Abstract
Due to the ever-increasing consumption of poly (ethylene terephthalate) (PET) for the industries of packaging and electronics, the waste non-degradable PET has brought serious ecological pollution. However, the current recovery rate of waste PET is still limited, and the mechanical and heat-resistant properties are too poor to meet the requirements of practical applications. The recycling of waste PET is of practical significance to material/energy saving and environmental protection, contributing to the sustainable development of economy and society. In this work, an innovative method was proposed to fabricate strong and heat-resistant materials by using waste PET bottle flakes via carbon dioxide (CO2) treatment at ambient temperature. The results show that the crystallinity of the PET samples treated by CO2 at 800 psi is increased by 30.6%, the tensile strength and Young's modulus are increased by 21.9% and 20.6%, respectively, compared with untreated samples. Moreover, the dynamic mechanical analysis indicates that the heat-resistant performance of CO2-treated samples is significantly improved, whose storage modulus increased 33.5% and glass transition temperature increased 17.7 °C. Furthermore, aiming to investigate how the CO2-treatment improved the mechanical performance of the waste PET, the sorption-desorption experiments were conducted to examine the sorption kinetics of CO2 in the matrix, combined with the Avrami model employed to analyze the crystallization kinetics of PET under high-pressure CO2. It demonstrates that the enhancement of the tensile strength is ascribed to the transition of crystals from two-dimensional structures to three-dimensional structures with an increment in the CO2 pressure.
Published Version
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