L型异型材气辅共挤气辅段长度的预测
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摘要
以L型双层共挤异型材为研究对象,采用Phan-Thien and Tanner(PTT)本构方程,应用Arrhenius方程来描述温度对黏度的影响,通过有限元方法分析了聚丙烯(PP)/聚苯乙烯(PS)熔体在气辅共挤口模内的三维黏弹非等温流动过程,对比分析了不同流率下气辅共挤口模所需的最短气辅段长度,同时分析了口模出口面的剪切速率及第一法向应力差的分布情况。结果表明,气辅共挤并不能完全消除挤出胀大,但能极大限度地降低挤出胀大;通过分析流道内的压力、剪切速率及第一法向应力差分布可以确定一个合适的气辅段长度;随着熔体流率的增加,气辅共挤口模所需的最短气辅段长度也相应地增加,但增速并不明显。
Taking L-shaped coextrusion profi le as an example,the three-dimensional non-isothermal viscoelastic fl ow process of polypropylene(PP) and polystyrene(PS) in gas-assisted coextrusion die were investigated by the finite element method,the polymer melts were characterized by Phan-Thien and Tanner(PTT) constitutive equation and the Arrhenius equation was used as temperature-dependent viscosity law. The shortest gas-assisted length needed for the gas assisted die as well as the distribution of pressure,shear rate and the fi rst normal stress difference at die exit were discussed in different fl ow rate. The results revel that die swell can't be eliminated absolutely in gas-assisted coextrusion,but it can be reduced vastly. An appropriate gas-assisted length can be obtained after analysing the distribution of pressure,shear rate and the fi rst normal stress difference in the die. The shortest gasassisted length needed for the die increase as the fl ow rate increase,but the increasing speed is low.
Taking L-shaped coextrusion profi le as an example,the three-dimensional non-isothermal viscoelastic fl ow process of polypropylene(PP) and polystyrene(PS) in gas-assisted coextrusion die were investigated by the finite element method,the polymer melts were characterized by Phan-Thien and Tanner(PTT) constitutive equation and the Arrhenius equation was used as temperature-dependent viscosity law. The shortest gas-assisted length needed for the gas assisted die as well as the distribution of pressure,shear rate and the fi rst normal stress difference at die exit were discussed in different fl ow rate. The results revel that die swell can't be eliminated absolutely in gas-assisted coextrusion,but it can be reduced vastly. An appropriate gas-assisted length can be obtained after analysing the distribution of pressure,shear rate and the fi rst normal stress difference in the die. The shortest gasassisted length needed for the die increase as the fl ow rate increase,but the increasing speed is low.
引文
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[2]黄兴元,柳和生,周国发,等.气体辅助挤出的实验研究[J].中国塑料,2005,19(3):17–19.Huang Xingyuan,Liu Hesheng,Zhou Guofa,et al.The experimental study of air-assisted extrusion of polymer[J].China Plastics,2005,19(3):17–19.
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[6]黄兴元.聚合物气体辅助口模挤出成型的理论及实验研究[D].南昌:南昌大学,2006.Huang Xingyuan.Theoretical and experimental study of polymer gas-assisted extrusion from dies[D].Nanchang:Nanchang University,2006.
[7]肖建华,柳和生,黄兴元,等.气辅挤出胀大比与滑移段长度的关系[J].高分子材料科学与工程,2009,25(7):166–169,174.Xiao Jianhua,Liu Hesheng,Huang Xingyuan,et al.The relationship between extrudate swell ratio and the length of slip part in gas-assisted extrusion[J].Polymer Materials Science and Engineering,2009,25(7):166–169,174.
[8]Arda D R,Mackley M R.Sharkskin instabilities and the effect of slip from gas-assisted extrusion[J].Rheol Acta,2005,44(4):352–359.
[9]Phan-Thien N,Tanner R I.A new constitutive equation derived from network theory[J].Journal of Non-Newtonian Fluid Mechanics,1977,2(4):353–365.
[10]徐佩弦.高聚物流变学及其应用[M].北京:化学工业出版社,2003:59–60.Xu Peixian.Polymer rheology and its application[M].Beijing:Chemical Industry Press,2003:59–60.
[11]黄益宾,柳和生,黄兴元.聚合物双组分复合共挤成型的挤出胀大研究[J].应用基础与工程科学学报,2010,18(4):657–665.Huang Yibin,Liu Hesheng,Huang Xingyuan.Study on extrudate swell in polymer bicomponent coextrusion process[J].Journal of Basic Science and Engineering,2010,18(4):657–665.
[12]Ishikawa T,Kihara S,Funatsu K.3–D numerical simulations of nonisothermal fl ow in co-rotating twin screw extruders[J].Polymer Engineering and Science,2000,40(2):357–364.
[13]Wu Tingqi,Jiang Bo,Xu Shuhua,et al.Three-dimensional nonisothermal simulation of a coat hanger die[J].Journal of Applied Polymer Science,2006,101(5):2 911–2 918.
[14]肖建华,柳和生,黄兴元,等.气辅挤出口模中滑移段长度对压力降和第一法向应力差的影响[J].高分子材料科学与工程,2009,25(6):167–170.Xiao Jianhua,Liu Hesheng,Huang Xingyuan,et al.Infl uence of slip length of gas-assisted extrusion die on pressure drop and fi rst normal stress[J].Polymer Materials Science and Engineering,2009,25(6):167–170.
[2]黄兴元,柳和生,周国发,等.气体辅助挤出的实验研究[J].中国塑料,2005,19(3):17–19.Huang Xingyuan,Liu Hesheng,Zhou Guofa,et al.The experimental study of air-assisted extrusion of polymer[J].China Plastics,2005,19(3):17–19.
[3]柳和生,卢臣,黄兴元,等.T型异型材气辅口模挤出胀大的数值模拟和实验研究[J].塑性工程学报,2008,15(1):158–161.Liu Hesheng,Lu Chen,Huang Xingyuan,et al.Numerical simulation and experimental study on die swell of T-shaped plastic profile extrusion from a gas-assisted die[J].Journal of Plasticity Engineering,2008,15(1):158–161.
[4]肖建华.气辅挤出成型中挤出物直径的理论预测和实验研究[J].工程塑料应用,2009,37(5):35–37.Xiao Jianhua.Theoretical predict and experimental research of product diameter in gas-assisted extrusion[J].Engineering Plastics Application,2009,37(5):35–37.
[5]黄益宾.聚合物气体辅助共挤成型的理论和实验研究[D].南昌:南昌大学,2011.Huang Yibin.Theoretical and experimental study on polymer gasassisted co-extrusion[D].Nanchang:Nanchang University,2011.
[6]黄兴元.聚合物气体辅助口模挤出成型的理论及实验研究[D].南昌:南昌大学,2006.Huang Xingyuan.Theoretical and experimental study of polymer gas-assisted extrusion from dies[D].Nanchang:Nanchang University,2006.
[7]肖建华,柳和生,黄兴元,等.气辅挤出胀大比与滑移段长度的关系[J].高分子材料科学与工程,2009,25(7):166–169,174.Xiao Jianhua,Liu Hesheng,Huang Xingyuan,et al.The relationship between extrudate swell ratio and the length of slip part in gas-assisted extrusion[J].Polymer Materials Science and Engineering,2009,25(7):166–169,174.
[8]Arda D R,Mackley M R.Sharkskin instabilities and the effect of slip from gas-assisted extrusion[J].Rheol Acta,2005,44(4):352–359.
[9]Phan-Thien N,Tanner R I.A new constitutive equation derived from network theory[J].Journal of Non-Newtonian Fluid Mechanics,1977,2(4):353–365.
[10]徐佩弦.高聚物流变学及其应用[M].北京:化学工业出版社,2003:59–60.Xu Peixian.Polymer rheology and its application[M].Beijing:Chemical Industry Press,2003:59–60.
[11]黄益宾,柳和生,黄兴元.聚合物双组分复合共挤成型的挤出胀大研究[J].应用基础与工程科学学报,2010,18(4):657–665.Huang Yibin,Liu Hesheng,Huang Xingyuan.Study on extrudate swell in polymer bicomponent coextrusion process[J].Journal of Basic Science and Engineering,2010,18(4):657–665.
[12]Ishikawa T,Kihara S,Funatsu K.3–D numerical simulations of nonisothermal fl ow in co-rotating twin screw extruders[J].Polymer Engineering and Science,2000,40(2):357–364.
[13]Wu Tingqi,Jiang Bo,Xu Shuhua,et al.Three-dimensional nonisothermal simulation of a coat hanger die[J].Journal of Applied Polymer Science,2006,101(5):2 911–2 918.
[14]肖建华,柳和生,黄兴元,等.气辅挤出口模中滑移段长度对压力降和第一法向应力差的影响[J].高分子材料科学与工程,2009,25(6):167–170.Xiao Jianhua,Liu Hesheng,Huang Xingyuan,et al.Infl uence of slip length of gas-assisted extrusion die on pressure drop and fi rst normal stress[J].Polymer Materials Science and Engineering,2009,25(6):167–170.
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