Comprehensive and profound understanding of polypropylene (PP) double-wall corrugated pipeComprehensive and profound understanding of polypropylene (PP) double-wall corrugated pipe
Rapid urbanization and industrialization have increased the threat of sewage to the environment; solid waste pollution, landfills, industrial wastewater, and sewer leaks can all pollute groundwater, and the related cleaning work requires a long time and expensive costs. The traditional underground drainage pipes mainly include concrete, clay and plastic (PE, PVC) and other pipes, but the traditional hard pipes have the problem of fragility. The consumption of resources; due to the material characteristics of PVC and PE plastic pipes, there are also great limitations in caliber and ring stiffness. How to solve and perfect the problems faced by underground drainage systems, polypropylene drainage pipes give a brand new solution.
This article mainly introduces the market development, application and production of polypropylene (PP) double-wall corrugated pipe, and compares it with polyethylene (PE) double-wall corrugated pipe by combining the test data of domestic manufacturers.
1. Product introduction of polypropylene (PP) double-wall corrugated pipe
1.1 Product structure and common specifications
The structure of PP double-wall corrugated pipe is the same as that of common PE double-wall corrugated pipe. It is made of modified polypropylene and co-extruded by inner and outer extruders. It is formed in one time, the inner wall is smooth, the outer wall is sinusoidal corrugated, and the inner and outer walls It is a hollow and tightly welded tube with a ring structure.
Product specifications: The maximum caliber of foreign countries can reach DN1800mm, and the current domestic production can reach up to DN1200mm, but basically all are between DN200mm-800mm.
Product series: The data shows that the rigidity of the PP double-wall corrugated pipe ring can reach SN14, and there are four series in China: SN4, SN8, SN10 and SN12.5.
1.2 Product development history
In Europe, PP pipes have been used for drainage and sewage for more than 25 years, and have achieved good application practice results. The United States and Australia have also successively developed PP double-wall corrugated pipes; the processing and application of PP double-wall corrugated pipes in China have only just begun in recent years. The "Polypropylene (PP) Pipeline Seminar for Underground Drainage and Sewage" co-sponsored by the Drainage Professional Committee of the China Urban Water Supply and Drainage Association was held in Beijing. More equipment manufacturers and pipeline manufacturers began to pay attention, promoting the development of PP double-wall corrugated pipes in China.
1.3 Product material selection
At present, domestic suppliers of special materials for PP buried drainage and sewerage pipelines are: LyondellBasell Industrial Company (Basel Hostalen PP H2483 for the outer structural wall; Hostalen PP H2464 for the inner solid wall), Borouge Hong Kong Limited The company (PP-B HM) and Yangzi Petrochemical (J340).
The PP-B HM raw material synthesized by Borouge is a high-modulus polypropylene product made of homopolypropylene (PP-H) and a small amount of polyethylene as a comonomer. The vinyl chain end is introduced into the PP matrix The rubber phase is formed, so that the material can not only obtain a higher modulus, but also maintain excellent impact resistance. PP-B HM can produce larger diameter pipes, and can reduce the wall thickness, and the long-term durability is more excellent.
1.4 Product application
1) Municipal engineering: used as drainage and sewage pipes.
2) Construction engineering: used as a rainwater pipe, underground drainage pipe, sewage pipe, ventilation pipe, etc.
3) Railway and highway communication: used as protective tubes for communication cables and optical cables.
4) Industry: Widely used in sewage pipes in chemical industry, hospital, environmental protection and other industries.
5) Agriculture, garden project: used for irrigation and drainage of farmland, fruit tea garden, and forest belt.
6) Road engineering: used as infiltration and drainage pipes for railways and highways.
7) Mine: used as mine ventilation, air supply and drainage pipes.
8) Double-wall corrugated pipe with openings: can be used as a seepage pipe for saline-alkali highways.
9) Golf course, football field project: used as a water seepage drain for golf and football fields.
1.5 Product application advantages
The traditional hard pipe has the problem of fragility; PVC-U double-wall corrugated pipe has poor brittleness at low temperature, and large-diameter processing is difficult due to poor material flowability; PE double-wall corrugated pipe has low rigidity, easy deformation, and large backfill engineering. It is easy to cause road collapse; polypropylene (PP) double-wall corrugated pipe has the characteristics of high ring rigidity, light weight, good flexibility, etc. At the same time, the product also has excellent corrosion resistance, chemical resistance, crack resistance, ductility, Long service life, easy installation and other advantages.
1.6 Product assembly method-socket aprons connection
1.7 Product standards and performance indicators
Polypropylene (PP) pipes have been used in drainage and sewage systems in Europe for a long time, and have standardized relevant standards; in Australia and New Zealand, there are already standards for solid and structural wall pipes; in the United States, polypropylene for buried drainage and sewage ( PP) The relevant standards for pipelines began to be implemented in 2010; the relevant standards are: European standards EN 13476-1: 2007, EN 13476-2: 2007, EN 13476-3: 2007 and BS EN 1852-1: 2009; American standard ASTM F2376-10, ASTM F2881-11.
At present, there is no corresponding technical specifications and standards for PP sewage bellows. Basel said that the 2012 National Standards Association has agreed to draft a national standard for PP sewage bellows, but so far there is no official approval, so the standard project has not been initiated.
At present, domestic production enterprises refer to the national standard of PE double-wall corrugated pipe "Part 1 of buried polyethylene (PE) structure wall pipeline system: polyethylene double-wall corrugated pipe material" (GBT19472.1) as the production basis, and Guangdong XX announced on the enterprise website The index of PP double-wall corrugated pipe is as follows:
1.8 Product Application Case Hainan Dongfang City Application
The geographical conditions in Dongfang City, Hainan Province are relatively poor, and soil settlement often occurs. The pipeline needs to be buried deep, and the pipeline needs to have sufficient rigidity and toughness to resist the force applied by the soil. . Shanghai XX pipeline adopts PE bellows forming machine to produce PP-B HM corrugated pipe. The ring stiffness meets the requirements of SN12 (the actual result reaches SN14), and the weight of the pipeline is reduced by 11%, which can well resist the burial depth or settlement. Deformation, and light weight, easy to install.
There are relatively many foreign application cases. They are used in the Helsinki Eastern Sewage Transmission Project in Finland, the German Airport Runway Reconstruction Project, and the German Industrial Wastewater Transmission Project.
1.9 Problems in product production and application
1. At present, there is no national standard or industry standard related to PP bellows in China. Not many manufacturers are willing to invest in equipment modification to specialize in the production of PP bellows;
2. PP bellows of a certain caliber can be produced normally on PE bellows production equipment, but if large-diameter pipes are needed and more materials are saved, a special PP bellows forming machine is still required;
3. At present, it is difficult to process large-diameter PP bellows (more than 800mm) with PE bellows equipment, mainly due to the high PP-HM modulus. During the production process, the melt pressure is lower than the PE melt pressure. If it is not reached, melt fracture will occur during processing.
4. The market prospect is unclear: PP double-wall corrugated pipe is still in the development period, and the market acceptance situation is not very clear;
2. Industry background
2.1 Foreign applications
In Europe, PP pipes have been used for drainage and sewage for more than 25 years, and have achieved good application practice results. The United States and Australia have successively developed PP double-wall corrugated pipes.
2.2 Domestic application
The Nordic Chemical Company has specially developed a variety of high-stiffness PP materials for pressureless drain pipes with modulus ranging from 1300MPa-1900MPa. Domestic petrochemical enterprises and production equipment manufacturers have also developed high-rigidity PP materials and production processing production lines: Yangzi Petrochemical Company successfully developed large-diameter polypropylene PP bellows special materials, and the test was successful; Weifang Zhongyun Research Co., Ltd. developed new water cooling PP double-wall corrugated pipe production line, compared with the ordinary cooling mode, the output can be increased by as much as 3 times, and the power consumption can be reduced by more than 50%; Dalian Sanlei began researching polypropylene (PP) double-wall in 2004 For the manufacturing technology of bellows, the first production line was exported to Europe in 2005. At present, dozens of PP double-wall corrugated pipe production lines have been exported to all parts of the world.
At the 2012 annual meeting of the China Plastics Processing Industry Association Plastic Pipe Professional Committee, Gudi Technology Co., Ltd. published the "Polypropylene Double-Wall Bellows Development Status and Application Advantages" article on the development status of polypropylene double-wall bellows at home and abroad and The advantages of industrialization were analyzed; the 14th National Plastic Pipe Production and Application Technology Promotion Conference in 2012, Shanghai AD and Borouge published the article "New PP-B HM material used in the production of double-wall corrugated pipes in China". HM material is introduced, and the production process and product performance of PP bellows and HDPE bellows are compared.
2.3 Comparative analysis of alternative products
2.3.1 Comparison of the structure of PP bellows and HDPE bellows
Ring stiffness is an important parameter for the resistance of plastic buried drainage pipes to external loads. The formula is defined according to the ring stiffness:
The same diameter pipe needs to achieve the same ring stiffness. If the material has a higher modulus, the value of the moment of inertia can be smaller, and the design of the waveform can be smaller, thinner, and shorter, which saves the material. With the same waveform design, the material has a higher elastic modulus, and the ring stiffness has been greatly improved; while the same ring stiffness needs to be achieved, the material has a higher elastic modulus, and the pipe diameter can be made larger.
2.3.2 Comparison of polypropylene (PP) double-wall corrugated pipe and polyethylene (PE) double-wall corrugated pipe
The waveform design of PE is adopted. Due to the different materials, the production process is also different. It is understood that Shanghai AD Company produced PP-B HM double-wall corrugated pipe on the PE double-wall corrugated pipe forming machine through process adjustment and compared the performance of HDPE and PP-B HM double-wall corrugated pipe.
It can be seen from the table that the elastic modulus of HDPE is 1100MPa, the elastic modulus of PP-B HM is 1700MPa; the density of HDPE pipe is 0.95g / cm³, and the density of PP-B HM pipe is only 0.90g / cm³; the processing temperature is slightly higher and the production speed It is faster than HDPE bellows.
Group A has the same ring stiffness compared to the difference in weight: For 300mm pipes, PP-HM can save 10% of the material under the same ring stiffness SN8; for 800mm pipe, PP-HM can save 21% of the material, and Ring stiffness to SN10.
Group B, under the same secret weight conditions, compared the different ring stiffness, for 300mm pipe, PP-HM ring stiffness increased by 25%, 800mm pipe increased by 75%.
2.3.2 Weight comparison of bellows of different materials
According to the latest design data of CORMA, it is easy to form polyolefin materials with higher corrugation, which can make up for the smaller elastic modulus, but the weight of polyolefin material is much lighter than PVC, and the same ring stiffness is achieved under the rational design of corrugation. More savings, PP bellows saves the most material. The larger the caliber, the more material saving the PP double-wall corrugated pipe.
Compared with PE and PVC-U corrugated pipes, polypropylene (PP) double-wall corrugated pipes have many advantages such as high ring stiffness, light weight, small friction coefficient, chemical resistance, impact resistance, etc., and can completely replace existing municipal pipelines To realize its unique advantages in municipal drainage and sewage projects;
However, the polypropylene (PP) double-wall corrugated pipe is still in the development stage in China, the production equipment, process technology, and standards are still being regulated, and the polyolefin corrugated pipe market is chaotic, and the product quality is uneven, which affects PP to a certain extent. Market share of double-wall corrugated pipes