Thermal stability of phosphinated diethyl tartrate

Organohalogen flame retardants, particularly brominated aromatics, are popular, effective, low cost, and widely used in the plastics industry. However, an increasing concern about persistence in the environment and potential negative health effects of these materials has generated intense interest in the development of alternatives. Ideally, these should have all the positive attributes of the materials that will be replaced. In addition, it is desirable that the new materials be as “green” as possible, e.g., based on renewable resources and be degradable to nontoxic products in the environment. A series of new, non-halogenated flame retardants based on tartaric acid is being developed. Tartaric acid is a by-product of the wine industry and is readily available locally on an annual basis (Michigan is the thirteenth largest producer of wine in the U.S.). It can be readily converted to the corresponding diethyl ester. This ester may serve as the base for the development of a series of new, non-halogenated flame-retarding agents. The presence of the reactive hydroxyl groups allows the introduction of a variety of phosphorus-containing moieties. For example, treatment of diethyl tartrate with diphenylphosphinyl chloride generates diethyl 2,3-di(diphenylphosphinato)-1,4-butanedioate. This material may serve as a monomer for the preparation of various phosphorus-containing polymers and oligomers via step-growth transesterification. The thermal stability of this compound has been assessed by thermogravimetry.