Effect of vinyl silane-treated Amaranthus spinosus plant root cellulose on load-bearing and time-dependent properties of pineapple fiber–vinyl ester composite

This study investigates the enhancement of vinyl ester composites reinforced with pineapple fiber and silane-treated cellulose derived from the roots of the Amaranthus spinosus plant. The cellulose was extracted through a chemical process and subjected to a silane treatment to improve its compatibility with the vinyl ester matrix. The composites were fabricated using a 350cps viscosity vinyl ester resin, reinforced with 40 vol% pineapple fiber mats and varying percentages (0.5, 1, 2 and 4 vol%) of silane-treated cellulose. Among the composites, specimen VP3, containing 2 vol% silane-treated cellulose, demonstrated superior performance across all tested properties. It achieved a tensile strength of 142 MPa, a compression strength of 221 MPa and a flexural strength of 242 MPa, indicating optimal reinforcement. VP3 also showed the highest fatigue life, with 44,000 cycles at 30% UTS, and exhibited the lowest creep strain, indicating excellent resistance to time-dependent deformation. Thermally, VP3 exhibited a TG % of 95% and a degradation temperature of 410 °C, reflecting enhanced thermal stability. The dynamic mechanical analysis revealed a storage modulus of 6.1 GPa and a low loss factor of 0.65, indicating minimal energy dissipation and superior mechanical performance. The silane treatment played a crucial role in improving fiber–matrix adhesion, leading to better load transfer, reduced internal friction and enhanced overall properties. SEM analysis supported these findings by highlighting the presence of fiber breakage and pullout in specimens with lower silane-treated cellulose content, while VP3 showed minimal defects, confirming the effectiveness of the silane treatment and uniform filler dispersion. This study concludes that the optimized combination of pineapple fiber and silane-treated cellulose in VP3 offers the best balance of mechanical, thermal and viscoelastic properties, making it a promising material for advanced composite applications.