Surface roughness in dynamically crystallized isotactic polypropylene films

The relationship between the dynamic crystallization conditions and surface topography of iso ‐polypropylene ( i ‐PP) films was examined with fractal geometry. When i ‐PP was crystallized from a melt at cooling rates in the range between 1 and 100 °C/min, the generated surface topography presented self‐affine behavior at least in the scale range from 0.1 to 100 μm. Moreover, the calculated roughness exponent of these surfaces increased with the cooling rate used to crystallize the samples, which meant a smoother surface at higher crystallization rates. This behavior could be qualitatively explained in terms of the temperature effect on the nucleus stability, the molecular mobility, and the surface tension. In addition, the morphology of quenched samples was analyzed, and different hypotheses were proposed to explain the unusual observed behavior.