SL EOS Research Articles

Prediction of Solubility of α-Olefins in Polyolefins Using a Combined Equation of StateMolecular Dynamics Approach

In the present study, the Sanchez−Lacombe equation of state (i.e., SL EOS) was employed to calculate the solubilities of α-olefins in polyolefins over a wide range of pressures and temperatures. The characteristic parameters (i.e., P*, T*, and ρ*) of the pure components, appearing in the Sanchez−Lacombe EOS, were estimated using a molecular dynamic procedure (MD). For all binary systems examined, a single binary parameter, kij, accounting for the interactions between the penetrant molecules and the polymer chains was used to fit model predictions to available solubility measurements. The value of the binary interaction parameter was found to depend on the type of the penetrant molecules, the comonomer type in the ethylene copolymers, and the polymer crystallinity as well as the selected experimental conditions (i.e., temperature and pressure). The theoretically calculated solubilities were found to be in excellent agreement with the corresponding experimentally measured values, demonstrating the capabilit...

CO2-Induced PMMA Swelling and Multiple Thermodynamic Property Analysis Using Sanchez−Lacombe EOS

The Sanchez−Lacombe equation of state (SL EOS) is often used to describe polymer−gas systems because of its inherent ability to hand compressible fluids, but it has rarely been tested for correlating multiple thermodynamic properties of these systems. The real value of an EOS as a process design tool is the ability to describe all thermodynamic properties, not just those it has been fit to. Because of the relatively small amount of data for polymer−gas systems, there is no heuristic to determine which property should be used to fit the EOS to give the best representation of other properties. We test this idea by looking at dilation, solubility and Tg in the CO2−PMMA system. Although CO2 sorption phenomena in polymers have been extensively investigated, the study of CO2-induced polymer dilation is rather limited in comparison. A new experimental technique based on ADSA (axisymmetric drop shape analysis) was developed in this work to measure volumetric properties. The dilation isotherm was measured over temperatures of 40−200 °C and pressures up to 100 bar. The experimental swelling data are then modeled using the SLEOS and the correlated interaction parameter between gas and polymer decreases linearly with temperature within the range 40−160 °C. The applicability of SLEOS to describing thermodynamic behavior of gas−polymer mixture is demonstrated by successfully predicting the CO2 sorption at 30−60 °C and Tg depression.