(348a) Improving the Mechanical Recycling of Polyolefins Using Intrinsically Dynamic Polymers

Polyolefins, namely poly(ethylene) and poly(propylene), make up over half of the plastics that are used in most consumer products. Yet, recycling these materials remains challenging. Mechanical recycling entails extruding the polymers at high temperatures and shear rates, resulting in forces sufficiently high to cleave chains, generate radicals that undergo undesired chemical reactions – ultimately resulting in a recycled polymer with inferior mechanical properties. Here, we employ low-cost dynamic polymers containing disulfide bonds to improve the mechanical recycling of polyolefins (HDPE, LLDPE, PP). Using a combination of rheology, DSC, and tensile testing, we show that the presence of these dynamic polymers during extrusion (i) reduces chain scission, (ii) promotes reactive grafting onto broken chain ends, and (iii) allows for the ‘healing’ of grafted chain ends upon thermal treatment. As such, this work outlines a robust strategy to enable mechanical recycling of polyolefins without causing performance degradation.