Abstract: Polyethylene terephthalate (PET) accounts for 10.2% of the plastic produced worldwide and is nearly exclusively used for single use bottle packaging. Over the past few decades, recycling PET has become a major initiative around the world as result of increased pollution levels and climate change. Improvements in the reprocessing of recycled polyethylene terephthalate (rPET) for product applications will in turn diminish the demand for virgin PET and ultimately have a favorable impact on our environment. However, it has been challenging to reprocess the rPET because of its thermal degradation at elevated temperatures. The focus of this study is to address this issue and understand the effect that reprocessing has on the structure and the mechanical properties of rPET with different reprocessing conditions. The goal of this project is to develop an innovative fast processing method for compression molding rPET. Samples will be prepared from the molded rPET for thermal and mechanical testing, including differential scanning calorimetry (DSC), flexural, and impact testing.
Abstract: Although recycled plastics provide a low-cost and environmentally friendly alternative for a wide range of applications, there are several factors that significantly limit its desirability. Most notably among these is thermal degradation of polymers during their recycling process, which may compromise their mechanical performance and cause unpleasant odor. In this work, a headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) method was employed to help understand thermal degradation of low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) under a typical processing temperature (200°C) for plastic recycling. Volatile compounds from the three plastics before and after heating were monitored. The results show that each plastic has a unique volatile compound profile. They had notably differences in thermal stability and released different degradation products. LDPE had t he lowest thermal stability among the three materials studied in this work and gave out a lot of volatile compounds after 20 min of heating. Accelerated degradation of PP was detected after 30-min heating, while HDPE was still relatively stable after heated for 40 min. The volatile compound analysis carried out in this work could be used as an effective way to identify the type of plastics and evaluate their extent of thermal degradation. The results of this research may aid the plastic recycling industry in improving product quality.