Ground tyre rubber as an enhancer for waste plastic biodegradation: microscopic, kinetic and thermodynamic insights

Abstract

Plastic waste is a major global issue because it takes a long time to decompose using current waste management techniques. This increasing concern about the breakdown of plastic waste has led to much interest in developing biopolymers. This study aims to investigate how adding ground tyre rubber (GTR) to high-density polyethylene (HDPE), low-density polyethylene (LDPE) and polyethylene terephthalate (PET) can accelerate the biodegradation process of these plastic materials. Composite materials made from a plastic or polymer-GTR matrix are created by blending 90% to 50% polymer with GTR using a twin-screw extruder known as thermal blending method. Polymer-GTR composite materials are tested in a laboratory using a CIS 24 PLUS incubator at temperatures of 37 °C, 30 °C and 20 °C. The experiments included a combination of air, moisture and other factors that could affect the rate of biodegradation. After being exposed to the environment for 30, 60 and 90 days, samples are collected and analysed. Adding GTR to plastic can make it more porous, making it easier for bacteria to break down the material. Moreover, GTR helps microbes to attach and provide carbon source for their metabolism within the polymer matrices. The thermal stability of waste plastic-GTR biocomposite materials are indicated by a decrease in activation energy (HDPE = 20.63 to 17.93 kJmol⁻¹, PET = 18.8 to 15.95 kJmol⁻¹ and LDPE = 25.71 to 23.39 kJmol⁻¹). Estimated values for enthalpy decrease from 23.19 to 5.15 kJmol⁻¹, 25.77 to 5.15 kJmol⁻¹ and 48.96 to 43.81 kJmol⁻¹, whereas the entropy increases from − 335.38 to − 310.02 Jmol⁻¹ K⁻¹, − 333.22 to − 306.03 Jmol⁻¹ K⁻¹ and − 378.53 to − 370.38 Jmol⁻¹ K⁻¹ for HDPE, PET and LDPE respectively. In summary, the study discovered that adding GTR through thermal blending can boost the biodegradation of plastic waste. This environmentally friendly approach could help reduce pollution caused by plastic waste.