Production process conditions and control of PVC pipes

Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.

In the production process, because PVC is a heat sensitive material, even adding heat stabilizer can only increase the decomposition temperature and prolong the stability time without decomposition, which requires that the forming and processing temperature of PVC should be strictly controlled. In particular, RPVC is often decomposed due to improper temperature control because its processing temperature is very close to the decomposition temperature. Therefore, the extrusion temperature should be determined according to the formula, extruder characteristics, head structure, screw speed, temperature measuring point position, error of temperature measuring instrument and depth of temperature measuring point.

1、Temperature control

Temperature control is an important control factor in extrusion operation. The temperature of the control factors required for extrusion molding are barrel temperature, machine diameter temperature and die temperature. The temperature is too low, the plasticization is poor, the appearance of the pipe is dull, the mechanical properties are poor, and the product quality can not meet the requirements: if the temperature is too high, the materials will decompose and the product will change color.

2、Screw speed

With the increase of screw speed and extrusion capacity, the output can be increased, but it is easy to produce poor plasticization, resulting in rough inner wall and reduced strength of the pipe. At this time, the head pressure should be adjusted to optimize the output and quality. The temperature control of screw affects the conveying rate, plasticization and melting quality of materials. The extruded pipe needs cooling water to reduce the screw temperature, which is conducive to improving the plasticization quality. The screw cooling water temperature is about 50 ~ 70.

3、Traction speed

In the extrusion operation, the adjustment of traction speed is very important. After extrusion, melting and plasticization, the material is continuously extruded from the head and then pulled into the setting device, cooling device, traction device, etc. the traction speed shall match the extrusion speed. Generally, in normal production, the traction speed should be about 1% ~ 10% faster than the extrusion speed of pipes.

4、Compressed air and pressure

Compressed air can inflate the pipe to maintain a certain roundness. The required pressure shall be appropriate. The pressure is too low, the pipe is not round, the pressure is too high, the core mold is cooled, the inner wall of the pipe is cracked and not smooth, and the quality of the pipe is reduced. At the same time, the pressure is required to be stable. If the pressure is large or small, the pipe is easy to produce bamboo knots.

5、Temperature of sizing device and cooling device

Different sizing methods and cooling methods are adopted for extruding different plastic products. The cooling medium can be air, water or other liquids. The temperature needs to be controlled. The temperature is mainly related to production efficiency and internal stress of the product.

If you need more information, Ningbo Fangli Technology Co., Ltd. welcomes you to contact for a detailed inquiry, we will provide you with professional technical guidance or equipment procurement suggestions.