The difference between high-density, low-density, and linear low-density polyethylene

Differences between High Density, Low Density, and Linear Low Density Polyethylene
Time: July 29, 2021
Low Density Polyethylene (LDPE) Polyethylene with a relative density of 0.910-0.925 is called Low Density Polyethylene, while polyethylene with a density between low and high density is called Medium 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 High Density Polyethylene (HDPE)
Polyethylene with a density of 0.941~0.965 is called High Density Polyethylene. HDPE is produced by high-pressure method, hence it is called High 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 has the difference between homopolymers and copolymers. The so-called copolymerization refers to the process of polymerization, which involves the infiltration of a small amount of alpha olefin. 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 overall 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 also enhances its barrier properties against water vapor and gases The difference between LDPE, LLDPE, and HDPE: 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 combustion flame and blue on the bottom; 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 differs structurally from general low-density polyethylene because it does not have long branched chains The linearity of LLDPE depends on the divergent 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 higher 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 divergent 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 Higher tensile strength, penetration resistance, tear resistance, and increased elongation are the characteristics of LLDPE, making it particularly suitable for film production HDPE (High Density Polyethylene): HDPE is a highly crystalline, non-polar thermoplastic resin The original appearance of HDPE is milky white, with a certain level of semi transparency in the thin section.
Date: July 29, 2021

Date: July 29, 2021
PE has excellent resistance to most household and industrial chemicals 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 high temperatures of -40F. Linear low-density polyethylene (LLDPE) is almost inert to chemical reactions and does not undergo any chemical reactions with any substances, 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 tools normally Performance differences between LDPE and HDPE: Tensile strength: LDPE is 7-14 MPa, while HDPE is 24-31 MPa. Operating 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 by ethylene radical polymerization 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, The difference between PE and PE is that PE is polyethylene HDPE is high-density polyethylene, also known as high-pressure polyethylene LDPE is low-density polyethylene, also known as high-pressure polyethylene HDPE and LDPE are both types of PE
Time: July 29, 2021

Time: July 29, 2021
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 becomes milky white particles after granulation, with a linear structure and little branching phenomenon. It is 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 high 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 high-pressure polyethylene, medium pressure polyethylene, and high-pressure polyethylene according to production methods. The production methods of polyethylene are different, and their density and melt index (implying fluidity) are also different Density and melt flow rate (MFR) are also key indicators for identifying and distinguishing different varieties and grades of polyethylene
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
Time: July 29th, 2021
Time: July 29th, 2021