A sustainable recycling process for end-of-life vehicle plastics: A case study on waste bumpers

End-of-life vehicle (ELV) recycling has considerable potential value and a wide range of applications. Plastics form an increasing percentage of the total weight of automobiles as their lightweight. Recycling plastics from automobiles is important for achieving the overall recycling goal from a sustainability standpoint. In this study, the whole recycling process of automotive plastic parts was explored, using waste bumpers as an example, in which paint removal and recycled polypropylene (RPP) modification were the important links. First, LS-Dyna was used to run simulations to determine the best paint removal process parameters for surface coating treatment, and experiments were then conducted to confirm the paint removal effect. Second, component, morphological, and Gel Permeation Chromatography (GPC) analyses were conducted. As per the results, the degradation was primarily caused by surface oxidation of the ELV bumper, and the molecular weight of RPP was lower than that of new PP. Finally, the thermal and mechanical properties of RPP, modified RPP, and the new bumper were compared. The addition of nano-montmorillonite(nano-MMT), virgin PP, and a compatibilizer could improve the thermal and mechanical properties of RPP while satisfying the application requirements of the new bumper. This process provides a valuable idea for the sustainable recycling of used ELV plastics.

Influence of the grade on the variability of the mechanical properties of polypropylene waste

The prior properties of recycled polypropylene depend on the origin of waste deposits and its chemical constituents. To obtain specific properties with a predefine melt flow index of polypropylene, the suppliers of polymer introduce additives and fillers. However, the addition of additives and/or fillers can modify strongly the mechanical behaviour of recycled polypropylene. To understand the impact of the additives and fillers on the quasi-static mechanical behaviour, we consider, in this study, three different recycled polypropylenes with three different melt flow index obtained from different waste deposits. The chemical constituents of the additives and filler contents of the recycled polypropylenes are determined through thermo-physico-chemical analysis. Tensile and bending tests performed at different strain rates allow identifying the mechanical properties such as the elastic modulus, the yield stress, the maximum stress, and the failure mechanisms. The results obtained are compared with non-recycled polypropylene and with few researches to explain the combined effect of additives. Finally, a post-mortem analysis of the samples was carried out to make the link between the obtained mechanical properties and microstructure.