Mf. Champagne et al., GENERATION OF FIBRILLAR MORPHOLOGY IN BLENDS OF BLOCK COPOLYETHERESTERAMIDE AND LIQUID-CRYSTAL POLYESTER, Polymer engineering and science, 36(12), 1996, pp. 1636-1646
Polymer blends comprising liquid crystal polymers, LCP, as a minor com
ponent can be formed into fibrillar-type morphology. This morphology e
nables the generation of improved mechanical properties in the draw di
rection, in a manner comparable to unidirectional composites. In this
paper, the results obtained for blends of a polyetheresteramide block
copolymer, PEBA, with a liquid crystalline copolyester are presented.
Films prepared using a single-screw extruder were melt drawn on calend
ering rolls. The blends' storage modulus increased with draw ratio, la
mbda, reaching a maximum value for lambda = 3-4. The storage modulus o
f blends containing 30 wt% LCP, and drawn to lambda = 4 to 12, was fou
nd to increase nearly 50-fold in comparison to neat PEBA (from 18 MPa
to almost 1 GPa). The blends' morphology was characterized by dissolvi
ng the PEBA matrix, followed by gravimetric and microscopic analysis o
f the LCP phase. As expected, the average fiber diameter decreased as
a function of lambda(-0.5). The fiber content as a function of h follo
wed a trend parallel to that of the modulus. Longitudinal and transver
se moduli followed the Halpin-Tsai predictions for unidirectional comp
osites. Properties of compression molded specimens prepared from these
blends compared favorably with glass fiber composites.