Microstructural, mechanical, and thermal‐insulation properties of poly(methyl methacrylate)/silica aerogel bimodal cellular foams

Abstract

ABSTRACTNovel poly(methyl methacrylate) (PMMA)/silica aerogel bimodal cellular foams were prepared by melt mixing and a supercritical carbon dioxide foaming process. The effects of the silica aerogel content on the morphologies and thermal‐insulating and mechanical properties of the foams were investigated by scanning electron microscopy, mechanical tests, and heat‐transfer analysis. The experimental results show that compared to the pure PMMA foam, the PMMA/silica aerogel microcellular foams exhibited more uniform cell structures, decreased cell sizes, and increased cell densities (the densities of the foams were 0.38–0.45 g/cm3). In particular, a considerable number of original nanometric cells (ca. 50 nm) were evenly embedded in the cell walls and on the inner surfaces of the micrometric cells (<10 μm). A 62.7% decrease in the thermal conductivity (0.072 W m−1 K−1) in comparison to that of raw PMMA after 0.5 wt % silica aerogel was added was obtained. Mechanical analysis of the PMMA/silica aerogel foams with 5 and 2 wt % silica aerogel showed that the compressive and flexural strengths were distinctly improved by 92 and 52%, respectively, and the dynamic storage moduli increased. The enhanced performance showed that with the addition of silica aerogel into PMMA, one can obtain thermal‐insulation materials with a favorable mechanical strength. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44434.