High density polyethylene (HDPE) is an opaque white waxlike material, lighter than water, soft and ductile, but slightly harder than LDPE, also slightly able to stretch, non-toxic, tasteless, used for extruding packaging film, rope, woven bags, fishing nets, water pipes, injection molding low-grade daily necessities and shells, extrusion blow molding containers, hollow products, bottles, etc.
Product Description:
Features: Melting point of 130 ºC, good heat resistance, cold resistance, chemical stability, high rigidity, toughness, and resistance to environmental stress cracking.
Suggested processing conditions: 130-180 ºC for the rear section of the barrel, 180-220 ºC for the front section of the barrel, 170-210 ºC for the mouth mold, and internal cooling method.
Usage: Mainly used as agricultural film, industrial packaging film, pharmaceutical and food packaging film, mechanical parts, daily necessities, building materials, wires, cable insulation, coatings, and synthetic paper.
| Advantages: |
| |
| 1. Resistance to most domestic and industrial chemicals. |
| 2. Non-moisture absorption and good waterproof steam, can be used for packaging and moisture proof and seepage. |
| 3. Good electrical performance, especially high dielectric strength, suitable for wire and cable. |
| 4. Medium to high molecular weight grades have excellent impact resistance. |
| HDPE 5502 |
| Properties |
Unit |
Test Method |
Value |
| Density |
g/cm3 |
ASTM D792 |
0.955 |
| Melt Flow Rate |
g/10min |
ASTM D1238 |
0.35 |
| Tensile Strength at Yield |
Mpa |
ASTM D638 |
27 |
| Elongation |
% |
ASTM D638 |
600 |
| Flexural Modulus |
Mpa |
ASTM D790 |
1370 |
| Low Temperature Brittleness |
ºC |
ASTM D746 |
-75 |
| Izod Impact 23ºC |
kJ/m2 |
ASTM D256 |
/ |
| Flammability File |
Class |
UL94 |
94HB |
HDPE
Nature: Natural, cylindrical or oblate particles, smooth and smooth, with a particle size of 2-5 mm in any direction, free from mechanical impurities, and thermoplastic. The powder is white powder, and qualified products are allowed to have a slight yellow color. It is insoluble in general solvents at room temperature, but can swell when in long-term contact with aliphatic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons. It is slightly soluble in toluenand amyl acetate above 70 ºC. Heating in the air and oxidation under the influence of sunlight. Capable of withstanding erosion from most acis and alkalis. Low water absorption, able to maintain softness at low temperatures, and high electrical insulation.
Usage: It can be used to produce various sizes of hollow containers, pipes, rolling and tying tapes for packaging, ropes, fishing nets, weaving fibers, wires and cables, etc. for film products, daily necessities, and industrial use.
Ultra high molecular weight polyethylene (UHMWPE) refers to a general term for polyethylene with a molecular weight of over 1 million, mainly used in high-end fields such as plastic modification, pipes, high-strength boards, fibers, etc. Ultra high molecular weight polyethylene is polymerized from ethylene, and the production process is similar to that of ordinary slurry high-density polyethylene. Both use Ziegler catalysts to polymerize ethylene under certain conditions, that is, ethylene polymerization, separation, and drying.
General characteristics
Polyethylene resin is a non-toxic and odorless white powder or particle with a milky white appearance and a waxy texture. It has a low water absorption rate of less than 0.01%. The polyethylene film is transparent and decreases with increasing crystallinity. Polyethylene film has a low water permeability but high air permeability, making it unsuitable for fresh-keeping packaging and suitable for moisture-proof packaging. Flammable, with an oxygen index of 17.4, low smoke during combustion, with a small amount of molten droplets, yellow on top and blue on the flame, and a smell of paraffin. Polyethylene has good water resistance. The surface of the product is non-polar, making it difficult to bond and print, and has been improved through surface treatment. Multiple branched chains result in poor resistance to photodegradation and oxidation. [6]
Polyethylene with a molecular weight ranging from 10000 to 100000 is considered ultra-high molecular weight polyethylene. The higher the molecular weight, the better its physical and mechanical properties, which are closer to the requirements of engineering materials. But the higher the molecular weight, the greater the difficulty of its processing. Polyethylene has a melting point of 100-130 ºC and excellent low-temperature resistance. Good mechanical properties can still be maintained at -60 ºC, with usage temperatures ranging from 80 to 110 ºC.
It is insoluble in any known solvent at room temperature, and can be slightly dissolved in solvents such as toluen, amyl acetate, and trichloroethylen above 70 ºC.
chemical properties
Polyethylene has good chemical stability and can withstand dilute nitri aci, dilute sulfuric aci, and any concentration of hydrochlori aci, hydrofluori aci, phosphori aci formi aci, ammoni, amines, hydroge peroxid, sodiu hydroxid, potassiu hydroxid, and other solutions at room temperature. But it is not resistant to the corrosion of strong oxidizing acis, such as sulfuric aci, concentrated nitri aci, a mixture of chromic aci and sulfuric aci, which will slowly corrode polyethylene at room temperature. At temperatures ranging from 90 to 100 ºC, concentrated sulfuric aci and concentrated nitri aci can rapidly corrode polyethylene, causing it to break down or decompose. Polyethylene is prone to photo oxidation, thermal oxidation, and ozone decomposition, and is prone to degradation under ultraviolet radiation. Carbon black has excellent light shielding effect on polyethylene. After being irradiated, reactions such as cross-linking, chain breakage, and the formation of unsaturated groups can also occur.
Mechanical properties
The mechanical properties of polyethylene are average, with low tensile strength, poor creep resistance, and good impact resistance. Impact strength LDPE>LLDPE>HDPE, other mechanical properties LDPE<LLDPE<HDPE. Mainly influenced by density, crystallinity, and relative molecular weight, its mechanical properties increase with the increase of these indicators. The environmental stress cracking resistance is not good, but it improves when the relative molecular weight increases. Good puncture resistance, with LLDPE being the best
thermal properties
The heat resistance of polyethylene is not high, and it improves with the increase of relative molecular weight and crystallinity. Good low-temperature resistance, and the brittle temperature can generally reach below -50 ºC; And with the increase of relative molecular weight, the lowest can reach -140 ºC. The linear expansion coefficient of polyethylene is large, up to (20-24) x 10-5/K. High thermal conductivity.
electrical properties
Due to the non-polarity of polyethylene, it has excellent electrical properties with low dielectric loss and high dielectric strength. It can be used as frequency modulation insulation material, corona resistant plastic, and high-voltage insulation material.
Environmental characteristics
Polyethylene is an inert polymer of alkanes and has good chemical stability. At room temperature, it is resistant to corrosion by aci, alkali, and salt aqueous solutions, but not resistant to strong oxidants such as fuming sulfuric aci, concentrated nitri aci, and chromic aci. Polyethylene is insoluble in general solvents below 60 ºC, but it may swell or crack when in long-term contact with aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, etc. After the temperature exceeds 70 ºC, it can be slightly dissolved in toluen, amyl acetate, trichloroethylen, turpentine, mineral oil, and paraffin.
Due to the presence of small amounts of double bonds and ether bonds in polyethylene molecules, exposure to sunlight and rain can cause aging, which requires the addition of antioxidants and light stabilizers for improvement. [6]
Processing characteristics
Due to their good fluidity, low processing temperature, moderate viscosity, and low decomposition temperature, LDPE and HDPE do not decompose at high temperatures of 300 ºC in inert gases, making them a type of plastic with excellent processing performance. But the viscosity of LLDPE is slightly higher, requiring an increase in motor power of 20-30%; Easy to cause melt fracture, it is necessary to increase the gap between the molds and add processing aids; The processing temperature is slightly higher, up to 200-215 ºC. Polyethylene has a low water absorption rate and does not require drying treatment before processing.
Polyethylene melt belongs to non Newtonian fluids, and its viscosity fluctuates less with temperature, but decreases faster with an increase in shear rate and shows a linear relationship, with LLDPE showing the slowest decrease.
Polyethylene products are prone to crystallization during the cooling process, therefore, attention should be paid to the mold temperature during processing. To control the crystallinity of the product and give it different properties. The molding shrinkage rate of polyethylene is large, and it must be considered when designing the mold.
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