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The nature of HDPE Pipe

2021-07-17

High-density polyethylene (HDPE) is a white powder or granular product. It is non-toxic, tasteless, crystallinity is 80%-90%, softening point is 125-135℃, service temperature can reach 100℃; hardness, tensile strength and creep are better than low-density polyethylene; wear resistance, electricity Good insulation, toughness and cold resistance; good chemical stability, insoluble in any organic solvents at room temperature, corrosion resistance to acids, alkalis and various salts; low permeability to water vapor and air, water absorption Low; poor aging resistance, environmental stress cracking resistance is not as good as low-density polyethylene, especially thermal oxidation will reduce its performance, so antioxidants and ultraviolet absorbers must be added to the resin to improve this deficiency. High-density polyethylene film has a lower thermal deformation temperature under stress, so pay attention to it when applying it.

In this century, a revolutionary progress has taken place in the pipeline field, that is, "plastics instead of steel". With the rapid progress of polymer materials science and technology, the deepening of the development and utilization of plastic pipes, and the continuous improvement of production processes, plastic pipes vividly demonstrate their excellent performance. Today, plastic pipes are no longer mistaken as "cheap substitutes" for metal pipes. In this revolution, polyethylene pipes have become more popular and have increasingly dazzling brilliance. They are widely used in gas transportation, water supply, sewage, agricultural irrigation, mine fine solids transportation, and oil fields, chemicals, post and telecommunications, especially in fields such as It has been widely used in gas transportation.

HDPE is a thermoplastic polyolefin produced by copolymerization of ethylene. Although HDPE was launched in 1956, this plastic has not yet reached a mature level. This general material is constantly developing its new uses and markets.
my country’s domestic high-density polyethylene (the high-density polyethylene here does not include the high-density polyethylene produced by the full-density polyethylene device) includes three major companies: PetroChina, Sinopec, and CNOOC. As of the end of 2006, it belongs to the high-density polyethylene of PetroChina. There are 4 sets of polyethylene plants, namely Lanzhou Petrochemical High-density Polyethylene Plant, Daqing Petrochemical High-density Polyethylene Plant, Liaoyang Petrochemical High-density Polyethylene Plant, and Jilin Petrochemical High-density Polyethylene Plant.
High-density polyethylene is usually manufactured by Ziegler-Natta polymerization method. Its characteristic is that there are no branches on the molecular chain, so the molecular chain is arranged regularly and has a higher density. This process uses ethylene as a raw material in a tubular or kettle-type low-pressure reactor and uses oxygen or organic peroxide as an initiator to initiate the polymerization reaction.

High-density ethylene is an environmentally friendly material, and it can be recycled and reused after heating to the melting point. It should be noted that plastic materials can be divided into two categories: "Thermoplastic" (Thermoplastic) and "Thermosetting" (Thermosetting). "Thermosetting plastic" becomes a solidified state after being heated to a certain temperature. Even if it continues to be heated, its state cannot be changed. Therefore, products with environmental protection issues are "thermoset plastic" products (such as tires), not "thermoplastic" products (such as plastic pallets. Note: pallets are called "splints" in Hong Kong and Macau), so not all " "Plastic" is not environmentally friendly.

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