The Theory And Experimental Study In Continuous Extrusion Of Microcellular Plastics

The continuous extrusion is one of the main molding technologies on microcellular plastics processing, which also become one of the hot researches on the molding of microcellular plastics. There are four requirements must be satisfied during the process of continuous extrusion on microcellular plastics, as follows: firstly, the polymer melt must be established at high-low-high pressure distribution in the gas injection port; secondly, the gas and polymer melt become homogeneous system before they arrive at capillary nozzle; thirdly, the designed capillary nozzle must be a great pressure drop and pressure drop rate, only in this way to make homogeneous system become a large number of bubbles through capillary nozzle; finally, after become bubbles, the designed cooling and molding devices make bubbles cool, solid and shape. The four requirements become main research content on continuous extrusion of microcellular plastics. To the above four requirements, the theory and experimental researches on continuous extrusion of microcellular plastics have been conducted in this paper, which yields the following main achievements:By consulting relevant literature and books, the assembled single screw and capillary nozzle have been designed and used on continuous extrusion of microcellular plastics, some parts of these have been checked about strength. Based on the existed experimental equipment, some devices of supercritical CO2 system have been designed as production and measurement supercritical CO2. At present, the experimental platform has been basically built on continuous extrusion of microcellular plastics.On the base of the special POLYFLOW software, numerical simulation have been made on the part of screw in the front of gas injection port, pin screw and capillary nozzle. During the part of screw in the front of gas injection port, the pressure field and mass flow have been analyzed by changing the material viscosity and screw speed in the gas injection port, which provide the theoretical basis for the follow-up supercritical CO2 injection pressure and volume flow. During the design of the three pin screws, the effects of the pin screw mixed ability have been analyzed under different geometric parameters, CO2 concentration, melt flow and melt temperature. During capillary nozzle, the pressure field, velocity field and die swell have been analyzed by changing some parameters, which are the CO2 concentration, melt volume flow rate and melt temperature.For the experiment, on the base of the built experimental platform, this combines the simulation results by changing the process parameters, and then study on the correlation of the experiment. In the experiment, the further improvements have been made on the experimental devices.