Tunable Polyethylene-polypropylene Blends via Compatibilization through Nitrene Insertion-Enabled Dynamic Covalent Crosslinking

Abstract

Polymer blends offer a cost-effective way to create new materials with enhanced properties. However, blending different polymers often results in phase separation with weak interfacial adhesion, leading to inferior mechanical properties. Given that high-density polyethylene (HDPE) and isotactic polypropylene (iPP) are the largest volume polymers, there is significant interest in developing blends of these materials. Applying a singlet nitrene-facilitated dynamic crosslinking method recently developed in our lab, in this study we prepared a series of HDPE/iPP blends across a range of compositions with enhanced compatibility and tunable thermomechanical properties. By incorporating a small amount of a dynamic crosslinker featuring a siloxane core and bis-aromatic sulfonyl azides (bis-ASA) into varying compositions of HDPE and iPP, we achieve significant improvements in the compatibility. AFM and SEM imaging analyses reveal that the compatibilized blends exhibit superior homogeneity compared to control blends. Additionally, these blends show significant improvements in elongation at break, toughness, and oxidative stability. The dynamic crosslinking further enhances the blends’ creep resistance while retains reprocessability, paving the way for the development of tailorable polymer blends for various applications.