Processing Technology of Chlorinated Polyvinyl Chloride (PVC-C) Pipe

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”.

1、Extruder

Parallel or conical twin-screw extruders are usually used to extrude CPVC pipes. Considering that CPVC is easier to plasticize than PVC, it is easier to control the extrusion production of CPVC pipes by using parallel twin-screw extruders. If lead salt stabilizer is used in the formula, the extruder shall have good plasticizing performance; If organic tin is used as stabilizer in the formula, the compression ratio of extruder screw shall not be too large.

2、Processing technology

   Mixing of materials

The mixing process of CPVC resin is the same as that of PVC resin, which requires two processes: high-speed mixing and low-speed cooling mixing. Generally, the high-speed mixing temperature should be controlled at 115~125 ℃, not too high, otherwise it is easy to mix yellowing materials, causing material decomposition or "superplasticization" during extrusion. The temperature of low-speed cooling and stirring shall be controlled at 40~50 ℃ and shall not be too high, otherwise the mixed materials will absorb too much moisture in the air and affect the performance of the products due to the large difference between the mixed materials and the room temperature.

Extrusion temperature

The extrusion process of CPVC pipes focuses on the process temperature, which will directly affect the plasticizing quality of pipes. Generally, the process temperature will vary greatly due to the different plasticizing properties of the extruder, sometimes the difference will be 20~30 ℃. Theoretically, the processing temperature of CPVC material is higher than that of PVC, but in fact, according to our years of processing experience, the processing temperature of CPVC is 5~8 ℃ lower than that of PVC. This is because the melting viscosity of CPVC is higher than that of PVC, and a lot of friction heat will be generated between molten molecules. At this time, if the extruder provides it with too much heat, it is easy to cause material decomposition.

In the process temperature setting, the curve should be kept as smooth as possible, which is beneficial to the plasticization quality of the CPVC resin, and the curve up and down is not conducive to the plasticization of the pipe.

The whole process temperature control can be roughly divided into three parts: barrel, combiner core and mold. The barrel temperature decreases from Zone 1, and the combiner core temperature is slightly lower than the barrel temperature. In the mold temperature setting, it is worth noting the temperature of the die and the core mold. The temperature of the die should be about 10 ℃ lower than the temperature of the heating section of the barrel, otherwise the longitudinal shrinkage of the pipe will be affected, The pipes with no requirements for longitudinal shrinkage rate are not subject to this restriction. The heating of the core mold can be disconnected after the pipes are pulled out normally. The heat of the CPVC melt and the heat generated by the friction of the core mold can completely maintain the temperature of the core mold.

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.