The Numerical Simulation And Experimental Study Of Instability For Gas-assisted Co-extrusion

Gas-assisted coextrusion is a new type of technology on polymer coextrusion. It provides a gas layer between the melt and die wall, so the flow boundary of coextruded melt changes to full slip in the die and the friction between the melt and die wall is thereby reduced greatly., so does the interfacial instability. On the basis of the former studies, the experimental study and numerical simulation of gas-assisted coextrusion have been conducted in this paper. The main work is listed below:1,Based on the viscous dissipation and heat exchange and the characteristics of gas-assisted full slip coextrusion molding and the theories of rheology,hydrokinetics and poly calorifics etc., under reasonable assumptions, a full three dimension steady non-isothermal viscoelastic theoretical model of describing gas-assisted coextrusion molding process is established.2,Considering the viscous dissipation and heat exchange, to get the result of the interfacial instability, simulations on traditional coextrusion and gas-assisted coextrusion were carried out on the basis of the stable finite element discrete techniques of Giesekus method.3,Through the simulation, all kinds of the flow fields under different processing conditions and parameters have been obtained. The influencing rules of the viscoelasticity property parameters and process parameters on the interfacial instability of the gas-assisted full slip coextrusion molding and traditional coextrusion are analyzed.4,Compared the two processes, the research results showed that the gas-assisted full slip coextrusion molding process has the better interfacial instability than traditional coextrusion.5,Carryed on the experiments and compared the result with the simulated result.