cross-linking: 1. A comparatively short connection composed of either an element, a chemical group, or a compound that bridges between neighboring chains of atoms in a complex chemical molecule (especially a polymer). Cross-linking changes a plastic from thermoplastic to thermosetting, and it increases strength, durability, heat and electrical resistance, and resistance to solvents and other chemicals. Examples are: a) vulcanization of rubber with sulfur or organic peroxides, b) cross-linking of polystyrene with divinylbenzene (see 2. in this definition), and c) cross-linking of polyethylene by means of high-energy radiation or with an organic peroxide (see cross-linked polyethylene (XLPE or PEX). 2. The bonding of linear polymers into a resinous product with a material such as divinylbenzene (DVB) producing a tridimensional exchanger product. The cross-links give the resin structure its strength, insolubility, and resistance to melting and distorting over a range of temperatures. Cross-linking also determines the tightness or porosity of the resin structure, and the degree of cross-linking is a factor of the resin's ability to withstand chemical oxidation. Standard softening resin is usually 8 percent cross-linked with divinylbenzene or 8 percent DVB. Anion resins can be from 2 percent to 8 percent cross-linked. Acrylics can also be used instead of DVB for cross-linking..