Mechanical–Chemical Recycling of Low-Density Polyethylene Waste with Polypropylene

Abstract

The global increasing consumption of thermoplastic such as polyethylene and polypropylene has caused the generation of enormous amount of polymeric waste that are a challenge for solid waste management and represents a severe polluting agent, mainly for the marine life. Mechanical recycling is an important alternative to decrease the volume of polymeric waste. However, the mixture of different thermoplastic and other materials on the same object depreciates the properties of the recycled polymer due to the formation of immiscible blends. The aim of this study has been to evaluate the recycling of the post-industrial low-density polyethylene waste (LDPE waste) in presence of polypropylene using thermomechanical processing and thermochemical treatment of the material. For it, blends of LDPE waste and virgin polypropylene (PP) containing until 30 wt% of PP has been prepared with incorporation of zeolite ZSM-5 and Ziegler–Natta catalysts and submitted to the thermal treatment under controlled conditions of temperature and nitrogen flow. The results show the action of zeolite catalyst as modifier of the polymeric structure during step of the thermomechanical processing of the material. The catalysts have caused considerable changes on properties of the LDPE/PP blends, depending of the experimental conditions. The treatment of polymeric waste in presence of catalyst presents potential for recycling of polymeric materials with high contamination by other polymers and can generate recycled materials with improved properties.