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
Foam rubber Foam rubber Foam rubber (also known as cellular, sponge, or expanded rubber) refers to rubber that has been manufactured with a foaming agent to create an air-filled matrix structure. Commercial foam rubbers are generally made of either polyurethane or natural latex. Latex foam rubber, used in mattresses, is well known for its endurance. Polyurethane is a thermosetting polymer that comes from combination of Methyl di-isocyanate and polyethylene and some other chemical additives. Foam rubber was first produced in 1929 by Dunlop Rubber researcher chemists E. A. Murphy and Eric Owen using whipped latex. In 1937 isocyanate based materials were first