Analysis of layer-by-layer phase transformation of a polyoxymethylene copolymer film

Isothermal and non-isothermal crystallization of a polyoxymethylene copolymer was performed using a differential scanning calorimeter (DSC) and the resulting crystalline development was interpreted by means of the nucleation and growth model. Morphological investigations on DSC crystallized specimens were performed by scanning electron microscopy and correlated to the results of an analysis of data based on the Avrami model. The onset of crystallization in a limited portion of the specimens rather than in the whole volume has been recognized. The novelty of this work consists in a new explanation of fractional Avrami exponents, ascribed to a layer-by-layer crystallization of specimens from the surface to the interior.