A thermotropic liquid-crystalline polymer (LCP) was found to be miscible with poly(ethylene terephthalate) (PET) for LCP contents up to 35 wt% and immiscible at higher LCP contents. The melts of the miscible blends are isotropic under the polarizing microscope. They crystallize with a single transition during rheological cooling measurements. In the solid state, the miscible blends showed a single glass transition, as represented by a single peak of loss modulus G" versus temperature, which decreased linearly with LCP content. Addition of a small quantity of LCP has a dramatic effect on rheology. For example, addition of 2 wt% LCP reduces the viscosity by about 60%. This effect is most pronounced for PET of higher molar masses. The melt viscosity decreases exponentially with the LCP content in the range of composition where the blends are miscible, but there is no significant further reduction of viscosity when the LCP content exceeds 50 wt% as the phase separation appeared. Addition of LCP also changes the distribution of the relaxation times of PET and broadens the zero-shear viscosity regime.
Посилання на статтю:
Miscibility and viscoelastic properties of blends of a liquid-crystalline polymer and poly(ethylene terephthalate) / Y. G. Lin, H. W. Lee and H. H. Winter // Polymer. – 1993. – Vol 34. – P. 4703-4709.