How To Distinguish LLDPE From LDPE?
Oct 09, 2024| LDPE is non-toxic, tasteless, odorless, and has a density of 0.910-0.940g/cm3. It is polymerized with oxygen or organic peroxide as a catalyst under high pressure of 100 ~ 300MPa, also known as high-pressure polyethylene.
LLDPE is non-toxic, tasteless, odorless, with a density between 0.915-0.935g/cm3. It is a copolymer of ethylene and a small amount of advanced alpha-olefin (such as butene-1, hexene-1, octene-1, tetrmethylpentene-1, etc.) polymerized under high pressure or low pressure under the action of a catalyst. The molecular structure of conventional LLDPE is characterized by its linear backbone, with few or no long branched chains, but containing some short branched chains. The absence of long branched chains makes the polymer more crystalline.
- Comparison of LLDPE and LDPE
1.Melt flow characteristic
The melt flow characteristics of LLDPE are adapted to the requirements of new processes, especially thin film extrusion processes, to produce high-quality products. LLDPE is used in all traditional markets of polyethylene, and its resistance to stretch, penetration, impact and tear makes LLDPE more suitable for thin films. Its excellent resistance to environmental stress cracking, low temperature impact and warping makes LLDPE suitable for tubing, sheet extrusion and all molding applications.
2.LLDPE and LDPE uses
LLDPE forms a higher crystalline structure because there are no long branched chains. The larger crystallinity of LLDPE produces a product with higher rigidity. This higher crystallinity also increases the melting point of LLDPE by 10 ~ 15℃ compared with LDPE. Higher tensile strength, resistance to penetration, tear resistance and increased elongation are the characteristics of LLDPE, making it particularly suitable for thin films.
LDPE has good softness, extensibility, transparency, cold resistance and processability. Its chemical stability is good, can withstand acid, alkali and salt aqueous solution; Good electrical insulation and gas permeability; Low water absorption; Easy to burn. The property is soft, with good extensibility, electrical insulation, chemical stability, processing performance and low temperature resistance (resistance to -70℃).
3.Process
LDPE: With good processing properties, suitable for a variety of plastic processing processes, including injection molding, extrusion, blow molding, etc.
LLDPE: The processing temperature is slightly higher than LDPE, but because of its linear structure, the melting flow is good, suitable for blow molding, extrusion molding, especially in the production of film and pipe has more advantages.
- Method of differentiation
LDPE:Sensory identification: soft feel; White transparent, but the transparency is average;
Combustion identification: burning flame yellow and blue; When burning smokeless, there is a paraffin smell, melt dripping, easy to draw wire.
Widely used in the production of plastic bags in daily life, food packaging, shrink film, extrusion coating and so on.
LLDPE:LLDPE can swell in contact with benzene for a long time, and become brittle in contact with HCL for a long time.
Suitable for products requiring higher tensile strength and tear resistance, such as industrial packaging film, agricultural film, stretch wrap film, lining, pipe, cable jacket, etc.
In summary, LLDPE and LDPE play important roles in different types of seepage prevention projects. HDPE, LDPE and LLDPE three kinds of materials have good insulation and moisture-proof, impermeability, non-toxic, tasteless, odorless performance makes it in agriculture, aquaculture, artificial lakes, reservoirs, river applications are also extremely extensive.
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