Microcellular polymeric foams based on 1-vinyl-2-pyrrolidone and butyl-acrylate with tuned thermal conductivity

Microcellular polymers have been produced by ScCO2 foaming, based on 1-vinyl-2-pyrrolidone (VP) and butyl-acrylate (BA). Three different copolymers were prepared, varying the compositions of VP and BA, following a simple radical polymerization process using an UV initiator. The samples a good foaming behavior and also excellent flexibility and handle ability, with expansion ratios between 1.53 and 1.72, and cell sizes in the microcellular range (below 5 mu m). However, it was observed that the gas distribution and, consequently, the cellular structure inside the polymer foams was highly dependent on the VP and BA proportions, leading to very different thermal conductivity values, even for similar volume gas fraction values. These results were related to the copolymer nanostructuration, which seems to have an influence in the final pore structure, thus opening the possibility of designing microcellular foams with similar macroscopic characteristics but different thermal conductivity values. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45872.