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Rubber Industry Terminology

Rubber industry terminology can be confusing at first. The Holz Rubber Team has put together a collection of important industry terms so that you and your team can become experts on the subject of rubber too.

Abrasion Resistance

The ability of rubber compound to resist surface wearing by mechanical action


The change in physical and chemical characteristics of an elastomer that has been exposed to a particular environment over time


Any organic compound that slows the process of oxidation


Any substance that slows the severe oxidizing effect of ozone on elastomers. Exposure to ozone typically causes surface cracking in many rubbers

Compression Molding

A molding process in which the uncured rubber compound is placed directly into the mold cavity, and compressed to its final shape by the closure of the mold

Compression Set

The permanent deformation experienced by a rubber material when compressed for a period of time. The term is commonly used in reference to a test conducted under specific conditions wherein the permanent deformation, expressed as a percentage, is measured after a prescribed period of time. A low compression set is desirable in molded rubber parts such as seals and gaskets, which must retain their dimensions to maintain an effective seal.

Cross-linking Agents

A chemical or chemicals that bond the polymer chains of a rubber together during the molding process


A) One complete cycle
B) The thermo process that causes a chemical change in the raw stock, turning it into the finished rubber part

Cure Time

The preset time needed to complete the curing process


One of several measures of the hardness of a material. Hardness may be defined as a material’s resistance to permanent indentation


A rubber’s ability to return to its original size and shape after removal of the stress causing deformation such as stretching, compression, or torsion. It is the opposite of plasticity. The term elasticity is often loosely employed to signify the “stretchiness” of rubber


General referred to in terms of tensile (pull apart) testing, elongation is the increase in length of a test specimen, expressed as a percentage of its original (unstretched) length… relative to a given load at the breaking point.


When part or all of a component is forced from its groove by high continuous or pulsating pressure


A measurement of the resistance to penetration of a rubber sample by an indenter. High values indicate harder materials while low values indicate softer materials.

Injection Molding

A molding method in which a rubber or plastic material is heated and forced under pressure into the mold cavity

Mooney Viscosity

A measure of the plasticity of a polymeric compound determined in a Mooney sheared disc viscometer


A measure of resistance of a material to deformation. It is measured by the force required to reach a predetermined compression or extension

Oil Resistant

Ability of vulcanized rubber to resist swelling and other detrimental effects of exposure to various oils


To soften a material and make it plastic or moldable, either by means of a plasticizer or application of heat


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)


A long molecular chain material formed by the chemical combination of many similarly structured, small molecular units


The capability of returning to original size and shape after deformation


A common name for both naturally occurring and synthetically made elastomers


Premature curing of compounded rubber stock during processing or storage, with the potential for adversely affecting material flow and plasticity during subsequent shaping and curing processes.

Shore Hardness

A durometer or hardness test that measures the depth of an indentation in the material created by a given force on a standardization presser foot. The two most common scales are ASTM D2240 type A and type D scales. The A scale is for softer plastics, while the D scale is for harder ones

Tear Resistance

Resistance to the growth of a cut in the seal when tension is applied

Tensile Strength

The force required to rupture a sample of stated geometry


A polymer resulting from the chemical combination of three monomers


A material which when thermally processed undergoes a reversible phase change to become plastic and capable of being molded to a desired shape. Upon cooling, the material reverts to its original properties

Thermoplastic Elastomer (TPE)

A material which combines the processing characteristics of a plastic but displays rubber-like properties upon completion of processing


A material, either an elastomer or plastic, which when thermally processed undergoes an irreversible chemical reaction to achieve its final material state


Property of resisting fracture or distortion. Usually measured by impact test, high impact values indicating high toughness


Thermoplastic Elastomer combines the rubber-like performance of elastomers with the processing advantages of plastic. Scrap material can be recycled without significant loss in physical properties, unlike thermoset materials.


The measurement of the resistance of a material to flow under stress


The thermally initiated, irreversible process whereby polymer chains are cross-linked to form the final physical and chemical state of rubber.