Novel synergists for flame retarded glass-fiber reinforced poly(1,4-butylene terephthalate)

Poly(1,4-butylene terephthalate) (PBT) is an important engineering thermoplastic polymer which is very often reinforced by glass fibers (GF) to improve its mechanical properties. Applications of GF-PBT could be limited due to its high flammability and flame retardants (FRs) must be incorporated into the polymer. In this work, the selected FRs are aluminum diethylphosphinate (OP 1240) and a combination of melamine cyanurate and of aluminum diethylphosphinate (OP 1200). Synergists are investigated in formulations of GF-PBT containing OP 1200 or OP 1240 according to different fire scenarios [limiting oxygen index (LOI), UL-94 and mass loss calorimetry]. It is found that polyhedral silsesquioxanes (POSS)-based molecules are synergists of interest combined with OP 1200 and OP 1240. The combination of the layered potassium acetate modified kaolin with OP 1200 also appears to be beneficial.