AbstractScaling parameters for two PVT equations of state are evaluated for 11 polymer melt systems using a nonlinear least square fitting algorithm that analyzes all of the experimental data simultaneously. Two different criteria are considered in this evaluation. In the first method, the fitting criterion is the difference between the calculated and experimental volume. In the second method, the criterion is the difference between the calculated and experimental pressure. In both cases, the differences between the scaling parameters obtained using the simultaneous fit procedure and those obtained using the earlier consecutive fit procedure are a few percent, which can have a significant effect in some calculations. In addition to being a more consistent method of evaluating scaling parameters, the simultaneous fit procedure leads to much better agreement between calculated and experimental values, in some cases by a factor of 2.
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