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ELASTICITY. That property of material by virtue of which it tends to recover its original size and shape after deformation. If the strain is proportional to the applied stress, the material is said to exhibit Hookean or ideal elasticity.
ELASTOMER. A material which, at room temperature, stretches under low stress to at least twice its length and snaps back to the original length upon release of the stress. The term elastomer is commonly applied to synthetic rubber polymers.
ENGINEERING PLASTICS. Thermoset and thermoplastic materials whose characteristics and properties enable them to withstand mechanical loads (tension, impact, flexure, vibration, friction, etc.) combined with temperature changes. The reliability and predictability of engineering plastics makes them suitable for application in structural and load-bearing product design elements. Polycarbonate, ABS, acetal, and nylon are among the widely used engineering plastics.
ENVENOMATION. The process by which the surface of a plastic close to or in contact with another surface is deteriorated. Softening, discoloration, mottling, crazing, or other effects may occur.
EPOXY PLASTICS. Plastics based on resins made by the reaction of epoxides or oxiranes with other materials such as amines, alcohols, phenols, carboxylic acids, acid anhydrides, and unsaturated compounds.
ETHYLENE PLASTICS. Plastics based on resins made by the polymerization of ethylene or copolymerization of ethylene with other unsaturated compounds.
ETHYLENE TETRAFLUORETHYLENE COPOLYMER (ETFE). A moldable variety of fluorocarbon (fluoroplastic) polytetrafluorethylene (PTFE), for example, teflon (TFE).
EXOTHERM; EXTHERMIC HEAT. Heat generated by a chemical reaction; in polymers a particular problem since the heat must be dissipated.
EXPANDABLE PLASTIC. A plastic which can be made cellular by thermal, chemical, or mechanical means.
EXPANDED PLASTICS. (See FOAMED PLASTIC.)
EXTENDER. A substance, generally having some adhesive action, added to an adhesive to reduce the amount of the primary binder required per unit area. (See BINDER, FILLER.)
EXTRACTION. The transfer of a material from a plastic to a liquid in contact with it.
EXTRUSION. A method whereby heated or unheated plastic forced through a shaping orifice becomes one continuously formed piece.
EXTRUSION, AUTOTHERMAL. A method of extrusion in which the conversion of the drive energy, through friction, is the sole source of heat.
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