Morphology of multiphase polymer blends: Continuous phase formation in ternary systems

Morphology development in the immiscible ternary blends based on oligomers, liquid polymers, and high-molecular-mass PS, PMMA, and PP was studied. The phase structure of polymer systems was determined by methods of optical sp ectroscopy and electron (scanning and transmission) microscopy, in combinat ion with the selective phase dissolution (solvent leaching) and computer-ai ded image analysis techniques. Small (1-5 wt %) PP additives produce a dual effect on the structure of a 45/55 PMMA-PS binary blend composition, leadi ng to the transition from dispersed to continuous PMMA phase and increasing the degree of PMMA dispersion. This behavior is observed only for the blen ds where the spreading coefficients of both components are negative, which implies that no encapsulation of the internal phase takes place. A mechanis m explaining this phenomenon is proposed and some problems pertaining to de tection of the co-continuous phases in ternary polymer blends are discussed .