Analysis of different polypropylene waste bales – evaluation of the source material for polypropylene recycling

Given the large amount of PP waste generated every year, mechanical recycling ofpost-consumed PP products is essential. However, the use of the thereof obtained recyclates inmore demanding applications is still restricted by their quality. To determine possible reasons forthe low and inconsistent quality of recyclates depending on the source material, the aim of thiswork was to investigate different PP waste bales (“pure”, mixed with other polymers), commerciallyavailable at different sorting centres. The amount of PP, the content of contaminations (polymericand foreign impurities) as well as the ratio of differently processed PP products was investigatedfour times a year. The analysis showed that up to 13% of PE is present in “pure” PP bales.Furthermore, a considerable amount of impurities was found in some bales. The sorting of theobtained PP samples according to their processing methods indicated seasonal fluctuation, whichmay be one reason for inconsistent recyclate quality. These results highlight the importance of proper sorting and treatment of PP waste bales before reprocessing.