Thermoplastic polyurethanes coatings, types

Global consumption of thermoplastic mbbers of all types is estimated at about 600,000 t/yr (51). Of this, 42% was estimated to be consumed in the United States, 39% in Western Europe, and 19% in Japan. At present, the woddwide market is estimated to be divided as follows styrenic block copolymers, 48% hard polymer/elastomer combinations, 26% thermoplastic polyurethanes, 12% thermoplastic polyesters, 4% and others, 9%. The three largest end uses were transportation, 23% footwear, 18% and adhesives, coatings, etc, 16%. The ranges of the hardness values, prices, and specific gravities of commercially available materials are given in Table 4. 

The worldwide annual production of thermoplastic elastomers of all types is estimated at about 2,500,000 metric tons in 2005 [47] with a value of almost 12 billion. Production is expected to rise to about 4,200,000 metric tons in 2014 [48]. This is equivalent to an annual growth rate of about 5.3%. In 2009, North America consumed about 25% of this amount. Western Europe about 20%, and China about 33%. Japan and other Asia/Pacific countries accounted for most of the rest. The styrenic block copolymers represented about 45% of the total market and polypropylene/EPDM or EPR combinations (including thermoplastic vulcanizates) about another 30%. The thermoplastic polyurethanes and the thermoplastic polyesters together made up another 20% [48]. Major end uses are transportation, footwear, industrial goods, wire insulation, medical (growing very rapidly), adhesives, coatings, and so on. 

As the substrate sheet, a thin plastic film or tightly packed nonwoven cloth, such as polyester spanbond nonwoven cloth of approximately 0.15 mm, is used. A synthetic rubber, such as styrene-butadiene rubber or thermoplastic polyurethane elastomer, is used as a binder. In addition, a surfactant for hydrophilicity, an antioxidant for prevention of thermodeformation, and a silica-type inorganic filler for prevention of tackiness are used. For the superabsorbent polymer particles, various synthetic polymers, for example, polyacrylate and polyvinyl-type superabsorbent polymers, can be used. For this apphcation, the particle sizes are an important parameter, because they polymer is required to be within the coating layer, and as the absorption rate is no retarded, quickly protrude from the layer when swelling. 

Adhesives in relation to coated fabrics can be thought of as either the tie-coat to bond the surface coating to the fabric, or the surface coating itself, directly bonded to the fabric. The types of polymers used in coating fabrics are rubbers, PVC, polyurethane, acrylics and silicones the coatings are usually cross-linked to increase durability but some topcoats can be thermoplastic, for example polyurethanes, to facilitate thermal bonding of seams in production of garments or other articles. 

Powder coatings are not necessarily based on epoxy resins the first powder coatings were based on thermoplastic polymers, and polyolefin, vinyl polymer and polyamide coatings are still used. While those based on epoxy resins are very prominent, there are also polyester, polyurethane and acrylic thermosetting types which we will describe here. 

Coatings (qv) present a unique stabilization challenge because of their high surface-to-volume ratio. Coatings, like polymers, are classified as either thermoplastic or thermoset. Thermoplastic coatings are those that are composed mainly of individual polymer chains, sometimes partially branched. Ebcamples of this type are acrylic latex paints, polyurethane dispersions, and nitrocellulose lacquers. 

A versatile aryl phosphite which can be used as a stabilizer in many types of polymers including adhesives, styrenics, engineering thermoplastics, polyesters (to regulate viscosity and improve color stability), polyolefins (as a catalyst adjuvant), polyurethanes (to prevent scorching and improve color stability), coatings, epoxies, auid PVC where regulatory approval in food contact is not required. 

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