Polysiloxane-based Organoclay Nanocomposites as Flame Retardants

Polydimethylsiloxane-aromatic dianhydride copolymers (PS-Oxy-PAA and PS-DAH-PAA) were blended through several techniques with organoclays Cloisite 30B, 10A and Na+ ranging from 1 to 5 wt.%. Thermal and flame-retardant analysis revealed an in-situ blending approach was optimal, which led to the generation of a nanocomposite, PS-Oxy-PAA/30B (5 wt.%), with comparable heat release capacity (170.5 J/g-K) and total heat release (12.0 kJ/g) as seen with some commercial polymers. Concomittant dispersion and FTIR analyses revealed that the enhanced thermal stability observed with PS-Oxy-PAA/30B (5 wt.%) is not dispersion related, since the organoclay was exfoliated in all composites formed. The driving force is the interaction between the carbonyl groups of the PS-Oxy-PAA and the hydroxyl groups of the organoclay, which is limited in all other cases. These results suggest judicious selection of organoclay and siloxane copolymers can faciliate the design of new environmentally safe, heat processible, nonhalogenated alternatives to traditional flame-retardant polymers.