Preparation Of Mesoporous Silica-Based Embedded Nanocomposite Foaming Agent And Its Foaming Properties

Microcellular foams possess homogeneous distribution and particularly small cells. Due to their ultra-small cell size and high cell density, microcellular foams not only have light weight but also have lower dielectric constant, higher mechanical strength, better thermal stability, more excellent thermal insulation and acoustic properties than conventional polymer foams. The supercritical fluid precipitation method is the most popular one to produce microcellular foams which experimental conditions are very rigor. In addition supercritical fluids (for example supercritical CO2, etc.) have low solubility and high diffusivity in the polymer matrix, which makes controlling cell morphology difficultly. This paper mirrored the idea of nano-sized mesoporous composites and proposed a new mechanism to obtain microcellular foams. OBSH and mesoprous silica was composited through impregnation method. This self-made nanocomposite foaming agents had good dispersion and favourable compatibility with the polymer matrix. It realiased the super-refining treatment of OBSH. The novol nanocomposite foaming agent was applied to produce microcellular epoxy foams.(1) Mesoporous silica microspheres were prepared by TEOS as silica source, and hexadecyl amine as surfactant. Different TEOS dropping methods? synthesis temperature and calcined treatment was optimized.The particle size was about 800 nm. The pore size of mesoporous silica was 2.1 nm. The salts and complex salts with the same molarity (0.5mol/L) were used to enlarge thecell diameter of MS, including NaCl, KNO3, LiCl and their complex salts. The average pore diameter was adjusted to 35.8 nm by the complex salt which improved the pore loading capacity of the guest molecules.(2) The mesoporous silica was modified by three silane coupling agent (KH550, KH560, KH570). The modification results were confirmed and compared by characterization with FTIR, SEM and 29Si CP/MAS NMR. The experimental data showed that after modified by three kinds of silane coupling agents, the degree of aggregation were all significantly improved, wherein KH550 is the best modifier.25? and 2 mL were the favorable reaction condition.(3) 4,4'-oxybis benzene sulfonamide (OBSH) and mesoporous silica was composited trough impregnation method to produce a novel nanocomposite foaming agent.29Si CP/MAS NMR,13C CP/MAS NMR and TG-DTA were used to characterize the materials. All the evidence proved that OBSH had been successfully assembled into the pores of mesoporous silica. When the impregnation solution concentration is 0.4mol/l, the loading amount of OBSH reached maximum.(4) The OBSH-KH550-SiO2 nanocomposite foaming agent was applied to produce microcellular epoxy foams. Washing methods, dosages of self-made nanocomposite foaming agent, reaction temperature and adding amount of curing agent were discussed as four single factors. Based on single factor investigation, the optimum condition was obtained by L9 (34) orthogonal experiment. The microcellular epoxy foams with the average cell size as small as 34.4?m and the cell density up to 1.3×106 cells/cm3 were achieved. OBSH Detailed structure and morphology characterizations suggested that the foaming agent exhibited a better foaming performance than pure OBSH and the direct mixtures of OBSH and nano fillers.