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Characterization of liquid crystalline polyester polycarbonate blends

1989; Wiley; Volume: 29; Issue: 9 Linguagem: Inglês

10.1002/pen.760290906

1548-2634

Táriq M. Malik, Pierre J. Carreau, N. Chapleau,

Advanced Materials and Mechanics

Abstract Mechanical and rheological properties of blends of a thermotropic liquid crystalline polyester with a polycarbonate have been investigated. The blends are fibrillar in character and exhibit great hardness and toughness due to high degree of molecular orientation which develops during the melt blending and processing steps. Increases of the Young modulus by 100 percent are observed for blends containing only 10 percent of liquid crystalline polymer, LCP. Time‐dependent behavior of the blends was investigated by performing solid state relaxation measurements and the relaxation modulus was also found to increase by the addition of LCP. The effect is relatively small in the glassy zone of viscoelastic response, but increases through the transition and viscous flow regions. The melt viscosity of the polycarbonate is slightly shear thinning whereas that of the unblended LCP increases rapidly with decreasing shear rate at low shear rate. This suggests the presence of yield stresses as confirmed by measurements on the Rheometics RSR in the stress sweep mode. The melt viscosity of the blends was found to be similar to that of the unblended polycarbonate, but more shear‐thinning and less viscous. Preliminary results of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) are also presented.