Development of novel flame retardants for polyurethane foams
In line with current environmental concerns, a non—halogenated, high phosphorus content flame retardant for polyurethane foams is preferred. Cyclic phosphorus compounds have a high percentage of phosphorus and should therefore exhibit good flame retardant activity when incorporated into polyurethane foams. One such group of compounds, known as phospholenes, had previously been successfully synthesised but in poor yields and with only a few derivatives being prepared. This work was concerned with identifying and then optimising synthesis routes to a variety of model phospholene oxide esters, that were proposed to have potential as novel flame retardants. Kinetic and mechanistic studies of the simplest synthesis reaction were also investigated. Once optimisation of both stages of the two stage synthesis were successful in raising the yields from -25% to >90%, a flow reactor was designed and constructed to facilitate production of the model compounds in large quantities (-P 1/2 kg) required and then incorporated into polyurethane foams at a variety of loadings. These flame retarded polyurethane foams were prepared and extensive flammability tests were subsequently performed to fully evaluate the model compounds' performance as flame retardants. The model compounds exhibited favourable flame retardant properties, but their physical properties prohibited their use as commercial flame retardants. However the work completed has shown the potential, within this area of compounds, for the commercial development of suitable flame retardants.