Phase equilibria of polypropylene samples with hydrocarbon solvents at high pressures

Abstract

ABSTRACT:The objective of this work is to provide high-pressure phase equilibrium data for polypropylene (PP) samples (two commercial and one metallocenic grades) with some hydrocarbon solvents (propane, propylene, n-butane and 1-butene). The experiments were carried out in a high-pressure variable-volume view cell in the temperature range of 75-150°C, for polymer compositions ranging from 0.3 to 10 wt %. Phase transitions were recorded visually as cloud points and identified as liquid-liquid and vapor-liquid transitions. When pressure transition data obtained for olefins and paraffins of similar chain length and at similar temperatures and polymer compositions are compared, it may be observed that paraffins lead to the decrease of the pressure transition values. Therefore, the one-phase region is larger for paraffins than for olefins. In the range of commercial interest analyzed, it is also observed that the influence of polymer average molecular weight upon the cloud points is negligible. Experimental data are then used to build the P-T diagrams for these systems, allowing the identification of the LCST (Lower Critical Solution Temperatures) and LCEP (Lower Critical End Points) curves. Finally, the original SAFT equation of state (SAFT-EOS) is used to model the experimental data. It is shown that the SAFT-EOS provides an excellent description of the solution behavior in the whole experimental range analyzed.

Phase behavior of soybean oil, castor oil and their fatty acid ethyl esters in carbon dioxide at high pressures

“…The experimental apparatus and procedure used in this study are described in detail elsewhere [31][32][33][34][35]. Phase equilibrium measurements (cloud points) were carried out in a high-pressure variable-volume view cell.…”

Phase behavior of olive and soybean oils in compressed propane and n-butane

“…Over the past decade, the Statistical Associating Fluid Theory (SAFT) Radosz 1990, 1991) has been successfully employed in the calculation of phase equilibrium of systems containing macromolecules, especially those with polymers (Ndiaye et al, 2001;Chen et al, 1992;Dariva et al, 2001). The success of SAFT-EoS is probably due to the better modeling of molecules, which are considered to be a collection of spherical segments with repulsive (hard-sphere) and attractive (dispersion) force fields.…”

High-pressure phase equilibrium data for the (carbon dioxide + l -lactide + ethanol) system

“…The experimental apparatus and procedure have been used in a variety of studies [20][21][22][23][24] and was extensively validated [25,26]. Briefly, the experimental setup consists of a variable-volume view cell with two sapphire windows (one for light input and one for visual observation), an absolute pressure transducer (Smar, model LD 301), a portable programmer (Smar, model HT 201) for pressure acquisition, and a syringe pump (ISCO, model 260D).…”