Abstract
Binary systems consisting of small halogenated molecules dissolved in oligomers have been investigated.
Pressure/composition isothermal data were used to calculate the activities by the Flory equation which provides a good description of such systems and includes the possible immiscibility region calculated from the Gibbs excess energy.
The interaction χ parameter can be calculated as well, which accounts for the essentially enthalpic contribution to the non ideality.
Deviations from ideality can also be determined by boiling temperature isobaric measurements. The slope of the composition with respect to boiling temperature profile appears as an important term modelling the free rise of a polyurethane system foamed by physical blowing agents. Adopting such a model and utilizing the Flory equation to describe the χ dependence on the temperature, the profile of the blowing agent mole fraction with respect to boiling temperature and its slope have been determined and cream, gel times along with density and bulk temperature profiles have been simulated. Simulation shows that calculated kinetics and density profiles are significantly dependent on using experimental data relative to blowing agents such as CCl3F, CHCl2-CF3 and CH2F-CF3. The last two compounds in this study have been assumed to be model molecules focusing attention on their opposite deviation from ideality with respect to CCl3F.
Work is in progress to evaluate how this simulation is suitable to describe the real foaming processes
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