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

Novel 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 0.38-0.45g/cm(3)). In particular, a considerable number of original nanometric cells (ca. 50nm) were evenly embedded in the cell walls and on the inner surfaces of the micrometric cells (<10m). 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. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44434.