Properties of sodium hydroxide treated agave sisalana fiber reinforced composites filled with pectin

Abstract This study investigates the mechanical, physical, and thermal performance of pectin-filled sisal fiber–reinforced polyester composites fabricated using untreated and NaOH-treated Agave sisalana fibers. Pectin filler was incorporated at 0 to 10 wt.% and the composites were characterized according to relevant ASTM standards. Compared with untreated fiber composites, NaOH-treated systems exhibited notable improvements in hardness, impact strength, tensile strength, flexural strength, shear strength, and compressive strength, indicating enhanced fiber–matrix interfacial bonding. Mechanical properties increased with pectin addition up to 6 wt.% (S-P6), which yielded optimum values, including a tensile strength of 101.57 MPa, flexural strength of 136.75 MPa, shear strength of 30.18 MPa, and compressive strength of 89.25 MPa for treated fibers. Water absorption was significantly reduced in treated fiber composites, demonstrating improved moisture resistance. Thermal conductivity showed a gradual increase with filler loading, reaching 0.205 W(m·K) −1 at 6 wt.% pectin. The results confirm that alkali-treated sisal fibers combined with an optimal pectin content of 6 wt.% produce sustainable composites with balanced mechanical strength, reduced water uptake, and improved thermal performance suitable for structural and semi-structural applications.