Preparation and characterization of some unsaturated polyester alkyds based on terephthalic and isophthalic acids

In this work unsaturated polyesters based on terephthalate acid and isophthalic acid have been prepared by a two-stage process. In the first stage the prepolymer bis(2-hydroxypropyl) terephthalate (PTP1) was prepared and purified. PTPl was heated at different temperatures within the range lSO-1800 C, and the changes in molecular weight distribution, on heating, and the considerable ester-interchanges were assessed by gel permeation chromatography (GPC) and nuclear magnetic resonance spectroscopy (NMR). Similar experiments were performed with the prepolymer (P(TP)J provided by Imperial Chemical Industries and the prepolymer bis(hydroxypropyl) isophthalate (PIP1) which was synthesised and purified. GPC and NMR were used to compare the temperature dependence of ester-interchange and polycondensation in the three prepolymers. In order to see the implications of the ester-interchange observed on the mechanism of the reaction between prepolymer and maleic anhydride, unsaturated polyesters produced at various temperatures in short reaction times have been fractionated by preparative GPC. High resolution 300 MHz proton NMR was used for the qualitative and quantitative analysis of the unsaturated polyester and its fractions~ $tructures were assigned to the oligomeric compounds and reaction mechanisms were outlined. -Finally the products of the reaction of (PTP1), propylene glycol, maleic anhydride (or fumaric acid) in various molar ratios were examined by NMR and GPC, and their results were compared with a study of unsaturated polyesters based on (P(TP)n) and (PIP1).