Read: PP-R is a random copolymer of propylene and ethylene. PP-R pipe is made of PP-R resin by extrusion molding, in the late 1980s and early 90s the development and application of plastic pipe products. Its excellent performance and a wide range of applications, has occupied a place in the plastic pipe market, is recognized as green products.However, due to poor performance of PPR pipeline low temperature, to the pipeline transport, installation and use have brought a certain Of the limitations, especially in the winter in northern China.Therefore, how to improve the PPR pipeline low temperature performance, is particularly important.
First, what is the PPR pipeline
PP-R is a random copolymerized polypropylene, which is what we call type III PP.It is by the propylene monomer and a small amount of ethylene monomer in the heating, pressure and catalyst under the effect of random copolymerization is copolymerized PP A. Compared with homopolymer PP, with excellent impact performance, but the price is higher.
PPR pipeline is divided into two types: Cold water pipes and hot water pipes. Not only can be used for ordinary water pipes, can also be used for pure drinking water system. Cold water pipe and hot water pipe is the biggest difference between the thickness of the wall:
(1) cold water pipe wall is about 2.8-3.5mm, outside the wall of the blue marked line;
(2) hot water pipe wall is about 4.2mm, the wall side of the red marked line;
(3) hot water pipe wall thick, can replace the use of cold water pipes, but the cold water pipe is never to replace the hot water pipe.
Second, PPR pipeline why there is low temperature brittleness
PP-R pipe below 5 ℃ has a low temperature brittle, most of the winter in China, the temperature is below 5 ℃, so seriously affected its performance. So why is this situation?
The ethylene monomer in the PPR molecular structure is randomly distributed to the long chain of propylene, in which the ethylene monomer is generally controlled between 3-5%, and the ethylene content and the polymerization of ethylene and propylene determine the characteristics of the cold brittleness. We often say that the glass transition temperature (Tg). When the temperature is low, the molecular structure of the branch and the section is defined, not free movement, so in the external impact, the molecules can not move between, the outside Energy into the internal friction heat consumption, so realized as low temperature brittleness.
External performance is that, in the case of low temperatures (especially in the winter), the pipe at low temperature flexibility has decreased, rigidity increased, the performance of brittleness in the external impact or excessive accident load, may occur The pipe is cracked in a straight line, and the cracking is started by the inner tube and extends outward.
Third, the risk of low temperature brittle
As the pipeline at low temperatures, it will show brittle.Therefore, to the transport, installation and use of the process have brought some risks.
(1) during the winter transport process, the pipeline will be in the transport by external impact, leading to rupture, affecting the use of performance, so the need to increase the protection measures, which will cause the cost increase;
(2) In the low temperature environment, the installation of the pipeline has brought great inconvenience, affecting the construction efficiency.Therefore, in the winter construction, should pay attention to the construction of water supply polypropylene (PP-R) pipe low temperature brittle characteristics, and develop Corresponding construction plan.
(3) the greatest danger is potential, the winter pipe in the transport, in the site and the installation process due to external injuries, these defects may not be observed with the naked eye, but in the course of the use of brittleness and toughness (transport hot water The risk of personal safety.
Fourth, improve the method of low temperature brittleness
(1)Blended with polyethylene PE , PE low temperature embrittlement temperature can reach -70 degrees, add the right amount of PE can change the PP low temperature performance, but PE will increase the excess of PP products will affect the hardness and layer, PE to the best linear material.
(2)Polyolefin POE toughening , POE has the general characteristics of thermoplastic elastomer, low density, heat resistance, excellent cold resistance, the use of a wide temperature range, is to change the PP low temperature ideal materials, usually add 3% -15% can make polypropylene PP to - 20 degrees, the use of POE cold grade toughened PP, not only to change the original PP more resistant to low temperature, the impact will be determined to increase.
(3)EPDM EPDM toughening , EPDM the most important feature is its superior resistance to oxidation, anti-ozone and anti-erosion ability and low temperature embrittlement resistance, the use of EPDM cold particles to change the PP cold and low temperature can reach -40 degrees. Cost relative to POE higher, But the performance is not comparable.
(4)PPR can be blended with PPB , PPB low temperature embrittlement temperature than PPR is better, add the right amount of PPB can change the PPR low temperature performance.
(5)PPR can change the way through their own crystallization, to change the low temperature brittle pipe , Mainly in the production process to change the cooling temperature of the pipe.