Copper Laminates

The bonding of metal to a plastic laminate is nowdays not an unusual application, a common example is the copper/plastic laminate used for printed circuits. No particular difficulty arises in the two stage process, a process in which the copper is bonded to the cured laminate, usually phenolic or epoxy. But problem arise in the one stage process with phenolic resin. Different phenolic resin, epoxy resins and curing agents all behave differently, as is reflected in the different blister and peel strengths obtained in bonding copper foil. Generally speaking, epoxy resins do not fulfil the combined requirement of high blister resistance and high peel strength as satisfactorily as some of the two polymer adhesive.

In a survey of adhesives for pronted circuit laminates, Rider draws attention to the corrosive effect of some hardeners used with epoxy resin having an influence on electrical properties.

Broken Bones
The mending of broken bones by adhesive bonding is a subject that has created much interest in recent years. As might be expected, a good deal of attention has been given to the use of epoxy resin. Experimental work has been done in Australia, USA. Switzerland and England, all very largely on animals. Evidence shows that the strength of the limb is regained more rapidly than by natural healing, although it does not appear that a technique has yet been developed that can be applied to human being with absolute safety.

Glass Adhesives

In the context here the word of glass refers to glass in the sheet form, as distinct from the fiber or filament form. The boding of glass fiber in the making of laminates is a different application, about which much has been written.

Epoxy resins were among the first high strength thermosetting adhesives capable of bonding glass, an application which is often of vital importance although the quantity of adhesive used is probably small. It is relatively easy to bond glass to glass but in bonding glass to other materials large differences in thermal expansion may exist. This makes it advisable to cure the adhesive at its operational temperature in order to minimize the risk of the glass breaking as the temperature changes.

Success largely depend on the nature of the glued assembly; if it is fairly massive and is required to operate through a range of temperature, the problem is difficult. The addition of a flexibilizer has obvious advantages, provided a decrease in other properties is acceptable; polysulfide rubbers have been comprehensively studied and probably offer the best solution in difficult conditions.

Although a good deal of the glass bonding done with bisphenol A adhesives is concerned with small objects, there are two large size applications that have been investigated, namely in curtain walling and in double glazed windows.