多层复合共挤成型分层界面变形机理研究

发布时间：2018-03-01 22:24

本文关键词： 共挤成型多相流动黏弹性黏性包围机理数值模拟　出处：《南昌大学》2017年硕士论文　论文类型：学位论文

【摘要】：共挤成型技术是目前聚合物多层复合材料的制造技术,如何控制聚合物多层复合材料共挤成型过程的层厚均匀性是制备高性能多层复合材料的主要技术瓶颈。聚合物多层复合材料共挤成型过程中由于黏性包围现象会导致分层界面变形畸变和层厚重构,严重影响高性能多层复合材料制品性能,解决这一技术瓶颈,方能实现聚合物多层复合材料共挤成型过程的层厚均匀性精密控制。而解决这一技术瓶颈的理论关键在于研究并建立黏性包围形成的机理理论,以此揭示多层黏弹性熔体共挤成型流动的黏性包围的形成机理,这对于解决目前制备高性能多层复合材料的主要技术瓶颈具有重要的理论和工程应用价值,因此本文系统研究了聚合物黏弹性流变性能参数和过程参数对多相多层黏弹性矩形共挤流动成型过程的黏性包围的影响。通过研究建立黏性包围——二次流动——第二法向应力差的关联理论,试图建立具有普适性和科学性的多相多层黏弹性熔体流动的黏性包围机理理论,为研发聚合物多层复合材料共挤成型过程的层厚均匀性的精密控形技术奠定科学的理论基础。首次研究提出了多相分层黏弹性熔体流动的黏性包围是由分层界面附近熔体的第二法向应力差驱动的二次流动所诱发的科学假设,科学假设认为黏性包围的趋势由分层界面附近熔体二次流动的方向控制,而黏性包围程度由分层界面附近熔体的二次流动速度控制;研究发现当上层熔体松弛时间由0.4s增至1.8s时,多层共挤成型分层界面三维黏性包围形貌先呈正向黏性包围现象,但随着上层熔体松弛时间增大,分层界面形貌转化为反向黏性包围现象,且三维黏性包围程度随着上层熔体松弛时间增大而增大。显然这一研究结果与低黏度熔体包围高黏度熔体的最小黏性耗散原理相矛盾,也与分层界面法向应力平衡黏性包围原理提出的在同时存在黏性和弹性分层时,黏性包围主要由熔体的黏性控制的结论相矛盾,传统机理理论无法诠释这一演化;当上层熔体材料系数由0.2增至0.8时,二层共挤成型分层界面三维黏性包围形貌先呈正向黏性包围,但随着上层熔体材料系数增大,分层界面形貌转化为反向黏性包围,且其包围程度随着上层熔体材料系数增加而增大,显然这一研究结果与最小黏性耗散黏性包围原理相矛盾,也与分层界面法向应力平衡黏性包围原理提出的在黏性分层一定时,黏性包围主要由熔体弹性控制的结论相矛盾;随着低黏度上层熔体进口流量的增加,二层共挤成型黏性包围分层界面界形貌主要体现为高黏度下层熔体包围低黏度上层熔体的反向黏性包围现象,其包围程度随着上层熔体进口流量的增加而增大;按本文提出的黏性包围机理科学假设,熔体黏弹性流变性能参数和过程参数变化诱发的正反向黏性包围的机理推论结果与其黏性包围界面形貌的模拟结果完全吻合,且按本文提出的黏性包围机理可知,由分层界面附近熔体第二法向应力差推论预测的熔体二次流动方向和二次流动强度与二次流动模拟研究结果完全吻合,充分验证了本文黏性包围的机理理论在不同熔体黏弹性流变性参数和过程参数条件下均具有普适性和可靠性。
[Abstract]:Coextrusion molding technology is the manufacturing technology of polymer multilayer composite materials, how to control the co extrusion process of composite multilayer polymer layer thickness uniformity is the main bottleneck of technology for preparing high performance multilayer composite materials. Composite polymer multilayer coextrusion molding process due to viscous encapsulation phenomena will lead to distortion and deformation of interfacial layer thickness reconstruction, serious effect of high performance multilayer composite products, solve the technical bottleneck, in order to achieve the co extrusion process of composite multilayer polymer layer thickness uniformity and precision control. To solve the key technical bottleneck theory is to study and establish the theory mechanism of viscous encapsulation is formed, in order to reveal the formation mechanism of viscous flow of viscoelastic melt surrounded by multilayer coextrusion the formation of this system, to solve the technical bottleneck of preparing high performance multi-layer composite material has Important theoretical and engineering application value, this paper studied the effect of viscous polymer system by viscoelastic rheological parameters and process parameters of multiphase multilayer coextrusion molding process of viscoelastic rectangular flow. Through the research on the establishment of Relevance Theory -- the two surrounded by the viscous flow of the second normal stress difference, trying to establish a universal and the science of multiphase multilayer viscous viscoelastic melt flow by theory, laid the scientific theoretical foundation for the research and development of polymer multilayer coextrusion molding process of composites layer thickness uniformity of the precision shape control technology. The first study of the multiphase stratified viscous viscoelastic melt flow is surrounded by two flow induced by the scientific hypothesis by second method stratified near the interface melt to stress difference driven, scientific hypothesis that surrounded the trend by interfacial viscous melt near two Control the direction of flow, and surrounded by two degree viscous flow velocity control layer near the interface of the melt; it was found that when the upper melt relaxation time from 0.4s to 1.8s, multilayer coextrusion molding stratified interface of 3D viscous morphology showed a positive first surrounded by viscous encapsulation phenomenon, but with the increase of the melt relaxation time, layered interfacial morphology into the reverse viscous encapsulation phenomenon, and three-dimensional viscous encapsulation increases with the increase of the upper melt relaxation time. The minimum principle of viscous dissipation obviously this results with low viscosity and high viscosity melt melt surrounded by contradiction, and interfacial normal stress balance principle of viscous encapsulation in the presence of the viscous and elastic layer, viscosity enclosed is mainly controlled by the melt viscosity of the conflicting results, the mechanism of the traditional theory cannot explain this evolution; when the upper melt material number by 0 .2 increased to 0.8, two layer coextrusion layered interface morphology showed a positive first surrounded by three-dimensional viscous viscous surrounded, but with increasing upper melt material coefficient, interfacial morphology into reverse viscosity surrounded, and its surrounding degree with the increase of the upper melt material coefficient increases obviously, the results of this study and the minimum bounding viscosity viscous dissipation principle with the contradiction, interfacial normal stress balance principle of viscous encapsulation in viscous stratification is surrounded mainly by viscous melt elasticity control conflicting results; with the increase of low viscosity melt into the upper mouth flow, two layer coextrusion molding clay layered interface morphology mainly surrounded by circles for high viscosity lower melt viscosity reverse surrounded by the upper melt surrounded by low viscosity phenomenon, which surrounds a degree increases with the upper melt inlet flow; viscous surrounded by this paper The mechanism of scientific hypothesis, simulation results and the morphology of the interface mechanism of viscous encapsulation surrounded by positive and negative viscous melt rheological properties of viscoelastic parameters and process parameters change induced by the inference result, and the viscosity by using this mechanism that surrounded by a layered interface, the melt near the second normal stress difference inference prediction two melt flow direction and two flow intensity and two flow simulation results agree well, fully verify the theoretical mechanism of the viscosity were surrounded with universality and reliability in different parameters of melt viscoelastic rheological parameters and process.

【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

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