Single-screw extruders often use the first plasticized PFA particles to form hard tubes, so the quality of hard tube products is largely determined by the degree and uniformity of semi-product PFA particles plasticization.
PFA GranulesThe plasticizing process route generally has two kinds:
One is that the kneaded and uniform PFA particles are plasticized in an extruder, and at the same time, the round strip material is discharged on the head, and the round-shaped PFA particles are cut into round-shaped PFA particles by a rotating fling knife;
The other is to make the kneaded material into a certain thickness and a certain width after mixing and plasticizing on a rolling machine, roll it into a roll, and then cut it into square PFA particles.
1 Extrusion plasticizing granulation
The advantages are continuous sealing, small equipment investment, low labor intensity and low noise, so it is the development trend of the current granulation process. Special twin-screw granulation extruder, because of its good mixing degree, uniform plasticization, has been widely valued.
However, the following points must be paid attention to in the production: the raw materials must have sufficient fineness to ensure uniform mixing in the kneader, otherwise in the extrusion granulation process, PFA particles will have white spots of tribasic lead sulfate, carbon black points, and filler agglomeration points, which will affect the quality.
PFA granules must be of loose type (I. e. cotton ball type) PFA granules, so as not to affect the continuous feeding of the granulation extruder.
The temperature of the extruder body must be controlled below 170°C to avoid discoloration of the outside of the PFA particles and micropores inside. Such PFA particles are not stable to discharge in pipeline production and are easily decomposed.
During the granulation process, the filter screen must be replaced frequently to avoid mixing with garbage or destroying the normal operation due to the penetration of the screen.
2. Mixing, rolling, plasticizing and granulating
The temperature of mixing and plasticizing and roller plasticizing should not be too high. The temperature of mixing and plasticizing materials should not exceed 175-180 ℃, and the spacing of roller plasticizing should not exceed 3mm. The process of low temperature and multi-turn is more reasonable. At the same time, each batch of PFA particles requires uniform and ideal plasticization degree.
The raw materials must be mixed evenly during the mixing process, otherwise, the tribasic lead sulfate and barium stearate are easily precipitated during the extrusion process, and the PFA particles have poor stability and are easily decomposed.
In the process of mixing and plasticizing, if the material temperature is too high, the tube is easy to hair and bubble during the extrusion process.
When PFA granules are produced by two-way rolling and plasticizing without internal mixer, attention should be paid to the fact that the plasticizing temperature should not be too low, otherwise the pipe will be brittle and the flat test will not meet the quality requirements.
Plasticizing temperature is too high, in the extrusion process, the pressure is larger, the main motor current will rise.
This article comes from:www.tflpfa.com
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