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Amorphous copolyesters based on bibenzoic acids and neopentyl glycol

Author:
Eliot Edling, Hans, Mondschein, Ryan J., Davis, Mark K., Long, Timothy E., Richard Turner, Sam
Source:
Journal of polymer science 2019 v.57 no.5 pp. 579-587
ISSN:
0887-624X
Subject:
acids, condensation reactions, copolymerization, crystal structure, crystallization, differential scanning calorimetry, ethylene glycol, glass transition temperature, melting, melting point, moieties, molecular weight, nuclear magnetic resonance spectroscopy, polyesters, thermal stability, thermogravimetry, thermoplastics, viscosity, weight loss
Abstract:
High Tg amorphous copolyester thermoplastics were synthesized by incorporating 4,4′‐bibenzoate (4,4′BB) and 3,4′‐bibenzoate moieties into the polyester backbone via melt polycondensation. The high levels of crystallinity typically associated with 4,4′BB containing polyesters were suppressed through copolymerization of ethylene glycol, 1,4‐cyclohexane dimethanol, and neopentyl glycol (NPG) diols. NPG was shown to be highly effective in suppressing crystallization and was used to produce amorphous compositions with Tg’s as high as 129 °C. Diol ratios were determined by ¹H NMR spectroscopy and molecular weights were assessed with inherent viscosity (ηᵢₙₕ). Thermogravimetric analysis showed single‐step weight losses in the range of 395–419 °C. Differential scanning calorimetry was used to determine melting points and glass transition temperatures over a wide range of copolyester compositions and identified amorphous compositions. Dynamic mechanical analysis confirmed Tg’s and was used to study β‐relaxations below the Tg. Rheological analysis revealed the effect of NPG structures on shear thinning and thermal stability. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 579–587
Agid:
6277599