Winter is coming, how to protect the PPR pipeline from cold?
Introduction: PP-R is a random copolymer of propylene and ethylene, PP-R PP-R is a pipe resin by extrusion molding is made, in the late 1980s early 90s development of plastic pipe product applications. With its excellent performance and wide application fields, it has occupied a place in the plastic pipe market and is recognized as a green product. However, due to the poor low temperature resistance of the PPR pipeline, it has certain limitations for the transportation, installation and use of the pipeline, especially in the northern part of China in winter. Therefore, how to improve the low temperature resistance of PPR pipes is particularly important.
First, what is the PPR pipeline
PP-R is a random copolymer polypropylene, which is what we call type III PP. It is obtained by random copolymerization of propylene monomer and a small amount of ethylene monomer under the action of heating, pressurization and catalyst, and is a kind of copolymerized PP. It has excellent impact properties compared to homopolymerized PP, but at a higher price.
There are two main types of PPR pipes: cold water pipes and hot water pipes. It can be used not only for ordinary plumbing pipes, but also for pure drinking water systems. The biggest difference between cold water pipes and hot water pipes is the thickness of the pipe wall:
(1) The wall of the cold water pipe is about 2.8-3.5mm, and there is a blue marking line on the outside of the pipe wall;
(2) The wall of the hot water pipe is about 4.2 mm, and the wall side has a red marking line;
(3) The wall of the hot water pipe is thicker and can be used instead of the cold water pipe, but the cold water pipe can never replace the hot water pipe.
Second, why does the PPR pipeline have low temperature brittleness?
The PP-R tube has a certain low temperature brittleness below 5 °C. In most places in China, the temperature in winter is below 5 °C, which seriously affects its performance. So why is this happening?
The ethylene monomer in the PPR molecular structure is randomly distributed into the long chain of propylene, wherein the ethylene monomer is generally controlled between 3-5%. The ethylene content and the way in which ethylene and propylene are polymerized determine its cold-brittle character. That is, we often say the glass transition temperature (Tg). When the temperature is low, the branches and segments of the middle of the molecular structure are defined and cannot move freely. Therefore, when subjected to external impact, the molecules cannot move through each other, and the external energy is converted into internal friction heat energy, so it is realized. Low temperature brittleness.
The external performance is that, in the case of low temperatures (especially in winter), the flexibility of the pipe at low temperatures is reduced, the rigidity is enhanced, and the brittleness is exhibited. Under the impact of external force or excessive accidental load, the pipe may be cracked straight. And the cracking condition starts from the inner tube and extends to the outer tube.
Third, the danger of low temperature brittleness
Brittleness is exhibited when the pipe is at a lower temperature. Therefore, there are certain risks in the process of transportation, installation and use.
(1) During the winter transportation process, the pipeline will be impacted by external force during transportation, causing rupture and affecting the performance. Therefore, it is necessary to increase the protection measures, which will increase the cost;
(2) In the low temperature environment, the installation of the pipeline brings great inconvenience and affects the construction efficiency. Therefore, in the winter construction, attention should be paid to the low-temperature brittleness of the building water supply polypropylene (PP-R) pipeline, and the corresponding construction plan should be formulated.
(3) The biggest danger is the potential. Winter pipes are damaged by external forces during transportation, construction and installation. These defects may not be observed by the naked eye, but they will appear brittle and tough during use. ) Tube burst. Endangering personal safety.
Fourth, the method of improving low temperature brittleness
(1) Blending with polyethylene PE , the low temperature embrittlement temperature of PE can reach -70 degrees. Adding proper amount of PE can change the low temperature resistance of PP, but the excessive addition of PE will affect the hardness and stratification of PP products. Linear material is best.
(2) Polyolefin POE toughening , POE has the general characteristics of thermoplastic elastomer, low density, excellent heat resistance, cold resistance, wide temperature range, and is an ideal material for changing PP low temperature resistance, usually adding 3%-15 % can make polypropylene PP reach -20 degrees, use POE cold resistance to toughen PP, not only change the original PP is more resistant to low temperature, the impact determination will also increase.
(3) EPDM toughening EPDM, the most important characteristic of EPDM is its superior resistance to oxidation, ozone and erosion, and low temperature embrittlement resistance. EPDM cold resistant particles can be used to change the cold and cold resistance of PP. -40 degree. The cost is relatively higher than the POE, but the performance is incomparable.
(4) PPR can be blended with PPB. The low temperature embrittlement temperature of PPB is better than PPR. Adding proper amount of PPB can change the low temperature resistance of PPR.
(5) PPR can change the low temperature brittleness of the pipe by changing its own crystallization mode , mainly changing the cooling temperature of the pipe during the production process.
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