MICROWAVE FORMING AND WELDING OF POLYMERS

Microwave heating has a number of advantages over conventional heating due to the ability to heat specimens directly through specific interaction of electromagnetic radiation with the material. Thus it is possible to consider highly localised, rapid melting of thermoplastics using microwave radiation as a means of forming and welding. However, most polymers exhibit very low dielectric losses in the GHz region which means that it is difficult to heat them efficiently by this means. We have therefore studied the use of fillers such as talc, zinc oxide and carbon black as a way of increasing the susceptibility of common polymers to microwave processing. Carbon black was found to be the most efficient susceptor for high density polyethylene and its efficiency was directly proportional to its surface area