Random copolymer polypropylene pipe (PP-R pipe)
DATE：2022/8/24 9:41:21 / READ： / SOURCE：This station
Random copolymer polypropylene pipe (PP-R pipe)
Polypropylene can be divided into isotactic polypropylene and random polypropylene according to the spatial arrangement of - CH3 groups in its molecules. Random copolymerized polypropylene is a kind of resin based on copolymerized polypropylene and modified by ethylene. It is a new resin developed after homopolymer polypropylene (pp-h) and block copolymerized polypropylene (PP-B), referred to as pp-r.(1) Properties of random copolymerized polypropylene resins random copolymerized polypropylene resins can be produced in China, but the performance indicators and production conditions need to be improved. The properties of raw materials used to produce PP-R pipes shall meet the requirements of performance indexes in table 5-35.Good, the circumferential stress under high temperature conditions has better stability than other polypropylene pipes. Under the working conditions of 60 ℃ and 1.25mpa, the service life can reach more than 50 years. It has the characteristics of good thermal insulation effect, smooth inner wall and small liquid flow resistance when used for hot water transportation. However, due to the low melt flow rate of the resin and the high viscosity of the melt, it is difficult to process the molded pipe after the resin is melted. (2) Resin for forming random copolymer polypropylene pipe conditions for extruding random copolymer polypropylene resin to form pipes, random copolymer polypropylene resin with ethylene content of about 3% (mass) shall be selected, which is granular and has a density of 0.89 ~ 0.91g/cm ³ In this range, the molecular weight is high and the melt flow rate (MFR) is less than 0.5g/10min. The performance parameter value of the resin shall meet the conditions in table 5-35. (3) Equipment conditions for extrusion molding of random polypropylene pipe the extrusion molding process of random polypropylene pipe is the same as that of ordinary polypropylene pipe. Single screw universal extruders are used. The raw materials are extruded from the molding die after extrusion and melting, and then cooled and shaped by vacuum sizing method. After the pipe is cooled by sufficient spray water, it is cut according to the specified length. Thereby completing the extrusion molding production of the random copolymer polypropylene pipe. Due to the low thermal conductivity, high molecular weight and low melt flow rate of the random copolymer polypropylene resin, that is, the viscosity of the resin in the molten state is high, so it needs more heat from the crystal to the high elastic state and then to the molten viscous flow state in the extrusion process, that is, the power consumption is large; The transformation process of raw material form has some special requirements on the structure of the equipment. The thickness dimension can be set, recorded and corrected by the computer, (4) the extrusion process and operating conditions of the random copolymer polypropylene pipe ① the temperature control of the extruder is: 185 ~ 200 ℃, 200 ~ 220 ℃, 220 ~ 240 ℃, 225 ~ 250 ℃ in the first zone, 230 ~ 2500 ℃ in the fifth zone. The mold temperature for forming pipes is controlled within the range of 210 ~ 240 ℃ (the working speed of the screw at this temperature is within the range of 30 ~ 45r / min). ② The temperature of the tube blank of the extrusion molding die is still very high. If there is adhesion between the outer diameter surface material of the tube blank and the inlet of the sizing sleeve, the cooling water ring sleeve shall be set in front of the sizing sleeve, and the temperature of the circulating water can be adjusted. The water temperature control here shall be subject to the pipe blank cooling to the non stick mold. ③ During the operation, pay attention to the matching between the pulling speed of the pipe and the speed of the die mouth of the pipe blank extrusion molding; The pulling speed is too fast, and the cooling and setting of the pipe blank in the vacuum sizing sleeve is not sufficient, which will lead to the phenomenon of tensile orientation, affect the ring stress, and lead to the reduction of the pressure resistance of the pipe during operation. ④ The spray water temperature in the cooling water tank shall be controlled within the range of 15 ~ 18 ℃. If the water temperature is too high and the crystal particles formed by the products are large, the impact resistance will decrease; If the water temperature is too low, high internal stress will be generated after the pipe is finalized, affecting the quality of the pipe. ⑤ The waste materials produced in the production can be directly used in the production after being crushed, dried and cleaned. However, the amount of admixture should not be too large, and it is appropriate not to exceed 7% to avoid affecting the quality of pipes. (5) Application characteristics of random copolymerized polypropylene pipes: random copolymerized polypropylene pipes are used in various construction industries. The maximum service temperature when used for conveying hot and cold water can reach 95 ℃, and the long-term service temperature is 70 ℃; In industrial production, it can be used to transport oil and various corrosive liquids; In people's daily life, it is used in drinking water and agricultural irrigation pipelines. It is non-toxic and does not pollute the environment. The service life can reach more than 50 years. The application characteristics of random copolymer polypropylene pipe are as follows. ① PP-R pipe body is light, non-toxic, corrosion-resistant, good strength, no pollution to the environment and long service life. ② Compared with common metal pipe, PP-R pipe has no corrosion, wear resistance, scale formation and acid and alkali resistance. ③ PP-R pipe has small resistance to liquid transportation and good thermal insulation performance for hot water transportation, which can save energy. Compared with the production process of PE cross-linked polyethylene pipe, the production process of PP-R pipe adopts simple equipment, no pollution to the production environment, easy operation, and long-term use of screw without cleaning. ⑤ The installation method of PP-R pipeline is simple, and the same material is used for hot welding, which is safe, reliable, convenient and fast, reliable in application and good in sealing.
Author：admin