PROPERTIES OF BLENDS OF A THERMOTROPIC LIQUID-CRYSTALLINE POLYMER WITH A FLEXIBLE POLYMER (VECTRA PET)

Blends of Vectra A900, a thermotropic liquid crystalline polymer (LCP), and poly(ethylene terephthalate) (PET) were studied over the entire composition range using scanning electron microscopy, differential scanning calorimetry, and rotational rheometry. There is some interaction between the polymers, as evidenced by melting- and crystallization-point depression in the PET phase. The shear rheology deviates substantially from simple mixing laws and from predictions of an emulsion model of dispersed blends. The viscosity of LCP-rich compositions exceeds that of either component at low rates and frequencies. The viscosity of PET-rich compositions falls below that of either component at low rates and frequencies. The latter observation cannot be explained by deformation and orientation of the LCP phase, since the dispersed LCP inclusions remain spherical following steady shear.