Saturday, February 25, 2012

Metal Bonding Application

Other important metal bonding application are in brake linings when the higher curing temperature is generally used and in copper to plastic laminates for printed circuits. In the latter application, hot settling nitrile/phenolic adhesives are reported as giving rather better peel strength and blister resistance than vinyl/phenolic adhesives (vinyl implying polyvinyl butyral), and are the adhesives generally used in the plated circuit process. Very high joint strength can be obtained in bonding cyclined rubber; and in bonding glass a strength of over 1000 psi with good weathering qualities is reported.

Improved adhesion in steel to steel bonding is claimed with a nitrile rubber containing carboxyl group, and further, such a polymer is more easily compatible with a phenolic resin.

Because the elastomer component in a copolymer of polar and nonpolar monomers, properties such as oil resistance and water absorption depend on the ratio of acrylonitrile to butadiene, as well as on the ratio of the rubber to phenolic resin. Thus as the nitrile content is increased the copolymer becomes more oil resistant and therefore less readily soluble in hydrocarbons. On the other hand, solubility in polar solvent is increased.

A study of the oil resistance of certain nitrile/phenolic and neoprene/phenolic adhesives shows, as one would except, the former to the generally superior; but the important factor of component ratio was not reported. Component ratio must also affect fatigue, but in the commercial forms of the adhesive resistance to fatigue is very good.

The durability of nitrile/phenolic adhesives has been investigated by exposing to the weather two commercial forms of the adhesive on various sites form Alaska to Panama. After a year, each gave over 80% of the original control joint strength, on both stressed and unstressed aluminum test panels. One aspect of durability is resistance to heat and in a comprehensive study by Black and Blomquist on the thermal deterioration of a number of synthetic adhesive polymers some valuable information has been obtained.