when the process conditions used are not the same, and therefore, only to generate three different varieties of polyethylene, the performance of the three kinds of materials have a big difference.
LDPE
LDPE for short
Commonly known as flower material or cylinder material
Scientific Name Low Density Polyethylene High Pressure Polyethylene
English Name low density polyethylene
Monomer ethylene ------ is a gas produced in petroleum refining
Native Color Polyethylene color is a translucent white waxy material, specific gravity is lighter than water, soft and tough, slightly elongated, non-toxic, odorless combustion characteristics of flammable, off the fire can continue to burn, the flame is yellow at the upper end, the lower end of the blue, the combustion of the melting, there are liquid droplets, there is no black smoke out, at the same time, issued by the burning of paraffin odor.
Advantages Acid and alkali resistance, resistance to organic solvents, excellent electrical insulation, low temperature, can still maintain a certain toughness.
Disadvantages of poor mechanical properties, poor air permeability, easy to deform, easy to age, easy to brittle, easy stress cracking, low surface hardness, easy to scratch. Difficult to print, printing, the need for surface discharge treatment, can not be plated, the surface has no luster.
Use for extruding packaging film, film, hose
Used for injection molding of low-grade daily necessities and shells
Used for extrusion blow molding containers
Injection performance of low-molecular-weight polyethylene, the melting point of 120 ° C, very much like the paraffin; the general melting point of polyethylene 140 ° C, the decomposition temperature of
300 ° C; the injection temperature of the adjustable interval is large, commonly used in other applications, and the temperature is very low, and it is easy to be used in the production of polyethylene. Adjustable range of injection temperature is large, commonly used in other raw materials for the change of material washing machine. Injection molding, the general use of temperature 170 ℃ - 220 ℃;
Because it is an olefin plastic, it does not absorb water, production, do not need to dry, but for product quality, can be used to 60 ℃ temperature drying 1hr, in order to discharge the floating water;
Polyethylene melt viscosity is large, the flow of long ratio is small, thin-walled products may be lack of glue, so the gate and runners are relatively large; the products are prone to static electricity, the surface is easy to
Polyethylene melting point is 140 ℃. The surface is easy to
absorb dust. Shrinkage rate of 16‰; overflow edge value of 0.05mm
HDPE
HDPE for short
Commonly known as the hard soft glue
Scientific name high-density polyethylene low-pressure polyethylene
English name high density polyethylene
Monomer ethylene - produced in the refining of petroleum A gas
The color of high-density polyethylene color is an opaque white waxy material, specific gravity is lighter than water, soft and toughness, but slightly harder than LDPE, but also slightly elongated, non-toxic, odorless combustion characteristics of flammable, away from the fire can continue to burn, the flame on the upper end of the yellow, the lower end of the blue, the combustion of the melting, there are liquid droplets, no black smoke out, at the same time, the emission of the combustion of the paraffin wax emitted Odor
Advantages acid and alkali resistance, organic solvents, excellent electrical insulation, low temperature, can still maintain a certain toughness. Surface hardness, tensile strength, rigidity and other mechanical strength are higher than LDPE, close to PP, tough than PP, but the surface finish is not as good as PP
Disadvantages of poor mechanical properties, poor ventilation, easy to deform, easy to age, easy to brittle, brittleness is lower than PP, easy to stress cracking, low surface hardness, easy to scratch. Difficult to print, printing, the need for surface discharge treatment, can not be plated, the surface has no luster.
Use for extrusion packaging film, rope, woven bags, fishing nets, water pipes
Used for injection molding of low-grade daily necessities and shells, non-load-bearing components, plastic boxes, crates
Used for extrusion blow molding containers, hollow products, bottles
Injection performance of the general HDPE melting point of 142 ° C, the decomposition temperature of 300 ° C; the temperature of the molding of the adjustable The interval is large. Injection molding, the general use of
Temperature of 180 ℃ - 230 ℃; because it is an olefin plastic, it does not absorb water, production, do not need to dry, but for product quality, can be used to 60 ℃ temperature drying 1hr, in order to discharge the floating water; polyethylene melt viscosity is large, the flow of long ratio is small, thin-walled products may be lack of glue, therefore, the gate and runners are relatively large; products are prone to electrostatic discharge, the surface of the easy to absorb dust. Shrinkage rate of 16 ‰; overflow edge value of 0.05mm
LLDPE
LLLDPE for short
Scientific name Linear Low Density Polyethylene Low Pressure Low Density Polyethylene
Monomer ethylene - a gas produced in the refining of petroleum
Native color Linear High Density Polyethylene Native color is an opaque white waxy material, specific gravity Lighter than water, soft and tough, but slightly
harder than LDPE, but also slightly elongated, non-toxic, odorless
Burning characteristics of flammable, away from the fire can continue to burn, the flame on the upper end of the yellow, the lower end of the blue, the combustion of the melting, there are liquid droplets, no black smoke out, at the same time, issued by the burning of the paraffin odor issued
LDPE HDPE LLDPE The difference between the three materials: LDPE and HDPE is mainly in the density of the difference, thus causing mechanical properties on the
difference, a rigid, a flexible; LLDPE and their differences, mainly in the molecular structure, LLDPE has more branched chain, so this material
materials that are flexible and rigid.
Advantages Acid and alkali resistance, resistance to organic solvents, excellent electrical insulation, low temperature, can still maintain a certain toughness. Surface hardness, tensile strength, rigid
Sex and other mechanical strength are higher than LDPE, but lower than HDPE; LLDPE puncture resistance is the best, tear-resistant, especially suitable for the production of film, the production of
film is thinner than the LDPE, but the strength of the high.
Disadvantages of poor mechanical properties, poor air permeability, easy to deform, easy to age, easy to be brittle, brittleness is lower than PP, easy stress cracking, low surface hardness, easy to scratch. Difficult to print, printing, the need for surface discharge treatment, can not be plated, the surface has no luster.
Use for extrusion packaging film, tape, cable; production of film, also known as paper film
Used for injection molding of low-grade daily necessities and shell
Used for extrusion blow molding containers, hollow products, bottles
Injection molding performance of the general LLDPE melting point of 170 ° C, the decomposition temperature of 300 ° C; the injection temperature of the adjustable interval is larger. Injection molding, the general use of temperature 200 ℃ - 260 ℃; its apparent viscosity, poor fluidity, a separate LLDPE difficult to injection molding, therefore, to increase the power of the injection molding machine or other low molecular weight plastics to increase its mobility; because it is olefinic plastics, it is not absorbent, the production of water, do not need to be drying, but for the quality of the product, can be used to 60 ℃ temperature drying 1hr, in order to drain the floating water; linear Low-density polyethylene melt viscosity, flow length ratio is small, fluidity is lower than LDPE and HDPE, thin-walled products may be lack of glue, therefore, the gate and runners are relatively large; products are easy to carry static electricity, the surface is easy to absorb dust. Shrinkage rate of 16 ‰; overflow edge value of 0.05mm