Industry Terms General Thermoset Thermoset refers to the family of materials which can only be melted once during original processing and cannot be remelted or reprocessed after the original part is made. This represents an additional raw material cost for the scrap material loss due to the lack of reprocessibility and, therefore, results in a higher priced product. Thermoset rubbers include such common materials as EPDM, Neoprene, butyl rubber, and Hypalon. Thermoplastic Thermoplastic refers to the ability of a material to be remelted without significant loss of properties. This includes materials such as TPU, ABS, polyethylene, Santoprene and many other common materials which can be remelted and reprocessed, resulting in a zero scrap loss. Heat Aging Heat aging refers to the unique process of aging a thermoplastic or thermoset product and examining the percentage of retained physical and chemical properties after exposure to heat for a prolonged period of time. Santoprene, for example, has outstanding heat aging properties up to 300ºF. Most thermoset rubbers do not; they show a severe increase in hardness and loss of elongation, resulting in a stiffer material than one started with. Moisture Absorption The test for rate of water absorption has two chief functions: first, as a guide to the proportion of water absorbed by a material and consequently, in those cases where the relationships between moisture and electrical or mechanical properties, dimensions, or appearance have been determined, as a guide to the effects of exposure to water or humid conditions on such properties; and second, as a control test on the uniformity of a product. This second function is particularly applicable to sheet, rod, and tube arms when the test is made on the finished product. (ASTM D-570) ASTM The letters stand for American Society for Testing and Materials. The number that follows is a designation of the exact test method used to determine the value given. Flammability Measure of the extent to which a material will support combustion.