Досліджено ефект розбухання під час екструзійного формування полімерних профілів, визначено залежно-сті розподілу швидкостей зсуву та лінійних швидкостей за довжиною профілю, проаналізовано залежність коефіцієнта розбухання від коефіцієнта налипання.
When designing the forming heads for production of profile-molded products must be considered patterns of mani-festation of elastic recovery polymer melt and the degree of slip on the walls of the forming tool.
The study aims to account for the influence of viscoelastic properties of polymer melts at changing the structure of the flow after the forming of the channel, which in turn leads to the need for change as a process of extrusion pro-cess parameters and structural dimensions of the forming tool.
When designing extrusion dies the elastic properties of the melt, i.e. the ability of the melt to store an imposed de-formation elastically (memory fluid) are generally not considered.
The elastic properties bring about effects, however, that are important for the design of the die.
Neglecting the elasticity of a melt can lead to relatively large errors in the computation of the pressure loss, demonstra-tion this with an example of flow of a high molecular and hence highly elastic PE-HD through a blow molding head.
The effect of viscoelastisity on the results in even more pronounced in the computation of the extrudate swelling.
Extrusion swelling phenomenon is expanding jet of polymer melt exits the forming tool. Expanding the jet may be due to two factors. The first is the manifestation of the elastic properties of the liquid. The second - a restructuring velocity profile in the transition from the regime of fluid flow to Poiseuille flow with a free surface. Tanner showed that the expansion of the jet is the interaction of both mechanisms.
In the production of polymer products by extrusion cross-section extruded polymer jet is increased compared to the channel cross-section profiling, which affects the final size and shape of the product. In technological practice, evaluate the effect of swelling ratio of extrudate diameter to the diameter of the forming channel. In the extrusion of complex profiles heterogeneity swelling of various elements of the intersection due to the fact that in different parts forming channels are different tensions that is the cause of viscoelastic deformation of various sizes. This may lead to a distortion of the profile up to a total inability to obtain the desired product configuration using a forming tool with a specific configuration forming channels.
In this article is shown that viscoelastic properties of polymers in the simulation of the flow at the outlet of the ex-truder forming tool allows you to calculate the change in cross-section extruded molded products.
Also built graphics of speed, pressure and flow stress viscoelastic fluid at the outlet of the extruder forming tool.