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Saturday, June 4, 2011

Carboxyl Substituted Polystyrene Adhesive

The presence of polar groups in an adhesive is a factor of known importance and reference has been made to the introduction of carboxyl groups into certain thermoplastic polymers. Work has been reported in Germany showing the relatively high strength obtained on aluminum test joint with a carboxyl substituted polystyrene adhesive used by the hot melt method.

The adhesive consisted of a copolymer of styrene and small amount of an appropriate carboxylic acid (not more than 0.5% acid substitution) and it was shown to give three times the strength of pure polystyrene. Furthermore, in America acrylonitrile/butadiene elastomers with carboxyl groups in the polymer chain have been described; one advantaged of these is the improved compatibility with phenolic resin in the formulation of two polymer adhesives.

Adhesion to glass is always of interest. In a comprehensive study tested a large number of polymers. Among purely thermoplastic ones found the highest strengths gives by plasticized polyvinyl acetate, plasticized polyvinyl butyral, and by polyvinyl chloride/acetate/alcohol. At the other extreme, polymethylmethacrylate and ethyl cellulose showed practicall no adhesion.

There is probably no application in which a large number of thermoplastic adhesion has been evaluated than in bonding non-woven textiles. In this way large application, emulsion forms of adhesive are of greater importance, including polyvinyl chloride/acetate copolymers, acrylic esters, and synthetic rubbers especially butadiene copolymer.

Generally speaking, most thermoplastic polymer, with the possible exception of the unsubstituted nylons, can be modified with many natural or synthetic resins such as copolymer on the one hand and glyptal or coumarone indene on the other. Formulator of adhesives are thus able to vary properties considerably to meet  the demand of many different applications.

Resin based on terpene polymers, coumarone indene resins by themselves, and the acetylene para-tert-butyphenol resin (frequently known as Kerosin), each themselves thermoplastic and of some adhesive value, are also of value in adding "tack" to many other thermoplastic adhesives.