Sustainable Fabrication of Anisotropic Conductive Composites from Discarded Biaxially Oriented Polypropylene Films

Abstract

Traditional mechanical recycling often compromises the structural and functional integrity of plastic materials, limiting high-value reuse. Here, a sustainable upcycling strategy is presented that transforms discarded biaxially-oriented polypropylene (BOPP) films into high-performance anisotropic conductive polymer composites through a low-temperature alternating lamination approach. By harnessing the intrinsic molecular orientation of BOPP and the chemical compatibility with polypropylene random copolymer (PPR), alternating BOPP insulating layer and PPR conductive layers containing conductive fillers are thermally welded at an optimized temperature of 160 °C, enabling strong interfacial bonding while preserving the orientation-induced mechanical advantages. This innovative processing method yields a remarkable 162% improvement in tensile strength and an extraordinary 1193% enhancement in toughness compared to conventional recycled technology. More importantly, the resulting composites exhibit outstanding electrical anisotropy, characterized by an in-plane conductivity of 11.4 S m⁻¹ while maintaining excellent through-thickness insulation. Such a unique integration of mechanical robustness and directional conductivity enables promising applications in next-generation intelligent electronics. This work not only establishes a scalable and eco-conscious route for upcycling industrial polymer waste into multifunctional, high-performance materials but also provides new design principles for the development of next-generation electronics.