Mechanical Properties of Phosphogypsum‐Reinforced Epikote 828 Epoxy Composites

ABSTRACT Phosphogypsum (PG), a byproduct of fertilizer production in Vietnam, is predominantly landfilled, posing significant environmental challenges. This study investigates PG as a reinforcing filler for epoxy resin composites with contents of 0, 3, 6, and 9 wt%. Comprehensive characterization using infrared spectroscopy (IR), thermogravimetric analysis (TGA), mechanical testing, and scanning electron microscopy (SEM) was conducted. Results confirmed that PG did not chemically react with the epoxy matrix but contributed to enhanced thermal stability. Mechanical properties showed slight reductions in tensile and izod impact strength, whereas flexural strength and fracture toughness improved considerably. The optimal performance was observed at 6 wt% PG, where flexural strength increased from 79.5 to 118.2 MPa and fracture toughness from 1.8 to 2.0 MPa m 1/2 . SEM analysis revealed porous PG particles (< 39.5 µm) dispersed in an epoxy matrix and rougher, zigzag fracture surfaces, indicating resistance to crack propagation pathways. Overall, PG demonstrates promise as a sustainable, low‐cost filler for epoxy composites, offering both performance enhancement and an effective approach to reduce industrial waste disposal.