Sustainable Transformation of Crosslinked NBR/PVC Waste into High-Performance Toughening Agents for Rigid PVC: Mechanochemical Synergy and Interfacial Engineering

This study presents a sustainable mechanochemical strategy to reuse waste NBR/PVC scraps as effective toughening agents for rigid PVC, addressing both waste management and material performance enhancement. Solid-state shear milling (S³ M) was employed to pulverize and devulcanize waste NBR/PVC particles (WNPP) at room temperature, breaking sulfur crosslinks and generating reactive powder. The activated WNPP was blended with rigid PVC, chlorinated polyethylene (CPE), and acrylonitrile-butadiene-styrene (ABS) to develop synergistic toughening composites. The optimized formulation (30 phr WNPP, 15 phr CPE, 10 phr ABS) achieved a remarkable elongation at break of 151%, a sevenfold increase compared to unmodified rigid PVC (20.5%), while maintaining a tensile strength of 28.8 MPa. Furthermore, co-milling PVC particles with WNPP for 10 cycles under S³ M significantly improved interfacial bonding, reducing WNPP particle size to 2–3 μm and enhancing dispersion uniformity. Despite a moderate decline in thermal stability (initial degradation temperature reduced by 15 °C), the composites exhibited superior energy dissipation, with fracture energy reaching 33.5 MJ/m³, and a widened damping temperature range (22.5 °C) due to heterogeneous phase interactions. Dynamic mechanical analysis and spectroscopic studies revealed that the synergistic effect of CPE and ABS facilitated a dual-network toughening mechanism, combining CPE’s elastomeric networks with ABS/WNPP hybrid particles. This work successfully provided a green pathway to valorize crosslinked NBR/PVC waste composites, offering mature operability for process scale-up.