Depression of melting temperature

Indeed, a sharp decrease of the melting enthalpy after a shock-wave treatment has been shown experimentally [72], a thermodynamic interpretation of these results can be found in [64], Depression of melting temperatures and enthalpies in organic crystals has been reported [73-76] and different models of these dependences are available [77, 78]. A simple empirical rule has been established the enthalpy of the defect formation is nearly proportional to the melting temperature, viz. in alkali halides AHi T = 2 10 (for AHi in kJ/mol and r in K) it was also shown that dTmldP=kVo, where V is the molar volume andA =5.7 10 K mol/J [79]. 

In general, a good solvent introduced to a polymeric system plasticizes the material and on heating the melting of such system occurs at lower melting temperatures than for pure polymer as described by Equation (9.3). A physical reason for the depression of the melting point is the increase in entropy due to the presence of solvent. The depression of melting temperature with respect to that of pure polymer is also observed in miscible blends and in copolymers as is described in Chapter 10 and Chapter 11. 

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