Cross-linking agent (English name: cross-linking agent) is a substance that acts as a bridge between linear molecules, so that multiple linear molecules can bond and cross-link to form network structure. Crosslinking agent in different industries have different names, such as: in the rubber industry used to be called "vulcanizing agent"; In the plastic industry known as "curing agent", "curing agent", "hardening agent"; In adhesive or coating industry known as "curing agent", "hardening agent" and so on. Although the above name has different, but reflects the chemical properties and mechanism is the same. Often molecules containing multiple functional groups of the material, such as organic diacid, polyols, etc.; Or compounds containing multiple unsaturated double bonds within the molecule, such as divinylbenzene and diisocyanate,N, N-methylene bisacrylamide (MBA), etc. Can be fed with the monomer, to be polycondensation (or polymerization) to a certain degree of cross-linking, so that the product into insoluble cross-linking polymer; It is also possible to retain a certain number of functional groups (or double bonds) in linear molecules, and then add specific substances for cross-linking, such as the curing of phenolic resin and vulcanization of rubber.
Crosslinker action
Crosslinking agent is mainly used in polymer materials (rubber and thermosetting resin). Because the molecular structure of the polymer materials as one long line, not crosslinked intensity at the low, easy to break, and there is no elastic, the effect of crosslinking agent is to produce chemical bonds between the molecules of the form, the linear molecules each other together, form a mesh structure, increase strength and flexibility of the rubber, rubber crosslinking agent is mainly used in the sulfur, in addition to promoter.
1, a variety of thermoplastics (polyethylene, PVC, chlorinated polyethylene, EVA, polystyrene, etc.) crosslinking and modification. Thermal crosslinking is generally 1-3%, plus diisopropylbenzene peroxide (DCP) 0.2-1%; When irradiation crosslinking dosage is 0.5-2%, DCP can no longer be added. Crosslinking can significantly improve the heat resistance, flame retardant, solvent resistance, mechanical strength and electrical properties of the product. It can significantly improve product quality and has no odor compared to peroxide system crosslinking alone. Typical for polyethylene, polyethylene/chlorinated polyethylene, polyethylene /EVA cross-linked cable and polyethylene high and low foaming products.
2, ethylene propylene rubber, all kinds of fluorine rubber, CPE and other special rubber vulcanization (and DCP, the general dosage is 0.5-4%), can significantly shorten the curing time, improve the strength, wear resistance, solvent resistance and corrosion resistance.
3, acrylic acid, styrene type ion exchange resin crosslinking. Compared with diethylbenzene crosslinking agent, it has the advantages of low dosage, high quality and excellent properties such as pollution resistance, high strength, large aperture, heat resistance, acid and alkali resistance and oxidation resistance. This is a new ion exchange resin developed recently and has a good prospect.