Induced folding model in the melt crystallization kinetics of nucleated high-density polyethylene

Melting and isothermal crystallization kinetics of nucleated high-density p olyethylene are observed by means of a conventional differential scanning c alorimeter. The temperature dependence of the isothermal crystallization ra te is analysed in terms of a model expression for the secondary nucleation free enthalpy which is derived under the assumption that the close vicinity of a nucleant molecule to a basal plane drastically reduces the local valu e of the folding free energy (induced folding). The linear dimensions of th e region where the latter happens to be depleted appear to be determined by those of a nucleant molecule. In large nuclei, the possibility that all st em pairs undergo induced folding by the same nucleant molecule has to be ex cluded. Both the basal and lateral specific surface free energies can be wo rked out from a fitting procedure, and are in good agreement with the liter ature data.