemical Co., Chemicals and Metals Department. 1992. Brochure 117-00991-92Hyc.
  36. ^ Adam, Norbert; Avar, Geza; Blankenheim, Herbert; Friederichs, Wolfgang; Giersig, Manfred; Weigand, Eckehard; Halfmann, Michael; Wittbecker, Friedrich-Wilhelm; Larimer, Donald-Richard; Maier, Udo; Meyer-Ahrens, Sven; Noble, Karl-Ludwig; Wussow, Hans-Georg (2005). "Polyurethanes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a21_665.pub2. ISBN 978-3-527-30673-2.
  37. ^ Waleed, H. Q.; Viskolcz, B.; Fiser, B. (2024). "Urethane Synthesis in the Presence of Organic Acid Catalysts—A Computational Study". Molecules (Basel, Switzerland). 29 (10): 2375. doi:10.3390/molecules29102375. PMC 11123846. PMID 38792235.
  38. ^ "Jeffcat Amine Catalysts for the Polyurethane Industry" (PDF). 2006. Archived from the original (PDF) on 2007-11-29. Retrieved 2007-10-23.
  39. ^ "Building quality with Air Products trimerisation catalysts" (PDF). 2003. Archived from the original (PDF) on 2007-11-29. Retrieved 2007-10-23.
  40. ^ "FOMREZ Specialty Tin Catalysts for Polyurethane Applications". 120-074-10. January 2001.
  41. ^ Randall, David; Lee, Steve, eds. (2002). "10". The Polyurethanes Book. The United Kingdom: Huntsman International LLC, Polyurethanes business. pp. 156–159. ISBN 978-0470850411. Archived from the original on 2018-05-24. Retrieved 2018-05-23.
  42. ^ Dernehl, C. U. (1966). "Health hazards associated with polyurethane foams". Journal of Occupational Medicine. 8 (2): 59–62. PMID 5903304.
  43. ^ "Health Alert: Polyurethane exposure" (PDF). Archived from the original (PDF) on 2004-10-19. Retrieved 2009-12-19.
  44. ^ McKenna, Sean Thomas; Hull, Terence Richard (2016). "The fire toxicity of polyurethane foams". Fire Science Reviews. 5 (1): 3. doi:10.1186/s40038-016-0012-3.
  45. ^ "Environmental Profiles of Chemical Flame-Retardant Alternatives for Low-Density Polyurethane Foam". United States Environmental Protection Agency. September 2005.
  46. ^ "Flame Retardants Used in Flexible Polyurethane Foam – Draft Update to a 2005 Alternatives Assessment". United States Environmental Protection Agency. June 2014. Archived from the original on November 21, 2014.
  47. ^ "Manufacturers" (PDF). greensciencepolicy.org. 2015. Archived (PDF) from the original on 2015-12-19.
  48. ^ "Help Wanted: Spray Polyurethane Foam Insulation Research". NIOSH Science Blog. CDC. 21 March 2012.
  49. ^ "Quick Safety Tips for Spray Polyurethane Foam Users". United States Environmental Protection Agency. 4 August 2015.
  50. ^ "Home : ISOPA". www.isopa.org.
  51. ^ Avar, G. (October 2008). "Polyurethanes (PU)". Kunststoffe International (10/2008): 123–7.
  52. ^ "Market Study: Polyurethanes and Isocyanates". Ceresana. July 2013.
  53. ^ Jakhmola, Swati; Das, Sonalee; Dutta, Kingshuk (2023-10-31). "Emerging research trends in the field of polyurethane and its nanocomposites: Chemistry, Synthesis, Characterization, Application in coatings and Future perspectives". Journal of Coatings Technology and Research. 21 (1): 137–172. doi:10.1007/s11998-023-00841-z. ISSN 1935-3804. S2CID 264908475.
  54. ^ "Discoloration of polyurethane foam" (PDF). Foamex Information sheet. Archived from the original (PDF) on 2010-09-24. Retrieved 2010-09-26.
  55. ^ Valentine, C.; Craig, T.A.; Hager, S.L. (1993). "Inhibition of the Discoloration of Polyurethane Foam Caused by Ultraviolet Light". Journal of Cellular Plastics. 29 (6): 569–88. doi:10.1177/0021955X9302900605. S2CID 208363195.
  56. ^ Blair, G. Ron; Dawe, Bob; McEvoy, Jim; Pask, Roy; de Priamus, Marcela Rusan; Wright, Carol (2007). The Effect of Visible Light on the Variability of Flexible Foam Compression Sets (PDF). Orlando, FL: Center for the Polyurethane Industry. Retrieved 2008-01-26.
  57. ^ Newman, Christopher R.; Forciniti, Daniel (2001). "Modeling the Ultraviolet Photodegradation of Rigid Polyurethane Foams". Industrial & Engineering Chemistry Research. 40 (15): 3346–52. doi:10.1021/ie0009738.
  58. ^ "Hydrolysis, The Crumbling of Shoe Soles explained | Safety Shoes and Gloves". www.safetyjogger.com.
  59. ^ Toward, Gary T. (June 2002). "Biodegradation of polyurethane: a review". International Biodeterioration & Biodegradation. 49 (4): 245–252. Bibcode:2002IBiBi..49..245H. doi:10.1016/S0964-8305(02)00051-3.
  60. ^ Russell, J. R.; Huang, J.; Anand, P.; Kucera, K.; Sandoval, A. G.; Dantzler, K. W.; Hickman, D.; Jee, J.; Kimovec, F. M.; Koppstein, D.; Marks, D. H.; Mittermiller, P. A.; Nunez, S. J.; Santiago, M.; Townes, M. A.; Vishnevetsky, M.; Williams, N. E.; Vargas, M. P. N.; Boulanger, L.-A.; Bascom-Slack, C.; Strobel, S. A. (2011). "Biodegradation of Polyester Polyurethane by Endophytic Fungi". Applied and Environmental Microbiology. 77 (17): 6076–84. Bibcode:2011ApEnM..77.6076R. doi:10.1128/AEM.00521-11. PMC 3165411. PMID 21764951.
  61. ^ "Could Plastic-Eating Mushrooms Solve mankind's Plastic Problem?". Sciencemint. 2021-04-14. Archived from the original on 2021-07-09. Retrieved 2021-07-02.
  62. ^ Cappitelli, F.; Sorlini, C. (2007). "Microorganisms Attack Synthetic Polymers in Items Representing Our Cultural Heritage". Applied and Environmental Microbiology. 74 (3): 564–9. Bibcode:2008ApEnM..74..564C. doi:10.1128/AEM.01768-07. PMC 2227722. PMID 18065627.
  63. ^ Tokiwa, Yutaka; Calabia, Buenaventurada P.; Ugwu, Charles U.; Aiba, Seiichi (2009). "Biodegradability of Plastics". International Journal of Molecular Sciences. 10 (9): 3722–42. doi:10.3390/ijms10093722. PMC 2769161. PMID 19865515.
[edit]
  • Center for the Polyurethanes Industry: information for EH&S issues related to polyurethanes developments
  • Polyurethane synthesis, Polymer Science Learning Center, University of Southern Mississippi
  • Polyurethane Foam Association: Industry information, educational materials and resources related to flexible polyurethane foam
  • PU Europe: European PU insulation industry association (formerly BING): European voice for the national trade associations representing the polyurethane insulation industry
  • ISOPA: European Diisocyanate & Polyol Producers Association: ISOPA represents the manufacturers in Europe of aromatic diisocyanates and polyols