Technical Status and Development Trend of PVC-U 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”.

PVC-U pipe is a kind of plastic pipe with PVC resin as the main raw material and no plasticizer. Based on the characteristics of high strength, high modulus, good weather resistance, low density, acid and alkali corrosion resistance and electrical insulation, this material with a history of nearly 100 years can still occupy an absolute advantage in the global plastic pipeline market.

At present, the main application fields of PVC-U pipes are building drainage pipes, normal temperature water supply pipes, electrical protection sleeves, fire protection pipes, outdoor building rainwater pipes, municipal water supply pipes, agricultural pipes, chemical anti-corrosion pipes, mine transmission pipes, etc. Generally, PVC-U pipes are manufactured by extrusion. With the large-scale of extruders, molds and other supporting devices, PVC-U pipes are developing towards large diameter of special specifications, and the weakness of poor toughness always restricts the improvement of PVC-U pipe performance and the expansion of application fields. In recent years, a lot of basic work has been done in the toughening and modification of PVC-U pipes, mainly from the aspects of raw materials, formula and processing methods, while improving the strength and toughness of PVC-U pipes.

The service performance of PVC-U pipe depends on the material formula and preparation process. In order to change a good formula material into PVC-U pipe with high strength, high ring stiffness, excellent toughness and convenient construction, it is also necessary to carefully study the processing technology and structural design of the pipe. With the need of the application field of PVC-U pipe and the innovation of process technology, in order to increase the ring stiffness of pipe, PVC-U reinforced pipe appears; In order to improve the toughness of pipes and facilitate construction, PVC-U double wall corrugated pipes appear; In order to strengthen the silencing ability of pipes, PVC-U inner spiral pipes appear; In order to transport the liquid to be insulated, PVC-U core layer foam pipe appears; In order to further increase the pipe diameter, PVC-U winding pipe appears.

Compared with polyolefin pipes, PVC-U pipes have the characteristics of high strength, good flame retardancy, high ring stiffness, excellent weather resistance and low price. At present, PVC-U pipes with small diameter (630 and below) have become mature in terms of process technology and market application. For the preparation of large-diameter pipes, in addition to the optimization of raw resin and production formula, the innovation of preparation technology has always been an important driving force for the development of PVC-U pipe industry. As a new preparation process of PVC-U large-diameter pipe, winding technology is mainly composed of two parts, that is, PVC raw materials with different formulas are extruded into hollow profiles (blanks) with specific shapes by extruder, and then PVC-U profiles are wound into large-scale hollow pipes with special winding equipment and special adhesive. At present, this technology can produce 300 ~ 3000 mm large diameter PVC-U winding pipe.

On the one hand, the process research of PVC-U pipe is developing towards the direction of large diameter. On the other hand, the reinforcement and toughening of PVC-U pipe is also an important direction of new process technology development. In recent years, the production technology of biaxially stretched PVC pipe has become more and more mature. This processing technology stretches the PVC-U pipe produced by extrusion method in the axial and radial directions at the same time, so that the PVC molecular chains in the pipe are regularly arranged in the biaxial direction, and a new PVC pipe with high strength, high toughness, high impact resistance and fatigue resistance is obtained, which is much better than the ordinary PVC-U pipe. For the development of the pipe, it is necessary to start with the synthesis of raw material resin, material formula design, development of production equipment and mold, formulation of process control parameters, comprehensive consideration, and targeted in-depth research and development, so as to obtain a technical breakthrough.