Chemical properties

All types of elastomers are susceptible to chemical attack of varying degrees. The compatibility of a rubber in a particular environment is a function of both the polymer structure, and the way in which it has been formulated.  Chemical incompatibility can have various effects on the rubber compound, depending on the exact form of chemical attack, with the effects being exaggerated or accelerated at elevated temperatures. The physical effects can be seen as:

• - Embrittlement and hardening
• - Softening and becoming tacky
• - Swelling
• - Volume loss

The most common effect is swelling – either due to a solubility effect, or chemical attack, resulting in a change in the elastomer’s polarity. Though the volume increase may be reversible, the effects on the polymer may not be.

Embrittlement and hardening are indicative of additional cross-linking, and softening is indicative of degradation of the polymer/crosslink network. Volume loss is most usually linked to extraction of plasticisers and process aids, resulting in a material that is less flexible.