Brittle-ductile transition behavior of the polypropylene/ultra-high molecular weight polyethylene/olefin block copolymers ternary blends: Dispersion and interface design

Ultra-high molecular weight polyethylene (UHMWPE), which possesses outstanding impact and crack resistance, can be potentially used to toughen polypropylene (PP). Unfortunately, enormous viscosity mismatch between them leads to the formation of large UHMWPE agglomerates and the deterioration of mechanical properties. In this work, a kind of Gel masterbatch mixing (GMM) method and olefin block copolymers (OBC) were used to realize the intimate mixing of PP/UHMWPE and strengthened interface interaction, separately. The results showed that UHMWPE-OBC phases with core-shell structure were formed and dispersed in PP matrix in a submicron size, which OBC was as a compatible shell between UHMWPE core and PP matrix. As the amount of OBC in the PP/UHMWPE/OBC (G-P/U(20)-O) blends increased, the core-shell structure was gradually improved and the brittle-ductile transition occurred when the OBC content reached to 5phr. After adding 7phr OBC and 20phr UHMWPE, the perfect core-shell structure was formed in G-P/U(20)-O(7) blends and the notched Izod impact strength was 55.47 kJ/m2, which was much higher than the 9.86 kJ/m2 (G-P/U(20)) and about 17.5 times larger than Pure PP. Furthermore, crystallization and rheological behaviors were measured to reveal the evolution of core-shell structure and the microstructure-properties relationship was also established to reveal brittle-ductile transition and toughening mechanism.