Parameter control and additive formulation optimization in PPR pipe production

Tests were made on the quality problems that occurred during the production of PPR pipes in polypropylene plants, and the phenomena that occurred during the test under different temperature conditions were analyzed.At the same time, data testing was performed to identify the key factors affecting product quality, so that Provide basis for device production and transformation.
I. Experimental part
1.1 Experimental equipment
TE-35 twin-screw extruder, BT1-FR005TNA5 universal material testing machine, K-TEC85E injection molding machine, STA449C integrated thermal analyzer (TG + DSC); SHR-100 high-speed mixer; CEAST7026000 melt indexer and related testing instruments
1.2 Test process
(1) Test process description. According to the actual production of the device, take a certain amount of PA14D powder, and perform uniform mixing in the SHR-100 high-speed mixer according to the ratio of the imported formula and the domestic compound antioxidant formula, and set up the TE-35 twin-screw extruder. The temperature was tested, and the temperature of different temperature control intervals of the TE-35 twin-screw extruder was adjusted in time to observe the phenomenon during the test. Before the test, the CE147026000 melt index meter was used to determine the MFR of the PA14D powder. The pellets were extruded at different temperatures on a TE-35 twin-screw extruder, and the change in the melt index was measured. Indicator detection and conclusion.
(2) Selection of formula. Formula one: 1681400ppm; 10102000ppm; calcium stearate 500ppm; pps8002700ppm. Formulation 2: Composite antioxidant 8000ppm
Results and discussion
2.1 Effect of extruder temperature on melt index (powder 0.224)
(1) Formula one. 230 ℃ / 0.264, 250 ℃ / 0.29, 270 ℃ / 0.317, 275 ℃ / 0.335, 280 ℃ / 0.373, 290 ℃ / 0.444, 300 ℃ / 0.52, 325 ℃ / 1.76, 350 ℃ / 5.8.
(2) Formula two. 230 ℃ / 0.223, 250 ℃ / 0.249, 270 ℃ / 0.283, 275 ℃ / 0.310, 280 ℃ / 0.316, 290 ℃ / 0.389, 300 ℃ / 0.495, 325 ℃ / 0.88, 350 ℃ / 2.65.
2.2 Change of head pressure
(1) Formula one. 230 ℃ / 4.554, 250 ℃ / 4.0, 270 ℃ / 3.75, 275 ℃ / 3.45, 280 ℃ / 3.40, 290 ℃ / 3.10, 300 ℃ / 2.70, 325 ℃ / 1.10,
350 ° C / 0.95.
(2) Formula two. 230 ℃ / 4.20,250 ℃ / 3.70,270 ℃ / 3.25,275 ℃ / 2.85,280 ℃ / 2.75,290 ℃ / 2.50,300 ℃ / 1.80,325 ℃ / 1.10,
350 ° C / 1.00.
2.3 Host current change
(1) Formula one. Temperature / current / feeding speed: 230 ℃ / 28.0 / 8, 250 ℃ / 27.1 / 8, 270 ℃ / 28.1 / 9, 275 ℃ / 27.7 / 9, 280 ℃ / 27.6 / 9, 290 ℃ / 27.2 / 10, 300 ℃ / 23.8 / 10, 325 ℃ / 19.6 / 10, 350 ℃ /18.5/10.
(2) Formula two. Temperature / current / feeding speed: 230 ℃ / 23.1 / 10, 250 ℃ / 21.8 / 10, 270 ℃ / 22.1 / 10, 275 ℃ / 22.4 / 10, 280 ℃ / 20.1 / 10, 290 ℃ / 19.8 / 10, 300 ℃ / 20.0 / 10, 325 ℃ / 19.5 / 10, 350 ℃ /19.0/10. (Since the TE-35's main unit has a rated current of 30, in order to ensure the normal operation of the main unit, the feeding speed of formula one is reduced. The above data is measured at a constant main engine speed at 9 rpm).
2.4 Analysis of product results after injection
According to the experimental results, we selected the pellets produced at 230 ℃, 250 ℃, 270 ℃, 280 ℃, 290 ℃ for injection analysis.
(1) Formula one. Temperature ℃ / tensile yield stress: quality index / 20.0-27.0. 230 / 25.2,250 / 25.9,270
/24.5,280/25.1,290/25.0.
(2) Formula two. Temperature ℃ / tensile yield stress: quality index / 20.0-27. 230 / 25.0, 250 / 25.1, 270 / 24.6, 280 / 24.9, 290 / 24.6.
(3) Formula one. Temperature ℃ / flexural modulus: quality index / 500-700. 230 / 634,250 / 635,270 / 630,280
/ 622,290 / 644.
(4) Formula two. Temperature ℃ / flexural modulus: quality index / 500-700. 230 / 581,250 / 651,270 / 616,280 / 633,290 / 601.
2.5 Calibration of output
We chose to calibrate the output of the two formulas under the conditions of relatively stable 280 ° C: Formula one: 260 g / min, Formula two: 320 g / min. Under the same condition of 280 ° C, the speed of the main machine is constant at 9rpm. In order to ensure that the TE-35 twin-screw extruder does not stop due to the large running current of the main machine, the feeding speed of formula one is 9rpm. The calibration speed of formula two is controlled at 10 rpm.
2.6 Analysis of results
(1) It is determined that the reasonable temperature control range of the extruder using the formula one in the PPR production process should be determined between 270 ° C and 300 ° C, and the reasonable temperature control range of the use of the formula two should be determined between 275 ° C and 300 ° C. If the temperature control is unstable, it will cause fluctuations in the index.
(2) The use of Formula One gives off an odor above 250 ℃, which is caused by the decomposition of thioester antioxidants.
(3) The smoothness of the draw bars of formula 1 and formula 2 is different. The material bar drawn by formula 1 has a rough feel, and the bar material of formula 2 should be smoother. This phenomenon is also consistent with the change of the head pressure.
(4) In terms of yellow index, the overall appearance of Formula One is better than Formula Two.
(5) From the comparison of the calibrated output and the data in Table 3, it can be seen that the use of formula two is better than formula one in terms of power consumption. Of course, the determination of power consumption should be completed through further calibration. The data we get is only an apparent display.