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This post was last edited by ljtjbx on 2015-7-27 13:26. The weekly topic is here again, as usual! Please continue to support us! What are the elastic behaviors of polymer melts during shear flow? What measures can be taken during the molding process to reduce the adverse effects of these elastic behaviors on the quality of the product? Answer: The most common elastic behaviors in the flow of polymers are end-effect and unstable flow. Increasing the temperature, reducing shear stress, and prolonging the flow time at high temperatures helps to homogenize the plastic structure and reduce its non-Newtonian behavior.
This post was last edited by Those who watch the sea on 2015-7-27 08:15. Answer: The most common elastic behaviors in the flow of polymers are end-effect and unstable flow. Increasing the temperature, reducing shear stress, and prolonging the flow time at high temperatures helps to homogenize the plastic structure and reduce its non-Newtonian behavior. What are the elastic behaviors of polymer melts during shear flow? What measures can be taken during the molding process to reduce the adverse effects of these elastic behaviors on the quality of the products?
Question: What are the elastic behaviors of polymer melts during shear flow? What measures can be taken during the molding process to reduce the adverse effects of these elastic behaviors on the quality of the product? Answer: (1) The main elastic behaviors during polymer flow are: inlet effect, demolding expansion, and unstable flow (melt fracture). (2) Measures: Increase the molding temperature, reduce shear stress, extend the flow time at high temperatures, decrease the convergence angle at the entrance of the die channel, increase the length-to-diameter ratio of the die, and reduce the relative molecular weight of the polymer, etc.
What are the elastic manifestations of polymer melts during shear flow? The most common elastic behaviors in polymer flow are end-effect and unstable flow. Increasing the temperature, reducing shear stress, prolonging the flow time at high temperatures, homogenizing the plastic structure, and reducing its non-Newtonian behavior can all help address these issues
End effect (inlet effect, mold withdrawal expansion)； Unstable flow (shark skin phenomenon, melt fracture phenomenon). Measures: 1) Increase temperature; 2) Reduce shear rate; 3) Change the geometric dimensions of the flow channel, such as increasing the length-to-diameter ratio L/D and reducing the convergence angle of the channel; 4) Apply traction or stretching to the extrudate at an appropriate speed. Briefly describe the various factors and mechanisms that affect the shear viscosity of polymer fluids.
If the purpose of heating is to remove moisture and other volatile substances, then this type of heating is called drying. If the goal is to make the material easier to mold, it is called preheating. Preheating of the material before molding is carried out to improve the quality of the product and to facilitate the molding process, by heating the molding material prior to molding. Drying: Aiming to remove moisture and volatile substances (for thermoplastics), heating before the molding of thermoplastic compounds serves primarily the purpose of drying; the temperature should be such that the compound does not melt into lumps or cakes. It should also be checked whether degradation and oxidation occur during the heating process; if so, it should be carried out at lower temperatures or in a vacuum
Manifestation: The most common elastic behaviors in the flow process of polymers are end effects and unstable flow. Measures: Increase the temperature, reduce shear stress, extend the flow time at high temperatures, homogenize the plastic structure, and reduce its non-Newtonian behavior in flow.
What are the elastic behaviors of polymer melts during shear flow? What measures can be taken during the molding process to reduce the adverse effects of these elastic behaviors on the quality of the product? Answer: The most common elastic behaviors in polymer flow are end-effect and unstable flow. Increasing the temperature, reducing shear stress, and prolonging the flow time at high temperatures help to homogenize the plastic structure and reduce its non-Newtonian behavior.
The most common elastic behaviors in the flow of polymers are end effects and unstable flow. Increasing the temperature, reducing shear stress, and prolonging the flow time at high temperatures help to homogenize the plastic structure and reduce its non-Newtonian behavior.
What are the elastic manifestations of polymer melts during shear flow? The most common elastic behaviors in the flow of polymers are end effects and unstable flow. What measures can be taken during the molding process to reduce the adverse effects of elastic behavior on the quality of the product? Raising the temperature, reducing shear stress, increasing the flow time at high temperatures, homogenizing the plastic structure, and reducing its non-Newtonian behavior.
What are the elastic behaviors of polymer melts during shear flow? What measures can be taken during the molding process to reduce the adverse effects of these elastic behaviors on the quality of the product? The most common elastic behaviors in polymer flow are end effects (inlet effects, mold release swelling) and unstable flow (melt fracture). Increasing the temperature, reducing shear stress, and prolonging the flow time at high temperatures help to homogenize the plastic structure and reduce its non-Newtonian behavior.