Morphological and fractal studies of polypropylene/poly(ethene‐1‐octene) blends during melt mixing using scanning electron microscopy

BACKGROUND: Polymer blending creates new materials with enhanced mechanical, chemical or optical properties, with the exact properties being determined by the type of morphology and the phase dimension of the blend. In order to control blend properties, morphology development during processing needs to be understood. The formation and evolution of polypropylene/poly(ethylene‐1‐octene) (PP/POE) blend morphology during blending are qualitatively represented by a series of time‐dependent scanning electron microscopy (SEM) patterns. The area diameter and its distribution of dispersed phase domains are discussed in detail. In order to characterize the formation and evolution of phase morphology quantitatively, two fractal dimensions, D_s and D_d, and their corresponding scaling functions are introduced to analyze the SEM patterns. RESULTS: The evolution of the area diameter indicates that the major reduction in phase domain size occurs during the initial stage of melt mixing, and the domain sizes show an increasing trend due to coalescence with increasing mixing times. The distribution in dispersed phase dimension obeys a log‐normal distribution, and the two fractal dimensions are effective to describe the phase morphology: D_s for dispersed phase dimension and D_d for the distribution in it. CONCLUSIONS: The fractal dimensions D_s and D_d can be used quantitatively to characterize the evolutional self‐similarity of phase morphology and the competition of breakup and coalescence of dispersed phase domains. It is shown that the fractal dimensions and scaling laws are useful to describe the phase morphology development at various mixing times to a certain extent. Copyright © 2007 Society of Chemical Industry