The reduced viscosity of polypropylene solution was measured by automatic capillary viscometer, and the effects of solution mass concentration, stirring time, stirring speed and standing time exposed to air on the measurement results of reduced viscosity of polypropylene solution were investigated. The results show that the mass concentration of polypropylene solution has a greater influence on the concentrated viscosity, and the choice of 0. 001~0. 005g·mL-1 to measure the reduced viscosity; when the stirring time is 2h and the stirring speed is 1200r·h-1, the polypropylene solution is completely dissolved into a homogeneous system; the polypropylene solution is dissolved in the air for a short time Standing still, the change of the reduced viscosity is small, and standing for a long time will cause the phase separation of the solution, and the reduced viscosity will decrease.
Fluid viscosity is an important parameter to distinguish non-Newtonian fluids from Newtonian fluids, and viscosity testing is used to characterize the viscosity-average molecular weight of polymers. The viscosity of polypropylene solution is an index to evaluate its flow performance, and it is a characteristic that hinders its relative flow inside the fluid. In general, the test error of a precision capillary viscometer is about 1%, or even smaller, and it is a relatively high-precision measuring instrument among all tools for measuring viscosity. Because the capillary viscometer is relatively simple in design and manufacture, the test operation layout and test temperature are easy to control, it can perform very accurate measurements, and the measurement results are relatively accurate, so it is widely used in the measurement of the viscosity of non-Newtonian fluids. In order to obtain more accurate measurement results of fluid viscosity, the author conducted experiments to study the influencing factors of the measurement results of reduced viscosity of polypropylene resin solution.
1. Test materials and test methods
1. 1 Test material
The test materials are: homopolypropylene pellets, produced by the Innovene gas phase process in the ethylene plant of Dushanzi Petrochemical Company, with a melt index of 2. 3~ 3. 7g·10min -1 ( 230 ℃ , 2.16kg ); the mass fraction is 99. 5% decahydronaphthalene, the molecular formula is C 10 H 18
1. 2. Test equipment
The test instrument is a group of German ULAB automatic capillary viscometer (Figure 1-3), the inner diameter of the capillary is ( 0.63±0.01) mm, the capillary viscometer consists of an emptying tube, a measuring tube, a sampling tube, It is composed of adding bulb, separating bulb, capillary, measuring bulb, buffering bulb, adding sample line and measuring marking line. In this test, a two-position viscometer was used for measurement.
Fig.1 Schematic diagram of viscometer
Fig. 2 JULABO VISCO-370 viscosity measuring system
Figure 3 Connection diagram of viscosity measurement system
1.3 Test steps
( 1) Weighing: Add a certain amount of polypropylene , and then add a certain volume of decahydronaphthalene solution to prepare polymer solutions with different mass concentrations.
( 2) Stirring and dissolving: Put the prepared grinding bottle containing polypropylene solution on a magnetic stirrer, keep the temperature at ( 150±1)°C, stir and dissolve at different speeds and times, and investigate the effect of stirring speed and time on Effect of specific viscosity of polymer solution.
( 3) Constant temperature sample: immerse the viscometer in a constant temperature Oil Bath, fix the viscometer on the bracket with clamps, and adjust the viscometer capillary to a vertical position. The temperature of the constant temperature bath is ( 135±0.01)°C, and the constant temperature is maintained for 15 minutes. Start the VISCO-370 test module , first clean the capillary viscometer with solvent, add 15mL of decahydronaphthalene solvent into the capillary viscometer, start the test module, the three test values of the flow time of decahydronaphthalene in the capillary are t 01, t02, t03, when the difference between the three values is greater than 1s, it needs to be re-tested, and the average value of t0=(t01+t02+t03)/3 is obtained by taking three similar flow times.
Then add a certain volume of completely dissolved polypropylene solution into the capillary viscometer without filtering , and start the program software to automatically test the solution flow time t. The test method is the same as t0. The average of the three test values .
( 4) Module calculation: After the solution flow time t test is completed, the software automatically calculates the values of kinematic viscosity, relative viscosity, specific viscosity, reduced viscosity and intrinsic viscosity .
( 5) Cleaning: After the test is completed, the capillary viscometer is automatically .
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