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Numerical and experimental studies on the effect of thickness difference between up and down gas layers on sheet polymer gas‐assisted extrusion forming
Author(s) -
Jiang ShiYu,
Liu HeSheng,
Huang XingYuan,
Yu Zhong,
Wang RuiZhe
Publication year - 2020
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.25485
Subject(s) - extrusion , materials science , isothermal process , extrusion moulding , composite material , die (integrated circuit) , molding (decorative) , blow molding , plastics extrusion , computer simulation , pressure drop , flow (mathematics) , volumetric flow rate , mechanics , mold , thermodynamics , nanotechnology , physics
Abstract In this study, to make gas‐assisted extrusion (GAE) can be better applied to conventional horizontal extrusion forming process, the thickness difference between up and down gas layer was simulated for the first time by GAE of molten high‐density polyethylene sheet. In order to ascertain the effects of the thickness difference of up and down gas layers on sheet extrusion molding, a method based on the model of two‐phase (gas and melt) flow was put forward, and an outer‐layer GAE isothermal numerical simulation made by POLYFLOW was explored and researched. The numerical results analysis indicated that when the thickness of down gas layer is increased, the velocities, pressure drop and shear rate of the melt increase. Compared with the simplified‐GAE simulation, GAE simulation method can well reflect the flow characteristics, the physical field distribution, and the morphology changes of melt extrudates. The experimental results show that with the increase of the thickness of the down gas layer, the melt falling can be obviously improved during extrusion. Thus, in the actual use of GAE for sheet production, not only the thickness difference between up and down gas layers should be reasonably controlled, but also other factors, such as melt inlet volume flow rate, gas pressure and temperature should be controlled accordingly. Finally, GAE forming technology can give full play to its advantages.