Abstract
This study investigated the mechanical and thermal properties of recycled polypropylene (rPP) composites reinforced with waste cardboard cellulose (WC) and modified with aluminum hydroxide Al(OH)3 and potassium alum (KAl(SO₄)₂·12H₂O) additives. The composites were fabricated using a twin-screw extruder and characterized before and after UV exposure .Waste cellulose was dispersed as a homogeneous suspension rather than a solution, as cellulose is insoluble in water.
Results showed that tensile strength increased by 15–30% with cellulose addition (10–30 wt.%), while elastic modulus improved by 20–40% depending on filler content and additive type. Composites containing Al(OH)₃ exhibited higher tensile performance compared to alum-modified ones. Impact strength showed a moderate enhancement with cellulose addition but slightly decreased with inorganic additives. DSC analysis revealed an increase in melting temperature (Tm) by 2–5°C and crystallinity (Xc) by 5–10% for cellulose-reinforced composites. Although no conventional compatibilizer such as maleic anhydride-grafted polypropylene (MAPP) was employed, the observed mechanical improvement is attributed to physical interlocking, hydrogen bonding interactions, and the stabilizing effect of inorganic additives .Alum-modified composites exhibited enhanced thermal stability, while cellulose-containing composites retained 85–90% of their initial mechanical properties after UV exposure, compared to 70–75% for neat rPP .