Polyester fabric (filament by filament) was pretreated in a microwave oven in the presence of solvents and subsequently dyed with commercial disperse dyes [Dispersol Red C-B (CI Disperse Red 91) and Dispersol Blue B-G (CI Disperse Blue 26)] at different temperatures and for different durations of time. It was observed that the solvent interaction with the polyester could be enhanced by using microwave heating. Solvent molecules interact rapidly, not only with the surface of the fibre but also with the interior parts. Scanning electron microscope results showed that structural modifications take place, which produce surface roughness and voids. This enhances the dye uptake by threefold in comparison to conventional methods.

The use of radio and microwave frequency is gaining importance for industrial applications such as heating, drying, and other processing. The most important advantage of using microwave is that it is non-contact or localized heating and the heat is produced within the material. This can be much more effective than indirect heating where the heat propagation is by heat conduction through the material. We have been investigating the influence of microwave radiation on different fibers for the last few years. In the present investigation we used microwave frequency of 2450 MHz to investigate its effect on polyester fibers. The polyester fibers were heat set in air as well as a liquid, which acted as a lossy substances. The liquid was chosen on the basis of earlier experiments, which showed the maximum effect. A comparative study was also carried out using conventional heating in silicone oil. Using the method of X-ray Diffraction (XRD) we calculated the changes in % crystallinity and orientation. It was found that as the time of treatment under microwave radiation increased from 15 sec. to 120 sec. the order factor was found to increase from 0.32 to 0.71.The crystalline orientation as determined from the azimuthal scan was also found to increase. Such structural changes can be highly beneficial for the processing of fabric in industry. The microwave radiation process is fast, reliable and energy saving.

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