An investigation of a copolyester of bisphenol-A with terepthalic acids and poly(2,6-dimethyl-1,4-phenylene oxide) and their mixtures by various methods

At first, the retention diagrams of some solvents on a copolyester of bisphenol-A with terephthalic and isophthalic acids in equal ratio (PAr), poly (2,6-dimethyl 1,4-phenylene oxide) (PPO) and their mixtures in compositions of 25/75, 50/50, 75/25 prepared by solvent casting were drawn by measuring their retention times in a wide temperature range by inverse gas chromatography (IGC) technique. The second order thermal transition points of the mixtures and their components were determined from their retention diagrams. The thermodynamic polymer-solvent interaction parameters of PAr, PPO and their mixtures with the studied solvents, solubility parameters of the polymers and polymer-polymer interaction parameters of mixtures were determined at temperatures between 220 oC and 260 oC. It was concluded that the polymers in the mixtures were miscible at studied temperature range since their solvent independent polymer-polymer interaction parameters obtained by means of the methods proposed by various researchers. It was concluded that the mixtures were immiscible at room temperature but miscible at 220 oC and 240 oC from the differential scanning calorimetry thermograms of the samples prepared by solvent casting at room temperature and quenched from high temperatures. The parameters obtained from the viscosity measurements of the mixtures were suggested that the polymers were immiscible at 30 oC but they come near to miscibility at 70 oC. However, a phase separation could not be observed in the mixtures on the polarized light microscopy from 260 oC to room temperature. A shifting of the carbonyl peak of PAr on the Fourier transform infrared spectroscopy-attenuated total reflection spectra from 1721 cm-1 to higher wave numbers by increasing ratio of PPO in the mixtures was interpreted as existence of a favorable specific interaction between polymers. The electrical conductivity of solvent cast films of PAr, PPO and their equimolar mixture dopped in various ratios with a few organic dopants were measured at dark and high vacuum in a wide temperature range. The conductivity of the mixture increased from 8.0.10-15 S/cm at room temperature to 3.0.10-13 S/cm at 240oC in the case of undopped sample while it increased up to 3.5.10-11 S/cm in the case of dopped ones. The morphologies of the nanocomposites prepared in various ratios by melt mixing of binary mixtures of PAr/Multiwalled carbon nanotube (MWCNT) and ternary mixtures of PAr/PPO/MWCNT were represented by means of light, scanning electrone and atomic force microscopies. The electrical conductivities of the nanocomposites were determined by measuring their surface and volume resistances at room temperature. By introduction of MWCNT, the conductivity of PAr was increased 10-2 S/cm while those of PAr/PPO mixtures were increased up to 10-4 S/cm. The mechanical properties of the nanocomposites were measured by dynamic mechanical analysis. The mechanical strength of PAr was increased by MWCNT however decreased by PPO. The decomposition temperatures of the ternary mixtures were higher than 460 oC although they decreased by introduction of PPO and MWCNT. Keywords: inverse gas chromatography, a copolyester of bisphenol-A, Ardel? D-100, poly(2,6-dimethyl 1,4-phenylene oxide), PPO, polymer-polymer interaction parameter, electrical conductivity.