Research of Materials Science June 2013, Volume 2, Issue 2, PP.16-22
Study on Dispersion Polymerization Process of Silica Aerogel/Polystyrene Core-Shell Composite Particles Gangqiang Geng a#, Suqing Wen b, Huan Wang c Department of Materials Science and Engineering, Chang,an University, Xi’an 710064, China Email: #agengangqiang@163.com,bsuqingwy@163.com,cwanghuan@163.com
Abstract Silica aerogel/polystyrene core-shell composite particles have been synthesized by dispersion polymerization. In the chemical synthesis microwave irradiation heating method is used to induce the polymerization. And study on the influence of the mass ratio of the silica aerogel and styrene monomer on the coating rate of the composite particles. Then study on the content of the initiator AIBN on the density of the composite particles and the conversion rate of the styrene monomer. Finally composite particle is confirmed to be a kind of strawberry shaped core-shell composite structure by SEM and energy spectrum analysis. Keywords: Silica Aerogel; Polystyrene; Core-shell Structure; Dispersion Polymerization
1 INTRODUCTION Now, polystyrene insulation board is widely used in the external wall insulation system [1]. But its inherent disadvantages, such as high thermal conductivity and poor flame retardant performance, can not be ignored. Silica aerogel [2] is a highly porous material with pore diameters in the range of 1~100nm. The porosity is up to 80% to 99.8%, which combined with the nanometer pore size makes the aerogel a highly insulating material with a thermal conductivity lower than of 0.020W/m•K. So it is a super thermal insulation material. However it is the defects such as low structural strength, high water absorption, high price that limit its application in the thermal insulation field. The core-shell composite materials[3,4], due to its distinctive physical and chemical properties,have a promising applications in the biomedical, optical, electrical, magnetic, catalytic and other fields[5-9]. In view of the above-mentioned facts about polystyrene and silica aerogel, based on organic-inorganic hybrid principle, silica aerogel/polystyrene core-shell composite particles have been synthesized by dispersion polymerization in order to achieve the effect of complementary advantages. In the chemical synthesis microwave irradiation heating method[10-14] is used to induce the polymerization of silica aerogel and styrene monomer.
2 EXPERIMENTAL 2.1 Material Absolute ethanol, silica aerogel, distilled water, standard sodium hydroxide (NaOH, 0.1N), the monomer, styrene, the initiator,2,2’-azobis (isobutyronitrile) (AIBN), and the stabilizer, PVP K30, the coupling agent, KPS.
2.2 Characterization 1) Conversion rate of the styrene monomer measurement [15] The conversion rate of styrene monomer is determined by weight method. Firstly a weighing bottle is placed in a vacuum drying oven drying to constant weight. Then put the liquid after polymerization reaction in the weighing bottle, which is put in the vacuum drying oven at 75 ℃ drying to constant weight. And obtain the total weight of polymerization reaction system. The conversion rate is calculated by the formula (2.1). - 16 http://www.ivypub.org/rms