Quantifying the Directionality of Liquid Crystalline Polymers in Extrusion Processes Using an Order Parameter

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.