Study on the Orientation Mechanism of High-Strength Liquid Crystal Polymer Fibre

Study on the Orientation Mechanism of High-Strength Liquid Crystal Polymer Spinning Fiber Han Zhifang (Chengdu Branch of the Chinese Academy of Sciences, Chengdu S10041) Stretch flow orientation, steady orientation movement and unsteady movement. The Lagrangian method was used to study the stability of axisymmetric spinning elongation. It is concluded that the molecular orientation of the liquid crystal polymer in the spinning process is more stable than the crucible, and its orientation motion has high resistance to dissolving orientation, and it is easier to form a high degree of orientation. This is to produce high strength and high modulus fibers, films and The basis of the molded product.

Day stability analysis, an important application of molecular orientation liquid crystal polymers in anti-dissolving orientation 1 melt spinning is the production of high-strength, high-modulus fibers, such as Kevlar-type fibers. Another important application is the use of liquid crystals in display technology.

Currently, liquid crystal displays have been widely used in computers. However, the rheological basis and applied basic research of liquid crystal polymers lag behind their development and application. For example, the mechanism of production of high-strength and high-modulus fibers by liquid crystal polymer materials remains to be further studied. At the same time, in the process of extrusion of liquid crystal helium molecules, the phenomenon of back extruding swell has been shown, which is significantly different from the general polymer melt. In the liquid crystal continuum mechanics, in order to describe its molecular orientation characteristics, the introduction of a vector to the vector that characterizes the dominant orientation of molecules in a neighborhood of any point acts on the liquid crystal polymer, which can either produce fluid motion or induce orientation. Vector (orientator vector) orientation motion. The main characteristic of the main chain or side chain type liquid crystal polymer is that the molecular chain orientation is easily formed under the action of the external force field. Actual 1) National Natural Science Foundation Project B test shows that when the liquid crystal polymer fluid passes through the spinneret, die or flow channel, even if orientation is obtained at low shear rate, general polymer can be achieved without post-stretching. The degree of orientation achieved after stretching. Therefore, by using the properties of liquid crystal polymers, ie, thermotropic liquid crystal polymers or composite materials blended therewith, high-strength, high-modulus fibers can be produced. (l) For liquid crystal polymer spinning, flow vectors are set. The velocity field is in the following form. In the vector and velocity fields (2) and (3), the vector transfer equation (1) is converted to dnzdnzdnz. The liquid crystal polymer orientation motion is much smaller than the fluid velocity, so the transport The inertial term in the equation can be omitted, ie the partial derivative of time can be used in place of its full differential, so the vector equation derived from the transport equation can be simplified to the steady-state liquid crystal polymer spinning elongation flow, which is derived from the above equation. Because it is the main stretching direction, a reasonable steady-state flow solution is the following two solutions, = 1, = 0. The initial vector when extruded from the spinneret hole should be parallel to the unit vector of the stretching direction, so the first one The solution is reasonable. 3 Unsteady orientation motion For the unsteady liquid crystal helium molecular spinning elongation flow, the integral is obtained from equation (5). If the initial condition is nzt=0 =1, there must be As0. Corresponding to the stationary flow solution = 1, nr =0. The non-unsteady theory of the vector-transport equation is based on the idea that when the initial time vector is the unit of the main tensile direction, it will continue to keep the direction vector for the direction of time. Now suppose that in the past (the liquid crystalline polymer has the anti-disorientation property in the spinning process, and the general cerium molecule does not have the property, this is a new concept proposed in this study. The stable molecular orientation degree is the liquid crystal polymer or its The burial explanation of the strength and the moduli of the yttrium modulus made by the composite material is a special property caused by the anisotropy of the liquid crystal polymer.

4 Stability analysis In this paper, the stability of liquid crystal polymer spinning will be studied using the Lagrangian method of fluid dynamics. This method was successfully applied to the study of the stability of viscoelastic fluid sheet in equation (2) and formula ( 3) Under the equation (4), the basic solution for the flow can be given by equation (7). The sum of the components of the vector component and the disturbance value represents the disturbance component. It can be understood that the amount of perturbation is caused by the de-orientation of the liquid crystal polymer when extruded from the spinneret hole. Linearization of the unsteady-orientation equation of motion (13) results in that the first term in the equation is the material derivative and the coefficient of the second term is independent of time. Therefore, in the Lagrangian coordinate, the solution of the equation can be set to In the following form, f = r = t is Lagrange coordinates. Substituting equation (15) into equation (14) yields that the full differential in the equation in the Lagrangian coordinate system can be replaced by partial differential, ie, the integral equation is used to derive the solution to the ordinary differential equation. Let i = If P(f) = P, the integral constant can be determined. Because A, fc, and t are all positive, -6Afct is negative. Therefore, the perturbation amplitude P(t) decays with time and can be oriented along the major axis without post-stretching the molecular orientation. The molecular orientation is stable and is not influenced by the disorientation. Spinning stretches differ. This conclusion is consistent with the previous conclusions, but also further confirmed the above conclusions. However, it should be pointed out that the basic equation (13) in the above stability study has taken into account the characteristics of axisymmetric symmetry, that is, it belongs to a two-dimensional space problem. The conclusion of this paper is derived under the following conditions: the stretch rate is constant, and the orientation motion has no substantial effect on the fluid motion. If you need to further study the problem, you should consider the stretching rate is not constant, the orientation of the movement of the fluid movement, you must study the fluid movement equation and the orientation equation of motion. Obviously, this study pointed out the main direction of the problem, namely that the orientation motion in the spinning liquid stretching molecules of liquid crystal molecules has the energy to maintain the orientation of the main stretching direction. Based on the following conclusions, the liquid crystal polymer spinning has a higher stability in the orientation of stretched molecules, and it is easier to form a 篼 orientation degree in the sliver, which is to produce high-strength and high-modulus fibers, films and molded products. The above conclusions are consistent with the current application of liquid crystal polymers.