Miscibility of a polyarylate with a liquid crystalline copolyester

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Abstract
The miscibility has been investigated for binary blends of a polyarylate (PAr) with a liquid crystalline copolyester of p‐hydroxybenzoate and ethylene terephthalate units in a 6/4 molar ratio (PET/PHB). The binary blends were prepared by solution precipitation. The transitions of the PET/PHB have been measured with a rheometrics dynamic spectrometer. The phases in blends have been studied with a differential scanning calorimeter, by ther‐mogravimetry and with a polarizing optical microscope. The blends exhibit two glass transitions (Tgs) over the composition range 10–90 wt %. The amorphous PET phase from the PET‐PHB is found to be partially miscible with PAr, which leads to a decrease of the PAr Tg. The amount of this partially miscible portion of PET has been estimated by the Couch‐man equation. On heat treatment of the blends at 250 to 300°C, transesterficiation takes place, as judged by the shift of the higher of the two Tgs. © 1993 John Wiley & Sons, Inc.