The role of recycling in UV and thermal ageing of polypropylene block copolymer

Abstract

While polypropylene (PP) copolymers containing small amounts of polyethylene are greatly used in automotive, packaging, healthcare and pipe applications an understanding on how their properties are affected with recycling and subsequent ageing is limited. This study involves a characterization of a PP block copolymer that has been recycled three times and has been subjected to thermal and UV ageing. The materials have been characterized by Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TGA), Fourier Transform Infrared Analysis (FTIR) and micro-indentation. Qualitative differences between the non-recycled, recycled and aged materials are discovered and discussed. The results showed that with recycling only the crystallinity of the polyethylene (PE) fraction is affected. Thermal ageing affected the crystallinity of both PP and PE fractions while UV ageing affected only the crystallinity of the PP fraction. The connection between crystallinity, oxidation and hardness changes with recycling and ageing of the material is discussed.