polyethylene aluminum plastic composite pipe
DATE：2022/8/18 9:11:28 / READ： / SOURCE：This station
polyethylene aluminum plastic composite pipe
Polyethylene aluminum-plastic composite pipe has only been used for heating and water supply in China in recent years. It is a new type of pipe which is compounded with aluminum pipe (or aluminum alloy pipe) after plastic is plasticized and extruded by an extruder. As this composite pipe is formed by compounding aluminum sheet and plastic (see Fig. 5-19 for structure), it has the comprehensive properties of two materials: corrosion resistance, non-toxic, moderate rigidity and flexibility, light weight, bendable and straight, but the geometric shape of the circle is unchanged, high pressure and high temperature resistance, and good thermal insulation. It can work in a medium environment of 50 ~ 110 ℃ for a long time without deterioration and deformation. The polyethylene plastic layer in the composite pipe is high-density polyethylene or cross-linked high-density polyethylene (cross-linked high-density polyethylene resin molding composite pipe is suitable for high temperature and high pressure applications). The aluminum pipe in the composite pipe is made of aluminum sheet or manganese aluminum alloy sheet, which is wound into a pipe shape and then welded. There are two kinds of winding welding forming methods for aluminum pipes: one is to wrap aluminum sheets into lap welds and weld them with ultrasonic welding machine; The other is that the aluminum sheet is wound into a butt weld and welded with inert gas or laser. At present, see table 5-17 for the specification of aluminum sheet welded pipe. As can be seen from Fig. 5-22, the die has four feed holes, which are respectively connected with two extruders for extruding PE melt and one extruder for extruding hot melt adhesive. The forming sequence of the aluminum-plastic pipe in the mold is as follows. First, weld the lap joint of the aluminum strip pipe into the mold with an ultrasonic welder to form the aluminum pipe, then coat the hot melt adhesive on the inner wall of the aluminum pipe, and then coat the PE melt on the adhesive layer of the inner wall of the aluminum pipe to form the PE plastic layer of the inner wall of the aluminum pipe. With the movement of the inner wall plastic layer pipe coated with the aluminum pipe toward the die mouth, the outer layer adhesive and PE melt of the aluminum pipe are successively coated on the outer wall surface of the aluminum pipe, and then moved out of the die mouth. After cooling, it is shaped into an aluminum-plastic composite pipe. Fig. 5-23 forming process sequence of butt welded aluminum-plastic composite pipe the processing of butt welded aluminum-plastic composite pipe is different from that of lap welded aluminum-plastic pipe in that the PE material is extruded with an extruder to form the inner pipe of the aluminum-plastic composite pipe. After cooling and shaping, the outer circle is coated with adhesive, and then the aluminum sheet is wound on the outer circle of the PE plastic pipe, Then, the aluminum sheet butt joint shall be welded firmly by laser welding (note that when the aluminum sheet pipe is wrapped around the outer circle of the inner PE plastic pipe, the size shall be slightly larger than the outer circle of the PE plastic pipe). After the aluminum seam is welded, the pipe shall be shrunk to make it firmly contact with the PE inner pipe. According to this method, the adhesive layer and PE melt layer are coated on the outer circle of the aluminum pipe to form the aluminum-plastic composite pipe. (3) Quality of aluminum-plastic composite pipe the quality requirements of aluminum-plastic composite pipe shall comply with the specific provisions of the national urban construction industry standard CJ / t108-1999 aluminum-plastic composite pressure pipe (lap joint pipe). See table 5-18 for specifications and dimensions of aluminum-plastic composite pipe. See table 5-19 for the working temperature and pressure of aluminum-plastic composite pipe.5.2.10 polyethylene silicon core composite pipe
Polyethylene silicon core pipe is a composite pipe, which is the outer layer of polyethylene silicon core pipe extruded by high density polyethylene; The inner layer of polyethylene silicon core pipe was extruded by mixing high density polyethylene powder with a certain proportion of silane lubricant with low friction coefficient. The friction coefficient of the inner wall of this composite pipe is very small (only 0.08 ~ 0.15). Because the inner surface of this pipe has very good lubrication performance, this composite pipe is currently used as a communication cable sleeve. The mechanical property of polyethylene silicon core pipe is the same as that of high-density polyethylene pipe. It has the advantages of good toughness, arbitrary bending, good water resistance, rust prevention, long service life, smooth inner pipe wall and small friction coefficient. When used for optical cable casing, the construction and installation are convenient and fast. (1) The polyethylene silicon core composite pipe is divided into inner and outer layers, and there is a color mark on the surface. HDPE material with density of 0954g / cm3 and melt flow rate of 0.1 ~ 0.5g/10min (6100mhdpe produced by Yangzi Petrochemical Company, MFR = 0.14g/10min) is selected for outer layer molding. The inner material of polyethylene silicon core pipe can be HDPE, a certain proportion of silane lubrication, or extruded with silicone mixture and solid lubricant. The color marking materials can be general extruded high-density polyethylene and color masterbatch. (2) Formula and equipment conditions: the extrusion process sequence of silicon core pipe is basically similar to the extrusion process sequence of polyethylene pipe. The difference is that since this pipe needs three kinds of materials to melt and compound, the plasticization of the three materials needs to be completed by three extruders, and then the three kinds of molten plasticized materials with different properties are extruded into the molding die of a composite pipe to form the pipe. The specific process sequence is as follows. Extrusion and plasticization of polyethylene silicon core pipe outer layer material - extrusion and plasticization of polyethylene silicon core pipe inner layer material composite pipe forming mold → vacuum sizing sleeve cooling and cooling and sizing → extrusion and plasticization of polyethylene silicon core pipe color marking material - composite pipe cooling and cooling and curing → traction → cutting → coiling → quality inspection → packaging and warehousing. The equipment for extrusion and molding of polyethylene silicon core pipe is the same as that for extrusion and molding of polyethylene pipe, except that three extruders are used for extrusion and plasticization of three materials Specifications and screw structure have their own characteristics. The outer layer of polyethylene silicon core pipe uses a lot of materials, and larger size extruder shall be selected; Less material is used for the inner layer, and smaller size extruder shall be selected; However, there are few materials used for color marking, so the extruder with the smallest specification in the extruder series should be selected. If the outer layer of polyethylene silicon core pipe is made of gradual change type screw with screw diameter of medium 90mm and length diameter ratio of 33:1 (preferably separated BM screw), the screw with screw diameter of medium 45mm and length diameter ratio of 28:1 shall be used for plasticizing the inner layer of silicon core pipe; For the plasticization of the color marking material, the universal screw of extruded HDPE material with a screw diameter of medium 20mm can be selected. (3) Process temperature when polyethylene silicon core pipe is extruded, due to the different materials used for the composite pipe, the plasticizing process temperature of the extruded materials by the three extruders is different. The outer layer of the silicon core pipe and the color marking line are made of high-density polyethylene. The temperature control of each section of the extruder barrel for extruding these two materials is the same as that of the extrusion process of ordinary high-density polyethylene pipe. As the HDPE resin is mixed with silane lubricant, the process temperature of each section of the extruder barrel is slightly different. The temperature of the feeding section of the barrel is 100 ~ 125 ℃, the temperature of the plasticizing section is 135 ~ 160 ℃, and the temperature of the homogenizing section is 170 ~ 185 ℃. The mold temperature for forming silicon core composite pipe is 175 ~ 190 ℃. (4) Key points of process operation ① when the inner and outer layers and color marking lines of polyethylene silicon core pipe are molded with HDPE resin, the melt flow rate of the selected materials shall be close to or the same. The flow rate of the melt extruded by the three extruders shall be the same, which is conducive to the mixing of the contact interface of the three kinds of melt extruded into the composite pipe mold by the three extruders at the same time. ② The working surface of the melt channel cavity in the composite pipe forming mold shall be smooth and flat without assembly bosses or plane joint gaps between parts; The manufacturing and assembly accuracy of each part is required to be high. ③ In order to ensure the smoothness of the inner wall of the composite pipe and the minimum friction coefficient of the inner surface of the product, the machining accuracy and smoothness of the outer working surface of the mandrel in the mold shall be strictly controlled, and the roughness Ra shall not be greater than 0.32 μ m。 ④ The formed composite pipe shall be cooled slowly, and the temperature of cooling water in the water tank shall be controlled within the range of 12 ~ 16 ℃. ⑤ The traction speed is matched with the extrusion speed of the pipe blank, and the traction speed of the extruded composite pipe is controlled within 10m / min.
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