Thermogravimetric analysis of aromatic boronic acids for potential flame retardant applications

The need for non-halogenated flame retardants continues to increase as more information about the toxicity of halogenated flame retardants and their pyrolytic byproducts becomes available. One class of non-halogenated flame retardants, organic boronic acids, has been reported in a number of papers as having flame retardant effects for cellulosic fibers as well as synthetic polymers. To improve this performance, an understanding of how the structure of the boronic acid affects its flame-retardant properties as well as its thermal stability is necessary. Reported herein are experiments aimed at achieving precisely this understanding, by investigating the thermal stability and degradation pathways of a broad variety of boronic acids, and using the resulting data to develop rules about the relationship between boronic acid structure (number of boronic acid moieties; presence/absence of functional groups, etc.) and the compound's thermal stability. These experiments highlight a number of boronic acids with exceptional thermal stability, with pyrene-1-boronic acid (compound 18) in particular showing stability up to 600 °C.