Advanced fabrication of ultra-high molecular weight polyethylene/ graphite nanoplates foam for enhanced oil–water separation and thermal insulation via a novel omnidirectional gas escape barrier mechanism

Frequent oil spill incidents and energy shortages severely hinder the sustainable development of society. Here, we fabricated oil adsorbing and thermally insulating ultra-high molecular weight polyethylene (UHMWPE)/graphite nanoplates (GNPs) foams using an eco-friendly supercritical carbon dioxide (scCO₂) microcellular foaming technology. A novel omnidirectional gas escape barrier mechanism was proposed, wherein GNPs inhibited gas escape while promoting gas retention, pivotal for cell growth during rapid gas release. GNPs could enhance crystallinity and melt viscosity of UHMWPE. Moreover, GNPs significantly improved the foaming behavior of UHMWPE, leading to the formation of open cells, a notable increase in the expansion ratio from 9.7 up to 35.9, and an extension of the effective foaming window by up to 17.1°C. The open-cell foam, incorporating 5 wt% GNPs, exhibited outstanding rapid oil–water separation, achieving an impressive adsorption capacity of 50.6 g/g and an adsorption rate constant of 3.4 × 10^-3 g/g·s⁻¹ for carbon tetrachloride. Additionally, the thermal conductivity of UHMWPE/GNPs foam was as low as 36.9 mW·m⁻¹·K⁻¹, highlighting its superior thermal insulation. This research offers valuable theoretical and practical insights for developing oil adsorbing and thermally insulating materials, contributing to environmental protection and energy conservation.