Determination of end‐group concentrations and molecular weight of poly(butylene terephthalate) by solid‐state fourier transform infrared spectroscopy

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Abstract
Molecular weight determination in poly(butylene terephthalate) (PBT) is hindered by the inherent difficulties of intrinsic viscosity (IV) determination in general and toxic solvents used in particular. In any case molecular weight does not include information as to the identity of end‐groups in the polymer chain. This report shows how the Fourier Transform Infrared method of Ward for PET can be adapted for alcoholic and acidic end‐group determinations in poly(butylene terephthalate) (PBT) and consequently for the number averaged molecular weight of PBT. A statistical analysis was performed on comparative IR‐ and IV‐derived molecular weight which revealed a correlation coefficient of better than 90 percent. The method is, therefore, recommended as an alternative to the standard IV technique, especially if simultaneous end‐group analyses are also required.