The heat of fusion of poly(ethylene terephthalate)

Abstract By use of the Clapeyron equation for the dependence of the melting point on pressure, the heat of fusion was found to be 32.5 cal/g, in good agreement with values determined by other methods. An equation for the dependence of the melting point on the degree of polymerization gave a heat of fusion of 27.6 cal/g when applied to hydroxyl‐terminated oligomers. This simple relation applied all the way down to the smallest member of the series, di(hydroxy ethyl) terephthalate.