Effect on the Impact Properties of Adding Long-Chain Branched Polypropylene in Polypropylene-Polyolefin Elastomer Cellular Polymers Produced by Core-Back Injection Molding

Different blends of a linear polypropylene (L-PP), a long-chain branched polypropylene (LCB-PP), and a polyolefin elastomer (POE) are prepared and foamed using core-back injection molding. The objective is to analyze the use of POE and LCB-PP as complementary strategies to improve cellular polymers' impact response. Different parameters are then studied in blends and injection molded plaques to understand the samples' mechanical behavior. Parameters such as the interfacial tension, elastomer morphology, extensional rheology, cellular structure, and crystallization behavior are characterized in detail. The addition of POE allows improving the impact response of both the solids and cellular polymers, but the stiffness is reduced. On the other hand, the substitution of L-PP by LCB-PP, in blends containing POE, results in solids and cellular materials with both better stiffness and better impact properties, due to the different crystalline morphology comprising the samples, a different cellular orientation, and thicker solid skin.

Automated summary

The study demonstrates that adding polyolefin elastomer (POE) to polyethylene materials can improve impact response but reduce stiffness, while substituting linear polypropylene (L-PP) with long-chain branched polypropylene (LCB-PP) in blends can improve both stiffness and impact properties simultaneously.