Sustainable Composites of Recycled Polypropylene and Luffa Biochar for the Reduction of Carbon Emissions

ABSTRACT The growing issues of plastic waste and rising atmospheric CO₂ require sustainable material solutions. This study develops composites from recycled polypropylene (PP) and luffa biochar (LB) via melt mixing. The materials were characterized for physicochemical, thermal, mechanical, and water absorption properties. Morphological analysis showed that LB was dispersed within the PP matrix, with a higher LB content resulting in reduced amorphous polymer regions. Thermogravimetric analysis indicated LB acted as a thermal barrier, enhancing stability by slowing PP degradation. Differential scanning calorimetry confirmed LB functioned as a heterogeneous nucleating agent, increasing crystallization temperature and enthalpy. Mechanically, LB improved flexural strength (42.36 MPa for PP to 59.12 MPa for LB70), flexural modulus (1.26–3.52 GPa), and Shore D hardness (62–77.33). However, tensile and impact strength declined with more LB due to poor interfacial adhesion and reduced ductile phases. The optimal LB size (75–100 μm) at 20 wt% maximized tensile strength. Water absorption increased with LB content, attributed to micro‐defects at the biochar–polymer interface, limiting use in humid environments. This work shows that composites of recycled PP and LB have potential for materials that prioritize hardness and durability, while being environmentally friendly.