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The melting behavior and the isothermal crystallization kinetics of linear and randomly branched poly(buty1ene terephthalate)a) (PBT) samples were investigated by differential scanning calorimetry. The multiple endotherms typical of linear PBT were observed also in branched samples and were found to be influenced both by temperature and degree of branching. The isothermal crystallization kinetic constants, obtained applying Avrami's treatment, were analysed on the basis of Hoffman's secondary nucleation theory. A decrease in the crystallization rate was observed as the content of branching units increased. This result was correlated to surface effects: the product of the surface free energies me was found to increase with the ramification content. As far as the nucleation process is concerned, the induction time was determined for all the samples at different crystallization temperatures, and the results suggested that in the presence of branching points the nucleation process is favoured.

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