TWI Knowledge Summary

Microwave welding of plastics

TWI's modified microwave multimode cavity machine for welding polymers

The possibility of using microwaves to weld thermoplastics has existed since the development of the magnetron in the 1940s. In 1993, TWI built a research facility to explore the feasibility of exploiting such an operation. The modified multimode cavity, similar in nature to a microwave oven, operates at a frequency of 2.45 GHz and has the capability to apply pressure to a joint.

Most thermoplastics do not experience a temperature rise when irradiated by microwaves. However, the insertion of a microwave susceptible implant at the joint line allows local heating to take place. If the joint is subjected simultaneously to microwaves and an applied pressure, melting of the surrounding plastic results and a weld is formed. Suitable implants include metals, carbon or one of a range of conducting polymers, but whichever is selected becomes a consumable in the welding process. The particular advantage of microwave welding over other forms of welding is its capability to irradiate the entire component and consequently produce complex three-dimensional joints. Welds are typically created in less than one minute.

The technique is still in the development stages and as such there are currently no reported industrial applications. However, it is anticipated that microwave welding may prove to be suitable for joining automotive under-body components and domestic appliance parts.

You can use the Weldasearch literature database to supplement what you find in JoinIT.

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