Lattice-reinforced polyurethane foam with stable thermal and mechanical performance under repeated vacuum cycling.

Developing thermally and mechanically robust insulation capable of maintaining performance under repeated vacuum cycling remains a critical challenge for aircraft, aerospace and cryogenic systems, where both thermal efficiency and structural integrity are required. This study focuses on overcoming the trade-off between low thermal conductivity and mechanical stability in polymer-based insulating materials that are prone to structural degradation under pressure fluctuations. Herein, we present a Kelvin lattice-reinforced foam that preserves intrinsic insulation properties of closed-cell polyurethane (PU). The lattice framework suppresses structural collapse during vacuum cycling, while the PU foam region preserves low thermal conductivity. As a result, the hybrid structure exhibits a peak stress enhancement of up to 25 times compared to pristine PU foam. Furthermore, after 50 vacuum cycles, the hybrid structure retains thermal conductivity to within 10%, and peak-to-plateau ratio by less than 20% from their initial values, demonstrating excellent retention of both thermal and mechanical properties. These results establish the PU-Kelvin hybrid as a viable insulation architecture for environments subject to repeated pressure fluctuations, including aircraft cabins, aerospace structures, and cryogenic applications.