Cross-linking

Name:
Cross-linking
Detailed information:
Cross-linking occurs in nature in substances made up of polypeptide chains that are joined by the disulfide bonds of the cystine residue, as in keratins, insulin, and other proteins. Polysaccharide molecules can also cross-link to form stable gel structures (dextran). Cross-linking can be effected artificially, either by adding a chemical substance (cross-linking agent) and exposing the mixture to heat, or by subjecting the polymer to high-energy radiation. Examples are (1) vulcanization of rubber with sulfur or organic peroxides; (2) cross-linking of polystyrene with divinylbenzene; (3) cross-linking of polyethylene by means of high-energy radiation or with an organic peroxide; (4) cross-linking of cellulose with dimethylol carbamate (10% solution) in durable-press cotton textiles. Cross-linking has the effect of changing a plastic from thermoplastic to thermosetting. Thus, it also increases strength, heat and electrical resistance, and especially resistance to solvents and other chemicals.

Chemistry structure:

See Vulcanization; Polyethylene; Keratin.