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Liquid crystalline polymers (LCPs) are among a high-performance class of materials, which derive unique mechanical, chemical, and electrical characteristics from their long-range molecular order. The evolution of anisotropic orientation in the LCP microstructure during processing, however, can adversely affect the macroscopic polymer behavior. Simulation of this anisotropy is crucial to the design of manufacturing processes producing the desired material properties, and the ability to quantify the polymer directionality is a necessary metric of the model. Using a Monte-Carlo approach introduced by Goldbeck-Wood et al., a practical method for simulating LCP orientation is used to model the polymer flow, and the directionality results are then used to calculate a quantitative molecular degree of order. This metric, known as the order parameter, is an ideal candidate for measuring the LCP orientation, ranging from zero to unity between the isotropic and perfectly aligned states, respectively, as it is sensitive to both the direction of the average molecular orientation, as well as to the distribution of crystals around the average orientation. The effects of varying process parameters in the directionality model on the order parameter are shown. Understanding of these relationships will ultimately drive the design of manufacturing processes for more isotropic materials.

With advances in technology and the introduction of new materials, the need for new processing methods to enable the benefits of these materials is growing. Liquid crystalline polymers (LCPs) are among a class of high performance polymers but the orientation of crystals in the final product can adversely affect their properties. Modeling the directionality of LCPs during manufacturing processes can provide information and insight into designing new processing methods in order to achieve desired material properties. In this study, a method of modeling the directionality of LCPs for steady state processes such as extrusion is developed. This method can be used for structured and unstructured meshes and as a result is robust to use for complex geometries. To demonstrate this method, a user defined function (UDF) is coded for ANSYS FLUENT and the orientations are shown for 2D cases. Results are shown for Poiseuille flow to verify the alignment of crystals along the shear direction. Results show very close agreement with physical phenomena involved in the rheology of LCPs which include the alignment of crystals in the direction of shear, annihilation of defect structure in quiescence and translation of crystals with the bulk of the fluid. Based on the presented results, the developed method shows very high potential for modeling directionality for steady state processes of LCPs on complex geometries.

It is known that liquid crystalline polymer (LCP) melts have a high elasticity which can be measured from its effect on the rheology on the cessation of shear. On the other hand, LCPs show very limited die swell after extrusion. In this paper, the results of experimental measurements of the die swell for a liquid crystalline material and polypropylene (PP), an amorphous polymer, are presented. The extrudate thickness 5 cm below the die lip is optically measured and the results are analyzed using ImageJ software. A numerical simulation of the die swell based on the capillary rheometry data and oscillatory rheometry is performed for LCP materials using ANSYS ® POLYFLOW ®. Different viscoelastic properties are used to model the LCP and optimum properties to model the die swell for the base volume flow rate are determined. Results show similarity between die swell modeling for the LCP at the base volume flow rate but increasing the die swell results in some deviation from the experimental results.

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