With the development of the floor heating industry, PE-RT floor heating plastic pipes have been widely used and have become a popular and fast-growing product series in recent years. Therefore, it is the general trend to accelerate the upgrading of the secondary central heating pipe network, realize "replacing steel with plastic" and fundamentally overcome the shortcomings of steel pipes.

Facing the rapidly growing floor heating market and the increasingly complex and diversified heating environment, a new type of thermal insulation composite plastic pipe - (PE-RT II type) prefabricated directly buried thermal insulation pipe, the full name is "high-density polyethylene outer protective pipe polyurethane foam (PE) -RT II type) prefabricated directly buried insulated pipes, filling the gap in domestic PE-RT II pipes for urban centralized heating secondary pipe networks and hot spring insulated pipes, expanding the application scope of PE-RT II pipes, and opening up the PE-RT II A new chapter in prefabricated direct buried insulated pipes.

Technical characteristics of PE-RT2 type pipe

1. Molecular structural characteristics

PE-RT II pipe is made of high-density (hdpe) polyethylene and ethylene copolymer. PE-RT II type pipe material has good impact resistance, crack resistance, scratch resistance, good flexibility and long-term creep performance, and has good low temperature (-40℃) and high temperature resistance.

PE-RT II pipes are divided into three types according to their comonomers:

1. Ethylene and octene copolymer - heat-resistant polyethylene (C2+C8);

2. Copolymerization of ethylene and hexene - heat-resistant polyethylene (C2+C6);

3. Heat-resistant polyethylene (C2+C4) copolymerized with ethylene and butylene.

PE-RT II and non-heat-resistant polyethylene

Through molecular design technology and the use of new synthesis processes, it is one of the industrial technical characteristics of synthesizing pressure-bearing pipeline materials above grade 80 or above.

2. PE-RT II molding processing characteristics

PE-RT II is a high-density polyethylene. As a heat-resistant polyethylene, it does not require cross-linking during processing. It overcomes the complexity of the cross-linked polyethylene process and the instability of cross-linking degree control, making the entire pipe homogeneous. Stable quality.

However, the processing temperature range of PE-RT II is not very wide, and its melt temperature is generally controlled at around 190°C. If the temperature of the pipe is too high, its melt strength will be low, which will affect its molding stability.

Injection molding of pipe fittings should also adopt a low-temperature and low-pressure mechanism, requiring uniform cooling. Because its thermal conductivity coefficient is twice that of polypropylene and polybutylene, its molding shrinkage and post-molding shrinkage are both larger than polypropylene. The degree of cross-linking of cross-linked polyethylene determines the long-term hydrostatic strength of cross-linked polyethylene, that is, its service life. Generally, the cross-linking degree of cross-linked polyethylene reaches more than 65%. The cross-linked structure is formed by a chemical reaction of cross-linking agent (peroxide, vinyl trimethoxysilane) under a certain temperature and pressure to realize polyethylene. It is formed by mutual cross-linking of branched chains. Its processing is difficult and there are many variable factors, and the degree of cross-linking is difficult to control.