Glossary of terms

Ageing:

Deterioration of a rubber compound’s physical and chemical properties over time. Ageing may sometimes appear as cracks on the rubber part’s surface.

Bonding:

A scientific process of chemically joining a rubber compound to a metal or plastic surface. The adhesive force between surfaces is created on a molecular level, between atoms and molecules.

Cavity:

A hollow shape inside a mould. Forms the shape of the rubber part in mould processing; different moulding methods use different systems of filling a cavity. There may be several cavities in one mould.

Compound:

Rubber compound is a homogeneous chemical substance consisting of elastomer(s) and associated chemicals. It is a raw material for rubber products.

Damping:

Vibration and impact absorption is a natural characteristic of rubber. This property pertains to the viscoelastic nature of rubber and can be adjusted by changing the compound’s properties. An appropriately designed and manufactured rubber part absorbs vibration energy and transforms it into heat.

Dissipation factor (tan δ):

Expresses the ratio of dissipated energy to elastic deformation energy. Dissipation factor measures the loss of force in a dissipative rubber compound.

Elasticity:

Material property of rubber; rubber’s ability to revert to its original shape and size after compression, tensile, or torsion stress is removed.

Elastomer:

Elastic polymer, i.e. an elastic substance with long polymer chains that reconfigure themselves to distribute an applied stress and revert to their original configuration after the stress is removed. The part of the rubber compound that determines its basic properties.

Flash:

Excess rubber on the surface of a moulded rubber part. It cannot be avoided in mould processing, but it is reduced and placed more conveniently in competent mould designs. Flash is usually removed when a rubber part is finished.

Hardness:

A measurement of rubber compound’s ability to resist penetration of an indenter. The strength and hardness of a rubber compound are two separate properties and they are not interdependent. A harder rubber is not necessarily stronger and more durable than a softer compound.

Modulus:

A measure of the force required to reach a predetermined deformation of a material. Usually the non-permanent (i.e. elastic) deformation of a rubber compound is measured in MPa.

Mould:

A metallic tool used to vulcanise a rubber part accurately into a desired shape by applying heat and pressure to the compound. These are generated by pressing the mould in a vulcanising press.

Polymer:

A substance comprising of numerous similar molecules; the properties of a polymer chain do not change remarkably even if a few molecules are removed or added. Polymer material is a mixture of one or more polymers and affiliated additives. The most common polymer materials are different plastics and rubbers.

Reinforcement:

A material or component that increases the material or structural rigidity of a rubber product. The material may be incorporated into the rubber compound, or the component may be bonded to the compound inside or outside the rubber part by vulcanisation.

Rigidity:

A material’s property of resisting deformation. This is a natural tendency of rubber compounds. The higher the rigidity, the more force is required to cause deformation.

Rubber:

A chemical compound of an elastomer or elastomers and other affiliated substances, which resists permanent deformation. The compound must be vulcanised in order to lose pliability and achieve the characteristic chemical and physical properties of rubber.

Viscosity:

The internal friction, i.e. ability to resist flow, of a fluid or other flowing material. Material flows easily if viscosity is low; resistance to flow under stress is high when viscosity is high.

Vulcanisation:

A thermally initiated and irreversible process of cross-linking polymer chains to each other, i.e. creating strong chemical bonds between the molecules. This process gives a rubber compound its typical chemical and physical properties. Vulcanisation is sometimes referred to as curing.

Weathering:

Deterioration of rubber’s physical and chemical properties after exposure to outdoor circumstances.