Thermal Expansion Behavior of Polystyrene Blended Porous Silica through Psuedo-Phase Separation
Narihiro MATSUDA, Masaki HIROSE, Kenji TAKASA, Mitsuru TANAHASHI and Kunihiko TAKEDA
Abstract:The liner thermal expansion coefficient of the polystyrene that was blended with porous silica has been studied. The specific porous silica was prepared using silica sol and potassium bromide (KBr) by the pseudo-phase separation method. Next, to remove KBr from the mixture of silica and KBr, this mixture was soaked into heated water. The porous silica was convenient in preparing the composite because the mechanical strength can be controlled by the processing temperature. The composite of the porous silica and polystyrene was obtained by blending in an extruder. The silica was smashed at the blending procedure by the shearing stress. The blend of the polystyrene with spherical silica was prepared to compare the effect of the silica particle in polystyrene. The coefficient of the liner thermal expansion (CTE) was measured in two regions of temperature: one was the below the glass transition temperature and the other was in the higher temperature region. The CTE of neat-polystyrene was much larger than the blends with the two kinds of silica particles and the CTE of the blend with the spherical silica was larger than that with the porous silica in both temperature regions. In particular, the difference of the CTE was remarkable in the higher temperature region and the thermal expansions were much lower than the calculation values by the equations which have been applied to the organic/inorganic composites. As the CTE is one of the fundamental characteristics of materials, it is regarded not to deviate from the theoretical value. The chain of the polystyrene could be considered to intrude into the pores in the porous silica because the diameter of the pore was too small to reject the intrusion of the chain in both temperature regions. Key Words:Porous, Silica, Phase separation, Polystyrene, Composite, Thermal expansion