Synergistic Toughening and Microcellular Foaming Properties of LCBPP with Oriented Elastomer Fibers and β-Nucleating Agents

Polypropylene’s low-temperature brittleness and poor impact resistance limit its long-term use. This study explores the enhancement of long-chain branched polypropylene (LCBPP) by blending it with thermoplastic polyester elastomer (TPEE) and β-crystalline nucleating agent WBG-II. Melt blending was performed using a torque rheometer, followed by cold-drawing in situ fibers and β-crystals to improve toughness. The crystallization and fracture morphology were analyzed by DSC and SEM. Microcellular LCBPP foams were prepared using supercritical carbon dioxide (scCO 2 ) as a blowing agent under varying foaming temperatures. The results showed that when the elastomer fiber content reached 20 phr, the impact strength of the cold-drawing LCBPP increased by 252%, compared to hot-drawing LCBPP with the same elastomer content. The foam’s cell size decreased from 87 to 49 μm, and its cell density increased from 3.2 × 10 8 cells/cm 3 to 5.6 × 10 8 cells/cm 3 . After five compression cycles, the foam’s permanent deformation reduced from 23.2% to 8.49%, significantly enhancing its resilience. These findings provide essential insights for improving the rebound and cushioning performance of polymer foams.