Structure and morphology of the in situ composites of a liquid crystalline polymer and polycarbonate

Abstract

SummaryIn situ composites were prepared via melt blending of a liquid crystalline polymer (LCP) and polycarbonate using a twin screw extruder. The structure and morphology of these composites were analysed using both transmission electron microscopy (TEM) and scanning electron microscopy. The LCP phases were able to orientate and form in situ submicrometre fibres during the extrusion and postextrusion drawing. TEM images as well as selected-area diffraction patterns were obtained from the materials. The effects of both composition, i.e. LCP content, and postextrusion draw-down ratio on the development of the in situ formed LCP fibres were studied in detail. A skin-core morphological differentiation is observed in these materials where well-defined LCP fibres of higher aspect ratios were formed in the skin region. However, a significant amount of unelongated LCP particles were found coexisting with the less well-defined fibres in the core region of the extrudates. This skin-core differentiation was found to be dependent on the composition and the processing conditions, e.g. draw ratio. In this instance, electron microscopy is proven to be a powerful technique not only for direct observation of the formation, dimensions and morphology of the in situ LCP fibres, but also for the qualitative and quantitative characterization of the molecular orientation and crystalline structures in these fibres using selected-area electron diffraction. It is observed that the skin-core differentiation becomes more distinct in the in situ composites containing a higher percentage of LCP but diminishes when the material is processed at higher post-extrusion draw ratio.

Effect of Organoclay on the Orientation and Thermal Properties of Liquid‐Crystalline

“…Thus it is possible to tune the orientation of LCP by adding the filler. For extruded materials, the structure and mechanical properties were found to be closely related to the extrusion conditions 2, 3. Thus the orientation of LCP in nanocomposites may depend on factors such as the draw ratio of the extruder, and the condition of moulding for example.…”

“…Liquid‐crystalline polymers (LCP) are well known for their excellent properties, such as high strength and stiffness, low melt viscosity, and their high chemical and thermal resistance 1, 2. Recently, the blending of thermotropic LCP with thermoplastics has attracted much attention because of the self‐reinforcement effect of LCP due to their rigid‐rod‐like molecular structure.…”

Simulation of Fibrillation of PC/LCP/Kevlar Blends and Its Characterizations

“…Representative SEM images of the PC/LCP/unmodified and modified Kevlar composites under the same processing parameter (2) have displayed in (Figure 7(a-f)), where changes in LCP morphology with the addition of unmodified and modified Kevlar fiber can be clearly observed and also skin/core morphology has also been observed, which is very common in PC/ LCP systems. [32,33] This is the product of the ''fountain flow'' at the flow front and shear flow near the walls of the die. (Figure 7a) shows the LCP fibrillation at skin region in bundle form in presence of unmodified Kevlar fiber (Series I2) but not in oriented fashion but in core region (Figure 7b), the fibrillation of LCP fibers are more prominent and appears in more oriented manner supporting the orientation tensor value obtained from mold flow simulation study although the Kevlar fibers are covered by the matrix.…”

Microstrcture development during the injection molding of PET/LCP blends

“…Finally, the most significant difference was detected in the core layer (Rg. 16) which covered between 60% and '70% of the cross section. The drop size in the core layer (-4 pm) is somewhat between that in the pellets (-6 pm) and the one in the gate region core (-2 pm), indicating 61 0 that some coalescence has occurred.…”