Coextruded Flow in Partially Miscible Systems

摘要

Coextrusion technology for solid rocket motors, is proposed to be improved to widen the limits on the range of property variation in functionally graded materials and reduce the associated disparities in processing characteristics. Helical coordinate system is suggested to model the coextruded flow and calculation of interlayer adhesive strength. The design aspects for the material components selected for the coextrusion system is revisited. A finite difference scheme is proposed for the numerical study. The interdiffusion term is proposed to be simulated by considering the concentration independent Diffusion term in Fick's's law of diffusion. A suitable theory for the diffusion in polymer polymer system is needed. Newton-Raphson method is applied for the iterative solution of the algebraic equations. Polymer polymer miscibility and phase behavior is a salient consideration. Marangoni effect can be used to improve interfacial mixing in coextrusion of bifunctional partially miscible and miscible polymer polymer systems. A temperature gradient imposed in addition to the density gradient by arranging the n-layers in certain order of densities leads to a interfacial tension gradient giving rise to the thermocapillary stress and cause flow at the interface. Asymptotic analysis was used at small and large Peclet numbers. This leads to the coupling of momentum and energy equations where convective transport is not negligible. Disturbance flow created by this mechanism has interesting features that are not present in the corresponding problem wherein the motion occurs due to a body force. The implications on the thermocapillary instability by the blend miscibility is discussed.