What is high density polyethylene ? Polyethylene of low pressure (PND for short) and high density is a material that belongs to the group of thermoplastic polymers. This raw material is characterized by qualities such as strength, ductility and durability. Due to its positive qualities, this type of product has found its application to create many types of products.
Material Description
High-density low-pressure polyethylene is a substance that is obtained by polymerizing ethylene hydrocarbon. It turns out at low pressure, hence the name. Various substances can participate in the process, and the temperature can also change. By changing these characteristics, it is possible to obtain HDPE with different densities.
In addition, they will differ in some properties. In the manufacturing process, high-density low-density polyethylene is marked in accordance with the highest PE-80 or PE-100 index. The difference between these brands is insignificant, but it is. The difference lies in the following parameters:
- Hardness.
- Tensile and tensile strength.
- Resistance to various kinds of mechanical damage, as well as deformation.
- The temperature at which the product can be operated, etc.
Material structure
Regardless of which technology was used for production, high-density low-density polyethylene will always have a linear internal structure. In other words, the structure of this substance will consist of polymer macromolecules with a large number of bonds. Random intermolecular bonds will also be present.
It is important to add here that the cost of finished products of this type is quite low. The thing is that the manufacture takes place on equipment that does not differ in high cost, the raw materials for this also need to be cheap, and a team of workers in which up to two dozen people can service the equipment and monitor the process. For example, for the successful manufacture of pipes from low-density polyethylene of high density, one workshop is enough.
Main characteristics
In the manufacture of these products, all manufacturers must be guided by the state standard 16338-85. This document contains all the basic technical requirements that the finished product must meet. Among these characteristics, the following parameters:
- The density of the finished film should be in the range from 930 to 970 kg / m 3.
- The material begins to melt at a temperature of + 125-135 degrees Celsius.
- The minimum temperature indicator at which the material will be as fragile as possible is -60 degrees Celsius.
- Tensile and tensile strength should reach 20-50 MPa.
- Products should decompose naturally for about 100 years.
- Subject to all manufacturing rules, the characteristics of low-pressure polyethylene allow it to operate from 50 to 70 years or more.
Issue of different brands
Basic types of polyethylene ND are available in powder form. Compositions of this material can be supplied in the form of colored or unpainted granules. The raw material of the granular type, which is subsequently used to create different products, must have particle sizes of 2 to 5 mm in diameter, while their shape must be identical. Varieties of products may vary. It can be of the highest, first or second grade.
What is low pressure polyethylene ? This raw material, using which, you can get quite rigid and solid components. These properties can be seen even if a thin film is made of it.
The best indicators of PND (from the point of view of chemistry and physics), is the tensile strength, which is approximately from 20 to 50 MPa. The second best quality of the material is elongation, which ranges from 700 to 1000%. The appearance of this film is rather nondescript, it is tough, and when touched it creates rustling. The smooth surface structure is usually not maintained.
Positive qualities of the film
If all the technical specifications in accordance with GOST 16338-85 for low-pressure polyethylene were met, then this material has the following advantages:
- Subject to temperature limits, there is high resistance to cracking / scratching, etc.
- Chemical and biological inertness, which manifests itself in the fact that the film is not afraid of the effects of chemically active substances, as well as microorganisms.
- Resistance to radiation of radiation, excellent indicators are shown also in quality of dielectric.
- It can act as a good insulating material when it comes to liquid or gaseous substances.
- For humans, as well as for the environment, the material is completely safe, non-toxic.
It should be noted that high-density low-pressure polyethylene according to GOST 16338-85 due to its properties can be used for waterproofing purposes, as a raw material for the production of gas pipes. Due to its inertness to many environmental components, polyethylene is perfect as a starting material for the production of containers used as storage devices for environmentally harmful substances.
Negative properties
Like any other material, HDPE is not without flaws. This substance belongs to the group of thermoplastics polymers, which, despite all their strength and great resistance to various kinds of negative influences, have the following negative characteristics:
- If the temperature exceeds the permissible norm, then the material quickly begins to melt.
- Raw materials are subject to aging if they are constantly exposed to sunlight, which is rich in ultraviolet light.
Although it is fair to say here that the last drawback can be eliminated, if you use a special coating, for polyethylene structures. In addition, there is an operation that is carried out at the stage of manufacturing the product. Protective agents are introduced into the structure of the substance to prevent aging.
Snolen - high density low pressure polyethylene
Snolen is a PND brand, which is produced by such an enterprise as OAO Gazprom Neftekhim Salavat. The company is one of the largest in the Russian market.
The main characteristics of the product manufactured by this company are as follows:
- High rate of resistance to the effects of salts, alkalis, as well as oils of mineral and vegetable origin.
- Inertness to biological types of stimuli.
- The possibility of recycling the product.
- The moisture absorption level is quite low.
- The minimum threshold for negative temperatures increased to -80 degrees Celsius;
- High electrical insulation properties.
Varieties of raw materials
High-density low-density polyethylene Snolen is divided into several types depending on the technology that was used for its manufacture.
Solen EB 0.41 / 53 is made by extrusion blow molding. The main purpose of this type of raw material is the manufacture of pipes used for the installation of water pipes in houses, in factories. The diameter of the products may vary. Also used in the automotive industry. Used for the production of packaging bags.
Another variety of low-density polyethylene of high density according to GOST 16338-85 is the brand Solen IM 26/64 and Solen IM 26/59. These two types belong to injection molded products. The method is used to create things like traffic cones, containers, boxes, buckets. The main scope of use is economic activity and the food industry.
Snolen is a type of low-pressure polyethylene that can be processed in such a way as cutting, welding, casting, press.
Other product types
The company is engaged in the production of products such as Snolen EF 0.33 / 51 and Snolen EF 0.33 / 58. These brands belong to the film types. The main application of the products is the production of thick and thin films. Most often, the film is used as packaging for various types of goods. Plastic bags are also made from the same brand.
Slolen 0.26 / 51 is a polyethylene brand that is used for the manufacture of pipes. Most often they are used for the installation of gas pipelines, as well as for water pipelines, which can be used for both cold and hot water. Pipes can vary in diameter and color. In addition, these products are successfully used in the chemical industry.
High-density low-density polyethylene P-Y342 (Shurtansky GKhK TU), GOST 16338-85
The company "Simplex" is another company that produces polyethylene for the production of tubular products.
The brand P-Y342 is the main one that is used for the production of pipes. As for the technical characteristics of this product, it is very similar to a brand such as PE-80. The main parameters of this polyethylene are as follows:
- The density is from 0.940 to 0.944 g / cm 3.
- The number of various inclusions included in the product does not exceed 5 units.
- Mass fraction of volatile substances in the composition does not exceed 0.05%.
- The tensile yield strength is not more than 16 MPa.
- Elongation at break is 750%.
In addition to brand 342, the company also produces brands 337 and 456, which have high technical characteristics.
Production is also engaged in LLC Stavrolen 277-73. High density low pressure polyethylene from this manufacturer is characterized by resistance to thermal oxidative aging. The materials combine a fairly high stiffness with a low warpage. They have a good glossy finish. The main direction of use is the production of household dishes, caps for aerosols, medical syringes and other items. For the production of products using the casting method.
Safety in accordance with GOST
In addition to describing the basic technical requirements that polyethylene must comply with, the document also indicates some safety rules.
Base grade polyethylene at room temperature should not emit toxic volatile substances. In addition, its surface must be safe for human skin. When working with such material, there is no need to use personal protective equipment. If the work is done with powder polyethylene, then it is already necessary to use protective equipment for the lungs. In particular, a universal respirator brand RU-60M is used. If the product is heated above 140 degrees Celsius, then the polyethylene begins to emit harmful volatile substances. These include carbon monoxide. The process of processing polyethylene can only be carried out in those production rooms in which there is good ventilation. In this case, the multiplicity of air exchange in the room should be at least 8. If exchange ventilation is equipped, then the air exchange rate should be equal to 0.5 m / s. If exhaust ventilation is installed, the parameter increases to 2 m / s.
Additional Information
Low-pressure polyethylene is supplied in batches. As a batch, the presence of polyethylene of one brand and one grade is considered if its quantity is not less than 1 ton. In addition, the batch must have a quality certificate, in which it is necessary to indicate the name and trademark of the manufacturer, the symbol, as well as the type of product, date of manufacture, batch number and net weight. At acceptance, tests are also carried out to determine the quality of the goods. If unsatisfactory results were obtained on at least one of the items, then it is necessary to conduct a check again, while doubling the number of the first sample. The results of such verification will apply to the entire batch of goods.