The difference between LDPE, LLDPE, and HDPE PE

LDPE (Chinese name: Low Density High Pressure Polyethylene): Sensory identification: Soft to the touch: White and transparent, but the transparency is average. Combustion identification: Yellow on the top and blue on the bottom of the combustion flame.
; When burned, there is no smoke, a smell of paraffin, melting droplets, and easy to draw LLDPE (linear low-density polyethylene). Linear low-density polyethylene is structurally different from ordinary low-density polyethylene because it does not have long branched chains. The linearity of LLDPE depends on the different production and processing processes of LLDPE and LDPE. LLDPE is typically produced by copolymerization of ethylene and higher alpha olefins such as butene, hexene, or octene at lower temperatures and pressures. The LLDPE polymer generated during the copolymerization process has a narrower molecular weight distribution than general LDPE, and its linear structure gives it different rheological properties. The melt flow characteristics of LLDPE are suitable for the requirements of new processes, especially the use of thin film extrusion technology, which can produce high-quality LLDPE products. The application of LLDPE in all traditional markets of polyethylene enhances its resistance to elongation, penetration, impact, and tear, making it suitable for use as a film. Its excellent resistance to environmental stress cracking, low temperature impact, and warpage make LLDPE attractive for pipe, sheet extrusion, and all molding applications. The latest application of LLDPE is as a lining layer for plastic film used in waste landfill and waste liquid tanks. Higher tensile strength, penetration resistance, tear resistance, and increased elongation are the characteristics of LLDPE, making it particularly suitable for film production. If hexene or octene is used instead of butene as a comonomer, even the impact resistance and tear resistance can be greatly improved. For a given resin with the same melt index and density, the impact and tear properties of hexene and octene LLDPE resins are improved by 300%. The longer side chains of hexene and octene resins act like "knot" molecules between the chains, improving the toughness of the compounds.
HDPE (High Density Polyethylene): HDPE is a highly crystalline, non-polar thermoplastic resin. The original appearance of HDPE is milky white, with a certain degree of semi transparency in the thin section. PE has excellent resistance to most household and industrial chemicals. Certain types of chemicals can cause chemical corrosion, such as corrosive oxidants (concentrated nitric acid), aromatic hydrocarbons (xylene), and halogenated hydrocarbons (carbon tetrachloride). This polymer is non hygroscopic and has good water vapor resistance, making it suitable for packaging purposes. HDPE has excellent electrical properties, especially high insulation dielectric strength, making it very suitable for wires and cables. Medium to high molecular weight grades have excellent impact resistance, even at room temperature and low temperatures of -40F
Low density polyethylene (LDPE) with a relative density of 0.910-0.925 is called low-density polyethylene, while polyethylene with a density between low-density and high-density is called medium density polyethylene
On the contrary, polyethylene with a relative density below 0.910; It has also been released Becoming very low density polyethylene (VLDPE), and even having a relative density less than 0.900, it is also known as ultra low density polyethylene (ULDPE) in foreign countries. Although there are many varieties of polyethylene, the main ones that dominate the polyethylene market are still low-density polyethylene and high-density polyethylene Traditional low-density polyethylene is produced by free radical polymerization of polymer grade ethylene using oxygen or peroxide as initiators under high temperature and high pressure Therefore, low-density polyethylene is also known as high-pressure polyethylene Low density polyethylene is a white resin with a wax like texture, characterized by a non-linear structure The molecular weight is generally between 100000 and 50000. Therefore, compared with medium density and high-density polyethylene, it has lower crystallinity and softening point, better flexibility, elongation, electrical insulation, transparency, and higher impact strength Low density polyethylene has poor mechanical strength and heat resistance, and another obvious weakness is its poor resistance to environmental stress cracking
Low density polyethylene is mostly used for film products, while the majority of film products are used for packaging Another part is used as agricultural film and building film Low density polyethylene packaging film can be used for food packaging such as candy, vegetables, frozen foods, etc. It can also be used as an inner lining film, shrink wrap film, elastic packaging film, heavy packaging film, and other non food packaging films
High density polyethylene (HDPE) is a type of polyethylene with a density ranging from 0.941 to 0.965. It is produced using low-pressure methods and is therefore referred to as low-pressure polyethylene
There are two production methods: liquid-phase method and gas-phase method Liquid phase method includes solution method and slurry method High density polyethylene can be classified into homopolymers and copolymers. The so-called copolymerization refers to the infiltration of a small amount of alpha olefin during polymerization. The addition of these small amounts of alpha olefin can reduce the density and crystallinity of polyethylene, resulting in better environmental stress cracking performance, higher surface hardness, and better dimensional stability compared to homopolymers High density polyethylene improves heat resistance and mechanical strength (such as tensile, bending, compression, and shear strength) compared to low-density polyethylene, and enhances its barrier properties against water vapor and gases High density polyethylene can be processed into pipes, plates, sheets, profiles, monofilaments, flat wires, and strapping using extrusion method; Blow molding can be used to produce large and medium-sized hollow containers Such as bottles, barrels, and large industrial storage tanks; What is the difference between LDPE, LLDPE, and HDPE PE, which can be used to produce various parts, daily necessities, and industrial products through injection molding? Please provide a detailed introduction to the material properties, applications, and other aspects. Thank you LDPE (Chinese name: Low Density High Pressure Polyethylene): Sensory identification: Soft feel: White and transparent, but the transparency is average. Combustion identification: Yellow on the top and blue on the bottom of the combustion flame; When burned, it is smokeless and has a smell of paraffin wax. It melts and drips, and is easy to draw. LLDPE (linear low-density polyethylene) is structurally different from ordinary low-density polyethylene because it does not have long branched chains. The linearity of LLDPE depends on the different production and processing processes of LLDPE and LDPE. LLDPE is typically produced by copolymerization of ethylene and higher alpha olefins such as butene, hexene, or octene at lower temperatures and pressures. The LLDPE polymer generated during the copolymerization process has a narrower molecular weight distribution than general LDPE, and its linear structure gives it different rheological properties. The melt flow characteristics of LLDPE are suitable for the requirements of new processes, especially the use of thin film extrusion technology, which can produce high-quality LLDPE products. The application of LLDPE in all traditional markets of polyethylene enhances its resistance to elongation, penetration, impact, and tear, making it suitable for use as a film. Its excellent resistance to environmental stress cracking, low temperature impact, and warpage make LLDPE attractive for pipe, sheet extrusion, and all molding applications. The latest application of LLDPE is as a lining layer for plastic film used in waste landfill and waste liquid tanks. Higher tensile strength, penetration resistance, tear resistance, and increased elongation are the characteristics of LLDPE, making it particularly suitable for film production. If hexene or octene is used instead of butene as a comonomer, even the impact resistance and tear resistance can be greatly improved. For a given resin with the same melt index and density, the impact and tear properties of hexene and octene LLDPE resins are improved by 300%. The longer side chains of hexene and octene resins act like "knot" molecules between the chains, improving the toughness of the compounds.
HDPE (High Density Polyethylene): HDPE is a highly crystalline, non-polar thermoplastic resin. The original appearance of HDPE is milky white, with a certain degree of semi transparency in the thin section. PE has excellent resistance to most household and industrial chemicals. Certain types of chemicals can cause chemical corrosion, such as corrosive oxidants (concentrated nitric acid), aromatic hydrocarbons (xylene), and halogenated hydrocarbons (carbon tetrachloride). This polymer is non hygroscopic and has good water vapor resistance, making it suitable for packaging purposes. HDPE has excellent electrical properties, especially high insulation dielectric strength, making it very suitable for wires and cables. The medium to high molecular weight grade has excellent impact resistance, even at room temperature and low temperatures of -40F.
The answer above is already comprehensive. To add, HDPE is now mostly used in pipes, such as drainage pipes.
. It is an ideal pipe material to replace traditional concrete pipes and clay pipes. Nowadays, it is a new technology and the country is promoting the use of linear low-density polyethylene (LLDPE). LLDPE is almost inert to chemical reactions and does not react with any substances, but only burns. LLDPE can swell when in contact with benzene for a long time, and become brittle when in contact with HCL for a long time, but it takes several years. It can be used to store these two things normally.
Performance difference between LDPE and HDPE: Tensile strength: LDPE is 7-14 MPa, while HDPE is 24-31 MPa. Usage temperature: LDPE is below 100 degrees, while HDPE is below 120 degrees. Shore hardness: LDPE is 41-45, while HDPE is 60-70.
Low density polyethylene (LDPE) is a thermoplastic obtained through the free radical polymerization of ethylene under high pressure. The processing temperature of low-density polyethylene is lower, about 160 degrees Celsius, with a density of 0.918-0.932 grams per cubic centimeter. Mainly used as the outer sheath of telecommunications cables. The processing temperature of high-density polyethylene (HDPE) is higher, about 180 degrees, and the density is also higher
HDPE,LDPE, Difference from PE
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PE is polyethylene. HDPE is high-density polyethylene, also known as low-pressure polyethylene. LDPE is low-density polyethylene, also known as high-pressure polyethylene.
HDPE and LDPE are both types of PE.
Polyethylene is mainly classified by density, and its properties vary depending on the variety and grade:
① High density polyethylene (HDPE): It is an opaque white powder that forms milky white particles after granulation. The molecules have a linear structure and rarely exhibit branching, making it a typical crystalline polymer. The mechanical properties are superior to low-density polyethylene, with a melting point higher than low-density polyethylene, about 126-136 ℃, and a brittleness temperature lower than low-density polyethylene, about -100~-140 ℃.
② Low density polyethylene (LDPE): It is a colorless, semi transparent particle with long branched chains in its molecules and loosely arranged between molecules.

③ Linear low-density polyethylene (LLDPE): Generally, only short branches exist in the molecule, and its mechanical properties are between high-density and low-density polyethylene. Its melting point is 15 ℃ higher than ordinary low-density polyethylene, and its low temperature resistance is also better than low-density polyethylene. Its environmental stress cracking resistance is several times higher than ordinary low-density polyethylene.
In addition, polyethylene can be divided into low-pressure polyethylene, medium pressure polyethylene, and high-pressure polyethylene according to production methods. The density and melt index (indicating fluidity) of polyethylene vary depending on the production method. Density and melt flow rate (MFR) are also key indicators for identifying and distinguishing different varieties and grades of polyethylene.
Processing and application can be achieved through methods such as blow molding, extrusion, injection molding, etc., and are widely used in the manufacturing of films, hollow products, fibers, and daily necessities. In actual production, in order to improve the stability of polyethylene against ultraviolet radiation and oxidation, and enhance processing and usage performance, a small amount of plastic additives need to be added. The commonly used UV absorbers are ortho hydroxybenzophenone or its alkoxy derivatives, and carbon black is an excellent UV shielding agent. In addition, antioxidants, lubricants, coloring agents, etc. are added to expand the application range of polyethylene.
More than half of the total production of low-density polyethylene film is blown into thin films, which have good transparency and certain tensile strength. They are widely used as packaging materials for various foods, clothing, medicine, fertilizers, industrial products, and agricultural films. It can also be processed into composite film using extrusion method for packaging heavy objects. Since 1975, high-density polyethylene film has also been developed, with high strength, low temperature resistance, moisture resistance, and good printability and processability. The biggest use of linear low-density polyethylene is also to make thin films. Its strength and toughness are superior to 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. In addition, polyethylene coating can be extruded and coated on paper, aluminum foil or other plastic films to produce polymer composite materials.
Hollow products made of high-density polyethylene have high strength and are suitable for use as hollow products. Bottles, barrels, cans, tanks, and other containers can be made by blow molding, or large containers such as tanker tanks and storage tanks can be made by casting.
The extrusion method of pipe sheet can produce polyethylene pipes, and high-density polyethylene pipes have high strength and are suitable for underground laying. The extruded sheet can undergo secondary processing. High density polyethylene can also be made into low foam plastics by foaming extrusion and foaming injection methods, which can be used as platens and building materials.
LDPE (density 0.915-0.93), MDPE (density 0.93-0.94), HDPE (density above 0.94), the higher the density, the stronger the film's ductility, heat resistance, oil resistance, chemical resistance, and waterproofing, but the transparency will decrease. This is the difference between LDPE film and HDPE film. Another characteristic that is not related to density is that the molecules of HDPE film are longitudinally arranged, making it easy for HDPE film to tear.
Low density polyethylene (LDPE) is typically made from ethylene as a monomer, with a yield of 98% Under high pressure ranging from 0 to 294 MPa, using oxygen or organic peroxides as initiators, the polymer obtained through polymerization has a density of 0 910～0. 9259/cm3. The density of very low density polyethylene (VLDPE) is below 0.910g/cm3. Low density polyethylene has long and short chains on its molecular chain. The crystallinity is relatively low, with a molecular weight of generally 50000 to 500000. It is a milky white, semi transparent wax like solid resin that is non-toxic. The softening point is relatively low, and it melts when it exceeds the softening point. It has good thermal bonding and processing properties, good flexibility, impact toughness, and low temperature resistance. It can work at -60 ° C to -80 ° C and has excellent electrical insulation (especially high-frequency insulation). LDPE has poor mechanical strength, low heat resistance, and poor resistance to environmental stress cracking, adhesion, bonding, and printability. Surface treatment such as chemical erosion and corona discharge is required to improve its adhesion and printability. Very low water absorption, almost no water absorption, excellent chemical stability, such as stability to acids, bases, salts, and organic solvents. Has high permeability to CO2 and organic odors, but poor permeability to water vapor and air. Easy to burn, with a wax like odor during combustion; Under the action of sunlight and heat, it is easy to age and degrade, changing color from white to yellow to brown, and finally turning black, with decreased performance or cracking. If a certain amount of antioxidants, UV absorbers, etc. are added, the performance can be improved. Crosslinking under chemical crosslinking agents or high-energy irradiation can improve softening point, temperature resistance, stiffness, solvent resistance, etc. Low density polyethylene (LDPE) is suitable for various molding processes in thermoplastic molding. It has good molding processability, such as injection molding, extrusion molding, blow molding, rotary molding, coating, foaming process, thermoforming, hot air welding, hot welding, etc. LDPE is mainly used as a film product, such as agricultural film, ground cover film, agricultural film, vegetable greenhouse film, etc; Packaging films such as candy, vegetables, frozen foods, etc; Blow molded film for liquid packaging (milk, soy sauce, fruit juice, tofu, soy milk); Heavy packaging bag, shrink wrap film, elastic film, inner lining film; Construction film, general industrial packaging film, and food bags, etc. LDPE is also used for injection molded products, such as small containers, lids, daily necessities, plastic flowers, injection molded stretch blow plastic containers. Medical devices, packaging materials for drugs and food, extruded pipes and sheets, wire and cable coverings, profiles, thermoformed products, etc; Blow molded hollow products, such as food containers for dairy products and jams, containers for drugs, cosmetics, chemical products, tanks, etc.
HDPE high-density polyethylene properties: high melting point, rigidity, hardness and strength, good hardness resistance, low water absorption, outstanding insulation performance and good radiation resistance. Uses: HDPE is suitable for making pipes, hollow bottles, injection products, heavy packaging films, woven bags, tear films, large bags, turnover boxes and silk, etc. Ultra high molecular weight polyethylene is synthesized using a Ziegler type high-efficiency catalyst low-pressure synthesis method, with molecular weight controlled above 1.5-3 million as needed. Considering the thermal degradation of molecules during the processing, high-density polyethylene with a viscosity average molecular weight greater than 1.7 million can be processed into various plastic products in order to have the following superior properties: 1. High wear resistance. UHMW-PE has the best and most eye-catching wear resistance among all current industrial and plastic materials. The higher the molecular weight of the material, the more wear-resistant it is, even surpassing many metal materials such as carbon steel, stainless steel, bronze, etc. For example, the service life of UHMW-PE pipes under strong corrosion and high wear conditions is 4-6 times that of steel pipes, and the conveying efficiency is improved by 20%. It fully demonstrates the superiority of "energy conservation, environmental protection, economy, and efficiency". 2. Corrosion resistance: It is not corroded in alkaline solution and can be used in concentrated hydrochloric acid at 80 ℃. Its performance is stable in 75% concentrated sulfuric acid and 20% nitric acid. It is also stable in seawater and liquid detergents. 3. With an extremely low friction coefficient and a static friction coefficient of 0.07, it has good self-lubricating properties and is an ideal material for bearings, shaft sleeves, sliders, and lining. Choosing UHMW-PE as the friction component of the equipment can not only improve the wear resistance life, but also achieve the effect of reed energy. 4. Impact resistance ranks first among plastics, and it is difficult for them to crack due to strong external impact or internal pressure fluctuations. Its impact strength is 10 times that of nylon 66, 20 times that of polyvinyl chloride, and 8 times that of polytetrafluoroethylene Especially in low-temperature environments, its impact strength reaches its highest value, and its flexibility provides an extremely safe and reliable guarantee for the conveying system. 5. The anti-aging material has stable performance and good anti-aging property. It can be buried on the ground or underground and will not age for 50 years. According to the ASTM method (load 460MP2), the hot deformation temperature is 85 ℃, and the operating temperature can reach 90 ℃. In special circumstances, it is allowed to use at higher temperatures. UHMW-PE is a material with excellent toughness and low temperature resistance. It still has a certain degree of ductility at -269 ℃ without any signs of brittle fracture. But the coefficient of linear expansion is large and the thermal conductivity is poor, so when designing plastic products, full consideration should be given. 6. The electrical performance has a high volume resistance, a breakdown voltage of 50KV/MM, and a dielectric constant of 2.3. It is suitable as a structural material for electrical engineering within a wide range of temperature and frequency. 7. Sanitary non-toxic UHMW-PE material is odorless, non-toxic, and odorless, with no corrosiveness, physiological inertness, and physiological adaptability. The US Food and Drug Administration (FDA) and the US Department of Agriculture (USDA) allow it to be used in processing settings that come into contact with food and drugs.