Petrie-Marshall and Cowie-Ferguson Models

While the P-M model uses the linear extrapolation of the liquid polymer enthalpy-temperature dependence to measure (])(y, the C-F approach is different It considers AH(oo, Ta) to be an adjustable parameter and is measured by curve fitting the AH(ta, Ta) versus logta plots. The function (])(ta) is also redefined as  

As discussed below, the C-F model has been extensively used to compare the aging behavior of polymer blends to that of the corresponding homopolymers, because of its simplicity. However, notably, this model cannot adequately describe all of the phenomenology associated with the glass transition, namely, its nonlinear character. The consequences of this when describing the physical aging process have been discussed in the literature [19, 20]. 

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