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

Useful polyols for rigid polyurethane foam manufacture may be obtained by g lycolysis of post-consuming poly(ethylene terephthalate) (PET) wastes. The physicochemical properties of about 100 polyesterdiols were measured, the p olyol molecular structure being built on three diacidic moieties and three glycolic moieties in various proportions. Viscosity, foaming agent compatib ility and storage stability are the most relevant physicochemical propertie s. Statistical analysis was made over more than 50 polyols. Molar ratios of th e constitutive moieties to terephthalic residue were taken as composition p arameter. From a Principal Component Analysis (PCA) it was found that 141b compatibility is of opposite viscosity and independent of polyol storage st ability, the properties being governed essentially by the glycolic moieties . Multiple regressions gave prediction equations for viscosity and 141b com patibility as a function of moieties amounts. The own effect of each structural unit was also investigated through some m ore homogeneous panels of polyols. Lack of storage stability appears when t he proportions of constitutive PET units in glycolic and acidic moieties ov ercome critical values. The viscosity of the polyols. increases greatly wit h decreasing hydroxyl value or increasing the proportion of aromatic diacid ic residues. (C) 2001 Elsevier Science Ltd. All rights reserved.