Blends of i-PP and SBS. I. Influence of thein situ compatibilization on the morphology

Abstract

This article concerns the in situ compatibilization of immiscible isotactic polypropylene/butadiene-styrene-butadiene triblock copolymer blends (i-PP/SBS) by means of a reactive mixture. For this purpose, maleated PP (PP-MAH) and SBS (SBS-MAH) were used as functionalized polymers and 4,4′-diaminediphenylmethane was used as a coupling agent between maleated polymers, resulting in a graft copolymer. Binary blends i-PP/SBS, nonreactive ternary blends i-PP/PP-MAH/SBS, and reactive ternary blends i-PP/PP-MAH/SBS-MAH with varying diamine and anhydride molar ratios were prepared. Torque measurements suggest a graft copolymerization during the melt blending for ternary reactive blends, but the extension of the grafting does not vary with the diamine and anhydride molar ratio, but with the elastomer concentration. The morphology of the blends was investigated by scanning electron microscopy. The morphology of binary and ternary nonreactive blends is similar, exhibiting elastomer domains disperse in the i-PP matrix, whose sizes increase with elastomer concentration. On the other hand, the elastomer domain size in the ternary reactive blends is practically independent of the blends composition and of the diamine and anhydride molar ratio. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 847–855, 2002