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
Butyl rubber and pulp, personal care products, pigment concentrates, for rubber and polymer modification, for protecting and sealing certain equipment for use in areas where chemical weapons are present, as a gasoline/diesel fuel additive, and chewing gum. The first major application of butyl rubber was tire inner tubes. This remains an important segment of its market even today. Isobutylene was discovered by Michael Faraday in 1825. Polyisobutylene (PIB) was first developed by the BASF unit of IG Farben in 1931 using a boron trifluoride catalyst at low temperatures and sold under the trade name . PIB remains a core business for BASF