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Saturday, November 8, 2008

Miscellaneous Polymers

Copolymers of butadiene and acrylonitrile are not readily compatible with an epoxy resin; nevertheless, a low molecular weight butadiene acrylonitrile copolymer is claimed to give especially good metal and glass to metal adhesion, without using pressure. In another example high peel strength is claimed; and in a similar system it is said to be advantageous to incorporate a phenolic resin; they are largely inreactive. But as reactive flexiblishing compounds, saturated and unsaturated polyesters with terminal carboxyl groups are of interest in adhesive formulations.

Polymethylmethacrylate, in substantial quantity, with a mixture of an epoxy and a thermosetting phenolic resins, is used for bonding PVC to metal. Polyvinyl chloride is not an early material to bond, and therefore it is significant that another epoxy adhesive claiming to give improve adhesion of PVC to metal also incorporates an acrylate polymer. This adhesive is include of vinyl polymer.

Having regard to the individual reactivity of polyisocyanates and epoxy resins, it is not surprising that there has been interest in using them together. A relatively early patent describes a metal adhesive produced by reacting equal parts by weight of a diisocyanate ad a bisphenol epoxy resin. A later patent describes a metal adhesive produced by applying separately and “polymerizing together” an epoxide resin and a polyurethane pre-polymer; a force of 36.2 kg/cm2, which is rather low, is said to be necessary to break the bond, but no details of the test are given. It is not clear if the term “polymerizing together” means polymerizing individually at the same time, or co-polymerizing. In this connection it is interesting to see that a reaction between epoxide and isocyanate groups to form an oxazolidone has been described. And in another patent an adhesive is made by reacting a polyepoxide and a diisocyanate, and subsequently adding an amine, which will of course react with both.

Epoxy resins
may be mixed with styrene to produce adhesives of low viscosity without added solvent and, rather surprisingly, a reaction is said to take place. Another adhesive formulation containing styrene, together also with a furfural acetone monomer, has been reported from Russia.