Synergism on tensile properties of injection molded polybutene‐1 /polypropylene blends

Abstract Blends of polybutene‐ 1 (PB‐1) and polypropylene (PP) have been injection and compression molded. A synergism appears in the ultimate elongation and the tensile strength for the injection moldings. The maximum point of the synergism at the composition of 25 wt% PB‐1 shifts to 50 wt% PB‐1 after annealing at 145° C for 1 h. A linear relation and negative deviation from the additivity rule for these two properties are observed for the compression moldings with quick cooling and slow cooling, respectively. Thermal analysis, polarized optical microscopy, and scanning electron microscopy (SEM) are used to study the occurrence of the synergism. The mutual interference between the two components on the crystal formation and the plasticization effect of PB‐ 1 on PP result in the synergism. An increased phase separation probably occurs during the compression molding with slow cooling. So, the blends compression‐molded with slow cooling having a higher amount of PP have brittle breaks, similar to pure PP.