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 0.38-0.45 g/cm 3 ). 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 lm). A 62.7% decrease in the thermal conductivity (0.072 W m 21 K 21 ) 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. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44434.

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Abstract-The superhydrophobic silica coating has a great performance of self-cleaning which can be applied in the field of energy saving, anti-icing, drag reduction, etc. In this paper, Trimethyltrimethoxysilane (MTMS) /Trimethylchlorosilan (TMCS) superhydrophobic silica coating with two-layer structure was dip-coated. Atomic force microscope (AFM) images show that the surface morphology of MTMS/TMCS silica coating was in micro and nano level, and Sa value was 231nm, which could achieve good superhydrophobic performance. MTMS/TMCS silica coating has better superhydrophobic performance than MTMS silica coating. The largest contact angle (CA) of MTMS/TMCS silica coating could reach 155.2°, the sliding angle was less than 10°. The MTMS/TMCS silica coating also has good performance of transmittance in the range of visible light and self-cleaning, the transmittance rate could reach more than 95%. All good performances of the MTMS/TMCS silica coating are from its micro and nano surface structure. Modification of TMCS solution would generate a more stable functional group.