Mechanical, Thermal, and Morphological Behavior of Sustainable <scp>PC</scp> / <scp>ASA</scp> Composites Reinforced With Walnut Shell Powder

ABSTRACT This study explores the effect of walnut shell (WS) powder as a bio‐based filler on the mechanical and thermal performance of polycarbonate (PC)/acrylonitrile–styrene–acrylate (ASA) composites. Composites containing 5–15 wt% WS were prepared by melt blending and characterized using FT‐IR, DSC, TGA, and SEM analyses. The addition of WS increased stiffness, reflected in a higher flexural modulus, but caused an average 25% reduction in tensile and impact strength because of weak interfacial bonding between the hydrophilic filler and the polymer matrix. FT‐IR spectra showed that the polymer phases remained intact and suggested limited hydrogen bonding between WS hydroxyl groups and the carbonyl groups of PC or ASA. DSC thermograms exhibited two glass transition temperatures, at approximately 113°C and 144°C, confirming partial immiscibility between the blend components. TGA results indicated a slight decrease in the onset degradation temperature but a higher char residue, increasing from 14.7% to 17.3%, suggesting better thermal stability at elevated temperatures. SEM micrographs revealed rough, irregular fracture surfaces with non‐uniform filler distribution. Overall, this study demonstrates that WS can act as an effective stiffening agent while preserving processability, offering a sustainable route to develop rigid and heat‐resistant PC/ASA composites.