1. The development process of polyethylene pipe

The performance of polyethylene pipe depends on its molecular structure, which is affected by catalyst type, polymerization type, polymerization conditions, molecular weight and molecular weight distribution, copolymer type and distribution, and high-density polyethylene pipe has experienced four leap stages.

The polyethylene pipe began in the 1950s and is mainly composed of polyethylene macromolecules that do not contain fat chains, do not contain copolymer monomers or have a very low content. Therefore, the density is high and the resistance to slow crack growth is poor.

In the second stage, from pe63 in the mid-1970s to medium-density PE80, the pressure resistance was relatively improved; Copolymer is used, which has a certain resistance to slow crack growth.

In the third stage, from the late 1980s to the 1990s, the third generation of polyethylene pipe special materials used bimodal polymerization technology to further improve the long-term hydrostatic performance of polyethylene and the ability to resist slow crack growth, that is, high-density bimodal PE100 pipe. Globally, since the early 1990s, the PE100 has gradually replaced the PE80. In China, the shift began around 2000. At present, PE100 pipeline has been widely used in the field of water supply pipeline; In the application of gas pipelines, PE100 has gradually replaced PE80 materials.

In the fourth stage, starting in 2001, polyethylene materials further improved pipeline performance through molecular structure design, new catalysts and polymerization technologies. 1pe125 resin is crosslinked by PE, and its grade is one grade higher than PE100. It enables PE tubes to withstand higher pressures with very thin tube walls. At present, the production cost is high and it is still in the development stage. 2 Further improve the resistance to slow crack growth and rapid crack growth ability of PE pipe, to meet the international requirements for new construction methods of PE pipe materials. Under external scratches and point loads, the 100-year design task of cracking resistant polyethylene pe100 reinforced concrete can still be achieved. (RC: Crack resistance). As can be seen from the figure, in the European market, pe100 reinforced concrete has been gradually quantified, and pe100 reinforced concrete pipes have become the high-end development trend of pe100 pipes in the international market.

2. What is slow crack growth resistance

Slow crack growth (SCG) One case is the residual stress in the production process; The other case is due to the construction process of human dragging and the impact of the surrounding environment and start from zero, such as the point load generated by the stone on the outer surface of the pipe, will form a stress concentration area, produce initial cracks, and develop into micro-crack holes, PE pipe material characteristics determine whether the cracks will continue to grow and develop into cracks, This can cause damage to the material or prevent the crack from further developing into a crack. This feature is the manifestation of slow crack propagation.

3. Performance comparison of PE80, PE100 and pe100rc

At present, the main mechanical properties of PE pressure pipes are: long-term hydrostatic strength or pressure resistance (MRS), slow crack growth resistance (SCG) and fast crack growth resistance (RCP).

First of all, compared with pe-80 material, the difference is that PE100PE100 reinforced concrete material is higher than Mrs, that is, the pressure level of the pipeline is higher. The PE100PE100 reinforced concrete pipe of the same specification can withstand higher pressures. From the perspective of resource conservation, using the PE100pe100rc can save nearly 34% of resources under the same pressure.

Secondly, the bimodal molecular weight distribution of PE100 makes its comprehensive physical and mechanical properties develop evenly, which has made great progress compared with PE80. The Pe100 rc further improves the long-term safety performance of pipeline systems.