These lower molecular-weight materials have better color stability to UV radiation and hydrolysis than the conventional grades. Other new grades are stabilized for use as wear layers for aircraft wings. These thermoplastic elastomers are generally tougher over a broader temperature range than the urethanes. Also, they are easier and more forgiving in processing. These materials can be processed by injection molding, extrusion, rotational molding, flow molding, thermoforming, and melt casting.
Powders are also available.
Copolyesters, which along with the urethanes, are high-priced elastoplastics, have excellent dynamic properties, high modulus, good elongation and tear strength, and good resistance to flex fatigue at both low and high temperatures. Resistance of the copolyesters to nonoxidizing acids, some aliphatic hydrocarbons, aromatic fuels, sour gases, alkaline solutions, hydraulic fluids, and hot oils is good to excellent. Thus, they compete with rubbers such as nitriles, epichlorohydrins, and polyacrylates. However, hot polar materials, strong mineral acids and bases, chlorinated solvents, phenols, and cresols degrade the polyesters. Weathering resistance is low but can be improved considerably by compounding UV stabilizers or carbon blacks with the resin.