Designing Resource-Efficient Polypropylene-Based Elastomers via Moderately Selective Catalyst for Toughening and Compatibilization

Polypropylene-based elastomers (PP-Es) offer superior mechanical properties, heat resistance, and compatibility with PP matrices compared to polyethylene-based elastomers (PE-Es). This study developed high-performance PP-Es with low α-olefin consumption through catalyst selection and chain structure design. Employing a moderately stereo- and regioselective bis(phenolate-ether) hafnium catalyst, as opposed to a highly selective metallocene catalyst, afforded PP-Es with higher molecular weight, enhanced mechanical properties, and similar crystallinity at a reduced comonomer requirement. When used as tougheners for brittle iPP, PP-Es significantly enhance tensile performance, markedly increasing elongation at break, far exceeding commercial PE-E systems (e.g., Engage 7447 and 8842), while maintaining high strength and transparency. Added to incompatible HDPE/iPP blends (30/70 and 50/50), PP-Es effectively compatibilized the phases, significantly increasing elongation at break while largely retaining strength. Furthermore, the compatibilization behaviors of PP-Es and PE-Es were compared across different HDPE/iPP ratios, together with their tensile and impact properties, establishing a clear link between compatibilizer chain structure, phase composition, and performance enhancement.