Welding
Plastics welding techniques have been around for over 50 years; both hot gas welding and spin welding were first reported in the 1930's. The total number of welding techniques for plastics has risen to 20, six of which are still in various stages of development and have yet to find industrial applications. These are laser welding, microwave welding, infrared welding, forced mixed extrusion welding, orbital welding and friction stir welding. More common welding methods are extrusion welding, hot gas welding, butt welding, spin welding and solvent welding.

Bonding
Using adhesives to bond plastics offers many advantages over traditional assembly methods, including reduced weight, assembly costs, cycle times and safety concerns. To gain the full potential of adhesives, designers need an understanding of the performance characteristics of each adhesive, and knowledge of the factors affecting the bondability of plastics.

The wide variety of plastics substrates, an invaluable asset when selecting design materials, becomes a serious limitation when selecting the optimum adhesive. The number of adhesives, coupled with the many grades of plastics, make it difficult to locate bond strength data for specific adhesive/plastic combinations. The designer must first select a plastic and then evaulate different adhesives to identify one which meets the performance requirements of the application. Such screenings typically occur without information on the adhesive's performance characteristics.

Other factors such as cure speed, environmental resistance, thermal resistance and suitability for automation play a role in selecting the best adhesive for an application. Lower performance adhesives include rubber base solvent cements, host melts, two-part epoxies and urethanes, but they are not suitable for high speed automated processes.

For more information, contact Mike at Ultra Acrylics, Inc.