Advancements in thermally insulating cyclic olefin copolymer cellular foams via supercritical fluid foaming: a review

Abstract

Thermally insulative polymer foams are critical for thermal management applications due to their ability to disrupt heat transfer pathways through their unique cellular structures. These materials are widely utilized in construction, aerospace, and renewable energy sectors. However, conventional polyolefin foams face limitations in commercial adoption due to their insufficient melt strength, which leads to large, non-uniform structures and low cell density. To address these challenges, we propose a promising strategy for preparing thermally insulative cyclic olefin copolymer (COC) foams using supercritical fluid foaming technology. As a result, these foams exhibit exceptional thermal insulation properties, attributed to their low solid-phase conductivity, high thermal radiation shielding capability, and the heterogeneous nucleation effect induced by phase separation from cyclic olefin segments. Consequently, recent advancements in COC foams have elucidated the underlying heat transfer mechanisms, enabling the fabrication of foams with thermal conductivity as low as 25.8 mW m⁻¹ K⁻¹, approaching that of air (26 mW m⁻¹ K⁻¹). This review provides a comprehensive analysis of the supercritical physical foaming mechanism, with an emphasis on CO₂ dissolution and diffusion dynamics, and explores the inherent relationships among processing parameters, cellular morphology, and thermal insulation performance. The advancement of COC foams represents a significant breakthrough offering a promising solution to alleviate global energy crises and climate change through enhancing thermal insulation efficiency.