The Research On The Rheological Rule Of The Polymer Injection Molding And The Processing Technology

The main methods of the micro products which are formed with polymermaterials are the injection molding and the micro extrusion. The main reasonis that polymer has faster molding, more resistant corrosion, lower density,and higher specific strength than metal. The main difference between micromolding and conventional molding is the influence of the micro scale effecton the viscosity, the elasticity of the polymer melt and the change of moldprocessing parameters. This paper focused on the influence of the micro scaleon the forming process of polymer. The main results in the thesis are asfollows:1, Using the advanced mechanical processing method, the micro diesand the rheological nose which was suitable for micro dies were made.2, The rheological experiment in the micro scale used the commonlypolypropylene (PP), the results show that: the viscosity of polymer melt in themicro capillary is lower than conventional capillary(1.5mm), in the0.25mmlower by33%-64%, in the0.20mm by35%-44%, in the0.15mm by71.2%-94.7%; 3, The coefficient correction model and the index correction modelwere founded based on the Power Law Viscosity Model and considering theeffect of micro scale. After verification, the results show that the two revisedmodels are more suitable for the viscosity in the micro scale than the PowerLaw Model.4, Two characterization methods (extrusion swell and the loss inletpressure) were used to describe the elasticity of the polymer melt in the microscales. The results show that the method of the loss inlet pressure describesthe elasticity better than the method of the extrusion swell.5, The elastic experiment showed that the elasticity increased with thedecrease of the micro scales at the same shear rate. The linear elastic modelwas set up based on the conventional linear elastic model and considering theeffect of micro scale. The result showed that linear elastic model in the microscales was more suitable for characterization of the elasticity in the microscales than elastic model in the conventional scales.6, The sliding speed and the thickness of the boundary layer werecalculated according to the formula of the boundary sliding layer. The resultsshowed that as the increase of the shear rate, the sliding speed increased in theboundary layer of the0.15mm diameter capillary, and the thickness of theboundary layer decreased in the0.15mm diameter capillary.7, The orthogonal experiment of micro heat exchanger was checked theprocessing of molding. The results showed that the holding pressure and the holding time were the main influence factors in the process of the moldingand the lower viscosity and the wall slipping phenomenon in the micro scaleswere helpful for the molding of the micro heat exchanger.