Effect of electron beam radiation dose on the foam formation in pre-ceramic polymer
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2010
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Radiation Physics and Chemistry
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Methylsilicone resin as a polymer precursor for a SiOC ceramic material was cured and foamed by electron beam (EB) irradiation in air prior to the pyrolysis under an inert atmosphere. Methylsilicone foams were obtained without additional foaming agent when exposed to accelerated electrons with radiation doses up to 9MGy and dose rate of 2.8kGy/s. During irradiation the polymer was melted and simultaneously gaseous products were formed by the methyl group oxidation and by the polycondensation crosslinking reactions. The formed gases could not escape from the molten polymer and began to aggregate into bubbles. The effect of the radiation dose on the polymer foam molecular structure, the gel fraction and the ceramic yield was analyzed. The results indicate that the maximum amount of crosslinking in methylsilicone, when EB radiation is used, occurred between 1.0 and 2.0MGy radiation dose. Methylsilicone foams were pyrolysed in N2 atmosphere at temperatures of 1200 and 1500 1C, resulting in amorphous SiOC and partially crystalline ceramic foams, respectively. A porosity of 84% was achieved in the pyrolyzed foams, with cell size ranging from 30 to 300mm and density of about 0.31gcm3.
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ROCHA, ROSA M. da; MOURA, ESPERIDIANA A.B.; BRESSIANI, JOSE C.; BRESSIANI, ANA H.A. Effect of electron beam radiation dose on the foam formation in pre-ceramic polymer. Radiation Physics and Chemistry, v. 79, n. 3, p. 301-305, 2010. DOI: 10.1016/j.radphyschem.2009.08.020. Disponível em: http://repositorio.ipen.br/handle/123456789/4730. Acesso em: 19 Mar 2025.
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