SEBS-g-MAH as a Reactive Compatibilizer Precursor for PP/PTT/SEBS Ternary Blends: Morphology and Mechanical Properties

This article highlights the effect of using maleic anhydride-assisted SEBS compatibilizer precursor on the morphology and mechanical properties of the polypropylene (PP)/poly (trimethylene terephthalate) (PTT)/poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) 70/15/15 ternary blends. In all ternary blends, the amounts of PP and PTT, respectively as the matrix and the primary minor components were kept constant at 70 and 15wt%; in turn, the amount of constituent polymers within the secondary minor phase containing reactive maleic anhydride grafted SEBS (SEBS-g-MAH) and nonreactive SEBS was changed. The mentioned compatibilizing system was first melt-blended in a co-rotating twin screw extruder and then added into the blend. Theoretical models were also employed to make a comparison with experimental values obtained from morphology characterization through the ternary systems. Accordingly, it is found that the blend containing only non-reactive SEBS exhibited fine dispersion of core-shell particles; however, by diminishing SEBS to SEBS-g-MAH weight ratio, the morphology changed from the pure core-shell to a multi-phase system consisting of both core-shell and detached particles. Eventually, this transition in the phase morphology caused some consequences and/or advantages on the mechanical properties, so that the blend consisting of 50/50 weight ratio of SEBS/SEBS-g-MAH exhibited the minimum value of modulus; in contrast, the impact strength of that sample was considerably higher than that of neat PP specimen. These alterations in mechanical properties could be ascribed to the formation of some especial microstructures, in another word, the impact of particle size and particle size distribution, which has been well-established through scanning electron micrographs.