Comparative Analysis of Virgin and Recycled Thermoplastic Polymer based on Thermochemical Characteristics

Plastics are among the most-used materials globally, with thousands of different grades and a wide range of applications. However, its end-of-life management is a common issue, despite most plastics produced today containing highly recyclable thermoplastics. The quality of recycled plastic material should be enhanced as it depends on several factors, such as cross-contamination, presence of additives, impurities and degradation rate. In this study, a comparative analysis of thermochemical characteristics of virgin and recycled commonly-used thermoplastic polymer, high-density polyethylene (HDPE), was performed to study the impact of recycling on the material properties. The proximate and ultimate analysis, identification of functional groups and thermal behaviour were performed to study the chemical changes in the recycled and virgin material. The results showed that recycled HDPE started to degrade at a lower temperature than virgin HDPE, with a lower degradation rate (92.7 wt.%) compared to virgin HDPE (99.6 wt.%) due to the presence of impurities and other factors. Calorific values of both samples were comparable, while the degree of crystallinity was 79.8 % for virgin HDPE and around 19 % lower for recycled HDPE samples. Significant differences between recycled and virgin material were also obtained in terms of melting and crystallisation enthalpies.