Permittivity and temperature characterisation of rubber compounds under high power microwaves - Electronics Letters

E, (3rd iteration. MMI E, (2nd iteration, MM) Znti,oduction: Rubber, natural or synthetic, is a coniplcx material that must be mixed with several other ingredients, not oiily to achieve the performance levels of the finished product but also to facilitate manufacture and reduce costs. From the electromagnetic point of vicw, each agent modifies the dielectric properties of the mix. The industrial vulcanisation chains use a microwave oven to pre-heat the profiles up to IOO'C, so the performance of the whole facility will strongly depend on their dielectric properties. In addition, as rubber is heated its dielectric properties change with both temperature and the complex chemical process associated with the vulcanisation. Despite its great industrial interest, very little is known about tlie dielectric properties of rubber as a fLiuction of power and temperature. Previous studies have used completely filled waveguides near a shorting plate to measure the rubber permittivity [I], but the field distribution of tlie TELo mode causes a non-uniform heating of the sample and makes the method unsuitable for this application. A new method employing a partially filled waveguide is presented in this Letter, where the small sample dimensions and its positioning in the waveguide ensures an almost quasi-homogeneous power distribution.