Measurement And Characterization Of Polymer Elongation Viscosity Based On Disc Type Rheometer

Compared with shear flow,the elongation flow has incomparable advantage for polymer’s processing.Professor Jinping Qu as well as his scientific research team from South China University of Technology research and develop the vane plasticizing and transporting equipments(ZL200810026054.X)and eccentric rotor plasticizing and transporting equipments(ZL201410206552.8),importing the global elongation flow into the procedure of polymer processing,and gradually make these technologies popularization and application.The characterizations of rheological property of the polymers have decisive influences on the optimizing of materials’ processing.The methods and equipments for characterizing polymers’ shear rheological behaviours have developed very well.While,The methods and equipments for characterizing polymers’ elongation rheological behaviours develop not that deep.So research and develop one device,which own features like simple theory,easy operation and stable property,to characterize the elongation rheological property of polymer is very important.Based on the traditional capillary rheometer,this article puts forward one measurement and characterization methods of polymer elongation viscosity that doesn’t rely on constitutive equations.At the same time,this paper puts forward one disc type polymer elongation rheometer.Then,this article adopts three different types’ industrial grade PE materials,like LDPE,HDPE and LLDPE,to explore the elongation rheological behavior of each PE and take analysis of the results.The experimental results and analysis indicate that: the method and device can describe the elongation rheological behaviors well for the three kinds PE,it own features like simple principle,easy operation,less complex parameter and better practicability.For LDPE,its extensional rheology behavior doesn’t conform to the power law and has evident phenomenon of “tensile hardening” as many classical model description.The tensile hardenability slides down with the increase of temperature.The elongation stress and elongation viscosity slides down with the increase of temperature,too.Because of the phenomenon of “tensile hardening”,there is a “turning point” in the curve of the melt flow rate followed by piston pressure.For HDPE,its elongation rheology behavior conforms to the power law very well and display typical phenomenon of elongation thinning.This article acquires the non-Newtonian index of HDPE at 190 ℃,200 ℃ and 210 ℃ based on this method,respectively.And the non-Newtonian index is 0.485,0.492 and 0.505,respectively.It can be seen that,the non-Newtonian property of HDPE declines with the increase of temperature.The elongation stress and elongation viscosity of HDPE declines with the increase of temperature,too.Its melt flow index increases by exponential form with the increase of pressure.For LLDPE,similar to LDPE,it also has the phenomenon of “tensile hardening”.Because LLDPE has relatively shorter molecular branch,so the elongation deformation rate corresponding to the phenomenon of “tensile hardening” occurs for LLDPE is relatively lower than LDPE.But dissimilar to LDPE,the elongation stress,elongation viscosity and melt flow index display special change rule with the increase of temperature.