The microwave processability of semicrystalline polymers

Abstract

Abstract The overall objective of these studies was to investigate the relationship between polymer structure and microwave absorptivity. In this paper, the microwave processing of semicrystalline polymers such as poly(ether ether ketone) (PEEK), nylons, and poly(ethylene terephthalate) (PET), via a cylindrical resonance wave cavity and a rectangular standing wave applicator is described. These polymeric materials were irradiated in low power (< 50W) electric fields at 2.45 GHz. Silicone flexible molds were necessary for improved processing of nylons and PEEK at temperatures below their T c Rapid heating rates were observed between the glass transition temperature, T g , and the melting temperature, T m , for all these polymers provided that T c was exceeded. Both dynamic mechanical thermal analysis (DMTA) and dielectric thermal analysis (DETA) spectra were utilized to predict the heating phenomena between amorphous and semicrystalline materials and to explain the rapid crystallizing rate of PEEK. above its glass transition temperature. Correlations were drawn between (a) the apparent activation energy and the critical temperature ( T c ) and (b) the shape of the dielectric spectra at 2.45 GHz and its shape in kHz region.