IN-SITU COMPOSITES BASED ON BLENDS OF A POLYETHERIMIDE AND THERMOTROPIC LIQUID-CRYSTALLINE POLYMERS SUBJECTED TO SHEARFREE DEFORMATIONS

The effects of shearfree elongational flows on the morphology and mech anical properties of blends of a polyetherimide (PEI) with thermotropi c liquid crystalline polymers (TLCP) have been investigated. Extruded sheets and injection molded plaques of PEI/Vectra A and PEI/HX1000 ble nds, with a TLCP concentration of less than or equal to 30 wt%, were s ubjected to uniaxial elongation, planar and biaxial deformations at 24 0 degrees C, above the glass transition temperature of the PEI, and at 265 degrees C, which is below the melting point of the TLCPs. Experim ental results revealed that each particular mode of shearfree deformat ion had a distinct effect on the morphology and properties of the blen ds. For instance, TLCP droplets were deformed into elongated fibrils b y application of uniaxial elongation, deformed into elongated ribbon-l ike structures after planar deformation, and deformed into a disc-like shape by application of equibiaxial flow. Regarding mechanical proper ties, it was observed that the tensile modulus and strength of molded plaques of PEI/HX1000 80/20 wt% increased to about twice their initial values (from 5.13 to 10.40 GPa and from 105 to 198 MPa, respectively) after a strain of 0.75 was applied in a direction parallel to the ini tial direction of the TLCP fibers. In addition, samples exhibiting equ al values of flow and transverse direction tensile modulus of similar to 5.0 GPa were obtained when molded plaques of PEI/HX1000 80/20 wt% w ere subjected to planar stretching in a direction transverse to the in itial direction of the fibers. Thus, by subjecting injection molded pl aques to planar stretching, it was possible to obtain a sample exhibit ing balanced flow and transverse direction mechanical properties and, consequently, reduced anisotropy.