Development of new vacuum insulation core panels using micronized nanocellular poly(methyl-methacrylate) (PMMA)

Thanks to their unique structure, nanocellular polymers can be micronized to generate a powdered material formed by micrometric particles with nanocells inside them. Due to the discontinuous structure, micronized nanocellular polymers present a significant reduction of thermal conductivity in comparison with their bulk counterparts. In this work, we produce and analyze insulating panels by compacting micronized microcellular and nanocellular poly(methyl-methacrylate) (PMMA). The compacted materials are self-standing and characterized by densities from 160 to 360 kg/m3, cell sizes between 400-4000 nm, and thermal conductivities between 37 and 51 mW/(m center dot K) at ambient pressure. When the panels are subjected to vacuum conditions, very low thermal conductivities are achieved, ranging 11-18 mW/(m center dot K), identifying these materials as promising candidates for vacuum insulation. The mechanisms allowing this significant reduction in the thermal conductivity are discussed.