Development and Modeling of High Temperature Polymeric Heater

Polymers are generally known for their excellent insulative properties. The addition of carbonaceous fillers such as carbon black and graphite within a polymer matrix can impart electrical and thermal properties making them good conductors. The resulting composites can be used in applications requiring and/or ranging from electromagnetic and radio frequency interference (EMI/RFI) shielding, electrostatic discharge (ESD) and heaters/heating elements to which metals have been the materials of choice. The advantages of using such composites include cost reduction, part consolidation, chemical resistance, lighter weight, and ability to easily design into complex three dimensional shapes via injection molding. For this work, various conductive thermoplastic composites were investigated as a metal (Ni-chrome heating element) alternative and/or substitute for use as heating elements through mechanisms of Joule heating. First, composites and test specimen were prepared via melt extrusion and injection molding respectively. Thereafter, electrical thermal and mechanical properties were characterized using both ASTM and non ASTM techniques. Results were then modeled using statistical software to determine correlations between formulations to responses and whether these results are desired and or meaningful. Results from experiments indicated significant advantage in using semi-crystalline polymers as the base carrier due to the superior electrical properties at equivalent filler loading compared to amorphous based composites, a criterion in joule heating. It was also determined that heating rate and maximum/plateau temperature was mainly a function of specimen resistance (formulation parameter) and voltage setting. Finally, the model obtained for plateau temperature was found to be significant. This indicated it is possible to develop polymeric type heaters with operating temperatures above 100ðC (current technology) and as high as 200ðC. Moreover, these composites would have self regulating properties other than