Effect of Cure Conversion on Glass Transition Temperature Tg

6 Effect of Cure Conversion on Glass Transition Temperature (Tg) 

With the advancement of a curing reaction, the of the resin will increase, but the goal is to quantitatively predict the of a resin as a function of cure conversion. Several models have been proposed to correlate the with the conversion or extent of curing (a). With the increase in conversion, the concentration of reactive functionalities decreases, and crosslinks or junction points are formed, leading to the departure from Gaussian behaviour. Steric hindrance affects chain conformation at high crosslink densities. The models are based on the statistical description of network formation and calculation of the concentration of jrmction points of different functionalities as a function of conversion. However, one issue that complicates the calculation and which is not fully resolved is whether to consider all the junction points or only those which are elastically effective. 

An equation (known as Dibenedetto equation) which has been successfully applied to correlate the experimental values of the T as a function of conversion for many thermosetting resin like epoxy, phenolics is given next [27]  

During advancement of the curing reaction, it was observed that the change in heat capacity decreases. Montserrat [30] proposed an equation to correlate Ac (t ) with the T of the network  

Neglecting the constant (x), which may be applicable for a particular case, we get  

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