Couchman-Karasz approach

The T of polymer blends can be related to the blend composition by different equations, as shown in Table 12.2. The T of miscible blends of poly(p-dioxa-none) with poly(vinyl phenol) (PPDO/PVPh) [74], as studied using the Fox [75], Gordon-Taylor [76], Couchman-Karasz [77] and Kwei [78] models, showed that the experimental data lay below the Fox equation, suggesting that the free volume of the blends was larger than predicted, assuming free volume additivity. On the other hand, the Gordon-Taylor and the simplified Kwei equations fitted the experimental T values appropriately. Other studies have shown that the Ta of SAN/PMMA blends was also effectively approached by the Gordon-Taylor relationship [79,80]. 

If a thermodynamic approach is used, as suggested by Couchman and Karasz, then... 

One of the properties that is affected by the production of miscible blends is the glass transition temperature or Tg. The Tg of miscible blends has been modeled using several different approaches in the literature (Wood 1958 Couchman and Karasz 1978). The simplest of these is the Flory-Fox equation ... 

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