One-Step Radical-Induced Synthesis of Graft Copolymers for Effective Compatibilization of Polyethylene and Polypropylene
Moritz Kränzlein, Shilin Cui, Jenny Hu, Anne M. LaPointe, Brett P. Fors, Geoffrey W. Coates
Abstract
The synthesis of copolymers from high-density polyethylene (HDPE) and isotactic polypropylene ( i PP) has gained increasing attention due to their ability to improve the recycling of incompatible mixed polyolefin waste feed streams. Herein, we report a new radical grafting process that yields HDPE- g - i PP copolymers from HDPE and i PP by using a commercially available peroxide. Tensile testing of brittle 70/30 HDPE/ i PP mixtures with these graft copolymers added showed promising compatibilization, improving the elongation at break of the blends from 20% up to 1080%. Detailed kinetic studies coupled with thermal and rheological characterization revealed optimized conditions for HDPE and i PP macroradical coupling and a deeper understanding of the grafting reaction. This optimization yielded HDPE- g - i PP copolymers that compatibilize HDPE and i PP blends at loadings as low as 2.5 wt %. The versatility of this macroradical grafting reaction was demonstrated by preparing an effective compatibilizer from untreated postconsumer waste plastics.