Design And Development Of Extrusion System For TPV Reactive Co-rotating Twin-screw Extruder

Thermoplastic elastomer(TPV)is a blend of polypropylene(PP)and Ethylene-Propylene-Diene Monomer(EPDM).It is a multiphase polymer composite with plastic and rubber properties.It is widely used in automobiles,buildings,electrical appliances and other fields.At present,most domestically produced TPV with excellent performance are manufactured by imported equipment,which has high equipment cost,long purchase cycle and expensive maintenance cost.Therefore,it is imperative to develop domestic TPV preparation equipment in response to market demand.In this paper,the extrusion system of TPV reactive co-rotating twin screw extruder is designed and developed according to the particularity of preparation for TPV from mixed EPDM/PP.The overall scheme of the TPV reactive twin screw extruder is determined according to the processing characteristics of the material used to preparation of the TPV and the high torque requirements of the reactive extruder,and the screw mandrel,barrel and exhausting insert are designed.Based on the determination of the main parameters of the screw element,Polyflow software is used to simulate the orthogonal calculation of the groove depth ratio,pitch and meshing clearance of the screw elements.Taking the pressure difference between inlet and outlet,shear stress,cumulative maximum shear stress,reflow coefficient and cumulative maximum residence time as evaluation indicators,the conveying capacity and mixing capacity of the screw element are analyzed.The groove depth ratio,pitch and meshing clearance of screw elements are determined.Furthermore,the mixing performance of kneading block with different staggered angles is simulated and analyzed,The results show that when the staggered angle increases,the weighted average shear stress,the cumulative maximum shear stress,the average backflow coefficient and the cumulative residence time all increase,while the pressure difference at the outlet and inlet decreases,indicating that the transport capacity is weakened and the mixing capacity of dispersion and dispersion is enhanced.Straight gear and helical gear disc are designed to enlarge the distributive mixing.Through analysis and comparison,it is found that the dispersive mixing ability of straight gear and helical gear disc is similar,but the distributed mixing ability of helical gear disc is better.According to the actual production conditions,the processing of screw element,barrel and mandrel is developed,and the assembly of transmission system,extrusion system,heating and cooling system and feeding system of twin screw extruder is completed.The heating and cooling function,melt pressure and melt temperature sensor and main motor function of the twin-screw extruder are debugged,and the exhaust performance of the exhausting insert is tested.Finally,TPV samples are produced by twin-screw extruder,and the mechanical properties and volatile organic compounds(VOC)are tested,The experimental results show that the TPV has excellent properties such as tensile strength,breaking elongation,tear strength and compression set,and the VOC content is far lower than the national standard,which completely meets the expected requirements.