Crystallization behaviors of polypropylene in SEBS elastomer compounds

Styrene-hydrogenated butadiene -styrene copolymer (SEBS)/polypropylene (PP) compounds were prepared with PP-S700 by internal mixer. The crystallization behaviors of PP in SEBS/PP elastomers were investigated by DSC. The crystallization orientation of PP in SEBS/PP elastomers was studied through XRD, and the degree of crystallization orientation was obtained. The results show that with increase of the PP content, SEBS/PP compounds change from an elastomer to a hard elastomer, as the dispersed PP phases gradually connect with each other to form two continuous phases with SEBS, leading to a remarkable increase in mechanical strength and storage modulus of SEBS/PP compounds. In addition, the formation of the two continuous phases partly makes the negative impact of PP on the elongation at break decrease. In the SEBS/PP elastomer, the crystallization temperature and crystallinity of PP both decrease with the content of SEBS. During the injection molding, the long chain orientation is along the direction of injection.