Development of an Engineering Material with Increased Impact Strength and Heat Resistance from Recycled PET

Abstract

The goal of the research was the concurrent enhancement of the impact strength and the heat resistance of recycled poly(ethylene terephthalate) (RPET). The morphology and the dynamic mechanical properties were examined at 0-5-10-15% ethylene-butyl-acrylate-glycidyl methacrylate (PTW) elastomer contents. The blends were crystallized for different time periods (0-20-40-60-180 s) at 150 °C and the morphology change during crystallization and its effect on impact resistance, stiffness, and thermal resistance were examined taking the three-phase model: crystalline fraction/mobile amorphous fraction/rigid amorphous fraction (CRF/MAF/RAF) into consideration. Based on DSC analyses it is proposed that before crystallization, the polymer chains covalently linked to PTW molecules contribute to the rigid amorphous phase (RAF). During thermal annealing, the relaxation of segments (which increases mobility) and ordering into crystals (which decreases mobility) have a complex effect and their resultant determines the ratio of the three phases and thereby also the macroscopic properties of the blends. After annealing the 15% PTW containing RPET blend at 150 °C for 180 s, a fivefold increase in notched impact resistance and a 50-fold increase in thermal resistance (expressed as E90’ value) were achieved compared to the neat RPET reference.