(CO2+2-Propanol) Mixture as a Foaming Agent for Polystyrene: A Simple Thermodynamic Model for the High Pressure VLE-Phase Diagrams Taking into Account the Foam Vitrification.

MARCO DONDERO, JOSE CARELLA, JULIO BORRAJO

JOURNAL OF APPLIED POLYMER SCIENCE

Wiley Periodicals, Inc.

Año: 2007 vol. 104 p. 2663 - 2671

0021-8995

The equation of state model developed byLacombe and Sanchez (J Phys Chem 1976, 80, 2352) isused in the form proposed later by Sanchez and Stone(Polymer Blends, Vol. 1: Formulation, 2000; Chapter 2) tocorrelate experimental vapor-liquid equilibrium (VLE) datafor the three binaries and the ternary systems. Experimentaldata from the binary systems carbon dioxide-isopropylalcohol (CO2-IPrOH), isopropyl alcohol-polystyrene(IPrOH-PS), and carbon dioxide-polystyrene (CO2-PS) areused to calculate VLE properties for the ternary systemCO2-IPrOH-PS. Two-dimensional VLE-phase diagramswere calculated and used to describe from a thermodynamicpoint of view the pressure, volume, and temperaturevalues that characterize a thermoplastic foamevolution process, from the extruder to the foaming die.For different initial mixture CO2 + IPrOH concentrations,pressure reduction produces liquid foaming until the vitrificationcurve arrests the final foam volume expansion.The dependence of the vitreous transition with the systemCO2 + IPrOH concentration while foaming is representedby the Chow (Macromolecules 1980, 13, 362) equation. Thecalculation procedure is proposed as a design tool toreduce the amount of experimental data usually needed asa requirement previous to the design stage.