The impact of multiple production cycles/the introduction of recycled material on the properties of Expanded Polypropylene

Abstract

The chemical company Kaneka Belgium N.V. provides polypropylene-based foam particles, used to produce moulded parts which are applied in different sectors. Today, the company’s customers are striving for sustainability following the European guidelines for 2030, which directly involve recycling of end products. In this context, it is compulsory for KB to start re-introducing a fraction of reprocessed material into their process. In order to do so, it is necessary to assess its effect on the properties and deterioration of the end product. First, this work focusses on the impact of going through multiple extrusion cycles on virgin material. In addition, the influence of adding stabilizers to the recipe at different reprocessing steps to prevent further deterioration is evaluated. Thirdly, the impact of implementing a fraction of external recycled particles into the recipe is elaborated. Different characterization techniques were performed: rheology, DSC and mechanical techniques. Generally, it can be concluded that the reprocessed samples remain stable with favourable properties, in contrast to the recycled samples who do not guarantee this stability. The rheological results demonstrated a decrease in viscosity, caused by β-chain scission. Adding the recycling stabilizer minimized this decrease. Secondly, the DSC curves indicated a small rise in crystallinity. Finally, the mechanical tests indicated a decrease in tensile strength, compression strength and elongation at break for both the recycled and reprocessed blends.