PP-R pipe
DATE：2022/3/14 8:55:42 / 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 (homopolymer polypropylene) pipe and block copolymerized polypropylene (block copolymerized polypropylene) pipe. Ene · R pipe has excellent impact resistance, corrosion resistance, high temperature resistance and good pressure resistance. Yang and anti-aging performance, as well as health and non-toxic, convenient installation, beautiful appearance and other characteristics. In recent years, Baowei has become one of the main products to replace galvanized steel pipes. PP-R pipes will not have adverse effects on human body and environment in the process of raw material production, forming, use and waste. Therefore, it is widely 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 alloy composite pipe and PP-R pipe) of Beifang in the future.1. Raw materials are randomly collected into a tree book Non toxic, colored or colored fruit
The density is 0.89-0.91g/cm, the relative molecular weight is high, and the mfr5g / 10 (230 ℃, 2160g) is below. It has high melt strength, which is conducive to the circumferential stress of the extruded random copolymerized polypropylene pipe. It has better stability than the ordinary polypropylene (pp-h) meal and block copolymerized polypropylene (PP-B) pipe, so it has limited service life at high temperature. The impact property of PP-R is higher than that of homopolypropylene (pp-h), which is equivalent to that of PP B and improves the impact property in use. For example, under the working conditions of 60 ℃ and 1.25mpa, it can be used continuously for more than 50 years, which is one of the reasons why PR pipes are widely used in cold and hot water supply, underground heating and high and low temperature heating equipment. Performance comparison of propylene resins of different brands:
Performance (pp-h) 1300 (PP-B) 8101 (PP-B) M910 ra130e (PP-R) (PP-R) 4220 test standard (ASTM)
Density / gcm-3 zero point nine one zero point nine zero zero point nine zero zero point nine zero zero point nine zero D1505
MFR/g·(10min) one point five zero zero point three seven zero point three three zero point two five zero point three six D1238
Breaking strength / MPs yield strength / mpa35 030.042.224.824.635.520.933.633.226.0 D638 D638
Elongation at break (%) five hundred six hundred and twenty six hundred and thirty seven hundred and thirteen seven hundred and seven D638
Bending strength / MPa twenty-eight point three twenty-seven point three eighteen point nine D790
Bending modulus / MPa one thousand three hundred and fifty one thousand and eighty-one one thousand and forty-one six hundred and thirty-three eight hundred and twenty-four D790
Rockwell hardness ninety seventy-nine point six seventy-one point two sixty-four point eight seventy-nine point four D785
Thermal deformation temperature / ℃ Vicat softening point / ℃ one hundred and five ninety one hundred and fifty-five one hundred and forty-eight seventy point nine D1525 D648
In addition, PP-R pipe material belongs to high crystalline polyolefin, and the chemical element in the molecule is C and, which is internationally recognized as a non-toxic and harmless material.
2. Main production equipment
PP-R has low thermal conductivity, high relative molecular weight, low MFR and high power consumption, The extrusion equipment shall have a large aspect ratio (no less than 301 driving power and accurate electronic temperature control device. Moreover, the screw adopts a new mixing screw to fully plasticize the materials and achieve the purpose of low-temperature extrusion. Due to the memory characteristics of PP-R, the ordinary pipe extrusion die cannot be used in the die. At present, the new spiral pipe extrusion die is mostly used in China. This kind of die has good shunting effect, no welding mark and small head compression ratio Improving product quality is also conducive to improving production efficiency. In addition, in order to ensure no leakage of PP-R pipe during welding construction, the design requirements of die and sizing sleeve affecting the pipe size are very strict. In the design, the barus effect (outlet swell) shrinkage rate and processing conditions of PP-R material shall be fully considered. 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 $50mm, the length of vacuum sizing box shall not be less than 6m; ф 50~ ф For pipes with diameter of 75mm, the length of vacuum sizing box shall not be less than 12m; For ф For pipes with a diameter of more than 75mm and the length of the vacuum sizing box is more than 18m, it is best to use two pumps for staged vacuum pumping.
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 → stacking of pipes - quality inspection and packaging → warehousing of finished products.
(2) In addition to the above material and equipment factors, in order to produce high-quality PP-R pipes, there must be good plasticization 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, for some new screws, increasing the rotating speed can 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.
Author：admin