Research On Polymer Plasticizing And Melting Mechanism Dominated By Volume Elongational Deformation

Polymer plasticating and conveying process are dividied into three stages including solidsconveying, melting and melts conveying in the traditional screw plasticating and conveyingprocess. The metling process occupy the most energy consumption in the plasitcating andconveying process and it has a serious impact on the plasticizing effect, blending effect,performance of the product,ect. The researches on the single-screw melting mechanism hasbeen formed a relatively complete theoretical system. The work ways and plasticating andconveying mechanism of the vane extruder based on the elongational rheology are totledifferent with the screw extruder, thus, the screw melting mechanism is not suitable for thevane plasticating and conveying process. Researches on the vane plasticating and conveyingmeltig process and mechanism and deeply investigating the effects of the different factors tothe vane plasticating and conveying process are benfit for the optimization design of the vaneextruder and have important scientific and practical significance to the development andimprovement of the polymer processing theory based on elongational rheology.The assembled vane extruder with visual effects is independently developed according tothe visualization technology of polymer melting process and the structural features of thevane extruder which is constituted of several groups of vane plasticating and conveying units.The experimental results of the assembled vane extruder show that the materials are atdifferent morphology in the vane plasticating and conveying process by using LDPE, HDPE,PP and PS. The the vane plasticating and conveying melting process is dividied into threestages including solids conveying, rich-solid suspension and rich-melt suspension.In the solids conveying stage, there is no clear limit between the solids conveying and themelting process in the vane plasticating and conveying process, and the solid particles arestarted to melt. The number of groups of VPCU increases with decreasing of the temperatureof the stator and the rotating speed of the rotor in the rich-solid suspension stage. Thetemperature of the stator has no effect on the melting process and the number of groups ofVPCU decreases with increase of the rotating speed of the rotor in the rich-melt suspensionstage. The melting mechanism in the solids conveying is dominated by pressure-inducedmelts removal and plastics energy consumption melting, in the rich-solid suspension stage ispressure-induced melts removal and in rich-melt suspension stage is viscous energydissipation melting.It firstly established a relatively complete physical and mathematical model of the solidsconveying stage, rich-solid suspension stage and rich-melt suspension stage. The analytical solutions of the conveying capacity in one cavity, the solids conveying pressure, the solidstemperature distribution, the melting amount of pressure-induced melts removal and plasticsenergy consumption melting in the solids conveying stage, the melting amount ofpressure-induced melts removal melting in the suspension stage and the melting height of thesolid particle A which is hardest to melt in the feeding zone and compression zone of therich-melt suspension stage are obtained.The solids pressure firstly increased slowly with rising of rotating angle of the push vane,and then when the rotating angle reaches a certain value, the pressure would increase sharply.Therefore the change of the solid paticles is divided into preloading stage and plasticcompression stage. The solid particle don’t generate platics derformation in preloading stage,thus, the pressure is little. And the solid particles generature huge plastics derformation in theplastic compression stage, thus, the pressre increase sharply. The melting amount of theplatics energy consumption increase linearly with the the pressure and eccentricity and lengthof the1st VPCU, and the rotating speed of the rotor has no effect on the PED melting in thesolids conveying process.There are a between the melting amount of pressure-induced melts removal melting in thesolids conveying stage and rich-solid suspension stage has a negative relation with therotating speed of the rotor and a quarter of the power of the pressure, and has a positiverelation with three-quarters of the power of the temperature of the stator. Therefore, it needmore groups of VPCU to complete the rich-solid suspension stage when the rotating speed ofthe rotor is lower.The number of groups of VPCU in the rich-melt suspension stage is depended on the solidparticle A which is hardest to melt. The melting height of the solid particle A is different withthe location of the solid particle A in the cavity in the VPCU. The melting height of the solidparticle A when it is at the middle of the cavity is higher then that when it is at the front vane.The temperature of the stator has important influence on the melting of the solid particle A.The total melting height of the solid particle A in one VPCU increase with the increase of therotating speed of the rotor.Finally, the theoretical models are calculated with the materials LDPE. The theoreticalpredictions of those models have better consistency with the experimental results of the visualVPCU device and the assembled vane extruder, which depicts thvalidity of those models.