Chiang Mai Journal of Science

Polycarbonate (PC)/multi-walled carbon nanotube (MWCNT) based electrostatic dissipative (ESD) composite was reprocessed by repeated injection molding to investigate if this material can be successfully recycled. The varied parameter was the number of cycles (1-6) at the processing temperature of 235-280^oC. The effects of reprocessing on the structure, rheological, electrical and mechanical properties were studied. The ESD properties such as electrical resistance, tribo-charge voltage, and decay time were in the static dissipative range for ESD application after reprocessing. The decreases in heat deflection temperature were insignificant. The tensile strength was slightly increased and almost no change was observed at the higher number of injection molding cycles (4-6 cycles). In contrast, the elongation at break and impact strength were decreased and began to slightly change at injection molding cycles of 4-6. The changes in mechanical properties partly resulted from the larger exposure to the shear stresses in the melt as the number of injection molding cycles increased, leading to better dispersion level of MWCNTs in the polymer matrix. There was no observable chemical change as well as material degradation after reprocessing for 1-6 cycles. However, the polymer chain scission was observed since the melt flow index increased and the storage modulus, loss modulus, and complex viscosity decreased when the number of injection molding cycles increased. Overall, it was concluded that the PC/MWCNT composite had high possibility for reprocessing because there were only minor material property changes after six injection molding cycles, except for its mechanical and rheological properties.