Structural, Thermal, and Mechanical Characterization of Vinyl Ester Composites Reinforced With <i>Juglans regia</i> Seed Shell Filler

ABSTRACT Vinyl ester (VE) composites were filled with 5–30 wt.% Juglans regia seed shell filler (JRSSF) to evaluate structural, thermal, and mechanical performance. Infrared spectroscopy established strong OH and CO interactions as evidence for effective filler–matrix bonding. X‐ray diffraction established the presence of an amorphous VE peak (2 θ ≈ 18.8°) together with new peaks corresponding to JRSSF crystallites, constituting a stable dual‐phase structure. Thermal analysis established three‐stage degradation, in which 20 wt.% JRSSF corresponds to the highest thermal stability. Mechanical properties were found to be best at 20 wt.%: tensile strength 33.4 MPa, modulus 2.13 GPa, flexural strength 56.3 MPa, flexural modulus 6.98 GPa, impact strength 9.78 kJ/m 2 , and hardness 38, whereas heat‐deflection temperature was raised from 66.6°C (neat VE) to 79.4°C at 30 wt.%. At over 20 wt.% filler, agglomeration, and poor wetting of the matrix decreased performance. Microscopic examination confirmed uniform dispersion and good interfacial adhesion to 20 wt.% with voids and pull‐outs at high loadings. The findings demonstrate that JRSSF, economic lignocellulosic waste, successfully improves the thermal stability, stiffness, and impact strength of VE composites, and 20 wt.% was found to be the best reinforcement level for structural and thermal applications.