With the progress of polymer material technology, the development and utilization of plastic pipe is deepening. In the past twenty years, the development and production of plastic pipe village in China have made great achievements. At present, plastic pipes have been developed for water supply pipeline engineering, including UPVC pipe, PE pipe, PB pipe, PEX pipe, PP-C pipe, PP-R pipe and metal-plastic composite pipe. The properties of these pipe trees are different, the production process has its own characteristics, and its main application range is different. However, its application in water supply pipeline engineering is light, easy to transport and install, the smooth resistance coefficient of the inner wall of the pipeline is small, and the corrosion resistance is low. The performance is good, does not constitute the secondary pollution to the water quality actually is the common. Based on the relevant data, this paper introduces the material properties, production standards, production technology and application scope of the new plastic pipe tree commonly used in water supply pipeline engineering in the market at present, for the reference of peers. First, hard polyvinyl chloride (UPVC) pipe is the main product of plastic pipe in China. The pipe fittings of UPVC water supply pipe were listed in the "Seventh Five-year Plan" scientific and technological research project in 1983. After more than ten years of technical development and application practice, both in the production of products and in practical engineering applications, they have accumulated. A large number of theoretical and practical experiences 1. The properties and production process of S4 are thermoplastic plastics. The finished UPVC tubes are light in material, with a density of 1350 (n1460k8/m3 (steel for 7800kg/m3), Vicat softening temperature 86 ℃, tensile resistance, etc.) Bending resistance, compressive strength is higher, but the impact strength is relatively low. The extrusion process is widely used in UPVC tube, and the extruder is divided into single screw and twin-screw. In terms of extrusion process, double-screw extruder is superior to single screw extruder. At present, domestic production of UPVC pipeline has more than 400 manufacturers. At present, most of the domestic manufacturers of UPVC water supply pipes produce pipes according to the national standard, but there are still quite a lot of manufacturers who are restricted by imported equipment or whose products are sold abroad, and adopt the British standard (BS), day standard (JIS),. Standard (DIN) or IS0 production pipe. For the users, the inner and outer diameter and wall thickness of the pipes produced according to different standards are different, which must be paid attention to when selecting. China UPVC water supply pipe design, construction, acceptance regulations, the selection of pipes must be in accordance with China's national standards. China formulated the UPV in 1988 C the national standard of water supply material, GB10002.1-88, was revised in 1996, and a new national standard, GB/T10002.1-1996, which was not equivalent to the international standard of IS04422:1990, was promulgated. The pipe fitting standard GB10002.1-88 is now being revised. According to the current national standard of pipe, the diameter (outer diameter) of pipe diameter (20mm) to diameters / diameters (0mm) is 28 diameters, and the pressure grade is 0.6Mpaol 1.6Mpa. there are 5 grades. According to the experience of many domestic water supply companies, outdoor UPVC pipeline should be selected. The caliber of UPVC water supply pipe is classified as 20mm "630mm in design, construction and acceptance code of pressure grade 1.0 Mpa, and the caliber classification stipulated in national standard of pipe is deleted, so as to facilitate the preparation of water supply enterprise.
3. The connection mode and fittings of UPVC water supply pipe are the important factors restricting its application in engineering. After more than 10 years of application practice, the development and development of pipe connection technology and fittings have made great progress. At present, flexible interface (R-R) pipes with caliber greater than or equal to 63mm can be produced in China, and flexible joints can be used to connect those with caliber below 63mm. It can be said that adhesive interface (T-S) will be gradually replaced by flexible interface, which is the trend of the times. In terms of accessories, the way in which accessories were made by hand in the early 1990s was already basic. Elimination. In recent years, manufacturers have produced three links, bends, and other joints connected by bonding, and some have replaced them with steel and plastic fittings. In April 1999, a factory in Jiangsu Province successfully developed fully plasticized three links, bends, and other accessories with flexible interfaces, with a caliber of 100 mm. There are three kinds of 150mm and 200mm, which basically meet the demand of UPVC water supply pipeline engineering in residential area. 4. The application range of UPVC water supply pipe is mainly suitable for outdoor buried water supply pipeline. The statistical data of domestic water department show that the diameter of water supply pipe is mostly 250mm or below. UPVC pipe is also used in building water supply (indoor water supply), but it is effective. The fruit is not ideal. In recent years, with the rise of polypropylene, polybutene, crosslinked polyethylene and aluminum plastic composite pipes, UPVC pipes will be rapidly discussed in the field of building water supply engineering. Secondly, polyethylene pipe (PE pipe) has been used in gas pipeline engineering for many years, with successful theoretical and practical experience. In recent years, there are a large number of applications in rural water supply projects. Abroad is widely used in municipal underground water supply pipes. Several domestic enterprises have devoted themselves to the development and research of this field. Generally speaking, it is still in its infancy. 1. Material properties and production process polyethylene is also a thermoplastic plastic, can be used for many times Processing and shaping. Density is one of the most important properties of polyethylene, which is divided into high density polyethylene (HDPE) (HDPE), medium density polyethylene (MDPE),) low density polyethylene (LDPE) (LDPE). The higher the density, the higher the relative hardness, softening temperature and tensile strength, but the higher the brittleness, the lower the flexibility and the lower the cracking resistance. High density polyethylene is generally used in water supply pipeline and high density and medium density polyethylene is commonly used in gas pipeline. The density of HDPE 950 kg/m' is lighter than that of UPVC, and the softening temperature is 120 ℃ higher than that of UPVC tube. Its flexibility and impact resistance are higher than UP. VC tube, the connection mode is superior to the UPVC tube can basically ensure that the connection does not leak (belong to the body connection). In addition, polyethylene itself is a non-toxic plastic. In Europe and America, the consumption of HDPE water supply pipe increases year by year, and the amount of UPVC pipe decreases year by year. The general view is that in water supply pipeline engineering, HDPE pipe will eventually replace UPVC pipe. Polyethylene pipe, like UPVC pipe, is produced by extrusion molding and injection molding. Four, crosslinked polyethylene (PEX) tube crosslinked polyethylene is to add organic silane to ordinary polyethylene raw materials. The linear molecular structure was modified into three dimensional crosslinked network structure, which changed the molecular structure of ordinary polyethylene and thus changed its properties. 1. The material properties and production process of PEX are the same as that of PE tubes. They are non-toxic, tasteless, voltage-resistant, stable and durable, and have unique temperature resistance (-70 ℃ cn l10 ℃). The production process of PEX tube is based on polyethylene as matrix resin, silane as bond bridge material and raw material through precision metering system. Enter a specially designed reactive extruder to transfer silicon The vinyl of alkane and polyethylene were grafted and formed in one step to form a three-dimensional molecular network. This one-step production process is widely used in the world at present, and the domestic imported production line is also a one-step production process. 2. At present, there are not many manufacturers producing PEX tubes in China, and their production technologies are all imported from abroad. The standards used are also to draw up their own corporate standards with reference to international standards and to report to local governments for approval. The caliber (outside diameter) of the PEX tube is now 16 MU 20mm 20mm / 25mm / 25mm / 32mm / 40mm / 501mm / 501mm / 63mm. Lattice
3, connection mode, fittings PEX pipe connection by the manufacturer of copper fittings and fastening ring, siphon type or card sleeve type connection. PEX pipe and other metal pipe connection, the use of special external thread clamp type or clamp sleeve connection accessories. Applicable scope PEX is suitable for indoor hot and cold water supply pipeline. The working pressure water of the system is equal to 0.6 Mpa. the long term working temperature is less than 75 ℃ (building water supply and sewerage specification). The Shanghai Engineering Construction Standardization Office issued the recommended local application standard, "Building Water Crosslinked Polyethylene" at the end of 1998. EX) Technical Specification for Pipeline Engineering, covering the design, construction and acceptance of PEX pipes. Fifth, polypropylene copolymer PP-R, PP-C tube polypropylene is colorless, tasteless, non-toxic white wax granular material, with excellent heat resistance and high strength, but low melt viscosity, there are brittle defects at low temperature. It must be modified to meet the needs of pipeline production. At present, the commonly used modification method is to make PE and PP (polypropylene) copolymerize at molecular chain level. The products are called polypropylene copolymers. The pipes produced by them are produced in the process of raw material production, processing and waste treatment. It does not cause damage to human body and environment, so it is called green construction. At present, there are two kinds of PP tube trees in domestic market, both of which are copolymers of PP and PE. The differences are as follows: (1) the polyethylene content of PP-C, is 7 (n ll, the content of 2PP-Rand the content of PE is 3 (N5PP-C is thinner than that of PP-R of the same specification; 4 according to the current German classification, PP-C belongs to the second generation (type 2), PP-R belongs to the third generation (type 3), and 6 PP-R has better impact resistance than PP-C. PP-C, P The physical and chemical properties of P-R are basically the same, so only three types of polypropylene (PP-R) are introduced below. 1. Material properties and production process PP-R are non-toxic, hygienic and recyclable. The Vicat softening temperature of PP-R is 131 ℃, the highest use temperature is 95 ℃, and the long-term use temperature is 70 ℃. The density 900k8/m:.PP-R pipe is produced by extrusion molding process, and the PP-R pipe is produced by injection molding process. 2, the production standard at present, the domestic has not yet formulated the unified national pipe standard. PP-R production line More from Germany, the introduction of PP-C production lines from South Korea. Manufacturers mostly refer to German standards to formulate their own enterprise standards. PP-R production specifications from 20mm to 160mm multiple diameter categories. 3. Hot melt connection is used between the connection mode and the fitting PP-R pipe and fittings. When PP-R is connected with metal pipe fittings, polypropylene pipe fittings with metal inserts are used as the transition, the pipe fittings and PP-R are connected by hot melt, and the metal tubes are connected by wire buckles. 4. PP-R pipe is suitable for indoor hot and cold water supply system in buildings, and widely used in heating system Unified In Europe, the use of PP-R is more common in building cold and hot water supply systems, and has risen to become the dominant product. Jilin Provincial Bureau of Construction and Jilin Provincial Bureau of Technical Supervision issued the Jilin Province Local Standard "Technical Standard for the supply of Water and Hot Water to buildings with modified Polypropylene (PP-C) ground radiation heating, Building Water supply and Hot Water supply (for trial implementation)" in July 1998. In December 1998, Shanghai Engineering Construction Standardization Office issued the recommended local standard, "Engineering Technical Specification for Building Water supply Polypropylene Pipeline (PP-R)".
Six, metal plastic pipe, metal plastic composite pipe, there are steel plastic pipe, copper plastic pipe, aluminum plastic pipe, steel skeleton plastic pipe and so on. Aluminum-plastic composite pipe is a new type of pipe tree developed rapidly in recent years. This paper introduces aluminum-plastic composite pipe. 1. The material properties and production process of aluminum-plastic composite pipe are made of aluminum alloy as the skeleton, and the inner and outer layers of the aluminum pipe have a certain thickness of plastic pipe. Plastic pipe and aluminum tube between a layer of bonding (affinity layer), aluminum and plastic can not be separated into one. At present, almost all plastics used in aluminum-plastic composite pipes are PE tubes, and PE tubes are divided into HDPE or PEX.. HDPE or The utility model is called universal aluminum plastic composite pipe, which is suitable for water temperature 40 ℃, and PEX for internal and external crosslinked polyethylene aluminum plastic composite pipe, which is suitable for water temperature 75 ℃. The external thickness of aluminum plastic composite pipe is not less than 0.4 mm, the inner layer polyethylene is not less than 0.8mm (2 times of outer layer thickness), the thickness of aluminum strip is 0.2--0.25 mm. Adhesives (hot melt adhesives) used in the adhesive layer mainly use copolymerized modified polyethylene or chemically grafted polyethylene. Aluminum-plastic composite pipe has good metal and non-metallic properties. The production of aluminum-plastic composite pipe has two processes: co-extrusion composite, step-by-step chimeric. The coextrusion compound is Internal and external plastic (including hot melt adhesive) and aluminum pipe one-time extrusion molding, generally suitable for the diameter of the pipe below 32mm by step by extruded plastic pipe. Extruded internal glue a coated aluminum tube one extruded outside plastic tube step by step 2. The main characteristics and applications of aluminum-plastic composite pipe are based on metal pipe, and the inner and outer welded polyethylene, cross-linked polyethylene and other non-metallic materials are formed, which have the advantages of metal pipe and non-metal pipe. The composite pipe consists of working layer (water resistant), supporting layer and protective layer (corrosion resistance). It is characterized by light weight, smooth inner wall, low resistance and good corrosion resistance. The composite pipe is the most ideal pipe for water supply and drainage pipe with diameter ≥ 300mm. It has the advantages of high strength of metal pipe, good rigidity and corrosion resistance of non-metallic pipe. The connection of the composite pipe should be cold working, the hot working way can easily cause the expansion, deformation and even melting of the lining plastic. Generally, there are thread, sleeve, clamps and other connections. As the composite pipe is a new type of pipe, there is no uniform design, construction and acceptance code in China. Design and construction personnel often apply galvanized pipe process to design and construction. 3. The classification of composite pipes and their characteristics and uses. At present, there are more common aluminum-plastic coatings in the market. Composite pipe, copper plastic composite pipe, steel plastic composite pipe, coated plastic composite pipe, steel skeleton PE pipe, etc.
1. Aluminum plastic composite pipe (PAP): aluminum plastic composite pipe is a new type of composite pipe made by extrusion molding process. It consists of five layers: polyethylene layer (or crosslinked polyethylene), adhesive layer, aluminum layer, adhesive layer, polyethylene layer (or crosslinked polyethylene). In which aluminum layer splicing welding, butt welding molding process. Aluminum plastic composite pipe is a plastic / metal composite pipe with metal pipe, so it combines the advantages of both metal pipe and plastic pipe. The inner and outer layers of PE have the characteristics of non-toxic corrosion resistance light weight and low embrittlement temperature. The heat resistance and mechanical strength of PE are improved obviously after crosslinking. Middle In addition to the enhancement of PE, the aluminum pipe has 100% oxygen insulation, completely eliminating permeability, good magnetic and antistatic properties, good plastic deformation ability, so that the pipe can be deformed arbitrarily, in addition to greatly improving the compressive strength of the pipe. By strengthening the longitudinal heat dissipation capacity of the pipe, the flame retardant effect of the pipe is increased, the thermal expansion coefficient is lower than that of the PE, and the comprehensive thermal expansion coefficient of the composite pipe is reduced, and the dimensional stability of the pipe is improved. So that aluminum-plastic composite pipe has unique properties and wide application range: 1 High pressure strength and good temperature resistance (PAP tube working temperature -40C, XPAP tube 60 ℃) Working temperature-40 ~ 95 ℃), sanitary non-toxic, long service life, can be used in the construction of hot and cold pipes. It can quickly eliminate the pressure shock in the pipeline system and will not produce water hammer noise. 3 using embedded clamping joint to connect, easy to install, pipe can be freely bent, can reduce pipe joints, elbows. Can bend not rebound, can bypass Liang Zhu and other components according to the actual situation, reduce a large number of bends, save 50 manual than galvanized steel pipe. 4 the coefficient of thermal expansion is 2.5 × 10 ~ (6) m / m ·m ~ (-1) K, which is only 1 / 8 of that of PVC pipe. 5 flame retardant property is far superior to PVC pipe Good corrosion resistance, can transport all kinds of corrosive liquids, gases. Steel-plastic composite pipe: PVC lined steel pipe. This is a new type of water supply pipe developed in foreign countries in the 1970s. Because of the weakness of PVC plastic pipes such as low strength and insufficient pressure, it seems to be reluctantly applied in situations where the load is relatively harsh. Metal pipes are required at this point. PVC lined steel tubes are developed on this basis. A thin-walled PVC pipe is inserted into the traditional water conveying steel pipe, which combines the two closely and becomes the PVC lined steel pipe. It has the advantages of plastic pipe and steel pipe to avoid their shortcomings. Its connection method is also For pipe thread, fully compatible with the original galvanized pipe system, the application is extremely convenient. Therefore, in Japan, America and Europe, the price of stainless steel pipes is much lower than that of traditional copper pipes, especially in high-rise buildings. PE powder resin lined steel pipe. This is a new pipe developed in the late 70 s and early 80 s abroad. The development goal is to have the same performance as PVC lined steel pipe but better economic performance. It is made by melting a layer of PE powder resin into the inner wall of the pipe. In recent years, some developers in Shanghai, Sichuan and Zhejiang have put this kind of pipe into the market at a price lower than the price of aluminum-plastic composite pipe. Field, is very competitive. According to the characteristics of the lined steel pipe, it can be considered as a plastic pipe, that is to say, the lined steel pipe is a steel pipe with the advantages of plastic pipe. In addition, it is worth mentioning that recent developers in Sichuan have developed a kind of water supply lined plastic pipe with intellectual property rights. It is made by mechanical combination of galvanized welded steel pipe with convex mesh pattern of inner wall and non-toxic propylene plastic pipe. Besides all the advantages of the steel-plastic composite pipe in the market at present, the inner layer steel pipe has the convex mesh pattern made by special technology, which greatly enhances the reliability of the composite and solves the different materials of the inner and outer layer. The consistency of thermal expansion between steel and plastic pipes is unique because of its convenient installation and high reliability.
3. Steel skeleton PE pipe: steel skeleton PE pipe is made of high quality low carbon steel wire as reinforcing phase, high density polyethylene as matrix, and the spot welding of steel wire is carried out simultaneously with plastic extrusion filling. A new type of double-sided anticorrosive pressure pipe formed by continuous drawing film on the production line. Pipe diameter Φ 50 ~ Φ 500, flange connection, mainly used in municipal, chemical and oil field pipe network, the price is more expensive. Coated steel pipe: coated steel tube is a layer of polyethylene (PE) resin with thickness of 0.5~1.0mm, ethylene acrylic copolymer (EAA), epoxy (EP) powder, non-toxic polypropylene (PP), which is melted into the inner wall of the pipe. Or non-toxic polyvinyl chloride (PVC) and other organic compounds, the steel-plastic composite pipe not only has the advantages of high strength, easy connection and water impact resistance of steel tubes, but also overcomes the corrosion, pollution, scaling and low strength of plastic pipes when exposed to water. Poor fire performance and other shortcomings, design life can be up to 50 years. The main drawback of the pipe is that it must not be bent when installed, hot working and welding cutting, etc., the cutting surface shall be applied to the non-toxic room temperature curing glue brush provided by the manufacturer. The main specifications are Φ 15-Φ 100.