POLYOL AND BLOWING AGENT BINARY-SYSTEM DESCRIBED BY MEANS OF THE FLORY MODEL

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 pro vides a good description of such systems and includes the possible imm iscibility region calculated from the Gibbs excess energy.The interact ion chi parameter can be calculated as well, which accounts for the es sentially enthalpic contribution to the non ideality. Deviations from ideality can also be determined by boiling temperature isobaric measur ements. The slope of the composition with respect to boiling temperatu re profile appears as an important term modelling the free rise of a p olyurethane system foamed by physical blowing agents. Adopting such a model and utilizing the Flory equation to describe the chi dependence on the temperature, the profile of the blowing agent mole fraction wit h respect to boiling temperature and its slope have been determined an d cream, gel times along with density and bulk temperature profiles ha ve been simulated. Simulation shows that calculated kinetics and densi ty profiles are significantly dependent on using experimental data rel ative to blowing agents such as CCl3F, CHCl2-CF3 and CH2F-CF3. The las t two compounds in this study have been assumed to be model molecules focusing attention on their opposite deviation from ideality with resp ect to CCl3F. Work is in progress to evaluate how this simulation is s uitable to describe the real foaming processes