Enhancing the mechanical performance of polyolefin blends through immersion annealing

Conventional mechanical recycling methods for polyolefins at high temperature high shear environment can trigger unwanted chain scission and crosslinking, breaking down the polymer into lower-molecular-weight fragments with fewer tie chains connecting crystalline lamellae. As a result, the recycled materials show noticeably weaker mechanical properties, posing a major challenge for reusing post-consumer polyolefins. To address these issues, previous approaches have relied on chemical crosslinking or the addition of compatibilizers. However, these methods tend to be time-intensive, expensive at large scale, and add further complexity to recycling streams. In this presentation, we will discuss an immersion annealing method that swells polyolefin blends containing high and low MW fractions, promoting their co-crystallization, which leads to significantly improved mechanical performance of the blended materials. Specifically, our results show an over 6-fold increase in extensibility of polypropylene (PP) blends, effectively enabling their reuse and extended lifetime. This work presents an innovative and straightforward method to address the recycling challenges of low MW PP without the need for additives,