Hybrid Polypropylene Composites With Nanofillers and Basalt Fibers

ABSTRACT

Recycled polypropylene (PP) typically exhibits insufficient mechanical strength, limiting its broader application as a polymer matrix. The effects of nanofillers—cellulose nanofibers (CNF) and halloysite nanotubes (HNTs)—and basalt fibers (BF) reinforcement on the properties of recycled PP were investigated. The morphological, mechanical, rheological, and thermal properties of the materials were characterized using scanning electron microscopy (SEM), mechanical testing, rotational rheometry, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). SEM analysis revealed that the incorporation of CNF led to agglomeration due to its poor compatibility with the PP matrix, which is consistent with the slight reduction in mechanical properties. In contrast, SEM images of the HNTs‐ and BF‐reinforced composites showed a nearly homogeneous dispersion within the PP matrix. The incorporation of 5 wt.% HNTs into the PP matrix had no effect on the mechanical properties. For the PP/20B5C and PP/20B5H hybrid composites and the PP/25B fiber‐reinforced composite, tensile strength increased by 50%, 62%, and 60%, while the tensile modulus increased by 148%, 150%, and 145%, respectively. The shear storage modulus at 100 rad/s for PP/20B5C, PP/20B5H, and PP/25B increased 2.3, 5.1, and 2.2 times, respectively, relative to neat PP. The crystallization temperature increased by up to 6°C, particularly for hybrid composite, compared to neat PP. The results demonstrate that sustainable nano‐ and fiber‐scale fillers can effectively enhance the performance of recycled PP, highlighting their potential to expand the reuse of recycled PP in semi‐structural applications.