Ecofriendly Flame-Retardant Polystyrene Composites: Exploiting the Synergistic Effects of Phytic Acid, Polyethyleneimine, and Expandable Graphite

Ecofriendly flame-retardant polystyrene (PS) composites were developed using the synergistic effects of phytic acid (PA), polyethyleneimine (PEI), and expandable graphite (EG). PA was chemically hybridized with PEI, and the hybrid (PAE) was incorporated into PS together with EG. The flame-retardant performances of the resulting composites were evaluated using the limiting oxygen index (LOI), UL-94 vertical burning test, and cone calorimetry test. The strong interaction between EG and PAE provided an effective barrier against heat and oxygen, thereby improving the flame retardancy. The best-performing composite (PA:PEI:EG = 1:1:1 (w/w/w), total flame-retardant loading = 10 parts per 100 parts of PS) exhibited an LOI of 27.7% and a UL-94 V-0 rating. The peak heat release rate (148.8 kW/m2) and total heat release (91.2 MJ/m2) of this composite were lower than those of pure PS by 79.2% and 34.0%, respectively. This study provides guidelines for the production of flame-retardant PS and other polymeric materials.