The association equilibrium constants and enthalpy of novolac type phenolic resin blend were determined. All the parameters were obtained from the results of Fourier transform infrared spectroscopy of low molecular weight analogues in dilute cyclohexane solutions. All the association parameters of novolac type phenolic resin obtained from the model compound were used to predict the miscibility window of phenolic/poly(adipic ester) blend, and that were consistently well with the actual phase behaviour. The results show that the association parameters of phenolic provide a reasonable utilization of Painter-Coleman Association model.