Copolymerization.—The term applied when two or more substances polymerize at the same time to yield a product which is not a mixture of separate polymers but a complex having properties different from either polymer alone. For example, vinylite is produced by polymerization of a mixture of vinyl acetate and vinyl chloride.
C-stage resins.—Thermosetting resins in the final stage in which they are infusible and insoluble. The state of the resin in the final molded article.
Curing.—The change of a binder from the soluble-fusible condition to the substantially insoluble-infusible form by chemical action. The heat-setting of a resinoid. Action is analogous to vulcanization of rubber.
Dielectric strength.—Voltage gradient at which a continuous electrical discharge will take place between two electrodes when the material in question is placed between the electrodes and a potential difference is applied to them.
Elastic.—A substance which exhibits rubberlike properties or “high elasticity” over a wide range of applied forces.
Elastic deformation.—When a substance reverts to its original dimensions on release of an applied stress.
Elastic limit.—The point at which a body begins to yield under a stress; that is, when the stress is equal to or greater than the internal friction.
Elasticity.—The property by virtue of which a body reverts to its normal bulk or shape after deformation by an applied force.
Extrusion molding.—A molding procedure for extended shapes of uniform cross section, whereby a heat-softened substance is forced through an orifice of form coinciding with the cross section of the article.