PP-R pipe
DATE：2022/3/26 9:02:13 / READ： / SOURCE：This station
PP-R pipe
Random copolymerized polypropylene pipe, abbreviated as PP-R pipe, is the third generation of new polypropylene pipe after pp-h (homopolypropylene) and PP-B (block copolymerized polypropylene) pipe. PP-R pipe has become one of the main products to replace galvanized steel pipe in recent years because of its excellent impact resistance, corrosion resistance and high temperature resistance, good pressure insulation and aging resistance, sanitation, non toxicity, convenient installation and beautiful appearance. PP-R pipe will not have adverse effects on human body and environment in the process of raw material production, molding, processing, use and waste, so it is known as "green environmental protection pipe". The Ministry of construction of the people's Republic of China has determined that PP-R pipe will be the first product among the three new types of pipes (cross-linked PE pipe, aluminum-plastic composite pipe and PP-R pipe). Casting film production line www.handler com1. Raw material PP-R pipe parts are made of random copolymerized polypropylene synthetic resin with B content of about 3% (mass fraction). It is tasteless, non-toxic, natural color or colored granular material. The density is 0.89-0.91g/cm, the relative molecular weight is high, and mfr5g / 10min (230 ℃, 2160g) is below. It has high melt strength and is conducive to extruding pipe blank. The hoop stress of random copolymerized polypropylene pipe at high temperature has better stability than ordinary polypropylene (pp-h) pipe and block copolymerized polypropylene (PP-B) pipe, so it has longer service life at high temperature. The impact performance of PP-R is higher than that of homopolypropylene (pp-h), which is equivalent to that of PP B, which greatly improves the impact performance in use. For example, under the working conditions of 60 ℃ and 125mpa, it can be used continuously for more than 50 years, which is one of the reasons why PP-R pipe is widely used in cold and hot water supply, underground heating and high and low temperature heating equipment. In addition, PP-R pipe material belongs to high crystalline polyolefin, and the chemical elements in the molecule are C and h. This kind of material is internationally recognized as non-toxic and harmless material. Casting film production line www.handler com
2. The main production equipment PP-R has low thermal conductivity, high relative molecular weight, low MFR and high power consumption. The extrusion equipment shall have large aspect ratio (not less than 30:1) and driving power and accurate electronic temperature control device. Moreover, the screw should adopt a new mixing screw to fully plasticize the materials, so as to achieve the purpose of low-temperature extrusion. Due to the memory characteristics of R, the ordinary extrusion die can not be used. At present, new spiral extrusion dies are mostly used in China. This kind of die has good shunting effect, no welding mark and small head compression ratio, which can not only improve product quality but also improve production efficiency. In addition, in order to ensure no leakage during the welding construction of PP-R pipe, the design requirements of die and sizing sleeve affecting the pipe size are very strict. The barus effect (outlet swell) shrinkage rate and processing conditions of PPR material shall be fully considered in the design. The design principle is that the inner diameter of the die is greater than that of the vacuum sizing sleeve, and the inner diameter of the die and sizing sleeve is greater than that of the pipe. The calculated size of the inner diameter of the die and sizing sleeve shall be accurate to 2 decimal places. PP-R pipe adopts vacuum sizing method. Due to poor thermal conductivity of PP-R, large heat release during cooling, thick pipe wall and pipes with diameter less than 450mm, the length of vacuum sizing box shall not be less than 6m$ 50~ ф For pipes with diameter of 75mm, the length of vacuum sizing box shall not be less than 12m; For pipes with a diameter of more than $75mm, if the length of the vacuum sizing box is more than 18m, it is best to use two pumps for staged vacuum pumping. Casting film production line www.handler com
3. Preparation process (1) production process flow measurement of main and auxiliary raw materials → mixing → hot melt extrusion → mold forming → vacuum cooling and setting → water tank cooling and setting → traction → coding and printing → fixed length cutting → pipe stacking → quality inspection and packaging → finished product warehouse.
(2) In addition to the above material and equipment factors, high quality PP - R pipes should be produced There must be good and stable melt flow, and process control is also very important. The molding process temperature of PP-R pipe is generally between 210 ~ 260 ℃; The extrusion speed has a great influence on plasticization. Generally, the screw speed of the main engine does not exceed 40R / min; However, some new screws increase the speed, but enhance the shear effect and strengthen the plasticization, which can realize low-temperature and high-speed extrusion. The vacuum degree is generally 0.05 ~ 0.08mpa. Casting film production line www.handler com
Author：admin