Extensional Rheology Of Dilute Polymer Solutions By Dripping-onto-Substrate Method

With the development of geology,chemical industry,food processing,biomedicine,national defense and aerospace,petroleum industry and polymer material processing,the research of rheology has become more and more important.The research of polymer rheology occupies an important position in the research of biological rheology,polymer rheology,suspension rheology,industrial rheology,solid rheology and so on.Measuring and using polymer extensional rheology is still a challenging subject.The development of instruments for measuring polymer dilute solution extensional rheology is difficult,and has not yet reached the level of universal application.In spinning rheology,industrial rheology such as inkjet printing,and food rheology,an accurate and sensitive characterization of the extensional flow properties of dilute solutions is required.Therefore,the study of extensional rheology of dilute solutions has important significance and application prospects.This topic is mainly aimed at the extensional rheology study of dilute polymer solutions with low shear viscosity.In order to study the extensional rheology of polymer dilute solutions with a shear viscosity of less than 50 m Pa·s,we built the dripping-onto-substrate(DoS)extensional rheometry.Through the reasonable assembly of the imaging system,distribution system and reaction system,after the instrument is built,in order to ensure the successful operation of the instrument and its repeatability test,we have determined the reasonable parameters of the instrument in many experiments,such as nozzle and glass under.The distance between the plates H,the flow rate Q,and the specifications of the lower glass plate,etc.The unique advantages of DoS include significantly improving the inertial oscillation problems caused by other devices during the test,and the transition from inertia-capillary mechanism/viscositycapillary mechanism to elastic-capillary mechanism and elastic-capillary mechanism to end stick can be observed.Transition of elastic-capillary mechanism,and smaller relaxation time can be measured.At present,the instrument has been able to test the extensional rheology test of polymer dilute solutions,and for some specific polymer dilute solutions,the rupture kinetics and extensional rheology of some specific polymer dilute solutions have been studied.This article briefly introduces the basic concepts of polymer dilute solution and extensional rheology;summarizes the basic measurement devices and techniques of extensional rheology;introduces the dripping-onto-substrate extensional rheometry in detail and further discusses the viscoelastic fluid measured by this technique.The extensional rheological experiment.In the experiment,polyethylene oxide solutions with different molecular weights and different concentrations were first used,and the tensile rheology experiment was done with the substrate drop method tensile rheometer,and the dependence of tensile viscosity and tensile relaxation time on concentration and molecular weight was obtained.Subsequently,for a new type of telechelic association polymer CouTAP solution,the reaction system of the DoS device was improved,and an ultraviolet light source was added as a new reaction system.It was found that the CouTAP solution sample itself is very suitable for DoS devices.Because in the course of the experiment,we found that as the degree of dimerization increased,different rupture dynamics appeared during the entire stretching process.We can not only observe the pure inertia-capillary force phase phenomenon of D0 and D0.28,but with the increase of the degree of dimerization,we can also see the transition of the sample solution from the inertia-capillary force phase to the elastic-capillary force phase.In the follow-up study on the tensile rheology of the aqueous dispersion of single-layer graphene oxide,we found that the evolution mechanism of the tensile process conforms to the tensile process of the power law mechanism,and the yield stress of the sample was obtained in the shear experiment curve.The study of the rheological properties of this sample can help us better understand the physical and chemical properties of single-layer graphene oxide.