Pyrolysis of waste high density polyethylene (HDPE) and low density polyethylene (LDPE) plastics and production of epoxy composites with their pyrolysis chars

High density polyethylene (HDPE) and low density polyethylene (LDPE) plastic wastes were pyrolysed in the temperature range of 300-700 °C, liquid, gas and solid fractions (char) were quantified and pyrolysis char was used as additive in production of epoxy composite. Effects of pyrolysis temperature on products fractions, char quality and composite quality were investigated. In the composite composition, char was included as 10-50 wt% of epoxy to determine the effects of additive dosage on the composite quality. The char additives and produced composites were characterized by FTIR and SEM. Mechanical properties, namely tensile strength, surface hardness and electrical properties were determined for the epoxy composite materials. Epoxy composite materials produced with HDPE pyrolysis char additive obtained at 300 °C (ER300) showed the most ideal behavior in terms of elongation at break and tensile strength. With increasing pyrolysis temperature and char doses elongation at break and tensile strength of composites generally decreased. While tensile strength showed an increase by 32% at 10% wt% dose for composite (ER300) with HDPE char obtained at 300 °C, the increases were 21%, 14%, 14% and 13% for ER400-ER700 composites prepared with 10 wt% HDPE chars obtained at 400-700 °C pyrolysis temperatures, respectively. Despite this, LDPE chars a small decreased the tensile strength of epoxy. The hardness of neat epoxy was improved from 79.8 Shore D up to 86.3 and 87 Shore D by the LDPE and HDPE char additives, respectively. The study offers a new recovery approach for HDPE and LDPE type plastic wastes.