Potential Synergism between Novel Metal Complexes and Polymeric Brominated Flame Retardants in Polyamide 6.6

While environmental concerns have caused polymeric brominated primary flame retardants (PolyBrFRs) to be effective replacement monomeric species, few alternatives for antimony trioxide (ATO) have been developed beyond the zinc stannates (ZnSs). Previous research, which explored the interactions of aluminium (AlW), tin (II) (SnW) and zinc (ZnW) tungstates with several phosphorus-containing flame retardants in polyamide 6.6 (PA66), is extended to two PolyBrFRs: brominated polystyrene (BrPS), and poly(pentabromobenzyl acrylate) (BrPBz). On assessing the effect of each tungstate on the thermal degradation and flammability in combination with each PolyBrFR using TGA, UL94, LOI, cone calorimetry and TGA-FTIR, only ZnW and SnW showed significant increases in LOI (>26 vol.%). Both ZnW-BrPS- and ZnW-BrPBz-containing formulations yielded average UL94 ratings ≥ V-2 and TGA char residues (corrected for metals content at 500 °C) in air > 15 wt.%. BrPS-containing samples, especially those containing ZnW and SnW, generated peak heat release rates approximately 50% lower than the equivalent BrPBz samples. These reductions did not correlate with respective increases in LOI, suggesting that tungstate-PolyBrFR combinations influence pre-ignition differently to post-ignition behaviour. Calculated synergistic effectivities indicate that ZnW functions as a synergist in both pre- and post-ignition stages, especially with BrPS. TGA-FTIR and char analyses showed that, in addition to the vapour-phase activity normally associated with PolyBrFRs, condensed-phase processes occurred, especially for the ZnW-PolyBrFR combinations. Additionally, ZnW demonstrated significant smoke-suppressing properties comparable with zinc stannate (ZnS).

Synthesis and mechanical properties of nano-Sb2O3/BPS-PP composites

In view of the limitation of wide application of polypropylene(PP) with low strength, poor low-temperature brittleness and easy combustion, a kind of PP matrix nanocomposites was designed and prepared. Sb2O3 nanoparticles (nano-Sb2O3) modified by silane coupling agent of KH550 were dispersed into brominated polystyrene(BPS)-PP matrix by ball milling dispersion and melt blending method, respectively. And the nano-Sb2O3/BPS-PP composites samples were obtained by injection molding method. The effects of nano-Sb2O3 particles on mechanical properties of nano-Sb2O3/BPS-PP composites were investigated. The results showed that the surface of nano-Sb2O3 particles was successfully modified by the KH550 and the interfacial adhesion between nano-Sb2O3 and PP matrix was improved. With increasing of the mass fraction of nano-Sb2O3, the tensile strength and impact strength of nano-Sb2O3/BPS-PP composites were improved accompanying by increasing of crystallinity and refining grain of the composites. When the mass fraction of nano-Sb2O3 was 3 wt%, the tensile strength of nano-Sb2O3/BPS-PP composites was 43 MPa, which was 30.3% higher than that of PP. When the mass fraction of nano-Sb2O3 was 2 wt%, the impact strength of the composites was 44.19 kJ·m−2, which was 30.8% higher than that of PP.

Study on the flame retardancy of nano-Sb2O3/BPS-PBT composites

To improve the flame retardancy of polybutylene terephthalate (PBT), PBT-based flame retardant composites containing antimony trioxide nanoparticles (nano-Sb2O3) and brominated polystyrene (BPS) were investigated. Nano-Sb2O3, BPS, and PBT were dispersed by ball milling method to obtain composite powders, and the nano-Sb2O3/BPS-PBT samples were prepared by melt blending and injection molding methods. The flame retardancy of nano-Sb2O3/BPS-PBT composites was investigated. The results showed that nano-Sbs2O3 can obviously improve the flame retardancy of PBT-based composites. When the nano-Sb2O3/BPS-PBT composite contains nano-Sb2O3 with 5 wt% of mass fraction and BPS with 10 wt% of mass fraction, the nano-Sb2O3/BPS-PBT composite has excellent flame retardancy, in which the UL94 degree of flame retardancy achieves V-0 grade and the limit oxygen index is 28.3%.