Preparation And Characterization Of Multi-level Pore Structure Of Silica Aerogel/Polystyrene Composite Materials

SiO2 aerogels with nano-pore structure, is one of the most outstanding performance in the heat insulating material of the material, but its brittleness, high cost and low strength severely limit the range of applications in the field of thermal insulation material. Polystyrene foam board has a closed-micron pore structure, because of lightweight, excellent thermal insulation, good mechanical, strength and toughness, corrosion resistance, easy molding process productivity, and low cost, it becomes one of the most commonly used insulating material in the current room temperature and low temperature areas. The two designed nano pore-micron pore multi-level complex structure at the micro, to further suppress heat conduction and micron holes convection heat, thereby improving the insulation performance of polystyrene foam materials; it had an important practical significance and research value from the theory research of micro and nano materials and the development of innovative practices of performance materials.The main raw material for foam polystyrene panels can be made of polystyrene beads, the nano pores silica aerogels are introduced into the polystyrene beads prerequisite to build micro-nano pore complex structure, Studied technological factors and influence the process of aerogel particles uniformly dispersed into the polystyrene matrix, forming aerogel/polystyrene core-shell structured composite beads by suspension polymerization. Analyzing the effect of oil and water two-phase proportion and stirring rate suspension polymerization on the average particle size of the composite beads, volume range of core-shell structure coated with silica aerogel, and the impact of SiO2 Aerogel/PS composite glass transition temperature under the above process factors, the results showed that: composite beads prepared small particle size in average, when the oil-water ratio 1:5; In the composite dispersant system: organic dispersant(6mL 5% PVA),inorganic dispersant(tricalcium phosphate 3.0 g), stirring speed 300 rpm; the adding amount of SiO2 aerogels 1.5 g. The average particle diameter of the composite beads were prepared in approximately 1.505 mm, the particle size distribution is narrow, with the improving of oil/water ratio, the composite beads glass transition temperature also will be improved, the Tg of composite beads are about 93.3 ℃;the oil-water ratio is set to 1:5, increasing the stirring speed has little effect on the glass transition temperature of the composite beads.For comparative study of nano pores micro-nano composite affect the pore structure, selection of the commercialization of silica nano particles and polystyrene to form and synthesis composite beads without nano pores. First, in order to improve lipophilic nano silica particles and its compatibility with the styrene monomer during the polymerization process, studied a method to the KH-570(methacryloyloxy trimethyl silane) modified nano-silica powder, characterization of the modified results by using infrared spectrum and the dispersion experimental. Synthesized nano-silica/polystyrene core-shell structured composite beads by suspension polymerization, and characterization and performance tests for composite beads, the results showed that: when the amount of modifier is 40% of the powder, powder contact angle reaches a maximum and is 128.75o(keep the consistent hydrophobic angle with aerogel powder), and can maintain long-term stability at room temperature, oil absorption is 7.8mL/g, the powder in the oil phase is more evenly distributed and stable; from the infrared spectroscopy, the vinyl of KH-570 has been successfully grafted onto the nano-silica powder. Composite beads prepared when the oil-water ratio is 1:9, the composite dispersion(10-12 mL 5% PVA, tricalcium phosphate 2.0 g), the amount of BPO is 0.9 g, modified Nano silica is 1-2 g. When stirring speed is 180 rpm, the composite particles are more evenly, the glass transition temperature of nano-silica/polystyrene composite beads is 93.55℃.Finally, building three-dimensional thermal model of micro-nano composite pore structure for new composite according to the heat theory, through the analysis of a simple heat transfer model, giving analytical expressions of equivalent thermal conductivity of composite material, the two composite beads immersed n-pentane in the reactor, pre-expansion, curing, foam particles were prepared and tested for apparent density and morphology, the results showed that: SiO2 aerogel/Polystyrene composite beads have smaller apparent density, after the pre-expanded beads cell showed a closed micron holes.