Ideal Plastic Solution—Extrusion & Recycling
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PVC pipe is made by mixing PVC resin with additives such as stabilizers and lubricants, and extruder molding after pelletizing. It can also be extruded with powder at one time. PVC pipe has good chemical resistance and insulation. It mainly transports various fluids and is used as wire casing.
The PVC pipe is formed by using SG-5 PVC resin, stabilizers, lubricants, fillers, pigments, etc. These materials are appropriately processed and kneaded according to the formula. If the pipe is extruded by a PVC single screw extruder, the kneaded powder is granulated and then extruded; if a twin-screw extruder is used, the powder can be directly formed.
In the production process, since PVC is a heat-sensitive material, even if a heat stabilizer is added, it can only increase the decomposition temperature and prolong the stabilization time without decomposition. This requires that the molding processing temperature of PVC should be strictly controlled. Therefore, the extrusion temperature should be determined based on factors such as the formula, the characteristics of the extruder, the structure of the head, the screw speed, the position of the temperature measurement point, the error of the temperature measurement instrument and the depth of the temperature measurement point.
Control of temperature is an important control factor in the PVC pipe extrusion line operation. The temperature of the controlling factors required for extrusion molding is the barrel temperature, the diameter temperature, and the die temperature. If the temperature is too high, the material will decompose and the product will discolor.
Increasing the speed of the screw and increasing the amount of extrusion can increase the output, but it is easy to cause the phenomenon of poor plasticization, causing the inner wall of the pipe to be rough and the strength to decrease. At this time, the head pressure should be adjusted to achieve the best output and quality. The temperature control of the screw affects the material delivery rate, the plasticization of the material, and the melting quality. Extruded pipes need to pass cooling water to reduce the temperature of the screw, which is conducive to improving the plasticization quality. The temperature of the screw to pass the cooling water is about 50 ~ 70.
The adjustment of the traction speed in the re-extrusion operation is very important. The material is melted and plasticized after extrusion and is continuously pulled from the head to be hauled to enter the shaping device, cooling device, traction device, etc. The traction speed should be consistent with the extrusion speed match. In normal production, the traction speed should be about 1% to 10% faster than the extrusion speed of the pipe.
Compressed air can inflate the pipes and tubes to keep the pipes round. It is required that the pressure should be appropriate. The pressure is too small, the pipe is not round, the pressure is too large, the core mold is cooled, cracks appear on the inner wall of the pipe, the surface is not smooth, and the quality of the pipe is reduced. At the same time, the pressure needs to be stable. If the pressure is suddenly large or small, the pipe is prone to bamboo knots.
Different plastic products are extruded, different sizing methods and cooling methods are used. The cooling medium can be air, water or other liquids and the temperature needs to be controlled. The temperature is mainly related to production efficiency and product internal stress.
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