Synthesis and testing of nonhalogenated alkyne-containing flame-retarding polymer additives

In this paper, the synthesis and thermal properties of several alkyne-containing materials are discussed. The materials were synthesized using palladium/copper-or palladium/zinc-mediated cross-coupling reactions between multibrominated aromatics and phenylacetylene. Therefore, in one step, commercially available brominated flame retardants can be converted into nonhalogenated high-char materials using transition metal catalysis. The materials synthesized included polymers, oligomers, carbonates, and diphenyl ethers. The thermal properties of the synthesized materials were studied using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). In general, the DSC and TGA data showed that the synthesized materials were all high-char-yielding materials. Further, DSC data showed that the materials which had o-dialkyne substitutions (enediyne systems) generally cross-linked at lower temperatures than materials that had m-dialkynes. However, TGA showed that the materials with ortho substitutions, especially those with multiple ortho substitutions, generally had higher char yields than those with meta substitutions. The materials were blended into polycarbonate and tested for ignition resistance using the UL-94 flame test. Alkyne-containing oligomer 9, used in conjunction with 0.5 wt % of a bromide-containing flame retardant, provided flame retardancy in polycarbonate according to the UL-94 test. This indicates that alkyne-containing materials, acting as condensed phase flame retardants, can substantially lower the amount of halogen content needed for flame retardancy in polycarbonate.