Abstract
Recently, polymeric foams filled with a silica aerogel have been developed. The phase behavior of CO2/silicon alkoxide binary systems and CO2/silicon alkoxide/polymer ternary systems is an important factor that affects the design of novel processes. The phase behavior of a carbon dioxide (CO2)/methyl trimethoxy silane (MTMS)/polystyrene (PS) ternary system was measured using a synthetic method involving the observation of the bubble and cloud point. The phase boundaries were measured at temperatures ranging from 313.2 to 393.2 K and CO2 weight fractions between 0.01 and 0.08. The CO2/MTMS/PS system showed a similar CO2 mass fraction dependence of the phase behavior to that observed for the CO2/tetramethyl orthosilicate (TMOS)/PS system. When the phase boundaries of these systems were compared, the vapor-liquid (VL) and vapor-liquid-liquid (VLL) lines were found to be nearly identical, while the liquid-liquid (LL) lines were different. These results indicate that the affinity between the silicon alkoxide and polymer greatly influences the liquid-liquid phase separation.
Highlights
An aerogel is a porous material prepared by replacing the solvent within a gel with a gas upon supercritical drying without destroying its structure [1]
The CO2 /MTMS/PS system exhibited two different types of phase behavior with changes in the CO2 mass fraction. Such behavior is similar to that of CO2 /tetramethyl orthosilicate (TMOS)/polymer systems, whose details have been previously described [17]. This behavior is similar to that of CO2 /methyl methacrylate (MMA)/PDMS systems reported by Santos et al [20]
3) Reported by AKrevelen phase diagram for a CO2 /MTMS/PS ternary system was obtained over a wide range of temperatures, pressures, and polymer mass fractions
Summary
An aerogel is a porous material prepared by replacing the solvent within a gel with a gas upon supercritical drying without destroying its structure [1]. Aerogels with a porosity of more than 90% are promising materials due to their exceptional lightweightness and thermal insulation properties. While the thermal conductivity of a general insulator is about 20 to 45 mW/(m K), the thermal insulation property of aerogels was reported to be lower [3]. Their thermal conductivity is the lowest among free-standing solids due to their fine porous structure. An aerogel possesses a thermal insulation close to that of vacuum. It is considered for use as thermal insulator in industrial applications. It has been used for the preparation of thermal insulating glass
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