AN INVESTIGATION INTO WELDING OF ENGINEERING THERMOPLASTICS USING FOCUSED MICROWAVE-ENERGY

Microwaves have been used for many years in industrial heating applica tions because of their ability to heat materials volumetrically. The d ielectric properties of a material determine its ability to absorb mic rowave radiation. In this paper, the dielectric properties of engineer ing thermoplastic materials, which include ultra high molecular weight polyethylene (UHMW PE), polycarbonate (PC) and acrylonitrile-butadien e-styrene (ABS) polymers under room temperature conditions have been e xplored. In addition to this, a new novel process for joining such pol ymers using microwave energy is presented. Basically, the thermoplasti cs joining process is carried out in two separate stages, the first st age consisting of directly inducing microwave energy to the specimen j oint interface, whilst the second state comprise of applying primers i n the form of epoxy-based resin to promote the joining of the material s by means of microwave energy. Tensile tests were conducted to determ ine the bond strength achieved at the specimen joint interface. In add ition, microscopic examinations of the fractured joints were performed in order to analyze the overall bond quality. Finally, a comparison w as drawn between the heating time required, the bond strength and qual ity of joint achieved at the interface. Concluding remarks underline t he potential capability in terms of speed, joint strength and versatil ity for this high-energy-rate process. (C) 1998 Elsevier Science S.A.