聚合物多层气辅共挤精密成型机制的数值分析  

Numerical investigation on the mechanism of polymer multilayer gas assisted co-extrusion precision molding process

作　　者：周文彦[1] 周国发[1] 

机构地区：[1]南昌大学环境科学与工程学院,南昌330031

出　　处：《复合材料学报》2009年第3期90-98,共9页Acta Materiae Compositae Sinica

基　　金：国家自然科学基金(20274016);江西省教育厅科技攻关项目(s00123)

摘　　要：基于传统共挤成型技术,提出一种先进的气辅多层共挤精密成型技术。研究表明,气辅共挤成型技术不仅可实现挤出制品尺寸的精确自动控制,而且还起到明显的节能降耗的效果。通过建立的稳态有限元数值算法,对传统共挤成型和气辅共挤成型的成型过程和离模膨胀过程进行了系统的对比分析研究,并探讨了气辅共挤成型消除整体离模膨胀的机制。结果表明,多层共挤成型芯壳层熔体的离模膨胀是由黏弹性熔体的二次流动引起,主要取决于芯壳层熔体二次流动的方向与强度。熔体二次流动的方向与第二法向应力差的正负号有关,而熔体二次流动的强度则与第二法向应力差大小成正比。气辅共挤成型的气辅口模段可通过气垫膜层的壁面完全滑移作用,有效减小或消除芯壳层熔体的第一和第二法向应力差,使其二次流动消失,从而达到消除口模整体离模膨胀的目的。因此,气辅多层共挤精密成型技术能精确地控制共挤成型的复合产品最终外形和尺寸与挤出口模的形状和尺寸完全相同。此外,研究结果还表明气辅共挤成型的挤出压力相对传统共挤成型可降低约30%以上。Based on the traditional co-extraction, an advanced multilayer gas assisted co-extraction precision molding technology （GACEPMT） was put forward. The research shows thai GACEPMT can not only implement the automatic and accurate control of the product dimension, but also save energy. A comparative analysis on molding process and die swelling process of traditional co-extraction and gas assisted co extrusion was implemented by the stable finite element numerical algorithm established. Based on the above analysis, the mechanism of eliminating the co-extrusion die swell was disclosed. The research results show that the muhilayer co-extrusion die swell is caused by the viscoelastic melt secondary flow, and depends on the direction and strength of the melt secondary flow. The direction of the meh secondary flow depends on the sign of secondary normal stress difference, and the strength of the melt secondary flow is proportional to the secondary normal stress difference. The gas assisted segment of a gas assisted co extrusion die can reduce and eliminate the melt first or secondary normal stress difference by wall slip of air cushion, which eliminates the melt secondary flow near lhe exit of die. The goal of eliminating the co extrusion die swell was implemented by removing the melt secondary flow. So the GACEPMT can accurately control the shape and size of gas assisted co-extracting multilayer composite products and the shape and size of the gas assisted die are completely identical. Moreover, the results show that the extracting pressure can be reduced above 30% compared with traditional co extraction.

关 键 词：黏弹性 气辅共挤成型 数值模拟 离模膨胀 机制 

分 类 号：TQ320[化学工程—合成树脂塑料工业]