Phase Behavior of a Carbon Dioxide/Methyl Trimethoxy Silane/Polystyrene Ternary System

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

Pressure-volume-temperature relationships of trimethoxymethylsilane and tetramethyl orthosilicate at temperatures ranging from 303.2 to 363.2 K and pressures up to 160 MPa

The pressure-volume-temperature (PVT) relationships for trimethoxymethylsilane (MTMS, CH3(CH3O)3Si) and tetramethyl orthosilicate (TMOS, (CH3O)4Si) were measured at temperatures ranging from 303.2 to 363.2 K and pressures up to 160 MPa. Density measurements were carried out with an experimental apparatus based on the variable volume method. The standard uncertainties u(T) = 0.17 K and u(P) = 0.14 MPa, and the relative combined expanded uncertainty Ur (0.95 level of confidence) were Ur(ρ) = (0.0016 and 0.0022) for MTMS and TMOS, respectively. The obtained PVT relationships were correlated using the Tait equation and the Sanchez-Lacombe equation of state to determine the characteristic parameters