Performance of Glass Fiber Composites With Plastic‐Waste Pyrolysis Char as Filler

ABSTRACT Plastic pyrolysis offers circular solutions for mixed plastic waste but leaves a carbonaceous char that is often underutilized. This study evaluates plastic‐waste‐derived pyrolysis char (0–10 wt.%) as a filler in epoxy/E‐glass laminates (GFRP) and quantifies mechanical, thermal, microstructural, and electrical responses. Tensile behavior remained brittle across all systems; Young's modulus rose at 2.5 wt.% while ultimate tensile strength decreased at mid‐loadings and partially recovered at 10 wt.%. Flexural strength increased at 2.5 wt.%, dipped at 5–7.5 wt.%, and rebounded at 10 wt.%. Interlaminar shear strength improved markedly at high loadings (7.5 wt.% and 10 wt.%). Impact strength showed a modest gain at 2.5 wt.% but declined sharply at 5 wt.%. Hardness peaked at 5 wt.%. Fiber volume fraction fell with char, rationalizing strength/stiffness trends. TGA/DTG revealed three‐stage degradation with a single main peak. Four‐point probe tests detected no conduction at 10 wt.% (sub‐percolation). SEM linked property changes to dispersion at low loading (crack deflection) versus agglomeration and interfacial defects at mid/high loading. Overall, low to moderate char levels enhance stiffness and interlaminar shear strength with minimal reduction in mechanical strength, while higher loadings trade toughness for through‐thickness shear resistance.