1. Why does PPR pipe have low temperature brittleness?
Answer: PP-R is random copolymer polypropylene, which is what we call type III polypropylene. It is obtained by random copolymerization of propylene monomer and a small amount of ethylene monomer under heating, pressure and catalyst. The ethylene monomer is randomly distributed in the propylene long chain, and the ethylene monomer is generally controlled between 3-5%. The ethylene content and the polymerization method of ethylene and propylene determine its cold brittleness. In the case of low temperature, especially in the winter construction process, the flexibility of the pipe is reduced at low temperature, the rigidity is increased, and it is brittle. Under the impact of external force or excessive accidental load, the pipe may crack in a straight line. Bring inconvenience to construction. For this reason, relevant national regulations have made clear requirements for this issue. During construction in winter, attention should be paid to the low-temperature brittleness of PP-R pipes for building water supply, and corresponding construction plans should be formulated. GB/T50349-2005 has detailed regulations on this.
2. The manifestation of cold brittleness of PPR pipes in practical applications
Answer: When the ambient temperature is low, the toughness of the PPR pipe decreases, which is embodied as brittleness. When the pipe is impacted or pressed by external force, linear cracking will occur, and the cracking starts from the inner pipe and extends to the outer pipe. After the pipe is cracked by the force of a point, the crack will grow rapidly along the axis of the pipe in an instant. This characteristic is called rapid crack growth. In addition, in winter, the pipe material is injured by external force during transportation, construction site and installation, and the pipe will burst in brittleness and toughness (during hot water delivery) during use.