Flows of polymeric liquids undergo instabilities whose origins are quite different from those of Newtonian flows, due to their elastic character and the complexity of the fluid/solid boundary condition. One of these i...Flows of polymeric liquids undergo instabilities whose origins are quite different from those of Newtonian flows, due to their elastic character and the complexity of the fluid/solid boundary condition. One of these instabilities is well known as “shark-skin” which damages the surface appearance and properties of polymer extrudate while processing in blowmolding or piping, while it can be suppressed by employing various methods including coating the die surface and/or adding Polymer Processing Aid’s (PPA) to the polymer. In this article, the effect of various die materials on the properties of Polyethylene glycol (PEG) as a new type of PPA for suppressing the sharkskin phenomenon has been studied.展开更多
A new process for the fabrication of sharkskin bionic structures on metal surfaces is proposed.The sharkskin bionic surface was successfully machined on the surface of IN718 by laser sequencing of the abrasive belt su...A new process for the fabrication of sharkskin bionic structures on metal surfaces is proposed.The sharkskin bionic surface was successfully machined on the surface of IN718 by laser sequencing of the abrasive belt surface,laser processing of the layered scale-like structure,and ribbed texture grinding.The flexible contact properties of belt grinding allow ribbed structures to be machined uniformly on a hierarchical,scale-like microstructure.Sharkskin bionic microstructures with radii greater than 75µm were prepared after parameter optimisation.The influence of processing parameters on the geometrical accuracy of the microstructure was investigated,the microstructure microform and elemental distribution were analyzed,and the relationship between the ribbed microstructure and chemical properties of the surface of the bionic sharkskin on wettability was revealed.The results indicate that reducing the laser power and increasing the laser scan rate can reduce the laser thermal effect and improve the microstructure processing accuracy.The laser ablation process is accompanied by a violent chemical reaction that introduces a large amount of oxygen and carbon elements and infiltrates them at a certain depth.The wettability of the surface undergoes a transition from hydrophilic(contact angle 69.72°)to hydrophobic(contact angle 131.56°)due to the adsorption of C-C/C-H and the reduction of C=O/O=C-O during the placement process.The ribbed microstructure changes the solid-liquid contact on the surface into a solid-liquid-gas contact,which has an enhanced effect on hydrophobicity.This study is a valuable guide to the processing of hydrophobic layered bionic microstructures.展开更多
采用恒速型双毛细管流变仪研究了由限定几何构型催化剂和INSITE工艺开发的三元乙丙橡胶EPDM Nordel IP(3745P和3722P)高速挤出时的流动规律及挤出畸变特征。结果表明,EPDM Nordel IP为典型假塑性流体;Nordel IP 3722P与Nordel IP 3745P...采用恒速型双毛细管流变仪研究了由限定几何构型催化剂和INSITE工艺开发的三元乙丙橡胶EPDM Nordel IP(3745P和3722P)高速挤出时的流动规律及挤出畸变特征。结果表明,EPDM Nordel IP为典型假塑性流体;Nordel IP 3722P与Nordel IP 3745P相比较,前者的粘温依赖性较大且挤出物外观明显好于后者,挤出胀大比和入口压力降也较小。而后者的粘切依赖性较大,说明前者的塑料特性较明显,而后者的弹性体行为更加显著;Nordel IP 3745P在高速挤出时发生挤出压力振荡现象,此时流动曲线出现断裂,这与其门尼粘度较大、相对分子质量分布窄有关。展开更多
文摘Flows of polymeric liquids undergo instabilities whose origins are quite different from those of Newtonian flows, due to their elastic character and the complexity of the fluid/solid boundary condition. One of these instabilities is well known as “shark-skin” which damages the surface appearance and properties of polymer extrudate while processing in blowmolding or piping, while it can be suppressed by employing various methods including coating the die surface and/or adding Polymer Processing Aid’s (PPA) to the polymer. In this article, the effect of various die materials on the properties of Polyethylene glycol (PEG) as a new type of PPA for suppressing the sharkskin phenomenon has been studied.
基金supported by the National Natural Science Foundation of China[Grant No.52175377]the National Science and Technology Major Project[Grant No.2017-VII-0002-0095]the Graduate Scientific Research and Innovation Foundation of Chongqing[Grant No.CYB22009].
文摘A new process for the fabrication of sharkskin bionic structures on metal surfaces is proposed.The sharkskin bionic surface was successfully machined on the surface of IN718 by laser sequencing of the abrasive belt surface,laser processing of the layered scale-like structure,and ribbed texture grinding.The flexible contact properties of belt grinding allow ribbed structures to be machined uniformly on a hierarchical,scale-like microstructure.Sharkskin bionic microstructures with radii greater than 75µm were prepared after parameter optimisation.The influence of processing parameters on the geometrical accuracy of the microstructure was investigated,the microstructure microform and elemental distribution were analyzed,and the relationship between the ribbed microstructure and chemical properties of the surface of the bionic sharkskin on wettability was revealed.The results indicate that reducing the laser power and increasing the laser scan rate can reduce the laser thermal effect and improve the microstructure processing accuracy.The laser ablation process is accompanied by a violent chemical reaction that introduces a large amount of oxygen and carbon elements and infiltrates them at a certain depth.The wettability of the surface undergoes a transition from hydrophilic(contact angle 69.72°)to hydrophobic(contact angle 131.56°)due to the adsorption of C-C/C-H and the reduction of C=O/O=C-O during the placement process.The ribbed microstructure changes the solid-liquid contact on the surface into a solid-liquid-gas contact,which has an enhanced effect on hydrophobicity.This study is a valuable guide to the processing of hydrophobic layered bionic microstructures.
文摘采用恒速型双毛细管流变仪研究了由限定几何构型催化剂和INSITE工艺开发的三元乙丙橡胶EPDM Nordel IP(3745P和3722P)高速挤出时的流动规律及挤出畸变特征。结果表明,EPDM Nordel IP为典型假塑性流体;Nordel IP 3722P与Nordel IP 3745P相比较,前者的粘温依赖性较大且挤出物外观明显好于后者,挤出胀大比和入口压力降也较小。而后者的粘切依赖性较大,说明前者的塑料特性较明显,而后者的弹性体行为更加显著;Nordel IP 3745P在高速挤出时发生挤出压力振荡现象,此时流动曲线出现断裂,这与其门尼粘度较大、相对分子质量分布窄有关。
