Synergistic effect of thermoplastic polyester elastomer and polytetrafluoroethylene in situ fibrillation on the resilience and compression strength of long‐chain branched polypropylene foam

Abstract Excellent resilience and compression resistance are the key characteristics of cushioning and water–oil separation materials. Although polypropylene (PP) offers excellent performance and affordability of PP, it exhibits poor resilience. To address this shortcoming, polymer blends with long‐chain branched PP (LCBPP), thermoplastic polyester elastomer (TPEE), and polytetrafluoroethylene (PTFE) were prepared via melt blending, and their mechanical properties were tested. The LCBPP/TPEE/PTFE composites were subjected to physical foaming using supercritical CO 2 (scCO 2 ) as the blowing agent. The synergistic toughening mechanism of the elastomer/nanofiber and the effect of the structure and crystallization of the dispersed phase on the foam resilience and foam compression strength were investigated. The results revealed that fibrous PTFE and spherical TPEE formed a composite dispersed phase in LCBPP. The impact and tensile strengths of the unfoamed LCBPP were found to have been simultaneously optimized owing to the synergistic effect of the elastomeric toughening of TPEE and the reinforcement of the PTFE fiber–induced fibrous crystal structure. Compared with pure LCBPP, the impact strength of the LCBPP/TPEE/PTFE composite increased by 216%, whereas its tensile strength decreased by only 6%. In particular, the synergistic effect of TPEE/PTFE improved the resilience and compression strength of the LCBPP foam. Compared with the pure LCBPP foam, the permanent strain of the LCBPP/TPEE/PTFE foam was reduced by 13.8% after five cycles of compression and its compression strength increased by 27.3%. The experimental results of our study could be used to prepare LCBPP foams with exceptional resilience, high compression strength, and good application prospects.