BLOG: Microwave Emerging as Alternative Energy Source for Rapid Adhesive Cure
By Deb Bhattacharjee (adhesives.org blogger)
There has been ever increasing demand on rapid and effective cure of adhesives while maintaining the pot life in industrial processes. In addition to the conventional heat cure, UV radiation has emerged as an acceptable alternative for improving the productivity, though it is only possible when at least one of the substrates is transparent to light. The cure of opaque, filled or thick cross-section is problematic using UV triggered system. The converters, in collaboration with adhesive manufacturers, have been investigating alternate energy sources for rapid adhesive cure without impacting processability and ultimate bond strength. Microwave has emerged as a cost effective, scalable, commercially viable process over the last few decades.
The FDA approved limit of microwave energy that can emit from commercial ovens is far below the harmful people, and several safety features have already been incorporated with no harmful greenhouse gas emissions from the heat source. Microwave energy in the 0.3 GHz and 3.0 GHz frequency range (industrial/commercial microwave systems typically operate at 900 MHz or at the wavelength of ~32.7 cm)allows more efficient penetration of the microwave through the material preferably for non-metallic or partial metallic bonding. Energy is transferred through the material electro-magnetically, not as a thermal heat flux. Therefore, the rate of heating is not limited and the uniformity of heat distribution is greatly improved. Electromagnetic radiation is converted to heat energy in the overall adhesive mass very quickly. Advantages would include lower energy consumption, very rapid cure time, bonding to...