A MATERIAL FOR HOSES – CROSS-LINKED POLYETHYLENE (XLPE)
Before we understand what cross-linked polyethylene is, let's first understand what polyethylene is.
Polyethylene (PE) is a thermoplastic resin produced by the polymerization of ethylene. In industry, it also includes copolymers of ethylene and a small number of alpha-olefins. Polyethylene is odorless, non-toxic, feels like wax, has excellent resistance to low temperatures (the lowest use temperature can reach -100 ~ -70 ° C), has good chemical stability, and can resist the erosion of most acids and bases (not resistant to acids with oxidation properties).
Polyethylene is 1922 by the British ICI synthesis, 1939 began industrial production, in the United States formal industrial production, the war for the important radar with insulation materials and munitions, after the war, Japan Mitsui Petrochemical, Sumitomo Chemical (1958) began formal production, 1975 14 years plant annual output of 1.407 million tons, second only to the United States.
In 1933, the British chemical industry company Bonnemann found that ethylene can be polymerized under high pressure to produce polyethylene. In 1953, K. Ziegler of the Federal Republic of Germany discovered that with TiCl4-Al(C2H5)3 as the catalyst, ethylene could be polymerized at lower pressures. This method was put into industrial production by the Federal German company Hürst in 1955 and is commonly known as the low-pressure method of polyethylene.
Polyethylene is a typical thermoplastic, an odorless, tasteless, non-toxic, flammable white powder. PE resins are extruded and granulated into waxy pellets with a milky white appearance. Its molecular weight is in the range of 10,000 to loa million. The higher the molecular weight, the better the physical and mechanical properties and the closer it is to the required level of engineering materials. However, the higher the molecular weight, the more difficult it is to process. Polyethylene melting point is 100-130C-its low-temperature resistance is excellent. At -60 ℃ can still maintain good mechanical properties, but the use of temperature in 80 ~ 110 ℃.
Polyethylene chemical stability is good, room temperature can be resistant to dilute nitric acid, dilute sulphuric acid, and any concentration of hydrochloric acid, hydrofluoric acid, phosphoric acid, formic acid, acetic acid, ammonia, amines, hydrogen peroxide, sodium hydroxide, potassium hydroxide solution. However, it is not resistant to corrosion by strong oxidation, such as fuming sulphuric acid - concentrated nitric acid, chromic acid mixed with sulphuric acid. At room temperature the above solvents have a slow erosive effect on polyethylene, while at 90-100°C concentrated sulphuric acid and concentrated nitric acid rapidly erode polyethylene, causing it to break down or decompose.
Polyethylene is subject to aging, discoloration, cracking, brittleness, or chalking, and loss of its mechanical properties in the presence of an atmosphere, sunlight, and oxygen. At molding and processing temperatures, oxidation can also cause the melt to lose its kill, discoloration, and streaking, so care should be taken during molding and processing and use or when selecting materials. Because of these qualities, polyethylene is easy to process and mold, so its recycling is of great value.
1. Polyethylene has excellent chemical stability and is resistant to various chemicals such as hydrochloric acid, hydrofluoric acid, phosphoric acid, formic acid, amines, sodium hydroxide, and potassium hydroxide at room temperature, but nitric acid and sulphuric acid have a strong destructive effect on polyethylene.
2. polyethylene is easy to photo-oxidation, thermal oxidation, ozone decomposition, and easy to degrade under the action of ultraviolet light, carbon black has an excellent light shielding effect on polyethylene. Cross-linking, chain-breaking and the formation of unsaturated groups can occur as a reflection of radiation.
A milky white, translucent thermoplastic made by the homopolymerization of ethylene and copolymerization with small amounts of alpha-olefins. Density 0.86-0.96g/cm3, according to the density of the distinction between low-density polyethylene (also includes linear low-density polyethylene), ultra-low density polyethylene, etc.Odorless and non-toxic. Chemical resistant, insoluble in solvents at room temperature. Low-temperature resistance, minimum use temperature -70 ~ -100℃. Good electrical insulation, and low water absorption. Physical and mechanical properties vary according to density. Industrial low-density polyethylene is mainly polymerized by high pressure (110-200 MPa), and high temperature (150-300°C) free radical polymerization. Others use low-pressure coordination polymerization, and sometimes the same set of devices can produce polyethylene products with a density of 0.87 to 0.96 g/cm3, called full-density polyethylene process technology. Polyethylene can be processed into films, wire, and cable sheathing, pipes, various hollow products, injection molded products, fibers, etc. It is widely used in agriculture, packaging, electrical and electronics, machinery, automobiles, daily miscellaneous products, etc.
So how aboutCross-linked polyethylene (XLPE)?
Polyethylene (PE) is one of the five most versatile plastics and is one of the most widely used synthetic resins in industry, agriculture, and everyday life. However, polyethylene has poor resistance to high temperatures. The mechanical and chemical resistance properties sometimes do not meet the requirements of practical use either.
The modification of polyethylene has therefore been the key to the development and application of polyethylene products, and polyethylene cross-linking technology is an important technique for improving its material properties. Cross-linked polyethylene can lead to significant improvements in its properties, not only in mechanical properties, environmental stress cracking resistance, chemical resistance, creep resistance, and electrical properties. The temperature resistance of polyethylene can be increased from 70°C to over 100°C. The range of applications for polyethylene has thus been considerably broadened.
1、Heat-resistant performance: XLPE with a reticulated three-dimensional structure has very excellent heat-resistant performance. It will not decompose and carbonize below 200°C. The long-term working temperature can reach 90°C and the thermal life can reach 40 years.
2、Insulation performance: XLPE maintains the original good insulation characteristics of PE, and the insulation resistance is further increased. Its dielectric loss angle tangent value is very small and is not greatly affected by temperature.
3、Mechanical properties: Due to the establishment of new chemical bonds between the macromolecules, the hardness, stiffness, wear resistance, and impact resistance of XLPE have been improved, thus compensating for the shortcomings of PE which is susceptible to cracking due to environmental stress.
4. Chemical resistance characteristics: XLPE has strong acid and alkali resistance and oil resistance, and its combustion products are mainly water and carbon dioxide, which are less harmful to the environment and meet the requirements of modern fire safety
XLPE HIGH QUALITY HARD WALL HELIX STEEL WIRE AND ANTI-STATIC COPPER WIRE REINFORCED SUCTION AND DISCHARGE CHEMICAL HOSE
Hose made from cross-linked polyethylene has the advantages of high creep strength, corrosion resistance, lightweight, and good heat resistance.
Cross-linked polyethylene hose and PVC hose and ordinary polyethylene hose compared, cross-linked polyethylene hose does not contain plasticizers, will not mold and breeding bacteria; does not contain harmful ingredients, in line with FDA standards, can be used for drinking water pipe; heat resistance is good, ordinary PVC and polyethylene hose heat-resistant for 60-75 ℃, and cross-linked polyethylene hose for 90 ℃, the highest instantaneous temperature can reach 185 ℃, can withstand - 75 ℃ low temperature; use a wide range of temperatures. It can be used in a wide range of temperatures, from -75 to 95°C for a long time, with a service life of up to 50 years. High cross-linking, high density, good pressure resistance; good chemical resistance, excellent resistance to environmental stress cracking performance, even at higher temperatures can be used to transport a variety of chemicals and has accelerated hose stress material compared, to cross-linked polyethylene hose lightweight, only about 1/8 of the metal hose; corrosion resistance, good wear resistance. The wear rate is less than 1/4 of steel pipe, and the service life is 2-6 times that of steel pipe; the inner wall is smooth, the fluid flow resistance is small, and the conveying flow is larger than that of metal hose at the same pipe diameter, while the noise is much lower; the transmission performance is good, and the transmission volume of liquid is 30%-40% higher than that of steel pipe; the thermal conductivity is much lower than that of metal pipe, so it's heat insulation and heat preservation performance is excellent. When used in the heating system, no insulation is required, and the heat loss is small; it can be bent at will and will not be brittle; the electrical insulation performance is excellent, and the installation is simple and easy, with less than half the installation workload of metal pipes and low installation costs.