Permanent Set
The deformation remaining in a rubber specimen following both stress and relaxation over a period of time.
Permeability
The rate of gas flow through a particular rubber material.
Plasticizer
A chemical agent added to the rubber compound batch mix to soften the elastomer for processing, as well as to improve physical properties of the compound product (i.e., increase elongation, reduce hardness, improve tack).
Polymer
A long molecular chain material formed by the chemical combination of many similarly structured, small molecular units.
Post Cure
A second step in the vulcanization of certain elastomers, used to drive off residual decomposition products resulting from initial vulcanization.