Plastic Mechanical joining

With plastic materials, the designer also has a greater choice of bonding techniques than with many other materials. Thermosets must be adhesively bonded or mechanically joined, but most thermoplastics can also be joined by solvent or heat welding. Additionally, plastic parts can be designed for assembly by means of molded-in, snap-fit, press-fit, pop-on, and threaded fasteners so that no additional adhesives, solvents, or special equipment is required. 

Thermosetting plastics are joined either mechanically or by adhesives. Their thermosetting nature prohibits the use of solvent or thermal welding processes however, they are easily bonded with many adhesives. 

Energy is needed to break such a contact, more so with some joined items than others. If we consider the adhesion of plastic on glass, the highest adhesion will be obtained if the adhesive fills all the valleys and crevices of each adhered body surface. This will remove any air pockets that do not contribute to adhesion. The role of the adhesive or glue is to provide mechanical interlocking of the adhesive molecules. 

A variety of techniques is available for joining plastics to themselves or to other materials—mechanical fastening, welding, and bonding with adhesives—and all are used extensively. Each method has both advantages and drawbacks for plastics, bonding might be said to be preferable when they are to be joined with dissimilar materials. 

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