Simulation of Melt Spinning of Pitches

Abstract

Effects of process variables and material properties on melt spinning of pitches have been studied based on simulation using governing equations by Kase and Matsuo. It is shown that the tension F in a filament depends on spinning conditions as well as viscosity of pitch in the form of F∝μ₀W^1/6ƒ₁(v₀, v_L, v_A)/ƒ₂ (T₀, T_s, T_A, E). Here, W, v₀, v_L and v_A are, mass flow rate, velocity at the spinnerette, winding speed and cross-flow air velocity respectively, and T₀, T_s and T_A denote temperatures at the spinnerette, at the solidification point and of air. Temperature dependence of viscosity is simplified by an Arrhenius type equation with a pre-exponential factor μ₀ and a flow activation energy E. To improve spinnability, the maximum tensile stress σ_L should be decreased by increasing W, T₀ and T_A or by decreasing v_L, v_A, T_s, μ₀, and E. In other words, slower cooling of the filament with larger diameter for a pitch with smaller activation energy is preferable to better spinnability. Effects of these factors on diameter, temperature and strain rate of the spinning filament are also discussed.