Analysis of Single and Two-layer Coating Flows

Abstract

Modern optical fibers require a double-layer coating on the glass fiber in order to provide protection from signal attenuation and mechanical damage. The most important plastic resins used in optical fiber and wires are plastic polyvinyl chloride, low- and high-density polyethylene, nylon, and polysulfone. One of the most important things that affect the final product after processing is the design of the coating die. This thesis presents the theoretical analysis of double layer optical fiber coating extrusion process inside a pressure type die. From the modeling of Single and Double-layer fluids in coated process, a number of guiding results in general may be identified. Generally, it is concluded that coating thickness is directly controlled by die design, boundary of the die, polymer used for coating the optical fiber and the dragging velocity of the optical fiber. The analysis concentrates on flow conditions around the die exit: particularly so on shear and strain rates, and identification of the influence of slip. It is analyzed that the bond between the polymer and the continuum can become stronger by applying high pressure gradient and using the shear thickening polymer for coating. Moreover, it is observed that the thickness of coated fiber optics increases with the increase in slip parameter, dilatant parameter, elastic and Deborah number, while the temperature distribution decreases with the increase of these quantities. Shear stress decreases with increase of slippage at the boundary of the die only for a limiting value of the boundary slip coefficient. It is also found that for , the thickness of coated wire increases and decreases for It is also established that as we increase lies in the range the distribution of temperature increases while, decreases when we increase the power law index in the domain . The flow rate, force on coated fiber optics and the thickness of coated fiber optics increases as the pressure gradient through the annular gap is increased. The force on the surface of coated fiber optics and thickness of coated fiber optics increases as the elasticity of the polymer increases. It is observed, that the elasticity of the liquid reduces the speed of flow. Furthermore, it is concluded that the elasticity of the liquid decreases the temperature within the region.