Morphology, mechanical properties, and environmental impact of long glass fiber-reinforced polypropylene foams

This work evaluates the morphology, mechanical performance, and environmental impact of polypropylene composites reinforced with long glass fibers and processed via conventional injection molding, MuCell and Ku-Fizz foaming technologies, combined with the Core Back cavity expansion technique. SEM and micro-CT analyses reveal the characteristic skin-core cellular structures, with fine and uniformly distributed cells ranging from 5 to 250 μm in size and an enhanced cell density with mold expansion on the order of 10 6 cells·cm -3 . Due to the reduction in the load-bearing area, tensile, flexural, and impact properties decrease with the density, mitigated by substantial reinforcement from long fibers. Specific properties maintain comparable to solid materials in the direction of preferential fiber alignment. The combined effect of mold expansion and fiber reinforcement in the foamed materials results in flexural stiffness up to 50% higher than that of the solid counterparts. Complementary life cycle assessment reveals significant environmental benefits of both foaming technologies over conventional injection molding due to material savings and energy efficiency gains, with a reduction in environmental impact around 17%. The study highlights the industrial applicability of these composite foams manufactured by advanced microcellular injection molding as promising candidates for lightweight, high-performance, and environmentally responsible industrial applications.