Polymer degradation into the bore of the pipe, and fuel leakage and fire may follow. The problem of ozone cracking can be prevented by adding anti-ozonants to the rubber before vulcanization. Ozone cracks were commonly seen in automobile tire sidewalls, but are now seen rarely thanks to these additives. On the other hand, the problem does recur in unprotected products such as rubber tubing and seals. The polymers are susceptible to attack by atmospheric oxygen, especially at elevated temperatures encountered during processing to shape. Many process methods such as extrusion and injection moulding involve pumping molten polymer into tools, and the high
Silicone rubber cured by a platinum-catalyzed cure system, a condensation cure system, a peroxide cure system, or an oxime cure system. For the platinum-catalyzed cure system, the curing process can be accelerated by adding heat or pressure. In a platinum-based silicone cure system, also called an "addition" system (because the key reaction-building polymer is an "Addition reaction"), two different chemical groups (a silicone hydride and a vinyl) react in the presence of platinum (which serves as the catalyst). In this reaction, an ethyl group [C(H2)- C(H2)] is formed and there are no byproducts. Two separate components must be mixed to catalyze the