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
Sulfur 14th century the Latin ' was restored, for '; and by the 15th century the full Latin spelling was restored, for "sulfur, sulphur". The parallel "f~ph" spellings continued in Britain until the 19th century, when the word was standardized as "sulphur". "Sulfur" was the form chosen in the United States, whereas Canada uses both. The IUPAC adopted the spelling "sulfur" in 1990, as did the Nomenclature Committee of the Royal Society of Chemistry in 1992, restoring the spelling "sulfur" to Britain. Oxford Dictionaries note that "in chemistry and other technical uses ... the "-f-" spelling is now the standard form