What is Polyethylene Density?

Polyethylene (PE) is a thermoplastic resin made by the polymerization of ethylene. Industrially, copolymers of ethylene and a small amount of -olefins are also included. Polyethylene is odorless, non-toxic, feels like wax, has excellent low temperature resistance (minimum use temperature can reach -100 ~ -70 ° C), good chemical stability, can withstand most acid and alkali erosion (not resistant to oxidation) Nature of acid). Insoluble in common solvents at room temperature, low water absorption and excellent electrical insulation. [1]

Polyethylene (PE) is a thermoplastic resin made by the polymerization of ethylene. Industrially, copolymers of ethylene and a small amount of -olefins are also included. Polyethylene is odorless, non-toxic, feels like wax, has excellent low temperature resistance (minimum use temperature can reach -100 ~ -70 ° C), good chemical stability, can withstand most acid and alkali erosion (not resistant to oxidation) Nature of acid). Insoluble in common solvents at room temperature, low water absorption and excellent electrical insulation. [1]
On October 27, 2017, the list of carcinogens published by the International Agency for Research on Cancer of the World Health Organization initially compiled the reference, and polyethylene was in the list of 3 types of carcinogens. [2]

High-density polyethylene

Low-density polyethylene

Linear low density polyethylene

Medium density polyethylene

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Chinese name
Polyethylene
English name
polyethylene (PE)
Chemical formula
(C2H4) n
CAS Registry Number
9002-88-4
Melting point
92
Boiling point
270
Water soluble
difference
Density
0.95

Polyethylene material properties

It is a polymer polymerized by ethylene monomer. Polyethylene was synthesized by the British ICI in 1922, and began industrial production in 1939. It was officially produced in the United States. It was an important radar insulation material and military supplies during the war. Mitsui Petrochemical and Sumitomo Chemical (1958) Began formal production. In 1975, the plant had an annual output of 1.407 million tons, second only to the United States.
In 1933, British Bunerman Chemical Industries found that ethylene could polymerize to form polyethylene under high pressure. This method was industrialized in 1939 and is commonly referred to as the high-pressure method. In 1953, K. Ziegler of the Federal Republic of Germany discovered that using TiCl 4 -Al (C 2 H 5 ) 3 as a catalyst, ethylene can also polymerize at lower pressures. This method was put into industrial production by the Federal German Hearst Company in 1955.
Polyethylene
Ene. In the early 1950s, Phillips Petroleum Company of the United States discovered that using chromium oxide-silicon alumina as a catalyst, ethylene could polymerize to form high-density polyethylene at medium pressure, and industrialized production in 1957. In the 1960s, DuPont of Canada began to make low-density polyethylene by the solution method of ethylene and -olefins. In 1977, United Carbide Corporation and Dow Chemical Company successively made low-density polyethylene using the low-pressure method, which is called linear low-density polyethylene. Among them, the gas phase method of United Carbide Company was the most important. The performance of linear low-density polyethylene is similar to that of low-density polyethylene, but it also has some characteristics of high-density polyethylene. In addition, it has low energy consumption in production, so it has developed rapidly, becoming one of the most striking new synthetic resins.
The core technology of the low pressure method lies in catalysts. TiCl 4 -Al (C 2 H 5 ) 3 body invented by Ziegler, Germany
Polyethylene structural formula
It is the first-generation catalyst of polyolefin and has a low catalytic efficiency. About several kilograms of polyethylene are obtained per gram of titanium. In 1963, Solvay, a Belgian company, pioneered a second-generation catalyst with a magnesium compound as a carrier, with a catalytic efficiency of tens to tens of thousands of grams of polyethylene per gram of titanium. The second-generation catalyst also eliminates the need for a post-treatment step to remove catalyst residues. Later, a high-efficiency catalyst for the gas phase process was developed. In 1975, the Monte Edison Group of Italy developed a catalyst that can directly produce spherical polyethylene without granulation, which is called the third-generation catalyst, which is another revolution in the production of high-density polyethylene.
Polyethylene is a crystalline thermoplastic resin. Their chemical structure, molecular weight, degree of polymerization, and other properties are largely dependent on the polymerization method used. The polymerization method determines the type and degree of branching. The degree of crystallinity depends on the regularity of the molecular chain of the piece and its thermal history.
Polyethylene is sensitive to environmental stresses (chemical and mechanical effects), and its heat aging resistance is inferior to the chemical structure and processing strips of polymers. Polyethylene can be processed by common thermoplastic molding methods (see Plastic Processing). It has a wide range of uses, mainly used to make films, packaging materials, containers, pipes, monofilaments, wires and cables, daily necessities, etc., and can be used as high-frequency insulation materials such as televisions and radars. With the development of petrochemical industry, polyethylene production has developed rapidly, and the output accounts for about 1/4 of the total plastic output. In 1983, the total polyethylene production capacity in the world was 24.65Mt, and the capacity of devices under construction was 3.16Mt. According to the latest statistics in 2011, global production capacity reached 96Mt. The development trend of polyethylene production shows that production and consumption are gradually shifting to Asia, and China is becoming the most important consumer market.
In nuclear physics, astrophysics, reactor operation using polyethylene as a diffuser to measure
Polyethylene
Neutron. He has made his own contributions to the research of nuclear physics.
A kind of polyethylene (PE) plastic. The convenient bag we often mention is polyethylene (PE). Polyethylene is the simplest polymer and the most widely used polymer material. It is made up of repeating CH2 units. Polyethylene is formed by the addition polymerization of ethylene (CH2 = CH2).
The properties of polyethylene depend on how it is polymerized. High-density polyethylene (HDPE) is made by Ziegler-Natta polymerization under the conditions of moderate pressure (15-30 atmospheres) organic compounds. Under these conditions, the polymerized polyethylene molecules are linear and have long molecular chains with molecular weights up to several hundred thousand. If it is a radical polymerization under high pressure (100-300MPa), high temperature (190-210C), peroxide catalyzed conditions, low density polyethylene (LDPE) is produced, which is a branched compound structure.

Chemical classification of polyethylene

Polyethylene (PE) is a polymer made from the polymerization of ethylene. The product has been developed for about 60 years. The global polyethylene production ranks first among the five general-purpose resins.
Polyethylene is divided into high-density polyethylene, low-density polyethylene, and linear low-density polyethylene according to the polymerization method, molecular weight, and chain structure.
Low density polyethylene (LOW DENSITY POLYETHYLENE, LDPE) is commonly known as high pressure polyethylene. Due to its low density and softest material, it is mainly used in plastic bags and agricultural films. [3]
High density polyethylene (HDPE) is commonly known as low-pressure polyethylene. Compared with LDPE and LLDPE, it has higher temperature resistance, oil resistance, steam penetration resistance, and environmental stress cracking resistance. Good impact resistance and cold resistance, mainly used in blow molding, injection molding and other fields. [3]
Linear low density polyethylene (LINEAR LOW DENSITY POLYETHYLENE, LLDPE),
-Copolymers of olefins polymerized in the presence of a catalyst. LLDPE is similar in appearance to LDPE, with less transparency, but good surface gloss, low temperature toughness, high modulus, resistance to bending and stress cracking, and better impact strength at low temperature. [3]
LLDPE applications have penetrated almost all LDPE markets. At this stage, LLDPE and HDPE are in the growth stage of the life cycle; LDPE has gradually entered the mature stage of development at the end of the 1980s, and few LDPE equipment in the world have been put into production. Polyethylene can be formed by extrusion, injection, molding, blow molding, and melt spinning. It is widely used in industry, agriculture, packaging, and daily industry. It is widely used in China. Film is its largest user and consumes about low density. 77% of polyethylene and 18% of high-density polyethylene. In addition, injection molded products, wires and cables, and hollow products all occupy a large proportion of their consumption structure, and play a significant role in the plastics industry.

Polyethylene identification

Polyethylene is difficult to print (unless bulk modification or surface modification), so most of it is colorless or light-colored products. Of course, because of its good environmental aging resistance, artificial turf on sports fields is mostly made of polyethylene. The simplest identification method is to ignite a small sample with a gas flame (such as a lighter). The sample will continue to burn, smoke, and smell of burning a candle. Use your nails to scratch it. The scratched is low density polyethylene (LDPE), otherwise it is high density polyethylene (HDPE).

Structural characteristics of polyethylene

CH 2 = CH 2 + CH 2 = CH 2 + ····· CH 2 CH 2 CH 2 CH 2 ······
Shorthand: nCH 2 = CH 2 [CH 2 CH 2 ] n
Polymerization pressure : high pressure, medium pressure, low pressure;
Polymerization implementation methods : slurry method, solution method, gas phase method;
Product density : high density, medium density, low density, linear low density, ultra low density;
Product molecular weight : low molecular weight, ordinary molecular weight, ultra-high molecular weight.
structure
The molecule of polyethylene is a long-chain linear structure or a branched structure, which is a typical crystalline polymer. In the solid state, the crystalline part coexists with the amorphous form. The crystallinity varies depending on the processing conditions and the original processing conditions. Generally, the higher the density, the greater the crystallinity. The crystallinity of L.DP E is usually 55%-65%, and the crystallinity of HDPF is 80% -90%. Figure 2-1 shows the PE structure.
It can be seen from the figure that the PE molecules have a certain degree of branching. The LDPE has a high degree of branching. Contains 15 ^ -25 methyl side chains and a small amount of butyl side chains per 1,000 carbon atoms. Because the side chain or branch chain reduces the regularity of the molecule, it will contain a large amount of branched PE crystallinity , Density and rigidity are low. HDPE has low branching and only 5-7 ethyl side chains per 1000 carbon atoms in the main chain, so it has high crystallinity and good performance in density, rigidity and hardness. The degree depends on the molecular weight, branching degree and crystallinity of the polymer. For example, the elongation at break mainly depends on the high density and high crystallinity of PE. Its mechanical properties are good, but the ductility is poor. It will greatly help its structural modification and other modifications. Generally speaking, the tensile strength of HDPE is 20-25MPa, while the tensile strength of LDPE is only 10-2f5MPa. This value is away from the tensile strength of engineering materials (100 -200MPa)
It's a big difference.
Features
Polyethylene is a typical thermoplastic, which is a odorless, odorless, and non-toxic flammable white powder. The PE resins that are processed are waxy granules that are extruded and granulated, and the appearance is milky white. Its molecular weight is in the range of 10,000 loa. Those with a molecular weight exceeding 100,000 are ultra-high molecular weight polyethylene f UHMWPE3. The higher the molecular weight, the better its physical and mechanical properties, and the closer it is to the required level of engineering materials. But the higher the molecular weight, the more difficult it is to process. Polyethylene has a melting point of 100-130C. It has excellent low temperature resistance. It can still maintain good mechanical properties at -60 , but the use temperature is 80 ~ 110 .
Polyethylene has good chemical stability. It can withstand dilute nitric acid, dilute sulfuric acid and hydrochloric acid, hydrofluoric acid, phosphoric acid, formic acid, acetic acid, ammonia, amines, hydrogen peroxide, sodium hydroxide, potassium hydroxide, etc. at room temperature. Solution. However, it is not resistant to strong oxidative corrosion, such as a mixture of oleum, concentrated nitric acid, chromic acid and sulfuric acid. At room temperature, the above solvents will have a slow erosion effect on polyethylene, and at 90-100 ° C, concentrated sulfuric acid and concentrated nitric acid will quickly attack polyethylene, causing it to break or decompose.
Under the influence of air, sunlight and oxygen, polyethylene will age, discolor, crack, become brittle or powder, and lose its mechanical properties. At the molding processing temperature, due to the oxidation effect, the melt killing rate will be reduced, and discoloration and streaks will occur. Therefore, attention should be paid to the molding processing and use process or material selection. Because polyethylene has the above characteristics and is easy to be processed and formed, the recycling of polyethylene has a very profound value.

Polyethylene properties

1. Polyethylene has excellent chemical stability. It is resistant to various chemical substances such as hydrochloric acid, hydrofluoric acid, phosphoric acid, formic acid, amines, sodium hydroxide and potassium hydroxide at room temperature. Strong destructive effect
2. Polyethylene is susceptible to photooxidation, thermal oxidation, and ozone decomposition. It is prone to degradation under the action of ultraviolet rays. Carbon black has excellent light shielding effect on polyethylene. After irradiation, cross-linking, chain breakage, and formation of unsaturated groups can be reflected.
Milky white, translucent thermoplastic made from ethylene homopolymerization and copolymerization with a small amount of alpha-olefins. The density is 0.86 to 0.96 g / cm 3 , and the low-density polyethylene (including linear low-density polyethylene) and ultra-low-density polyethylene are classified according to the density. Tasteless and non-toxic. Chemical resistant, insoluble in solvents at room temperature. Low temperature resistance, the lowest use temperature is -70 -100 . Good electrical insulation and low water absorption. Physical and mechanical properties vary with density. Industrially, low-density polyethylene mainly uses high-pressure (110-200MPa) and high-temperature (150-300 ° C) radical polymerization. Others use low pressure coordination polymerization, and sometimes the same set of equipment can produce polyethylene products with a density of 0.87 to 0.96 g / cm 3 , which is called full density polyethylene process technology. Polyethylene can be processed into films, wire and cable jackets, pipes, various hollow products, injection molded products, fibers, etc. Widely used in agriculture, packaging, electronic and electrical, machinery, automotive, daily sundries and other aspects.

Polyethylene performance applications

Polyethylene
Polyethylene is a white waxy translucent material, which is soft and tough, lighter than water, non-toxic, and has superior dielectric properties. Easy to burn and continue to burn after leaving the fire. Low water permeability and large organic vapor transmission. The transparency of polyethylene decreases with increasing crystallinity. Under certain crystallinity, transparency increases with increasing molecular weight. The melting point of high density polyethylene is 132-135 ° C, and the melting point of low density polyethylene is low (112 ° C) and the range is wide.
It is insoluble in any known solvent at normal temperature, and can be dissolved in solvents such as toluene, amyl acetate, trichloroethylene, etc. in a small amount above 70 ° C.

Chemical properties of polyethylene

Polyethylene has excellent chemical stability. It is resistant to various chemical substances such as hydrochloric acid, hydrofluoric acid, phosphoric acid, formic acid, amines, sodium hydroxide, and potassium hydroxide at room temperature. Destructive effect.

Uses of polyethylene products

High-pressure polyethylene: more than half are used for film products, followed by pipes, injection molded products, wire coatings, etc.
Medium and low pressure polyethylene: mainly injection molded products and hollow products.
Ultra-high pressure polyethylene: Due to its excellent comprehensive properties, it can be used as an engineering plastic.
Melting point: 140
Melting enthalpy 292.88J / g

Polyethylene printing

Suitable for product labels with high resistance to water, oil and chemicals. Hanyuan Printing often uses this material in cosmetics, shampoos, washing and other daily chemicals that require moisture resistance and extrusion resistance during use. label. Excellent softness, especially suitable for plastic bags. It can also be used in cases where PVC label materials cannot be used due to environmental requirements.

Polyethylene processing

Polyethylene can be processed by blow molding, extrusion, injection molding and other methods, and is widely used in the manufacture of films, hollow products, fibers, and daily necessities.
Application film
Low density polyethylene is widely used as packaging materials for various foods, clothing, medicines, fertilizers, industrial products, and agricultural films. It can also be processed into a composite film by extrusion for packaging heavy goods.
Since 1975, high-density polyethylene film has also been developed. It has high strength, low temperature resistance, moisture resistance, and good printability and processability.
In addition, polyethylene coatings can also be extruded and coated on paper, aluminum foil or other plastic films to make polymer composite materials.
Hollow products
High-density polyethylene has high strength and is suitable for hollow products. Such as milk bottles, detergent bottles;
Tube sheet
The extrusion method can produce polyethylene pipes. The high-density polyethylene pipes have high strength and are suitable for underground laying. The extruded sheet can be processed twice. The high-density polyethylene can also be produced by foam extrusion and foam injection It is made of low-foam plastic for tabletops and building materials; protective sheaths (such as cable sheaths).
fiber
China is called Ethylene. It is generally made of low-pressure polyethylene as a raw material and spun into synthetic fibers. Ethylene is mainly used in the production of fishing nets and ropes, or used as batting after spinning into short fibers, and can also be used in industrial acid and alkali resistant fabrics.
Developed ultra-high-strength polyethylene fibers (strength up to 3 ~ 4GPa), which can be used as bullet-proof vests, composite materials for automobiles and offshore operations.
Sundries
Miscellaneous goods produced by injection molding include daily-use miscellaneous goods, artificial flowers, turnover boxes, small containers, bicycle and tractor parts, etc .; refrigerator containers, storage containers, household kitchen utensils, sealing caps, etc .; high density is required when manufacturing structural parts Polyethylene.

Polyethylene resin series

LDPE Polyethylene LDPE resin

Properties: odorless, odorless, non-toxic, matte surface, milky white waxy particles, density about 0.920g / cm3, melting point 130 145 . Insoluble in water, slightly soluble in hydrocarbons, toluene, etc. Resistant to most acids and bases, low water absorption, softness at low temperatures, and high electrical insulation.
Production process: There are two types of high-pressure tube method and kettle method. In order to reduce the reaction temperature and pressure, the tubular process generally uses low temperature and high activity primers to initiate the polymerization system. High purity ethylene is used as the main raw material, and propylene / propane is used as the density adjuster. The high activity initiator is used at about 200 Polymerization is carried out at 330 ° C and 150-300 MPa. Molten polymer that initiates polymerization in the reactor must be cooled and separated at high, medium, and low pressure. The high-pressure circulating gas is cooled and separated and sent to the inlet of an ultra-high pressure (300MPa) compressor. The medium-pressure circulating gas is cooled and separated. It is then sent to the inlet of a high-pressure (30 MPa) compressor, and the low-pressure circulating gas is cooled and separated and sent to a low-pressure (0.5 MPa) compressor for recycling. For granulation, when granulating, the enterprise can add suitable additives according to different application fields. The granules are packed and shipped from the factory.
Uses: Processing methods such as injection molding, extrusion molding and blow molding can be used. Mainly used as agricultural film, industrial packaging film, pharmaceutical and food packaging film, machinery parts, daily necessities, building materials, wires, cable insulation, coatings and synthetic paper.

LLDPE Polyethylene LLDPE resin

Properties: Because the molecular structures of LLDPE and LDPE are significantly different, the properties are also different. Compared with LDPE, LLDPE has excellent resistance to environmental stress cracking and electrical insulation, higher heat resistance, impact resistance and puncture resistance. Production process: LLDPE resin is mainly produced by full-density polyethylene equipment. Representative production processes are Innovene process and UCC's Unipol process.
Uses: Through the injection molding, extrusion, blow molding and other molding methods, the production of films, daily necessities, pipes, wires and cables.

HDPE Polyethylene HDPE resin

Properties: Natural, cylindrical or oblate particles. The particles are smooth and clean. The size of the particles should be 2mm to 5mm in any direction. There are no mechanical impurities and thermoplasticity. The powder is white powder, and qualified products can be slightly yellow. It is insoluble in common solvents at normal temperature, but can swell when exposed to aliphatic hydrocarbons, aromatic hydrocarbons and halogenated hydrocarbons for a long time. It is slightly soluble in toluene and acetic acid above 70 ° C. Oxidation occurs when heated in air and under the influence of sunlight. Resistant to most acids and bases. Low water absorption, can maintain flexibility at low temperatures, and high electrical insulation.
Production process: two production processes: gas phase method and slurry method. Among them, the slurry loop production process is represented by Phillips, Basell, and the Nordic North Star loop technology. The kettle slurry law is represented by the Mitsui CX process in Japan.
Uses: It adopts injection molding, blow molding, extrusion molding, rotomolding and other molding methods to produce film products, daily necessities and industrial hollow containers of various sizes, pipes, packaging calenders and ligatures, ropes, fishnets and braid Fiber, wire and cable, etc.
[-CH2-CH2-] n is abbreviated as PE, which is a thermoplastic resin made by the polymerization of ethylene. Industrially, it also includes copolymers of ethylene and small amounts of -olefins. Polyethylene is odorless, non-toxic, feels like wax, has excellent low temperature resistance (minimum use temperature can reach -70 -100 ), good chemical stability, can withstand most acid and alkali erosion (not resistant to oxidizing properties) Acid), insoluble in general solvents at room temperature, low water absorption, and excellent electrical insulation properties; but polyethylene is very sensitive to environmental stress (chemical and mechanical effects) and has poor heat aging resistance. The properties of polyethylene vary from species to species, mainly depending on the molecular structure and density. Products with different densities (0.91 to 0.96 g / cm3) can be obtained by using different production methods. Polyethylene can be processed by common thermoplastic molding methods (see Plastic Processing).

Polyethylene properties

General properties of polyethylene

Polyethylene
Polyethylene resin is a non-toxic, odorless white powder or granule, with a milky appearance, a wax-like feel, and a low water absorption rate of less than 0.01%. Polyethylene film is transparent and decreases with increasing crystallinity. Polyethylene film has low water permeability but large air permeability, which is not suitable for fresh-keeping packaging but suitable for moisture-proof packaging. It is flammable and has an oxygen index of 17.4. It has low smoke during burning, a small amount of molten drops, yellow and blue flames, and a paraffin odor. Polyethylene has good water resistance. The surface of the product is non-polar, it is difficult to adhere and print, and it has been improved by surface treatment. Many branches have poor resistance to photodegradation and oxidation.

Mechanical properties of polyethylene

Polyethylene has general mechanical properties, low tensile strength, poor creep resistance, and good impact resistance. Impact strength LDPE> LLDPE> HDPE, other mechanical properties LDPE <LLDPE <HDPE. It is mainly affected by density, crystallinity, and relative molecular mass. With the improvement of these indicators, its mechanical properties increase. The resistance to environmental stress cracking is not good, but it improves when the relative molecular mass increases. Good puncture resistance, of which LLDPE is the best.

Thermal characteristics of polyethylene

The heat resistance of polyethylene is not high, and it improves with the increase of relative molecular weight and crystallinity. Low temperature resistance is good, brittleness temperature can generally reach below -50 ; and as the relative molecular mass increases, the lowest can reach -140 . The linear expansion coefficient of polyethylene is large, up to (20 24) × 10-5 / K. Higher thermal conductivity.

Electrical characteristics of polyethylene

Because polyethylene is non-polar, it has excellent electrical properties with low dielectric loss and high dielectric strength.

Environmental characteristics of polyethylene

Polyethylene is an alkane inert polymer and has good chemical stability. It is resistant to the corrosion of acid, alkali and salt water solution at normal temperature, but not resistant to strong oxidants such as fuming sulfuric acid, concentrated nitric acid and chromic acid. Polyethylene is insoluble in general solvents below 60 ° C, but it will swell or crack after long-term contact with aliphatic hydrocarbons, aromatic hydrocarbons and halogenated hydrocarbons. When the temperature exceeds 60 ° C, it can be slightly soluble in toluene, amyl acetate, trichloroethylene, turpentine, mineral oil and paraffin; at temperatures above 100 ° C, it can be dissolved in tetralin.
Because polyethylene contains a small amount of double bonds and ether bonds, its weather resistance is not good. Sun and rain will cause aging. It is necessary to add antioxidants and light stabilizers to improve.

Polyethylene processing characteristics

Because LDPE and HDPE have good fluidity, low processing temperature, moderate viscosity, low decomposition temperature, and do not decompose at a high temperature of 300 ° C in an inert gas, it is a plastic with good processing performance. However, the viscosity of LLDPE is slightly higher, and the motor power needs to be increased by 20% to 30%; melt fracture is prone to occur, and the die clearance and the processing aid need to be added; the processing temperature is slightly higher, which can reach 200 to 215 ° C. Polyethylene has a low water absorption and does not need to be dried before processing.
Polyethylene melt is a non-Newtonian fluid, and its viscosity changes with temperature less, but the increase of shear rate decreases rapidly and has a linear relationship. Among them, the decline of LLDPE is the slowest.
Polyethylene products are easy to crystallize during cooling. Therefore, pay attention to the mold temperature during processing. In order to control the crystallinity of the product, it has different properties. The molding shrinkage of polyethylene is large, which must be considered when designing the mold.
production method
Polyethylene can be divided into high pressure method, medium pressure method and low pressure method according to the polymerization pressure; according to the medium, it can be divided into slurry method, solution method and gas phase method.
The high-pressure method is used to produce low-density polyethylene. This method was developed early. The polyethylene produced by this method has accounted for about two-thirds of the total polyethylene production. However, with the development of production technology and catalysts, its growth rate has increased. Significantly lags behind the low-pressure method. The low-pressure method includes a slurry method, a solution method, and a gas phase method. The slurry method is mainly used for the production of high-density polyethylene. The solution method and the gas-phase method can not only produce high-density polyethylene, but also add comonomers to produce medium and low-density polyethylene. Ethylene. Various low-pressure processes have developed rapidly. The medium-pressure method is only used by Phillips, which produces high-density polyethylene.

Polyethylene high pressure method

A method for polymerizing ethylene into low density polyethylene by using oxygen or peroxide as an initiator. Ethylene enters the reactor after two-stage compression. It is polymerized into polyethylene under the pressure of 100-300MPa, temperature 200-300 and the initiator. The reactants are separated under reduced pressure to recover unreacted ethylene for recycling. Polyethylene is extruded and granulated after adding plastic additives.
There are two types of polymerization reactors: tubular reactors (tube length up to 2000m) and kettle reactors. The one-way conversion rate of the tubular process is 20% to 34%, and the annual production capacity of a single line is 100kt. The one-way conversion rate of the kettle process is 20% to 25%, and the annual production capacity of a single line is 180kt.

Polyethylene low pressure method

There are three methods: slurry method, solution method and gas phase method. Except the solution method, the polymerization pressure is below 2MPa. The general steps include catalyst preparation, ethylene polymerization, polymer separation, and granulation.
The polyethylene produced by the slurry method is insoluble in the solvent and is in the form of a slurry. Slurry polymerization conditions are mild and easy to operate. Aluminium alkyl is commonly used as an activator, hydrogen is used as a molecular weight regulator, and a kettle reactor is often used. The polymer slurry from the polymerization kettle passed through the flash kettle, gas-liquid separator to the powder dryer, and then granulated (Figure 4). The production process also includes steps such as solvent recovery and solvent refining. By adopting the combination of different polymerization kettles in series or in parallel, products with different molecular weight distributions can be obtained.
Polyethylene
Solution polymerization is performed in a solvent, but both ethylene and polyethylene are dissolved in the solvent, and the reaction system is a homogeneous solution. The reaction temperature (140 ° C) and pressure (4 to 5 MPa) are high. It is characterized by short polymerization time, high production strength, and can simultaneously produce polyethylene of three densities of high, medium, and low, which can better control the properties of the product; but the polymer obtained by the solution method has a lower molecular weight, a narrow molecular weight distribution, and solids. Low content.
Gas phase polymerization of ethylene in a gaseous state generally uses a fluidized bed reactor. There are two types of catalysts, chromium-based and titanium-based, which are metered into the bed from a storage tank, and high-speed ethylene circulation is used to maintain fluidization of the bed and exclude the heat of polymerization. The resulting polyethylene is discharged from the bottom of the reactor (Figure 5). The pressure of the reactor is about 2 MPa, and the temperature is 85 to 100 ° C. The gas phase method is the most important method for producing linear low-density polyethylene. The gas phase method eliminates the steps of solvent recovery and polymer drying, and saves 15% of investment and 10% of operating costs compared with the solution method. It is 30% of the traditional high-pressure investment and 1/6 of the operating cost. As a result, it has developed rapidly. However, the gas phase method needs further improvement in product quality and variety.

Medium pressure polyethylene

Using a chromium-based catalyst supported on silica gel, ethylene was polymerized at a medium pressure in a loop reactor to produce high-density polyethylene.
Processing and application can be processed by blow molding, extrusion, injection molding and other methods. It is widely used in the manufacture of films, hollow products, fibers and daily necessities. In actual production, in order to improve the stability of polyethylene to ultraviolet rays and oxidation, and improve processing and use performance, a small amount of plastic additives need to be added. Commonly used ultraviolet absorbers are o-hydroxybenzophenone or its alkoxy derivative, etc. Carbon black is an excellent ultraviolet shielding agent. In addition, anti-oxidants, lubricants, colorants, etc. are added to expand the application range of polyethylene.

Polyethylene production process

There are many companies with polyethylene technology in the world. There are 7 companies with LDPE technology, 10 companies with LLDPE and full density technology, and 12 companies with HDPE technology. From the perspective of technological development, LDPE produced by the high-pressure method is the most mature method in the production of PE resins. Both the kettle method and the tubular method have matured. These two production technologies coexist simultaneously. Foreign companies generally use low temperature and high activity catalysts to initiate the polymerization system, which can reduce the reaction temperature and pressure.
The production of LDPE by high pressure method will develop towards large-scale and tube-type. The low-pressure method for the production of HDPE and LLDPE mainly uses titanium-based and complex catalysts. Most of Europe and Japan use titanium-based catalysts, while the United States mostly uses complex catalysts.
There are 11 types of polyethylene production technology applied in the world, and 8 types of PE production technology in China.
(1) High-pressure tubular and kettle-type reaction processes
(2) Mitsui Chemical Low Pressure Slurry Process CX Process
(3) BP gas phase method Innovene production process
(4) Double loop reactor LPE process of Chevron-Phillips company
(5) Double Star Process of Nordic Chemicals Bastar
(6) Low-pressure gas phase Unipol process
(7) Hostalen process of Basel Polyolefin Company
(8) Sclartech solution production process
Catalyst technology: The catalyst is a key part of the PE process and the focus of its technological development. Especially in 1991, the metallocene catalyst was industrialized in the United States, which made PE production technology enter a new stage of development.

Status of the polyethylene industry

Most of the world's major PE manufacturers have been involved in the field of metallocene PE (mPE) production, such as Dow Chemical, Eastman, Asahi Kasei, Atofina, Chevron-Phillips and other companies.
Japan's Asahi Kasei Chemicals purchased Dow Chemical's metallocene catalyst patent Insite and used the slurry production process to produce metallocene high density polyethylene (mHDPE) under the brand name Creolex. Due to its superior performance, mPE resin consumption has doubled every year since it entered commercial development in 1995. It is estimated that by 2010, the global mPE capacity will reach 17 million tons, of which: mLLDPE is 7 million tons and mHDPE is 6 million tons.
The E catalyst has been developed to the third generation. Japan's Mitsui Chemicals and Dow Chemical have jointly developed a new generation of post-metallocene catalysts. Unlike traditional metallocene and ZN-type catalysts, this catalyst can copolymerize polar monomers such as methyl methacrylate and vinyl acetate with olefins, which can be used to develop completely new types of cohesive, oil-resistant, and gas-barrier properties Polyolefin resin.
China attaches great importance to PE production technology, and PE production technology innovation has been included in the national technology innovation plan projects. In view of the fact that the domestic PE production is mainly based on the gas phase process, the product brand is difficult to switch, and there are many transition materials. Domestic PE production enterprises have carried out the reconstruction of the existing polyethylene production technology. Development of pulp external polyethylene external circulation process, and achieved practical results.
Most of the production units of the Uuipol process in China have been rebuilt and expanded using domestic condensation technology, and the output has exceeded the original design capacity of the unit by 120% to 200%.
Films are widely used as packaging materials for various foods, clothing, medicines, fertilizers, industrial products, and agricultural films (see color picture). It can also be processed into a composite film by extrusion for packaging heavy goods. Since 1975, high-density polyethylene film has also been developed. It has high strength, low temperature resistance, moisture resistance, and good printability and processability. The biggest use of linear low-density polyethylene is to make films. Its strength and toughness are better than low-density polyethylene, and its puncture resistance and rigidity are also good. Although its transparency is poor, it is still slightly better than high-density polyethylene. .
The high-density polyethylene of hollow products has high strength and is suitable for hollow products. Can be made into containers such as bottles, barrels, cans, tanks by blow molding, or large containers such as tanker tanks and storage tanks by casting.
The pipe sheet extrusion method can produce polyethylene pipes, and high-density polyethylene pipes have higher strength and are suitable for underground laying. The extruded sheet can be processed twice. High-density polyethylene can also be made into low-foam plastics by foam extrusion and foam injection, as tabletops and construction materials (see polymer materials for construction).
Miscellaneous goods produced by injection molding include daily miscellaneous goods and can also be used in industrial acid and alkali resistant fabrics. Has developed ultra-high-strength polyethylene fibers (strength up to 3 ~ 4GPa), which can be used as bullet-proof vests, composite materials for automobiles and offshore operations. Artificial flowers, turnover boxes (see color picture), small containers, bicycle and tractor parts, etc. High-density polyethylene is used in the manufacture of structural parts.
Polyethylene modification
The modified varieties of polyethylene mainly include chlorinated polyethylene, chlorosulfonated polyethylene, cross-linked polyethylene and blended modified varieties.
Chlorinated polyethylene is a random chloride obtained by partially replacing hydrogen atoms in polyethylene with chlorine. Chlorination is carried out under the initiation of light or peroxide. Industrially, it is mainly produced by aqueous suspension method. Due to the differences in the molecular weight and distribution of raw polyethylene, the degree of branching and the degree of chlorination, the distribution of chlorine atoms, and the residual crystallinity after chlorination, chlorinated polyethylene from rubbery to hard plastic can be obtained. The main use is as a modifier of polyvinyl chloride to improve the impact resistance of polyvinyl chloride. Chlorinated polyethylene itself can also be used as electrical insulation materials and floor materials.
Chlorosulfonated polyethylene When polyethylene interacts with chlorine containing sulfur dioxide, part of the hydrogen atoms in the molecule are replaced by chlorine and a small amount of sulfonyl chloride (-SO2Cl) groups to obtain chlorosulfonated polyethylene. The main industrial method is the suspension method. Chlorosulfonated polyethylene is resistant to ozone, chemical corrosion, oil, heat, light, abrasion and tensile strength. It is an elastomer with good comprehensive properties and can be used to make food-contact equipment parts.
Cross-linked polyethylene uses radiation method (X-ray, electron beam or ultraviolet radiation, etc.) or chemical method (peroxide or silicone cross-linking) to make the linear polyethylene into a network or body cross-linked polyethylene. Among them, the silicone cross-linking method has a simple process, low operation cost, and molding and cross-linking can be carried out step by step. Blow molding and injection molding are suitable. Cross-linked polyethylene's heat resistance, environmental stress crack resistance and mechanical properties are greatly improved than polyethylene, suitable for large pipes, cables and wires, and rotomolded products.
Blend modification of polyethylene Blend linear low density polyethylene with low density polyethylene, and then it can be used to process films and other products. The product performance is better than low density polyethylene. Blending polyethylene and ethylene-propylene rubber can make a wide range of thermoplastic elastomers.
Metallocene polyethylene
Metallocene polyethylene is a novel thermoplastic. It is the most important technological progress of the polyolefin industry in the 1990s, and is an important innovation after LLDPE production technology. Because it is polyethylene produced using a metallocene (MAO) as a polymerization catalyst, it is significantly different in performance from PE polymerized by conventional Ziegler-Natta catalysts. The unique excellent properties and applications of metallocene catalysts for the synthesis of metallocene polyethylene have attracted widespread attention in the market. Many world-renowned large petrochemical companies have invested huge manpower and materials to compete in development and research. topic.
In the early days, metallocene catalysts used in ethylene polymerization could only obtain waxes with a molecular weight of 20,000 to 30,000, and their catalytic activity was not high and had no practical significance, so they did not attract attention and promotion. Until 1980, Professor Kaminsky of the University of Hamburg, Germany discovered that a co-catalyst composed of a combination of dichloromethylene chloride (CP2ZrCl2) and methylalumoxane (MAO) was used to polymerize ethylene in a toluene solution. The reaction speed is equivalent to the enzyme reaction speed. MAO is a high degree of oligomerization methylalumoxane synthesized by dimethyl aluminum and water under conditions other than the polymerization system. Professor Kaminsky's discovery has injected vitality into the research of metallocene catalysts, attracted many companies to participate in development and research, and made considerable progress. In 1991, Exxon Corporation of the United States realized the first metallocene catalyst for the industrial production of polyolefins, and produced the first batch of metallocene polyethylene (mPE). Its trade name is "Exact".
Among metallocene polyolefins, mPE has the fastest and more mature development. The main varieties are linear low density polyethylene (LLDPE) and very low density polyethylene (VLDPE). There are two series of mPE, one is the film supply grade whose main goal is the packaging field, and the other is a plastomer with octene-1 as a comonomer, called POP (Polyolefine Plastmer). mPE film grade has lower melting point and obvious melting zone, and is obviously superior to traditional polyethylene in terms of toughness, transparency, heat viscosity, heat sealing temperature, low odor, etc. It can be used to produce heavy packaging bags and metal trash can linings , Food packaging, stretch film, etc.
The consumption of metallocene linear low-density polyethylene accounts for about 15% of the total consumption of linear low-density polyethylene, and this proportion is expected to reach 22% by 2010. According to statistics, the annual output of metallocene polyethylene in the world is about 15 million tons, of which products used in food packaging account for about 36% of total consumption, non-food packaging accounts for about 47%, and other aspects (medicine, automotive and Construction, etc.) accounted for about 17%.
Polyethylene has the largest output, the fastest development, and the most active variety development among synthetic resins. Whether polyethylene can achieve high performance depends largely on the performance of the catalyst. The metallocene catalyst has excellent catalytic copolymerization ability. It can copolymerize most interpolymers with ethylene, and can catalyze the polymerization of polar monomers, which is difficult to achieve with traditional catalysts. In the cycloolefin polymerization, traditional catalysts can only be used as catalysts. Ring polymerization, and double bond addition polymerization using metallocene catalysts.
Because many developed countries have adopted metallocene linear low-density polyethylene instead of conventional linear low-density polyethylene, the average annual growth rate of metallocene linear low-density polyethylene will be higher than that of linear low-density polyethylene. 15%. Nearly half of the growth in the production of linear low-density polyethylene in developed countries in the future will come from metallocene linear low-density polyethylene. It is expected that the demand for metallocene linear low-density polyethylene in the US market will increase to 1.34 million tons in 2009.

Polyethylene implementation standard

GB-T1037 --- 1988 Test method for water vapor permeability of plastic films and sheets Cup method
GB-T1040 --- 1992 Test method for tensile properties of plastics
GB-T1842 --- 1980 Environmental stress cracking test method for polyethylene
GB-T2918 --- 1998 Standard environment for conditioning and testing of plastic samples
GB / T5470 --- 1985 Test method for impact embrittlement temperature of plastics
GB-T6672 --- 1986 Determination of plastic film and sheet thickness by mechanical measurement
GB-T6673 --- 1986 Regulations for length and width of plastic films and sheets
GB-T9352 --- 1988 Preparation of Thermoplastic Compression Molded Samples
GB-T13663-2000 polyethylene pipe for water supply
GB-T13663.2-2005 Polyethylene (PE) pipe system for water supply Part 2 Fittings

Related materials for polyethylene

Excellent performance of modified ultra high molecular weight polyethylene pipe:
1. High impact resistance Ultra-high molecular weight polyethylene has the highest impact resistance and impact absorption energy of plastics. It is difficult to crack whether it is a strong external force impact or an internal pressure fluctuation. Its impact strength is 10 times that of nylon 66, 20 times that of polyvinyl chloride, and 4 times that of polyethylene. Especially in low temperature environment, its impact strength has reached a higher value. This flexibility of ultra high molecular weight polyethylene provides a safe and reliable guarantee for the conveying system.
2. High abrasion resistance Among many pipeline materials, the friction coefficient of ultra high molecular weight polyethylene is the smallest, and the ultra high molecular chain is particularly long, which makes the wear resistance of modified ultra high molecular weight polyethylene pipes in conveying various slurry It is 4-7 times longer than steel pipes and stainless steel pipes, and about 10 times longer than polyvinyl chloride pipes and polyethylene pipes, which greatly improves the service life of pipes.
3. Corrosion resistance Based on the ultra-high molecular weight polyethylene is a saturated molecular group structure, its chemical stability is extremely high, and it can withstand a variety of highly corrosive media (acid, alkali, salt) and organic within a certain temperature and concentration range. Attack of solvents.
4. Self-lubricating and non-sticking properties of non-scaling ultra-high molecular weight polyethylene, with the smallest friction coefficient. The inner wall of the pipe produced by the special process is anti-corrosion, anti-wear and non-fouling, so the flow resistance is very small, and the flow rate and flow rate can be maintained for a long time. Its inner diameter design can be 15.4% smaller than that of steel pipes.
5. Weather resistance and aging resistance. On the one hand, because there are very few unsaturated genes in the molecular chain of the ultra-high pipeline, and the molecular weight is large; on the other hand, the addition of high-quality modifiers makes the service life of the ultra-high pipeline greatly exceeds that of ordinary polyethylene. pipeline. After about 60 years of use, the ultra-high pipeline can still maintain more than 70% of its mechanical properties.
6, wide temperature suitability, long-term work at the temperature of -269 to 80 .
7, flame retardant special industries use natural fire environment, modified by adding flame retardants, special processing technology manufacturing, to overcome the flammability of ultra high molecular weight polyethylene itself, with flame retardant properties.
8. Light weight and easy installation. This product has good flexibility, can adapt to various geological conditions, and can be directly bent for laying. It adopts flange connection, no gasket is needed, and the connection is fast and simple.

The current situation of polyethylene

China's polyethylene industry has continued to develop in recent years. As of 2011, the annual production capacity of the plant has reached 10.82 million tons. During the 12th Five-Year Plan period, there will still be Fushun Petrochemical, Wuhan Ethylene, Sichuan Refining and Chemical, Daqing Petrochemical and other units put into operation. By the end of the 12th Five-Year Plan, the polyethylene production capacity will reach 16.67 million tons. Judging from the data in 2011, the national polyethylene production was 10.152 million tons, and the apparent demand was 172.727 million tons. It can be seen that there is still a shortfall of more than 7 million tons of domestic polyethylene that has to be imported. Therefore, imported products occupy an important proportion of China's polyethylene market with its relatively high performance and cost advantages. However, with the expansion of domestic production capacity and the diversification of olefin feedstocks during the 12th Five-Year Plan period, the self-sufficiency rate of polyethylene in China will greatly increase, and its external dependence will gradually decrease.
On the demand side, as a major consumer film of polyethylene, plastic films are mostly used in end-use consumption and transportation, and their growth in demand has a greater relationship with the development of the overall domestic economic situation, which has basically maintained a growth slightly higher than domestic GDP. Its growth momentum is stable and demand rigidity exists. From the statistics of flexible packaging film output, since 2006, it has increased at an average rate of 13%, which also confirms the steady growth of plastic films. Another important consumer area of polyethylene is plastic pipes. Its output has also increased with the accelerated pace of urbanization in our country and the increase in the implementation of municipal pipeline construction projects. In the next few years, municipal plastic pipes such as urban water supply and drainage, gas pipelines, and urban underground power and communication jacket pipes will continue to be the focus of development in recent years.

Problems in the polyethylene industry

In the steady development of the polyethylene industry, the problems in the industry itself cannot be underestimated. China is a little oil, short gas and rich coal country, but naphtha to olefins is the traditional main production method of olefin products in China, which will inevitably cause the existence of raw materials and cost pressures for polyethylene in China, and cracking under high oil prices Installation starts will be restricted. Secondly, China's petrochemical companies have limited research and development capabilities, and most of their products are concentrated in general-purpose materials, but their performance in high-end special materials is insufficient. In this regard, they have to rely on imports. In addition, petrochemical companies currently adopt pricing or delayed sales settlement strategies. Due to the cost of unlocking the delayed settlement model, traders cannot exercise their flexibility and have to follow the petrochemical guidance price to determine the selling price. In addition, the distribution of production capacity and industry is uneven, mainly in the three regions of North China, East China and South China. Of course, this is related to China's regional economic development and convenient transportation. However, the uncoordinated development has led to the three regional markets. Oversaturation is not in line with the country's strategy of vigorously promoting the development of the central and western regions.
At the same time, downstream plastic products factories also face many problems, such as the large number of small and medium-sized enterprises in the industry, low overall equipment level, backward production technology, irrational product structure, insufficient scientific and technological investment, weak innovation ability, and low product intensive Unbalanced regional development of the industry, disorderly market competition, and weak ability to withstand risks. In addition to the problems of the above-mentioned enterprises themselves, the development of SMEs also faces more prominent problems such as difficulty in financing, rising labor costs, and excessively rapid rise in raw material prices. Production and operation have become more difficult, and the external environment for the development of SMEs needs to be improved.
The 12th Five-Year Plan proposes the diversification of olefin feedstocks, and formulated the development plans for coal-to-olefins and shale gas. Although this has a significant effect on changing China's energy structure, careful analysis still cannot change the traditional position of naphtha to olefins.
China's recycled polyethylene industry originated in the 1980s. After two decades of development, in 2009, the entire industry gradually entered a period of stable development. However, with the turbulence of the market economy and the decline in profitability, the industry's development is facing a very The big dilemma is subject to various constraints:
1. Restrictions on raw materials. China's domestic waste recycling rate is still low, and recycling is done in a household-like manner, and the quality of supplies and supply are unstable. As a major consumer of plastic products, China's dependence on imported polyethylene waste plastics still remains above 30%, so the industry still faces constraints on the supply of raw materials, and the formalization of the recycling system is urgently needed.
2. Technical constraints. The sorting costs of polyethylene waste plastics account for one third of the processing and processing costs. Most of the employees are rural surplus labor, and the professional level needs to be improved. At the same time, due to technical constraints, the quality of recycled polyethylene particles is difficult to guarantee, and primary and low-level products still account for a large proportion, and their application fields are limited. Especially, high-end products have a small space.
3. Poor clustering. Due to the low concentration of the industry, the related equipment systems such as sewage treatment are not complete, policy supervision is difficult to exert, and the industry is developing disorderly.
4, policy constraints. China's recycled plastics industry lacks comprehensive tax management and auxiliary policies to encourage the development of the industry. Although it is an important industry of circular economy, in fact, the recycled polyethylene industry is in the middle of policy failure and market failure to a certain extent and cannot be supported. In fact, it has become a severe target for environmental protection. Some policies and actual production actually have a distant trend.
5. Poor cognition. The society's awareness of the environmental protection concept of plastic recycling is not high, the media public opinion is biased against the development of the recycled polyethylene industry, and the industry development is vague. For example, this year's Lianyungang "foreign garbage" incident and the Chenghai toy incident, the media have taken a broad approach to this.

Polyethylene diversification

Coal to olefin refers to the technology of using coal as a raw material to synthesize methanol and then methanol to olefin. The huge demand for olefins, the price advantage of coal, and the shortage of petroleum resources make coal-to-olefin projects extremely competitive in the market. It is one of the important ways to achieve China's coal-based oil energy strategy and ensure national energy security. It is understood that nearly 20 sets of coal-to-olefin projects are planned for construction in the next few years. However, coal chemical industry is a large-scale industry that is resource-intensive, technology-intensive, and capital-intensive. The device must be built in the place of raw material production, which uses a lot of water resources, and is technical Still immature. At the same time, the national energy-saving and emission reduction target during the 12th Five-Year Plan period has dropped by 17% compared with 2010, and coal-to-olefins have serious environmental pollution from coal mining to production, and the national entry barrier has gradually increased. The energy tax reform has also shown the petrochemical industry The urgency of industrial upgrading and transformation. In summary, whether coal-to-olefins can impact or replace the development of the polyethylene industry requires further consideration and observation.
In March 2012, the Ministry of Land and Resources announced in the "Shale Gas 12th Five-Year Plan" that China's recoverable shale gas resources are 25 trillion cubic meters. Although slightly lower than the data published by the EIA before, China's page Rock gas reserves still rank first in the world. China has abundant shale gas resources, good technical foundation and commercialization conditions. Once the policy is in place, after learning from the US shale gas development experience, China will combine its own resources and various conditions to develop a shale gas industry with Chinese characteristics. It is expected to become a new industry growth point.
Due to the very low shale gas permeability and the recovery rate of 10% -20%, the development technology requirements are high. The Ministry of Land and Resources requires that one is to do a good job of resource evaluation and find out the shale gas resources of our country; the other is to increase research efforts to form shale gas exploration and development technology suitable for China's geological conditions and realize major shale gas equipment Independent production and manufacturing; the third is to formulate policies for the shale gas industry, clarify the industry entry barriers and standards, and form an orderly competitive shale gas development pattern; the fourth is to increase policy support and promote the rapid development of the shale gas industry. In the planning, it is necessary to clarify the division of labor of the departments and form a joint work force so that the planning goals and tasks can be implemented.

Structural changes in polyethylene

The improvement of living standards has increased people's requirements for the functions and diversification of packaging materials, such as cling film, gas and light blocking film, selective permeability film, antibacterial film, and printing film. In the future, PE will be more applied to the film industry. Into.
Although the area of arable land in China has been decreasing for many years, the red line of 1.8 billion mu is insurmountable. With the development of agricultural science and technology, the demand for high-end agricultural films has gradually increased, and the demand for high-performance, thin, and multifunctional agricultural films has grown rapidly. However, agricultural film production enterprises are small in scale and dispersed in geographical distribution, and there are few high-end production enterprises. The standardization of the agricultural film market in the later period is imminent. In the future, agricultural film production will develop in a centralized direction. The production and application development of high-end agricultural films will also put forward new requirements for PE technology innovation.
Pipes are mainly used for infrastructure construction. Judging from the current situation of PE pipe enterprises, the enterprises in the industry generally have the problems of similar products, slow development of new products, and mainly relying on imports of raw materials. Enterprises need to further increase research and development efforts, market segmentation, and expansion of application fields. Only in this way can they reach a higher level in product application and thereby obtain more revenue. Although there are some problems in the overall pipe industry, the requirements of China's 12th Five-Year Plan for accelerating rural transformation, rural urbanization, low-rent housing, and affordable housing will still increase the market's demand for pipe raw materials to a certain extent. The market outlook for tube materials remains clear.
The development of the cable industry is closely related to the development of China's industrial economy, especially the development of the information industry. With the acceleration of power grid construction, especially the construction of UHV projects, the demand for wire and cable materials will increase; secondly, China's consumer electronics and microelectronics industries will continue to develop rapidly; again, China's 3G industry is emerging, and broadband networks Construction will accelerate and the future of the cable industry is bright.

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