Experimental study on viscosity properties of cyclic olefin copolymer (COC) flowing through micro capillary dies

• Published in: Polymer testing 2020-09, Vol.89, p.106635, Article 106635
• Main Authors: Lu, Jin, Qiang, Yuanbao, Wu, Wangqing, Jiang, Bingyan
• Format: Article
• Language: English
• Subjects: COC polymer; Micro-scale; Microinjection molding; Viscosity properties; Vogel equation
• ISSN: 0142-9418; 1873-2348
• DOI: 10.1016/j.polymertesting.2020.106635

As an emerging polymer, COC has been commonly used to make microfluidic chips by microinjection molding; and in this process, COC melt flows in a trans-scale cavity in which macro and micro scales coexist. Thus, in such a circumstance, understanding viscosity property of COC melt would be helpful to mold design, parameter determination of injection molding and prediction of molding quality. In this paper, viscosity properties of COC melt flowing in three dies with different diameters (500 μm, 200 μm, 100 μm) were investigated at three different temperatures (240 °C, 260 °C, 280 °C) by a capillary rheometer. The results showed that viscosity of COC melt flowing in different micro dies can be reduced significantly by increasing temperature, and visco-temperature property of COC melt could be described by Vogel equation in a considerable accuracy. It was found that temperature sensitivity of viscosity of COC melt varies with shear rate. Besides, as die diameter decreased, viscosity of COC melt was also reduced greatly. Moreover, in 500 μm die, viscosity of COC decreased constantly with shear rate; however, in 200 μm and 100 μm dies, viscosity witnessed an increase within a certain shear rate range. It implies that behavior of COC molecular chains might varies in different micro-scales. [Display omitted] •An emerging polymer (COC) was investigated.•Extremely micro dies were used in this study.•Vogel equation was applied in the study on visco-temperature property.•A never-seen viscosity property of COC was shown.•Flow curve was used for rheology analysis.