Analysis And Analysis Of PP Pipes For Hot And Cold Water Supply Pipes.

- Jul 08, 2018-

PP pipe PP material is a kind of polyethylene material. It was first developed by the American Ceramics (DOW) company in the late 1990s and gradually introduced to the market. It is a technology route using C4 grafting to improve the resistance of traditional PE materials. Heat. Less than ten years before the market, it has been less than five years since entering the Chinese market. There is no corresponding international standard or national standard. This reflects the immaturity of the material from one aspect and has not yet fully withstood the test of the market.


 Recently, we have extensively exchanged views on the application prospects of PP materials with international counterparts, and conducted detailed discussions with individual raw material suppliers. We found that the development of PE-RT materials has historical reasons: due to the earlier development of aluminum-plastic composites Although the tube (PEX/aluminum composite tube) and the cross-linked polyethylene (PEX) tube have excellent performance and high temperature resistance and low temperature resistance, the connection problem is always difficult to solve, and it is inevitable that water leakage will not occur in long-term use. Some raw material manufacturers have proposed that the process of graft modification rather than cross-linking not only solves the heat resistance of the material, but also gives the material the advantage of being able to be thermally fused. Through a period of effort, this idea has gradually become a reality, which is now the PE-RT material on the market. However, due to the poor heat resistance of the material body (polyethylene), the modified PE-RT material has improved in heat resistance index, but it has not yet reached the desired level. Currently, it is only in the low temperature floor. The field of radiant heating (<60 °C) has been promoted to a certain extent and gradually recognized, and has not been applied in the field of building hot water. The “ingenuity” of individual enterprises in China has promoted the application of PE-RT pipelines to building water supply, especially hot water, and even promoted the heat resistance of this material up to 110 °C. The strength is indeed great, which fully reflects the company’s fearlessness in innovation. spirit.


     Anyone with plastic knowledge knows that different materials have different performance characteristics. There is never a so-called “universal pipeline” in the market. PP is not, PB is not, PE-RT is not. There is no best, only the most suitable, scientific selection method is to choose the most suitable cost-effective pipeline according to the characteristics and requirements of different application fields. Objectively analyzing the technical indicators of PE-RT materials, we believe that the materials still have their merits, and there will be certain market prospects: compared with traditional PEX pipes and aluminum-plastic composite pipes, PE-RT pipes not only retain The characteristics of the hot-melt connection have also improved the thermal creep to some extent. If the material price is right, it is expected to have certain competitive advantages and market impact in the domestic floor radiant heating field, but if you enter the building hot water market And the high-temperature heat sink heating market is based on its own shortcomings.


    First, talk about heat resistance: comparing the ring stress index of PP pipe and PE-RT, it is found that the ring stress of PE-RT material is lower than that of PP-R material. The heat resistance directly affects the applicable field of the pipeline. It can be said that the current PE-RT material is not suitable for high temperature operation conditions. In view of this, some domestic enterprises have begun to learn from the molding principle of aluminum-plastic composite pipe to develop a double hot-melt PE-RT aluminum-plastic composite pipe to improve the heat strength of the pipeline. This practice is far more responsible than unrealistic and excessive exaggeration. There are many, but the product must also be subject to strict inspection and approval by the market.


    Elastic modulus E: PP-R has an elastic modulus of 850 MPa. PE-RT belongs to medium-density polyethylene. The elastic modulus is only about 550 MPa. It has good flexibility and insufficient rigidity. It is used in the construction water supply field, and the pipe straightness is not good. Easy to bend, easy to deform, and the pipeline is not beautiful.


Thermal conductivity: PP-R is 0.24, PE-RT is 0.42, nearly doubled. If it is used in floor heating, this is its strength. Good heat dissipation indicates better heat radiation, but it is used in hot water pipes. It is its shortcoming, good heat dissipation, large heat loss, higher surface temperature of the pipe, and easy to hot.


Weldability: Although PP-R and PE-RT can be hot-melt welded, PP-R is easier to operate, PP-R is rounded, and PE-RT is irregularly clogged, which is easy to block; welding temperature is also different. PP-R is 260 ° C, PE-RT is 230 ° C, using the PP-R special welding machine on the market is easy to over-weld to cause water leakage. In addition, since the PE material is easily oxidized, it is necessary to use a special tool to scrape off the scale of the surface before welding. Otherwise, the integrated pipe in the true sense cannot be formed, and the pipe is prone to water leakage, so the construction is more troublesome.


   Low temperature impact strength of PP pipe: This is the strength of PE-RT material from the index. PP is higher than PE and PE is more flexible than PP. This is determined by the nature of the material, but the problem of excessively exaggerating PP-R cold brittleness is It makes no sense that the PP-R tube has been used in China for more than ten years. The production enterprises have gradually reduced the hidden dangers caused by improper handling through effective packaging and enhanced publicity. The barbaric handling and construction are also the same. It will cause surface scratching and stress cracking of PE-RT pipe; any pipe must be insulated when used under low temperature conditions, otherwise the pipe will be cracked due to volume expansion caused by icing. Individual companies use unspeakable remarks to mislead the market and their intentions are clear.