Synergistic effect of organophosphate functionalized montmorillonite on properties and water resistance of intumescent flame-retarded SEBS

Polystyrene-b-(ethylene-co-butylene)-b-styrene (SEBS) is a widely used thermoplastic elastomer. However, it suffers from poor flame retardancy. Proper combination of organic-modified montmorillonite and intumescent flame retardant (IFR) works but is not stable due to easy absorption of moisture. In this study, a novel and stable halogen-free flame-retardant system is demonstrated by encapsulating a hydrophobic organophosphate, ie, bisphenol A bis (diphenyl phosphate) (BDP) into a stable micelle and then "attaching" the BDP micelles to the montmorillonite (called: side-intercalation). The resulted BDP modified montmorillonite (BMMT) has a large inter-platelet spacing and demonstrated synergistic effect with IFR on flame retardancy, tensile property, and water resistance for the composite with SEBS. In addition to more homogeneous dispersion of IFR and BMMT, a longer-lasting interfacial interaction between IFR and SEBS matrix with addition of small amount of BMMT also plays the role. The results suggest that BMMT can serve as an effective additive for formulating novel halogen-free flame retardants for the SEBS to meet increasingly stricter environmental requirements.