Polymer architecture via abstraction of a hydrogen, can create a mid-chain growth site. Branching can be quantified by the branching index. An effect related to branching is chemical crosslinking - the formation of covalent bonds between chains. Crosslinking tends to increase T and increase strength and toughness. Among other applications, this process is used to strengthen rubbers in a process known as vulcanization, which is based on crosslinking by sulfur. Car tires, for example, are highly crosslinked in order to reduce the leaking of air out of the tire and to toughen their durability. Eraser rubber, on the other hand, is not
Ethylene propylene rubber aprotic. Amorphous forms of EPM are flexible at low temperatures (with glass transition points around -60 °C). Via selection of certain sulfur compounds EPM can remain heat resistant up to 130 °C and up to 160 °C with peroxide curing. These two tables contain some of the main properties of EPM. EPM has a large number of uses due to the many ways in which the polymer can be designed, for example; it is used in automotive weather-stripping and seals, self-amalgamating tape, glass run channels, radiators, garden and appliance hoses, tubing, belts, roofing membranes, expansion joints, rubber mechanical goods, plastic