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Urea Formaldehyde Adhesive

Thermosetting Resin Adhesive Article Contents: Thermosetting Resin Adhesive Melamine Formaldehyde Adhesives Urea Formaldehyde Adhesiv...

Saturday, August 27, 2011

Thermosetting Component

In the most widely used two polymer adhesive the thermosetting component as a phenol formaldehyde resin, usually a one step resin from phenol itself and having a molar ratio of 1 phenol: 0.9 - 2 formaldehyde. The pH should and be high not above say pH 10, or compatibility with some polymers or side reactions may present a problem.

There is no fundamental reason with a potentially thermosetting novolak resin should not be used. Such a resin often has superior compatibility with synthetic rubber elastomers, a compatibility that is reduced if a relatively large amount of hexamethylenetetramine needs to be added to cure the novolak.

Rather surprisingly perhaps, phenolic resins are generally compatible, although not easily miscible, with a number of thermoplastic polymer. This compatibility frequently, although not invariably, persists in the cured state, incompatibility in the cured state is shown by clouding of the adhesive film,. Particularly good compatibility is shown between conventional alcohol soluble phenolic resins and polyvinyl ester and acetals.

Epoxy resin are of growing interest in two polymer adhesive system, and glycidyl ethers of bisphenol A and resorcinol are of special importance.

A number of other thermosetting resin have been mentioned from time to time, and in some cases the two polymer adhesives ascociated with them have found limited uses; for examples are urea and melanine resins. Urea resins have created interest in admixture with polyvinyl acetate but this two polymer adhesive has not become generally recognize as a separate type and is therefore discussed under urea resin. Melanine formaldehyde resins appear to justify more investigation, and etherified forms would make incompatibility less of a problem.

Furane resins would also seem to justify more comprehensive study because they are good solvents for many thermoplastic polymers. The solubility of thermoplastic polymers in furane monomers, reports a cement made by dissolving polyvinyl butyral in furfuryl alcohol of combinations of the furan derivatives with high polymers. Furfural, either by itself or as a resinous condensate with phenol, or perhaps with furfuryl alcohol might justify more investigation.