Plastics joining surface preparation

Adhesive Bonding - A method of joining two plastics or other materials in which an adhesive is applied to the parts surfaces. Bonding occurs through mechanical or chemical interfacial forces between the adhesive and adherend and/or by molecular interlocking. Surface preparation of the adherends and curing of the adhesive may be required. 

In the mid-seventies, spurred by developments from the DuPont Corporation, a new kind of two-component acrylic adhesive system was introduced to the joining industry. The DuPont technology has been widely licensed and is now referred to by numerous terms such as "second-generation acrylics", "reactive adhesives", "modified acrylics", "toughened acrylics", etc. These adhesives seemed to answer the need for improvements over some of the major disadvantages found in anaerobic structural adhesives, namely those of cost, the need for scrupulous surface preparation, and the ability to bond plastic surfaces. 

The most common general method of treating plastics is to abrade the surface and solvent-wipe away the debris. The abrasion tends to remove any detachable contaminants from the surface as well as roughen it, so that mechanical interlocking forces can develop at the interface. The author has shown that, for a variety of engineering-grade structural plastics, this simple surface preparation can adequately prepare the plastic adherends for durable joining... 

From the viewpoint of the adhesive technologist, plastics are an anomaly bonded joints can be made in which the plastic fails before the adhesive, but certain plastics are very difficult to bond. Although plastics often present difficulties in adhesive bonding (Table 4.2), all can be joined successfully with the correct choice of adhesive, joint design, and surface preparation [28] ... 

In many non-structural applications, adhesives are used to bond engineering plastics without the need for any surface preparation and indeed this brings out the benefit of using the adhesive, especially when bonding dissimilar materials (where ultrasonic welding or other joining methods may not be possible). 

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