Zinc Borate ZB-325 (Flame Retardant + Mold Inhibitor Synergist)

Zinc borate enhances halogen FR systems through two mechanisms: (1) Gas-phase synergy—Zn2+ reacts with HBr/HCl generated by halogenated FR during combustion, recycling halogen radicals to more active forms that interrupt the combustion chain reaction more efficiently; (2) Condensed-phase synergy—boron oxide (B2O3) released above 290°C forms a glassy protective char layer that insulates the polymer from heat and oxygen. Zinc borate typically allows 20–30% reduction in halogenated FR loadings to reach the same fire rating, improving mechanical properties and reducing cost. It also functions independently as a mold and mildew inhibitor in marine coatings.