Generally, the bonding of rubber use polyisocyanate adhesive or polyisocyanate adhesive modified by rubber adhesive. The organic solvent contained in the adhesive can make the rubber surface swelling. Polyisocyanate adhesive has a small molecular weight, which can penetrate into the inner surface of rubber and react with the active hydrogen in rubber to form covalent bond.Polyisocyanate can also react with moisture to form urea or biuret, and when heated and cured, isocyanate will self-polymerize, form a cross-linked structure, and form a polymer cross-linked interpenetrating network (IPN) with the rubber molecular cross-linked network, so that the adhesive layer has good physical properties.When polar rubber is bonded with ordinary polyurethane adhesive, good bonding can also be produced due to the chemical and physical interaction between the groups of various materials

Polar groups on PVC, PET, FRP and other plastic surfaces can form hydrogen bonds with ammonia ester, ester, ether and other groups in adhesives to form adhesives with a certain bonding strength.Some people believe that glass fiber reinforced plastics (FRP) contain OH groups, and the OH on the surface reacts with NCO in PU adhesive to form chemical adhesive relay.

Non-polar plastics such as PE, PP, its surface polarity is very low, with the polarity of polyurethane adhesive bonding may encounter difficulties, which can be solved by a variety of methods to polyolefin plastic surface treatment.One method is to use corona treatment to oxidize its surface and increase polarity.Another method is to use more isocyanate adhesive on the surface of the adhesive plastic as the adhesive coating agent (primer, primer).For example, when molten PE extrusion film is extruded on PET and other plastic films, due to the weak interface layer with low degree of polymerization on the surface of PE, the bonding strength is not ideal. When using primer, multiple isocyanates are diffused on the surface of hot polyethylene to strengthen the weak interface layer, and the composite film has a better peel strength.

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