Structural effects of diacidic and glycolic moieties on physicochemical properties of aromatic polyesterdiols from glycolysis/esterification of poly(ethylene terephthalate) wastes

Abstract : Useful polyols for rigid polyurethane foam manufacture may be obtained by glycolysis of post-consuming poly(ethylene terephthalate) (PET) wastes. The physicochemical properties of about 100 polyesterdiols were measured, the polyol molecular structure being built on three diacidic moieties and three glycolic moieties in various proportions. Viscosity, foaming agent compatibility and storage stability are the most relevant physicochemical properties. Statistical analysis was made over more than 50 polyols. Molar ratios of the constitutive moieties to terephthalic residue were taken as composition parameter. From a Principal Component Analysis (PCA) it was found that 141b compatibility is of opposite viscosity and independent of polyol storage stability, the properties being governed essentially by the glycolic moieties. Multiple regressions gave prediction equations for viscosity and 141b compatibility as a function of moieties amounts. The own effect of each structural unit was also investigated through some more homogeneous panels of polyols. Lack of storage stability appears when the proportions of constitutive PET units in glycolic and acidic moieties overcome critical values. The viscosity of the polyols. increases greatly with decreasing hydroxyl value or increasing the proportion of aromatic diacidic residues.