Use of recycled polypropylene/poly(ethylene terephthalate) blends to manufacture water pipes: An industrial scale study

Abstract

Poly(ethylene terephthalate) (PET) and polypropylene (PP) are two major polymeric materials that constitute many single-use plastic products. A common strategy to reduce polymeric waste is via mechanical recycling, a low cost and efficient process. However, from an industrial point of view, the reliability of this process is more easily achieved by a downgrade in the final properties of these materials, which limits the usage of recycled-based materials to less demanding applications. Furthermore, due to the intrinsic heterogeneity of the PP or PET waste, the use of these materials in industrial processing, tuned and developed for virgin neat materials, poses serious integrity problems. This aspect is particularly relevant in the case of plastics originating from the food packaging industry. This work explores the possibility of incorporating either PP or PET originated from plastic solid waste (PSW), in pipe manufacturing, with competitive mechanical properties compared to those prepared from virgin materials. To achieve this industrial solution, a process was developed using PP/PET 70/30 wt% formulations and the impact of replacing the virgin material by the different PSW in the microstructure, thermal and mechanical properties of the final material was analyzed. The impact of using a compatibilizer able to counteract the natural immiscibility between the PP and PET domains was also assessed. The developed formulation with recycled PET is a good example of the applicability of work developed at a laboratory scale into industrial-scale production.