ДОСЛІДЖЕННЯ ЗАЛЕЖНОСТІ НАПРУЖЕНЬ ЗСУВУ ПОЛІЕТИЛЕНУ ВІД ТЕМПЕРАТУРИ І ШВИДКОСТІ ЗСУВУ

Abstract

Polyethylene is increasingly used in various industries such as light, medical and others as a variety of packaging and structural materials. Rheological properties of polyethylene affect products quality. Therefore, knowledge of these properties affects the calculation methods of equipment that produces materials from polyethylene, as well as the control system of technological processes of such industries.When designing equipment for processing polyethylene, namely the forming channels of extruders, flat slotted heads, the question of accurate determination of its rheological properties depending on the temperature and shear rate arises. Depending on the specified rheological properties the geometrical sizes of the specified channels change. These rheological properties are usually determined on the basis of experiments conducted at certain shear rates and temperatures. When designing, there is a need to calculate the geometric dimensions of the forming channels at shear rates and temperatures other than experimental. Therefore, there is a problem of developing a method of calculating these dimensions on the basis of experimental data obtained at other shear rates and temperatures. On the basis of the conducted research, the equation of the dependence of the shear stress of polyethylene on its shear rate and temperature was obtained. In the equation, the shear stress is directly proportional to the conditional viscosity and the shear rate gradient in power, which is the flow index. It is shown that the conditional viscosity of polyethylene is well described by the Arrhenius equation, and the flow index has a quadratic dependence on temperature. The obtained generalized equation of shear stress of polyethylene from its shear rate and temperature will allow to more accurately calculate the geometric dimensions of the forming channels of extruders, slotted heads, as well as to improve control systems for these devices.