Study On Preparation And Properties Of Hollow Silica By Using Polymeric Micropheres As Template

P(St-MAA) copolymer microspheres were synthesized by soap-free emulsion polymerization using styrene (St) and methylacrylic acid (MAA) as monomers in this paper. The P(St-MAA)/SiO2 composite microspheres were prepared by using coupling agentγ- aminopropyltrimethoxysilane (APS) and tetraethyl orthosilicate (TEOS) as costructure- directing agent and silicon sources in the presence of the P(St-MAA) microspheres as template, hollow silica microspheres were obtained by removing the P(St-MAA) templates based on calcination. The diameter of the copolymer microspheres can be adjusted by the content of styrene, the size of hollow silica and the pore structure of shell can be changed simultaneously. The properties of the copolymer microspheres, composite microphere and hollow silica, such as structures, diameter and diameter distribution, thermal decomposition temperature, morphologies and pore structure were characterized by Fourier transformation infrared (FTIR), laser light scattering (LLS), thermogravimetric analyzer (TGA), transmission electron microscopy (TEM) and specific surface area and pore size analyzer separately. The results showed that the diameter of hollow silica microspheres can be controlled in 140-630nm by adjusted the size of the P(St-MAA) microspheres, and the shell of hollow silica is rich of pores.P(St-EA-MAA) copolymer microspheres were synthesized by seed emulsion polymerization of styrene (St), ethylacrylate ester (EA) with methacrylic acid (MAA) using sodium dodecyl benzene sulfonate (SDBS) as emulsifier, ammonium persulfate as initiator. The copolymer microspheres can be modified by changing the amount of MAA, heat treatment under different pH values and temperatures, adjusting the pH value and adding surfactant cetyltrimethyl ammonium bromide (CTAB). The properties of the copolymer microspheres, composite microspheres and hollow silica, such as structures, -COOH content, morphologies, thermal decomposition temperature and pore structure were characterized by FTIR, Zeta potential analyzer, TEM, TGA and specific surface area and pore size analyzer separately. The results showed that the -COOH content on the surface of copolymer microspheres can be adjusted by changing the amount of MAA, than the pore size of shell can be changed from microporous to mesoporous and the specific surface area of hollow silica microsphere can be significantly increased. The shape of P(St-EA-MAA) microspheres can be changed by the heat treatment under different pH values and temperatures, then the morphology of hollow silica can be changed also. In the process of silica coating, hollow silica shell thickness can be adjusted by the pH value, and the introduction of CTAB can significantly increase the shell thickness of hollow microspheres which makes the structure more stability, and introduced mesoporous into the shell, so the specific surface area was increased.Polyurethane aqueous dispersion coating was prepared as follows: the hollow silica which size, shell thickness is moderate, structural is stability, dispersion is good were blending with polyurethane. The effect of hollow silica microsphere dope content and the coating composition on coating thermal insulating was discussed. The results showed that coatings with good insulation properties can be obtained when the composition of coating is suitable and the hollow silica microspheres doped is moderate, which also have a potential application in the insulating coatings field.