Physical properties of blends of polycarbonate and a liquid crystalline copolyester

Abstract

Blends of polycarbonate (PC) and poly(ethy1ene terephthalate-co-p-oxybenzoate) (PET/PHBGO) were prepared by melt-blending. Physical and/or chemical interactions between the two phases of the system were studied by thermal analysis and infrared spectroscopy. Rheological measurements in shear flow were carried out both in the low and high shear rate regions in the temperature range of the existence of the mesophase. At low liquid crystalline polymer (LCP) content, the blends showed flow curves similar to those of the unfilled PC, while at higher LCP percentages the rheological behavior of the pure LCP was resembled. Moreover, in the whole shear range, the viscosity values of such blends were in between those of the pure polymers. The influence of the addition of 10% LCP on the mechanical properties of the PC was investigated. Fiber-spinning was performed under different experimental conditions, and it was found that opportune drawing conditions are necessary to improve the modulus of the matrix. Morphological analyses of the pure LCP and of the blends were related to the rheological and mechanical behavior of these systems. While the LCP exhibited an elevated dimensional stability, the inclusion of the LCP in PC matrix did not improve the dimensional stability of the blends.

Blends of a polyetherimide and a liquid crystalline polymer: Fiber orientation and mechanical properties

“…8 ) / ( 1 -A * B . 8 ) , ( 1 ) where E, is composite modulus in the direction of the fibers, Em the modulus of the matrix, 8 the volume fraction of the filler, A the 2 ( L I D ) , aspect ratio of the fibers, B the ( E f / Em -1 ) / ( E / / E , + A ) ,…”

In situ compatibilization of a polyetherimide and a thermotropic polyester using an epoxy resin

“…Moreover, under appropriate processing conditions [8,9], liquidcrystalline polymers can develop a fibrillar morphology with a high degree of orientation and originate in situ composites, where fibrous reinforcement can be formed directly during processing, as a consequence of their easy orientability and long molecular relaxation times [10][11][12][13][14][15][16][17]. Extensional flow rather than shear flow is preferred for the formation of the fibrillar phase.…”

The influence of a copolymer as adhesion promoter for polycarbonate and liquid crystalline polymer blends

“…The orientation of the rigid blocks produces a manyfold increase of the elastic modulus of TLCP. 12,15 In blends constituted by a random-coil polymer (matrix) and a nematic polymer (filler), the increase of mechanical properties depends on the composition of the blend and can be easily fore-83 seen, assuming a good adhesion between matrix and filler, on the basis of composite theory.l29l6…”

“…The wide scientific literature [3][4][5][6][7][8][9][10][11][12] concerned with blends based on TLCP clearly indicated the need of a deep investigation into the interaction mechanism between the liquid crystalline phase and the matrix, the adhesion between the matrix and filler being a factor of dramatic influence in the success of a composite design. To transfer the stress between the interface, a chemical binding is desirable, but a careful balance between the factors limiting the chemical miscibility is necessary to prevent the formation of a homogeneous mixture in which the absence of the liquid crystalline fibers segregated from the matrix will eliminate the reinforcement effect.…”