Controlled hot pressing for functional upcycling of waste polyethylene materials.

Plastic waste represents an escalating environmental challenge and necessitates scalable processing strategies consistent with the United Nations' Sustainable Development Goal 12 on responsible consumption and production. This work examines controlled hot pressing of polyethylene-based waste as a physical upcycling route for producing functional laminate sheets. Low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polyethylene-coated polypropylene (PP/PE composite) were investigated, with processing temperature, pressure, and dwell time systematically analysed using an orthogonal experimental design. LDPE exhibited the most favourable forming behaviour, achieving continuous sheet formation at 120-130 °C under a nominal pressure of approximately 0.59 MPa with limited thickness variation. Relative to unprocessed films, hot-pressed materials displayed reduced surface friction and increased water contact angles, indicating decreased surface wettability under the applied conditions. Microscopic observations revealed modified surface morphology after processing, while elemental mapping showed no pronounced changes in macroscopic elemental distribution. HDPE achieved comparable consolidation, whereas PP/PE composites did not form continuous laminates. The results indicate that controlled hot pressing provides a low-energy and reproducible pathway for converting post-consumer polyethylene films into functional materials for circular applications.