Numerical Simulation And Experimental Study On Plastic Profile Gas-assisted Coated Coextrusion

Plastic profile refers to the plastic products with non-circular cross section, such as corrugated, tank, T-shaped, L-shaped, etc. Plastic profile including lots of advantages compared with the other materials products, such as light weight, environmentally friendly, able to meet the complex structure. The plastic co-extrusion technology means two or more kinds of plastic materials extruded together, belongs to composite processing technique of plastic, have been widely used owing to without bonding, high efficiency, low cost, various sculpts of products and excellent dispersion. Gas-assisted coated co-extrusion is a new type of plastic extrusion process, it need to put the air into the equipment to form a stable air cushion layer between melt and die wall, so that the polymer melt in the die will no longer flowing in traditional non-slip adhesive shear flow, but changed into a fully non-adhesive slip shear flow. In addition, the extrusion swell rate and melt pressure of polymer melt will be significantly reduced when using the gas-assisted coated co-extrusion technology, and the cross-section of the extruded product will be consistent with the shape of die. In this paper, we used the numerical simulation and experimental to study gas-assisted coated co-extrusion with one-component polymer melt and two-component polymer melt, the main contents are as follows:Established the finite element model of coated co-extrusion based on the fluid mechanics and rheology principles. Using the PTT viscoelastic constitutive equations to simulate the movement of melt inside or outside the die both in traditional coated co-extrusion and gas-assisted coated co-extrusion.Analyzed the effects to traditional coated co-extrusion and gas-assisted coated co-extrusion in plastic profile about physical properties of materials and process parameters by numerical simulation, including the extruded flow rate, combinations of material, the thickness of melt layer, viscosity, relaxation time, material parameters ε and ξ. Contrasted the extrusion products by traditional coated co-extrusion and gas-assisted coated co-extrusion, and studied the length of gas in gas-assisted coated co-extrusion.An experimental platform of gas-assisted coated co-extrusion was built, designed and produced the L-type disposable die in gas-assisted coated co-extrusion. Verified the feasibility of gas-assisted technology in co-extruded of profiles by experiments, at the same time, the influence of pressure and temperature about the gas were analyzed. Finally, we proposed the matters needed to pay attention in the experiment.