Studies on the role of organophosphites in polyester blends: II. The inhibition of ester-exchange reactions



Ester-exchange reactions during melt extrusion of polyarylate, polycarbonate, and polyethylene terephthalate ternary blends result in a decrease of the melting point and the heat of fusion of the poly(ethylene terephthalate). When an organophosphite is used to suppress the ester-exchange reactions, it was found that whenever the phosphite is converted into a phosphonate, there is little change in both the melting point and the heat of fusion of the polyethylene terephthalate during prolonged exposure to high temperature in the blends. 31P nuclear magnetic resonance is employed to investigate the chemical changes and differential scanning calorimetry to evaluate the thermal stability of the blends. The organophosphite appears to be transformed through side-chain hydrolysis into other phosphorous species, such as diphosphonate in order to be an effective suppressant of the ester-exchange reactions.