Recycling of WasteLDPE Foam into High-PerformanceIn Situ Fibrillated LDPE/PS Composites via Fused Filament Fabrication

Foam materials are widely used in packaging, construction, and aerospace, but their poor degradability raises serious environmental concerns. This work proposes an upcycling strategy that combines fused filament fabrication (FFF) with in situ fibrillation to convert waste low-density polyethylene (LDPE) foam to high-performance microfibrillar composites. A mini corotating twin-screw extruder was developed to melt-blend waste LDPE foam with polystyrene and directly produce printable filaments while removing entrapped gas from the porous foam. During subsequent FFF printing, shear and extensional fields promoted the formation of oriented polystyrene microfibrils and induced oriented crystallization in the LDPE matrix. The foam-derived printed samples achieved a tensile strength of 23.01 MPa, comparable to that of virgin-material counterparts. This study provides a practical route for the high-value recycling of waste LDPE foam.