Morphology development in immiscible polymer blends

This paper presents the results obtained using a new method for analyzing polymer blend morphologies. The method is based on the selective solubilization of the matrix followed by a separation of the dispersed phase in suspension by filtering. A suspension of the nodular part going through the filter is obtained and can be analyzed with a particle counter. The other part of the dispersed phase retained by the filter is constituted of fibers. The average droplet diameters were compared with those obtained using a Scanning Electron Microscope on fracture surfaces for different compositions and flow conditions. The average diameter obtained with the counter technique increases with the dispersed phase content up to an optimum where simultaneously a decrease in the mean diameter and an increase of the fibrillar part are observed, which means that there is a concentration range where these two types of morphologies are present in the blends. The results indicates that the stability of the fibrillar part seems to determine whether the blend morphology will evolve into nodules by the Rayleigh mechanism or into phase inversion by coalescence of stable fibers.