Polymer Science Project on PolyurethaneSubmitted to Dr. John Paul

Submitted byHarshavardhan Gorakh Spring 2014

Chapter 1Synthetic Routes31.1Introduction and Structure31.2Preparation41.2.1Polyurethane4Chapter 2History6Chapter 3Production Statistics [2]8Chapter 4Processing134.1Raw Material134.2Flexible Foam134.3Rigid Foams16Chapter 5Application and properties175.1Flexible Foam:175.2Rigid Foam175.3C.A.S.E. (Coatings, Adhesives, Sealants, Elastomers)185.3.1Coatings:185.3.2Adhesives and Sealants:185.3.3Elastomers19Chapter 6Health and safety issues206.1Isocyanate206.2Tertiary Amine Catalyst226.3Polyurethane22Chapter 7Summary:23References:24

Synthetic Routes Introduction and StructurePolyurethanes are organic polymer and are well known for preparation of foams. They are the most versatile family of polymers. They can be ELastomers, they can be Paints they can be Fibers and they can be Adhesives. As name suggests, urethane linkages are present in the polyurethane polymer. Figure 1 and Figure 2 shows urethane monomer and linear polyurethane polymer respectively and Figure 3 shows segmented copolymer of urethane obtained from diisocyanate, a macroglycol and diol extender HO-(CH2)x-OH. The marvelously unconventional polyurethane is Spandex as shown in the Figure 4 below.

Figure 1: Urethane Monomer

Figure 2: Linear Polyurethane Polymer

Figure 3: Linear Segmented Copolymer of Urethane

Figure 4: Spandex Polymer also known as Lycra [1]PreparationThere are different types of polyurethane Polyurethane Polyurethanes are prepared by catalyzed addition polymerization of two monomers a diol (two alcohol groups) and diisocyanate (two isocyanate groups). Catalyst used for controlling gelation is 1,4-diazabicyclo[2.2.2]octane also known as DABCO which is tertiary amine.

The reaction is shown as follows: hu

Figure 5: Catalyzed Step Polymerization reaction for polyurethaneFor manufacturing of flexible foam a combination of tin and tertiary amine catalysts are used in order to balance the gelation reaction (urethane formation) and the blowing reaction (urea formation). The tin catalyst used include dibutyltin dilaurate, dibutylbis (laurylthio) stannate, dibutyltinbis (isooctylmercapto acetate), and dibutyltinbis (isooctylmaleate). Strong bases, such as potassiumacetate, potassium2-ethylhexoate, or amine epoxide combinations are the most useful trimerization catalysts. Also, some special tertiary amines, such as 2,4,6-tris(N,N-dimethylaminomethyl)phenol (Figure 5) (DMT-30), 1,3,5-tris(3-dimethylaminopropyl)hexahydro-s-triazine (Figure6), and ammonium salts (Dabco TMR) (Figure 7) are good trimerization catalysts.Figure 6: 2,4,6-tris(N,N-dimethylaminomethyl)phenolFigure7:1,3,5-tris(3-dimethylaminopropyl)hexahydro-s-triazineFigure 8: ammonium salts (Dabco TMR)

HistoryPolyurethanes can be found in liquid coatings and paints, tough elastomeric such as roller blade wheels, rigid insulation, soft flexible foam, elastic fiber or as an integral skin. No matter how polyurethane is transformed, the underlying chemistry is the result of research by Dr. Otto Bayer (1902-1982). Dr. Otto Bayer is recognized as the father of the polyurethanes industry for his invention of the basic diisocyanate poly-addition process.The origin of polyurethane dates back to the beginning of World War II 1937, when it was first developed as a replacement for rubber. The versatility of this new organic polymer and its ability to substitute for scarce materials spurred numerous applications. During World War II, polyurethane coatings were used for the impregnation of paper and the manufacture of mustard gas resistant garments, high-gloss airplane finishes and chemical and corrosion-resistant coatings to protect metal, wood and masonry.By the end of the war, polyurethane coatings were being manufactured and used on an industrial scale and could be custom formulated for specific applications. By the mid-50s, polyurethanes could be found in coatings and adhesives, elastomeric and rigid foams. It was not until the late-50s that comfortable cushioning flexible foams were commercially available. With the development of a low-cost polyether polyol, flexible foams opened the door to the upholstery and automotive applications we know today.Formulations, additives and processing techniques continue to be developed, such as reinforced and structural moldings for exterior automotive parts and one-component systems. Today, polyurethanes can be found in virtually everything we touchdesks, chairs, cars, clothes, footwear, appliances, beds as well as the insulation in our walls androof and moldings on our homes.

The generalized timeline is shown in following table.YearsAdvancement in Polyurethane

1937Invention of Polyurethane by Dr. Otto Bayer atI.G. Farbenin Leverkusen, Germany. Patented

1952-54Polyisocyanates became commercially available in 1952 and production of flexible polyurethane foam began usingtoluene diisocyanate(TDI) and polyester polyols.

1956-1957DuPontintroduced polyether polyol poly(tetramethylene ether) glycol.

1960sProduction of more than 45000 metric Tonnes of Polyurethane foams. The availability of chlorofloroalkane blowing agents, inexpensive polyether polyols, methylene diphenyl diisocyanate allowed polyurethane rigid foams to be used as high performance insulation materials. Dupont introduced urethane based synthetic leather.

1967urethane modifiedpolyisocyanuraterigid foams were introduced, offering even better thermal stability andflammabilityresistance. During the 1960s, automotive interior safety components such as instrument and door panels were produced by back-fillingthermoplasticskins with semi-rigid foam.

1969Bayer exhibited an all plastic car in Dsseldorf, Germany

1970Aqueous Polyurethane dispersions (PUDs), Elastomers, foot-ware, High resilience flex foam, urethane acrylate resins

1980Water-blown microcellular flexible foams were used to mold gaskets for automotive panels and air filter seals automotive energy absorber for safety, replacingPVCplastisol from automotive applications have greatly increased market share. Polyurethane foams are now used in high temperature oil filter applications.

1983Pontiac Fiero USA, made first plastic body automobile

1990Montreal Protocol restricted the use of chlorine containing blowing agent due to ozone depletion problem. Radiation Curable PUDs

2000-2008Chemical resistance co-solvent PUD/acrylic dispersion. Environmental constraints increased, with emphasis on energy saving and sustainability Economic crisis, slowdown in the consumption of polyurethane.

2008- presentMitsui 40% Non edible castor oil based polyols. plant based polyols will be price competitive with crude oil based polyols, external contraceptives, Musical instruments like Cello are being manufactured using polyurethane.

Production StatisticsAs per Research and Markets, the global market for polyurethanes was estimated at 13,650.00 kilo tons in 2010 and is expected to reach 17,946.20 kilo tons by 2016, growing at a Compound Annual Growth Rate (CAGR) of 4.7% from 2011 to 2016. In terms of revenue, the market was estimated to be worth US$33,033 million in 2010 and is expected to reach US$55479.68 million by 2016, growing at a CAGR of 6.8% from 2011 to 2016. North America, Asia-Pacific, and Europe dominate the polyurethane market and together accounted for 95% of the global polyurethane demand in 2010. North America and Western Europe are mature markets and are expected to grow at a sluggish rate. However, Asia-Pacific, Eastern Europe and South America are expected to drive the demand for polyurethanes in the coming decade. The furniture and interior industry dominated the polyurethane market, accounting for 28.01% of the total demand in 2010. The second largest end-use of polyurethanes is in construction industry, which accounted for 24.98% of the overall market in 2010. Electronic appliances, however, are the fastest growing market for polyurethanes. Polyurethane demand for electronic appliances is expected to grow at a CAGR of 7.3% to 2011. As per Global Industry Analysts, the global market for foamed plastics (polyurethane) is projected to reach 9.6 million tons by the year 2015, driven by resurgent demand from construction, furniture and bedding, and automotive markets. The need for low-cost and long-lasting materials and rising significance of energy efficiency in appliances and buildings is expected to foster growth in the foamed plastics market. The global economic meltdown led to significant decline in demand for polyurethane (PU) foams across the globe, largely due to the contraction in majority of the end-use markets including automotive and construction. Both flexible and rigid PU foams registered decline during 2008 and 2009, with the demand for flexible PU foams registering steeper decline in the US and Western Europe. The economic crisis forced several companies, particularly small manufacturers to shutdown production units permanently, while manufacturers with multiple production units sought reprieve by closing down some capacity. Europe, Asia-Pacific, and the United States dominate the world foamed plastics (polyurethane) market, as stated by the new market research report on foamed plastics (polyurethane). Buoyed by the robust Chinese, Indian and Hong Kong markets, Asia-Pacific region represents the fastest growing PU foams market, with a CAGR of 4.9% over the analysis period. Middle East has been witnessing healthy growth over the past few years. Increasing investments in polyurethane production, coupled with new encouraging regulations has largely contributed to market growth in the region. Demand for PU foams is highly dependent on diverse end-use applications particularly in furniture and automotive sectors. Subdued consumer spending, slowdown in new housing starts, decline in automotive production, and increase in the volume of imported furniture contributed to a significant decline in PU production, particularly in the US and Canada. Despite such adversities, the market is expected to register growth owing to the increasing concerns about energy conservation. This is evident by the rising demand for spray polyurethane foam in the industrial and residential applications as well as the use of polyurethane for insulating structures such as tents at Army bases. Furniture/Bedding represents the largest end-use market for PU foams, globally, with Asia-Pacific region offering enormous growth opportunities for the segment. An ageing health conscious population is driving significant changes in the bedding industry. Mattresses are categorized as innerspring, foam, water, and air-filled, among which foam mattresses are likely to witness a booming growth. PU foam plays a significant role in the construction of mattresses due to its effectiveness in relieving pressure points. Demand for reactive polyurethane hot melt adhesives is likely to increase, which could displace solvent-based adhesives. Global polyurethane market is largely dominated by the four stalwarts, which include Dow, Bayer, BASF and Huntsman, in terms of production capacity. Competitive factors determining the player market presence include price, quality, and assortment of products and services. Major players profiled in the report include BASF AG, Bayer AG, British Vita Unlimited, The Dow Chemical Company, FXI - Foamex Innovations, Huntsman Polyurethanes, Mitsui Chemicals Inc., Recticel S.A, and Woodbridge Foam Corporation.As per IAL Consultants, despite a challenging economy and declining production, the polyurethane industry continued to evolve over the past two years while addressing growing concerns over energy conservation, according to the 2008 End-Use Market Survey on the Polyurethanes Industry in the United States, Canada and Mexico. Research conducted by IAL Consultants on behalf of the Center for the Polyurethanes Industry (CPI) of the American Chemistry Council, shows that overall production of polyurethane in NAFTA declined by 6.7% pa during the past two years. The figure reflects a 7.7% annual decline in U.S. markets and 10.8% decline in Canada, while Mexico has shown positive growth for the third consecutive survey. The production of polyurethane in Mexico increased at an average annual rate of 9.6% over the past two years, partly due to increased domestic demand.With the dip in automotive output, decreased consumer spending, high levels of imported furniture and a drop-off of activity in new housing starts, we were prepared to see a decline in polyurethane production in the U.S. and Canada, said Neeva-Gayle Candelori, Director of CPI. Overall, the research shows that the industry continues to change. While some markets are mature, new ones have opened up. Renewable chemicals and energy efficiency continue to be important topics. Change is essential for evolution and it would be worrying if there were no signs of market evolution. Signs of growth in the polyurethane industry included continued increases in spray polyurethane foam demand for residential and industrial applications, as well as use of the material by the U.S. Army to insulate tents and other structures at bases in the Middle East. Polyurethane also is being used for effective wound dressings, pharmaceutical delivery media, reliable drug delivery, comfortable mobility aids and hygienic hospital environments. The demand for low-VOC and high-performance coatings related to product substitutions made the decline in the production of coatings, adhesives, sealants and TPU less severe. Though there was a sharp decrease in binder production as a result of the decline in OSB (oriented strand board) demand by the U.S. housing sector, the desire for safe and clean recreational areas has helped increase use of polyurethane binders in sports tracks and playgrounds in the past two years. New applications to improve quality of life are contributing to market evolution as well, such as new comfort levels in golf cart seating for the growing number of elderly. Manufacturers looking to comply with new regulations and secure certification are also finding ways to create opportunities for growth. The survey shows a boost to the rigid polyurethane foam market for thicker panels needed to meet new ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) standards. CARB (California Air Resources Board) regulation and the CertiPUR program also helped to secure business in the bedding industry for flexible polyurethane foam. The United States, representing 81% of the total polyurethane production in NAFTA, had a market breakdown similar to NAFTA overall. Imports of upholstered furniture continued to increase in the United States. Though statistics from the U.S. Department of Trade and Commerce did indicate a slight drop in overall imports during the past two years, these were a reflection of the current state of the housing market and declining consumer demand. In Mexico, production of rigid polyurethane foam dominated the market as new companies invested in the country and the appliance industry continued to grow. In 2008, the Mexican appliance industry produced 9 mln refrigerators and freezers compared to 11.3 mln in the United States. Mexican furniture and automotive markets also grew during 2008, driven by export and domestic demand. With 2.1 mln units in 2008, automotive production exceeded Canadas. Flexible molded foam end-use production increased due to the manufacture of automotive components and flexible slabstock production increased, as well. Though families currently prefer to buy new upholstered furniture over new mattresses, the bedding market has potential for further development. Despite a deficit of 5 million homes in Mexico, home ownership has increased. Canadas dependence on the United States resulted in a greater production decline than experienced in the U.S. The country was the third market in the NAFTA region and accounted for 8.9% of total production. Flexible foam slabstock accounted for 16% of total production, compared to 21% in 2006 and the fall in U.S. housing starts led to 54% of OSB production being idled. As an environmentally conscious country, the population continued to buy products marketed as eco-friendly, such as rigid polyurethane foam and flexible polyurethane foam. Rigid polyurethane foam accounted for 39% of production in 2008 compared to 28% in 2006, another sign of interest in greater energy efficiency. In the energy sector, components made from polyurethane cast elastomers, technical insulation coatings and sealants received increased capital expenditure for maintenance and development, mainly as a response to the high oil prices of 2007 and the first half of 2008.Once again, rigid polyurethane foam products accounted for the largest share of the 6.5 billion lbs of polyurethane produced in NAFTA in 2008. The figure reflects the relative strength in demand for rigid polyurethane foam as an insulation material. The past two years have witnessed stable demand from the construction industry. New housing starts have declined, but expenditures on remodeling and repairs increased. This development is largely responsible for the growing demand for spray polyurethane foam as internal wall insulation and the slower than expected decline in CASE products like elastomers used in thermal breaks in insulated windows, solar panels, wooden floor and turbine blade coatings, adhesives and sealants, and the steady demand for one component spray foams. The versatility of spray polyurethane foam also has contributed to its use in army tents and structures in the Middle East where it has contributed to fuel savings. As part of its industry-wide survey, IAL looked in depth at the factors affecting the declining demand for flexible polyurethane foam in the automotive, furniture and bedding industries: Furniture/Bedding: United States production of flexible slabstock foam fell sharply from 2006 - 2008. Flexible foam stock production dropped by nearly 25% in 2008 compared to 2007. The main impetus behind this decline is the decrease in furniture production due to lack of consumer demand and imports. Imports of upholstered furniture continued to rise until the end of 2007. The rate of imports is not expected to change in the near future as U.S. government incentives to first-time homebuyers will likely go towards imported goods. The bedding sector continued to use large volumes of flexible polyurethane foam during 2008. Mattresses manufactured in the United States used more foam per unit for deeper mattresses with softer toppers; more hybrid mattresses were produced, as well. Since the end of 2008, factors such as the reduced cost of lower density foams, thinner mattresses, and customers requiring faster delivery times for mattresses than other furniture delivery (2 -5 days), have helped protect the industry from imports.Transportation: While the automotive industry has experienced significant downsizing, it has also seen an increased demand for more economical vehicles. Production fell by 3.1 million since 2006, but there are now roughly 8 million flexible fuel vehicles on U.S. roads and more are expected in the future. Polyurethane foam used in automotive seating has trended toward becoming thinner, while density is increasing, offering more cabin space above the seat and allowing the required amortization of vibration. The decline in molded seat foam is related to the general down market in automotive production.

ProcessingRaw Material Common raw material used for manufacturing are Aromatic = Toluene Diisocyanate (TDI), 4,40-methylenebis(phenyl isocyanate) (MDI), polymeric MDI fast reactivity, not resistance to UV light can change color in sunlight and Aliphatic = HDI, IPDI, H12 monomers has resistance to UV lights but slower reactivity than aromatic. Polyols of ether or ester is used as a second reactant to react with above mentioned isocyanate. This polyols can be obtained from petroleum. New processes have been invented in last decade in Japan and India to prepare polyols from non-edible castor oil. Price of polyols made by new process is cheaper than that of petroleum based polyols.Flexible FoamFlexible slab or bun foam is poured by multicomponent machines at rates of >45 kg/min. One-shot pouring from traversing mixing heads is generally used. A typical formulation for furniture-grade foam having a density of 0.024 g/cm3 includes a polyether triol, mol wt 3000; TDI; water; catalysts, ie, stannous octoate in combination with a tertiary amine; and surfactant. Co-blowing agents are often used to lower the density of the foam and to achieve a softer hand. Co-blowing agents are methylene chloride, methyl chloroform, acetone, and CFC 11, but the last has been eliminated because of its ozonedepletion potential. HCFC blowing agents are replacing CFC 11. Additive systems and new polyols [3]are being developed to achieve softer low density foams. Higher density (0.045 g/cm3) slab or bun foam, also called high resiliency (HR) foam, is similarly produced, using polyether triols having molecular weight of 6000. The use of polymer polyols improves the load-bearing properties. Flexible foams are three-dimensional agglomerations of gas bubbles separated from each other by thin sections of polyurethanes and polyureas. The microstructures observed in TDI- and MDI-based flexible foams are different. In TDI foams monodentate urea segments form after 40% conversion, followed by a bidentate urea phase, which is insoluble in the soft segment. As the foam cures, annealing of the precipitated discontinuous urea phase occurs to optimize alignment through hydrogen bonding [3]. Flame retardants (qv) are incorporated into the formulations in amounts necessary to satisfy existing requirements. Reactive-type diols, such as N,Nbis(2-hydroxyethyl) aminomethyl phosphonate are preferred, but nonreactive phosphates are also used. Often, the necessary results are achieved using mineral fillers, such as alumina trihydrate or melamine. Melamine melts away from the flame and forms both a nonflammable gaseous environment and a molten barrier that helps to isolate the combustible polyurethane foam from the flame. Alumina trihydrate releases water of hydration to cool the flame, forming a noncombustible inorganic protective char at the flame front. Flame-resistant upholsteryfabric or liners are also used . There are four main types of flexible slabstock foam: conventional, high resiliency, filled, and high load-bearing foam. Filled slabstock foams contain inorganic fillers to increase the foam density and improve the load-bearing characteristics. High load-bearing formulations incorporate a polymer polyol. Slabstock flexible foam is produced on continuous bun lines. The bun forms while the material moves down a long conveyor. In flat-top bun lines, the liquid chemicals are dispensed from a stationary mixing head to a manifold at the bottom of a trough. More rectangular foams are produced by several newer processes. However, the most popular rectangular block foam process is the Maxfoam process. The high outputs require faster and longer conveyors. An exception is the Vertifoam process, in which the reaction mixture is introduced at the bottom of an enclosed expansion chamber. The chamber is lined with paper or polyethylene film, which is drawn upward at a controlled rate. Because the Vertifoam machine is much smaller than the horizontal machines, operationalsavings can be achieved . Two newer slabstock foam manufacturing processes have been developed. A high rate of block foam production (150220 kg/min) is required in order to obtain large slabs to minimize cutting waste. Bun widths range from ca 1.43to 2.2 m, and typical bun heights are 0.771.25 m. In a flexible foam plant, scrap can amount to as much as 20%. Most of it is used as carpet underlay and in pillows and packaging (see PACKAGING MATERIALS). The finished foam blocks are stored in a cooling area for at least 12 h before being passed to a storage area or to slitters where the blocks are cut into sheets. In the production plant the fire risk must be minimized. Temperatures of up to 1508C can be reached in the interior of the foam blocks. Blowing of ambient air through the porous foam allows dissipation of the heat generated in the exothermic reaction . Most flexible foams produced are based on polyether polyols. Flexible polyether foams have excellent cushioning properties, are flexible over a wide range of temperatures, and can resist fatigue, aging, chemicals, and mold growth. Polyester-based foams are superior in resistance to dry cleaning and can be flamebonded to textiles. In more recent years, molded flexible foam products are becoming more popular. The bulk of the molded flexible urethane foam is employed in the transportation industry, where it is highly suitable for the manufacture of seat cushions, back cushions, and bucket-seat padding. TDI prepolymers were used in flexible foam molding in conjunction with polyether polyols. The introduction of organotin catalysts and efficient silicone surfactants facilitates one-shot foam molding, which is the most economical production method. The need for heat curing has been eliminated by the development of cold-molded or high resiliency foams. These molded HR foams are produced from highly reactive polyols and are cured under ambient conditions. The polyether triols used are 45006500 mol wt and are high in ethylene oxide (usually >50%primary hydroxyl content). Reactivity is further enhanced by triethanolamine, 12 URETHANE POLYMERS Vol. 25 liquid aromatic diamines, and aromatic diols. Generally, PMDI, TDI, or blends of PMDITDI are used. Load-bearing characteristics are improved by using polymer polyol. High resiliency foams exhibit relatively high SAC (support) factors, ie, load ratio; excellent resiliency (ball rebound >60%); and improved flammability properties. Semiflexible molded polyurethane foams are used in other automotive applications, such as instrument panels, dashboards, arm rests, head rests, door liners, and vibrational control devices. An important property of semiflexible foam is low resiliency and low elasticity, which results in a slow rate of recovery after deflection. The isocyanate used in the manufacture of semiflexible foams is PMDI, sometimes used in combination with TDI or TDI prepolymers. Both polyesteras well as polyether polyols are used in the production of these water-blown foams. Sometimes integral skin molded foams are produced. Semirigid foams are also manufactured. These foams do not fully recover after deformation; they are used in the construction of energy-absorbing automobile bumpers. Integral skin molded foams have an attached densified water skin, which is produced during manufacture. The preferred isocyanate for integral skin foams is carbodiimide-modified liquid MDI, which is used with ethylene oxide-capped polyols or polymer polyols. Thicker skins are obtained by lowering mold temperatures and increasing the percentage of overpack.Rigid Foams Rigid polyurethane foam is mainly used for insulation (qv). The configuration of the product determines the method of production. Rigid polyurethane foam is produced in slab or bun form on continuous lines Figure 9, or it is continuously laminated bet ween either asphalt or tar paper, oraluminum, steel, and fiberboard, or gypsum facings Figure 10

Figure 9: Rigid foam processing

Figure 10: Rigid foam processing

Application and propertiesFlexible Foam:The largest markets for flexible polyurethane foam are in the furniture, transportation, bedding, carpet underlay and packaging industries. Most furniture cushioning is made of polyurethane foam, predominantly cut from slabs or buns having a density of 0.01920.0288 g/cm3. Polyurethane viscoelastic foam is used increasingly in bedding. High resiliency flexible foam having a density of 0.040 g/cm3 is used for seat cushions in higher priced furniture. Molded flexible polyurethane foam is used in the automotive industry for seating, instrument panels, head rests, and arm rests applications. Semiflexible molded polyurethane foams are used in dashboards and door liners. Semiflexible foams are also formulated for sound and vibrational control in automotive applications [3]. Other foam uses include textile laminates and interior padding. Specialty applications include reticulated foams for filtration and foams for such consumer products as sponges, scrubbers, squeegees, and paint applicators. Foams that provide radiation protection [4] and flame retardant foam that can be obtained using a general-purpose polyol [5] have been reported.Rigid FoamThe bulk of rigid polyurethane and polyisocyanate foam is used in insulation. There has been a major demand for spray foams in the construction industry [6]. The use of rigid foam continues to improve energy efficiency [6]. Laminates are used for residential sheathing and board for flatdeck commercial roofing. Commercial buildings are often covered with polyurethane spray foam. Pour-in-place foam is typically integrated in large-scale assembly operations, such as aircraft carriers. Insulation of trucks, railroad freight cars and cargo containers is performed by either spray or pour-in-place techniques. Tank and pipe insulation is either sprayed or cut from bun stock. Ships transporting liquid natural gas (LNG) are usually insulated with rigid PUIR foam laminates, which provide temperature stabilities from 180 to 1508C. The main fuel tank of the National Aeronautics and Space Administration (NASA) space shuttles is also insulated with PUIR foam. Rigid polyurethane foam is used in engineered foamed-in-place packaging of industrial or scientific equipment and in the molding of furniture, simulated-wood ceiling beams, and a variety of decorative and structural furniture components. Rigid foam is also used in movie props, for the repair of river barges, and in boat flotation applications.C.A.S.E. (Coatings, Adhesives, Sealants, Elastomers)Coatings: Urethane coatings have been one of the fastest growing sectors of the worldwide paint and coatings industries [7]. Polyurethane coatings are used wherever applications require abrasion resistance, skin flexibility, fast curing, good adhesion, and chemical resistance. The polyaddition process allows formulation of solvent-based or solventless liquid two-component systems, waterborne (aqueous) dispersions, or powder coatings. Polyurethane coatings are applied to products to improve their appearance and lifespan. Polyurethane coatings are used on automobile exteriors, in construction where building floors, steel trusses, and concrete supports are sprayed-coated to make them more durable and easier to clean. Coatings are used in the aerospace industry to protect external parts of aircraft from extreme temperatures, and help protect the skin from rust and pitting. Synthetic leather products are also produced using a urethane binder. These leather-type products are used for shoes, handbags, luggage, and apparel. Leather-like sheet materials with excellent water resistance have been reported [8].Polyurethane films having oxygen and water permeability are applied inbandages and wound dressings and as artificial skin for burn victims.Adhesives and Sealants:Polyurethane adhesives and sealants provide strong bonding and tight seals in a variety of applications. Polyurethane adhesives provide the rapid development of green strength, where the adhesive provides an initial bond before fully curing. This reduces the need for clamping and holding materials, thereby reducing costs and increasing manufacturing flexibility. Custom adhesives and sealants can be manufactured. Adhesives are used in the assembly of shoes, automotive interiors, windshield bonding, and as textile laminates. Conveyor belts are usually closed with polyurethane adhesives. Polyurethane binders are mixed with wood chips or sawdust to form fiberboard. Sealants are used in road repair, plumbing, and construction. Polyurethane sealants provide excellent stress recovery to retain shape after being pulled or bent, are fast curing, and adhere to non-primed concrete. These sealants and adhesives can be painted to match surrounding surfaces.ElastomersPolyurethane elastomers are rubber-like materials that can be created with a wide variety of properties and molded into almost any shape. They can provide resistance to abrasion, impact and shock, temperature, cuts and tears, oils and solvents, aging, mold, mildew, and fungus, and most chemicals. Polyurethane elastomers are used almost everywhere. Snowplow blades are made of the elastomers to reduce road damage caused by scraping, wheels for shopping carts, skateboards, roller coasters, and heavy trash containers made with polyurethane elastomers provide for high-load bearing capacity and abrasion resistance. Tubing and injection molded parts are used in the medical sector. Cast and RIM elastomers are used in auto fascia, bumper and fender extensions, printing and industrial rolls, industrial tires, and agricultural parts, such as oil well plugs and grain buckets. Elastomeric spandex fibers are a large market and these fibers are used in all types of hosiery, undergarments, swim wear and other sports clothing. Elastomers with improved antistatic behavior for these fiber uses have been reported [9].

Health and safety issuesFully cured polyurethanes present no health hazard; they are chemically inert and insoluble in water and most organic solvents. However, dust can be generated in fabrication, and inhalation of the dust should be avoided. Polyether-based polyurethanes are not degraded in the human body, and are therefore used in biomedical applications. Some of the chemicals used in the production of polyurethanes, such as the highly reactive isocyanates and tertiary amine catalysts, must be handled with caution. The other polyurethane ingredients, polyols and surfactants, are relatively inert materials having low toxicity.IsocyanateIsocyanates in general are toxic chemicals and require great care in handling. Oral ingestion of substantial quantities of isocyanates can be tolerated by the human body, but acute symptoms may develop from the inhalation of much smaller amounts. The inhalation of isocyanates presents a hazard for the people who work with them as well as the people who live in the proximity of an isocyanate plant. Adequate control of exposure is necessary to achieve a safe working environment. The suppliers Material Safety Data Sheets (MSDS) have to be consulted for the most current information on the safe handling of isocyanates. Respiratory effects are the primary toxicological manifestations of repeated overexposure to diisocyanates [10]. Once a person is sensitized to isocyanates, lower concentrations can trigger a response [11]. Most of the industrial diisocyanates are also eye and skin irritants. Controlling dermal exposure is good industrial hygiene practice. The 1997 American Conference of Governmental Industrial Hygienists (ACGIH) exposure guideline for TDI is 0.005 ppm as a TWA-TLV (an eight-hour time-weighted average concentration); the 1997 TLV for TDI in Japan is 20 ppb. Overexposure to TDI can cause chemical bronchitis (isocyanate asthma) in sensitized individuals. Transient acute asymptomatic changes in respiratory function and deterioration of lung function following long-term repeated exposure have also been encountered. Allergic sensitization may occur within months or after years of exposure to isocyanates. Animal studies using TDI showed no dermatological response at exposure concentrations up to 0.5ppm. A chronic gavage study indicated tumor formation in the animals, but the study was found to be of doubtful toxicological relevance because of the method used and the excessively high dose levels. Vapor exposure to MDI is limited by the low vapor pressure, corresponding to a saturated atmosphere of 0.1 mg/m3 at 258C. An acute aerosol inhalation study on PMDI using rats indicated that the 4-h LC50 is 490mg/m3 [12].The current ACGIH TLV for MDI is 0.051 mg/m3 (0.005 ppm) as a TWA. The OSHA PEL is 0.02 ppm as a ceiling limit. The toxicity of aliphatic diisocyanates also warrants monitoring exposure to its vapors. HDI has a moderate potential for acute systemic dermal toxicity; rabbit dermal LD50 is 570 mL/kg [13]. However, HDI is severely irritating to the skin and eyes. Irritation, lacrimation, rhinitis, burning sensation to throat and chest, and coughing have all been reported in humans following acute inhalation exposure to HDI. HMDI has a low eye and dermal irritation potential, as well as a low potential for acute toxicity. Exposure to HMDI aerosol can cause dermal sensitization of laboratory animals. IPDI can cause skin sensitization reactions as well as eye irritation. There are a multitude of governmental requirements for the manufacture and handling of isocyanates. The U.S. Environmental Protection Agency (EPA) mandates testing and risk management for TDI and MDI under Toxic Substance Control Administration (TSCA). Annual reports on emissions of both isocyanates are required by the EPA under SARA 313. Thermal degradation of isocyanates occurs on heating above 1001208C. This reaction is exothermic, and a runaway reaction can occur at temperatures >1758C. In view of the heat sensitivity of isocyanates, it is necessary to melt MDI with caution and to follow suppliers recommendation. Disposal of empty containers, isocyanate waste materials, and decontamination of spilled isocyanates are best conducted using water or alcohols containing small amounts of ammonia or detergent. For example, a mixture of 50% ethanol, 2-propanol, or butanol; 45% water, and 5% ammonia can be used to neutralize isocyanate waste and spills. Spills and leaks of isocyanates should be contained immediately, ie, by dyking with an absorbent material, such as saw dust. The total U.S. airborne emission of volatile TDI is estimated by the International Isocyanate Institute (III) to be