Study on tensile viscosity measurement in the film

Cellulose solution film blowing 2. The relative humidity is lower than 80%; Study on tensile viscosity test in process

Abstract: the tensile flow behavior of NMMO (N-methylmorpholine-N-oxide, also known as N-Methylmorpholine oxide) solution of cellulose under different process conditions was studied by non isothermal blow film extrusion experiment. The theoretical mathematical model in the extrusion process was discussed and deduced. The changes of bubble radius and film thickness with the processing direction of cellulose solution during the processing were measured, and the changes of tensile rate and apparent tensile viscosity along the processing direction were discussed. The results showed that the tensile viscosity of 9% cellulose solution was affected by the tensile rate and temperature during the processing, and showed a trend of first slightly decreasing and then gradually increasing along the processing direction; In the processing process, with the increase of the traction speed and the pressure difference between the inside and outside of the bubble (△ P), the thickness of the bubble decreases, the tensile rate increases, and the tensile viscosity decreases

key words: tensile viscosity; Film blowing; Cellulose solution

the cellulose tube membrane prepared by Lyocell process, like Lyocell fiber, also has the advantages of pollution-free production process and product degradability; Moreover, the film blowing process is biaxial stretching, and the physical properties are much better than that of the flat film with uniaxial stretching

the blown biaxially stretched tube film is used in this study. As shown in Figure 1, the NMMO aqueous solution of cellulose is extruded through the annular die to form a membrane tube. At the same time, compressed gas is input from the upper part of the die to fill and expand the membrane tube into a membrane bubble in the air gap and then enter the coagulation bath for molding. At the same time, a coagulation bath should also be input into the membrane tube to solidify the inner wall of the membrane tube. Both internal and external coagulation baths used in this experiment are water. Many foreign units are carrying out the research and development of NMMO cellulose films, such as Lenzing company in Austria, Courtaulds company in Britain, Terumo company in Japan, etc

there are still many difficulties in the separation and closure controller and computer analysis of experimental methods and results in the tensile flow involved in this paper. Therefore, there is not much research at present, resulting in a large influx of small enterprises without technical requirements. In the past 30 years, only Han and park's experimental and theoretical models have been the most classic in the study of rheology of film blowing process. However, the research object of this model is the melt of conventional polymers such as polyethylene, and the blowing direction is vertical upward, which is solidified by air cooling. In this experiment, cellulose solution was used for film blowing, and the processing direction was vertical downward. It was cooled by air and solidified in a coagulation bath. Therefore, the model adopted by Han must be modified before it can be applied. In this paper, the tensile flow behavior under different process conditions was studied through the blown film experiment of cellulose NMMO solution, and the change of tensile viscosity along the processing direction was measured

1 experimental part

1.1 main raw material

nmmo (C5H11NO2), with a mass content of 50%, German BASF company

Baoding cotton pulp, polymerization degree 488, Baoding pulp factory

901# wood pulp, polymerization degree 728, produced in the United States

antioxidant, propyl gallate (c10h12o3), produced by Shanghai No.2 reagent factory

1.2 main equipment

Abbe refractometer, 2wa860641, Shanghai Optical Instrument Factory

plastic film thickness gauge, ch-1-s, accuracy 0.001mm, Shanghai Liuling instrument factory

thermocouple thermometer, 010, Shanghai Loushan thermal instrument factory

tensiometer, reformed from szc- Ⅲ fiber tension tester of Donghua University

controlled stress rheometer, rs150l, HAAKE company, Germany

differential pressure gauge, PA, Dwyer instruments, USA

1.3 experimental process

first, prepare NMMO aqueous solution with 9% cellulose by mass according to the process requirements. During the film blowing process, the shape of the film bubble under each extrusion condition was photographed with a digital camera, and the tension of the cellulose film just after the coagulation bath (as shown in Figure 1) and the temperature of the film bubble before entering the coagulation bath were measured. Then, the thickness distribution of the film along the processing direction is measured with a thickness gauge

(to be continued)