BLENDS OF ALKYLOXY-SUBSTITUTED LIQUID-CRYSTALLINE AROMATIC POLYESTERSAND COPOLYESTERS WITH POLY(ETHYLENE-TEREPHTHALATE)

Blends containing poly(ethylene terephthalate) (PET) and a series of a lkyloxy laterally substituted liquid-crystalline copolyesters (HT05-X series 1) in various ratios were prepared in the melt at 260-degrees-C by mechanical mixing. The visual and light microscopical appearance o f the blends in the solid state and in the melt was found to be homoge neous for those blends which contained an aliphatic-rich HT05-X copoly ester. The homogeneous appearance can be explained by a colloidal disp ersion of the liquid-crystalline polymer (LCP) in PET. Obvious phase s eparation in the melt occurs slowly after long periods of time. Phase separation is forced by annealing at about 270-degrees-C, where a chan ge of viscosity is observed, and by shearing the sample. Characterizat ion of the blends by DSC experiments shows that the thermal behaviour of all blends is dominated by the phase transitions of PET and that th e LC-low-phase of the HTO5-X copolyesters with a high degree of alkylo xy substitution is suppressed. The WAXS diffraction patterns of all bl ends contained an amorphous halo. For blends with low HT05-X concentra tion, inner reflexions from the nematic sanidic phase, as exhibited by the HT05-X copolyester, could be observed. For blends with higher HT0 5-X copolyester concentration, characteristic reflexions from HTO5-X c opolyester crystals could be observed. The number of X-ray reflexions of the crystalline LCP in the blend is reduced compared to that of the pure LCP.