Free surface instabilities produced by slip at die exit in polymer melt flow and its suppression

聚合物熔体流动中模头出口滑移产生的自由表面不稳定性及其抑制

• 批准号: 14550157
• 负责人: MIZUNUMA Hiroshi
• 金额: $ 2.37万
• 依托单位: Tokyo Metropolitan University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550157/
• 关键词: Slip; Melt Fracture; Flow Instability; Extrudate Flow; Viscoelastic Fluid

In a polymer extrudate flow, extrudate often suffers surface fracture characterized by regular fine roughness or wavy distortion at a high extrudate velocity. The regular rough surface is called sharkskin fracture, and disturbance at a die exit is speculated to be its cause. In this study, we developed a compact device for two-dimensional extrudate flow and a microscopic visualization system, by which the flow instability was observed at the inside and the outside of the slit exit. It was found that the periodical flow was produced by adhesion failure. Next, we carried out the extrudate experiments using capillary dies, where the similar instability as the slit die extrudate was observed. In addition, the local adhesion failure at the die lip was observed to move circumferentially along the die lip, and this movement caused the spiral fracture. A tapered-exit die indicated lower critical shear stress for the initiation of melt fracture among the dies applied here. This result suggested the possibility that the geometrical modification of dies suppresses the melt fracture.

在聚合物挤出流动中，挤出物在高速下经常发生以规则的细小粗糙度或波状变形为特征的表面断裂。这种规则的粗糙表面被称为鲨鱼皮断裂，推测是模具出口处的扰动造成的。在这项研究中，我们开发了一个紧凑的装置，用于二维挤出流和微观可视化系统，通过该系统可以观察到在狭缝出口的内部和外部的流动不稳定性。结果表明，周期性流动是由粘附失效引起的。接下来，我们使用毛细管模头进行挤出实验，其中观察到与狭缝模头挤出物类似的不稳定性。此外，在模唇处的局部粘附失效被观察到沿模唇周向沿着移动，并且这种移动引起螺旋断裂。锥形出口模头表明较低的临界剪切应力之间的模具熔体破裂的开始在这里应用。这一结果表明，模具的几何修改抑制熔体破裂的可能性。

项目成果

Hiroshi Mizunuma, Hideyuki Takagi: "Cyclic generation of wall slip at the epit of plane Couette flow"Journal of Rheology. 47(2). 1-21 (2003)

Hiroshi Mizunuma、Hideyuki Takagi：“平面 Couette 流顶部壁滑移的循环生成”流变学杂志。

Hiroshi Mizunuma, Kazuhiro Hasegawa: "Melt fracture and near wall instability at the capillary die exit"Proceeding of the XIVth International Congress on Rheology. 1-3 (2004)

Hiroshi Mizunuma、Kazuhiro Hasekawa：“毛细管模具出口处的熔体破裂和近壁不稳定性”第十四届国际流变学大会论文集。

Hiroshi Mizunuma, Hideyuki Takagi: "Cyclic generation of wall slip at the die exit of plane Couette flow"Journal of Rheology. 47-3. 737-757 (2003)

Hiroshi Mizunuma、Hideyuki Takagi：“平面库埃特流模具出口处壁滑移的循环生成”流变学杂志。

Hiroshi Mizunuma, Hideyuki Takagi: "Cyclic generation of wall slip at the exit of plane couette flow"Journal of Rheology. 47・3. 737-757 (2003)

Hiroshi Mizunuma、Hideyuki Takagi：“平面库埃特流出口处的壁面滑移的循环生成”流变学杂志 47・3（2003）。

Hiroshi Mizunuma, Kazuhiro Hasegawa: "Melt fractne and near wall instabilities at the capillary die exit"Proceeding of the XIV International Congress on Rheology. 1-3 (2004)

Hiroshi Mizunuma、Kazuhiro Hasekawa：“毛细管模具出口处的熔体断裂和近壁不稳定性”第十四届国际流变学大会论文集。