GOSTs for polyethylene (pnd) pipes

How can you visually distinguish PND from PVD?

You can determine the type and quality of polyethylene by examining it visually and probing. The outward signs of each are different:

Both of these materials have gained widespread popularity in bag making. What is the difference between pnd and pvd garbage bags? For example, in pvd bags, you can carry sharp objects or boxes with sharp corners without fear of rupture. Due to the high degree of ductility and elasticity, such bags will not tear. But they will not be able to carry heavy and bulky products. Due to its strength, PND is able to withstand large weights, but if a sharp object breaks the structure, then a crack will go through the entire package. It can be concluded that the differences between PVD and PND packages are in strength.

Features of the operation of plastic HDPE pipes

It should be remembered that improper use, excessive heating and the sun's rays accelerate the aging of HDPE polyethylene materials, therefore it is so important to comply with the prescribed pressure and temperature regulations, and also to carry out the laying of the plastic pipeline hidden. The flammability of polyethylene obliges to avoid the installation of HDPE mains near potential sources of ignition

Repair of HDPE plumbing pipelines by welding is performed only after the media supply is turned off. In case of minor breakage, the damage can be easily repaired by means of electrofusion couplings or a hand-held polyethylene welding extruder. If a complete replacement is required, the new plastic tubing can be pulled inside the old one.

With minor punctures (up to 5 cm in diameter), you can do without cutting and replacing the damaged area. Special electrowelded HDPE plugs will help eliminate leaks without expensive electrofusion fittings made of polyethylene.

Possible problems

Most problems, such as leaking joints, crushing, tearing or puncture, are due to:

• Inconsistency of technical characteristics with operating conditions.
• Using low-quality polyethylene fitting elements or plastic fittings made from a different polymer.
• Violation of installation technologies.
• The absence of an insulating layer or a violation of its integrity.
• Placing a plastic HDPE pipeline above the freezing point of the soil.
• Excessively rigid fixation, not taking into account the percentage of linear expansion of the polyethylene.
• The absence of a protective box in areas with high mechanical stress (for example, under a car park or highway).

Because HDPE is extremely sensitive to shock loads, any excavation near the plastic pipeline should be done carefully. Even a small blow with a shovel can rupture the line. To prevent the very possibility of such an accident, it is better to close the HDPE polyethylene pipe with a protective box.

Packaging, transportation and storage

During transportation and storage of HDPE polyethylene pipes, the following should be avoided:

1. Sagging. To do this, the pipe sections must be laid on a flat, hard surface.
2. Free movement and rolling, as a result of which HDPE plastic pipes can be damaged. To avoid accidental falling, the stack must be securely fixed around the perimeter.
3. Internal surface contamination. To do this, each piece of plastic HDPE pipe is supplied with factory plugs, which are best not removed before installation.
4. Dragging, which increases the likelihood of deformation and damage to the HDPE polyethylene pipe.
5. Exposure to direct or even scattered sunlight.

Store only in an upright position with a stack height of no more than 2 m and at a distance of at least 1 meter from heating appliances.

To move plastic pipes from HDPE during unloading or installation, it is forbidden to use rigid metal slings and chains, which increase the risk of deformation or damage. It is better to replace them with soft but durable polymeric or fabric materials.

Material features

Specifications

Like all types of polyethylene, PE-80 is a thermoplastic polymer that melts when the temperature rises to a certain barrier and has a number of its own properties that are similar to other polyethylene products:

• The density of PE-80 polyethylene is 941 kg / m3, which is quite a lot for a polymer product and explains the hardness and strength of products made from it;
• Operating temperature range - from -70 to +120 0C, which is quite a lot for domestic and even industrial use;
• Material tensile strength - 700 hours for internal tension;
• PE-80 is resistant to strong chemical reagents - alkalis and acids;
• Does not biodegrade, that is, it is not exposed to mold, fungus, insects, etc.;
• It is an excellent insulator and insulator for liquids and gases;
• Possesses resistance to radiation radiation;
• Autumn has a long service life compared to natural substances, in standard conditions it exceeds the indicator of 60-80 years.

Composition

The difference between PE-80 and other polyethylenes, firstly, is that it is a high-density material of the HDPE group, which is obtained by polymerizing the initial hydrocarbon, ethylene, at low pressure, but at a high temperature and in the presence of a set of catalysts.

The group of HDPE polyethylene also includes substances labeled PE-100, PE-63 and others. Their difference lies in the presence or absence of additional bonds between molecules. Polymerizing, hydrocarbons form huge molecules with free branches, which can connect with each other. The percentage of such bonds can be more or less, directly affecting the degree of crystallinity and strength of the products. And the more "crystalline" and stronger they are, the higher the index is assigned to the material. So, PE-80 and PE-100 differ in the following properties:

• PE-100 has stronger intermolecular bonds and therefore is denser and heavier;
• Tightly bound molecules give greater strength to products, as well as greater resistance to the destructive actions of the environment (moisture, temperature jumps, sunlight) and chemical reagents;
• But PE-80 is more plastic and resistant to small deformations,
• PE-80 melts at lower temperatures, which is convenient when it is necessary to join polyethylene parts by welding and facilitates installation work;
• The peculiarities of production make PE-80 a cheaper material.

Getting polyethylene

Let's briefly describe the production technology of both main types of polyethylene.

This polyethylene, as the name implies, is synthesized at elevated pressure. The synthesis is usually carried out in a tubular reactor or autoclave. The synthesis takes place under the action of oxidizing agents - oxygen, peroxides, or both. Ethylene is mixed with a polymerization initiator, compressed to a pressure of 25 MPa and heated to 70 degrees C. Usually, the reactor consists of two stages: in the first, the mixture is heated even more, and in the second, polymerization is carried out directly under even more severe conditions - temperatures up to 300 degrees C and pressure up to 250 MPa.

The standard residence time of the ethylene mixture in the reactor is 70-100 seconds. During this period, 18-20 percent of ethylene is converted to polyethylene. Then the unreacted ethylene is sent for recirculation, and the resulting PE is cooled to and subjected to granulation. The polyethylene pellets are cooled again, dried and sent to packaging.Low density polyethylene is produced in the form of uncolored granules.

HDPE (High Density PE) is produced at low reactor pressure. For synthesis, three main types of polymerization process are used: suspension, solution, gas-phase.

For the production of PE, a solution of ethylene in hexane is most often used, which is heated to 160-250 degrees C. The process is carried out at a pressure of 3.4-5.3 MPa during the contact time of the mixture with the catalyst for 10-15 minutes. The finished HDPE is separated by solvent evaporation. The resulting polyethylene granules are steamed at a temperature above the PE melting point. This is necessary to transfer low molecular weight fractions of PE into an aqueous solution and remove traces of catalysts. Like LDPE, finished HDPE is usually colorless and is shipped in 25 kg bags, less often in big bags, tanks or other containers.

Characteristics and scope

Physicochemical features of high pressure PE:

• Density - 900-935 kg / m³.
• Melting temperature - 105 - 115⁰С.
• Temperature minimum - (-120⁰С).
• The maximum operating temperatures are from -45 to 70⁰C.
• The coefficient of relative elongation (stretching, plasticity), depending on the modification of polyethylene, is 50 - 600%.
• Resistant to deformation, tearing and impact. Impact resistance - 10 - 17 MPa.
• Smoothness of the surface.
• Air and moisture proof.
• The maximum operating pressure of the circuit is 2.5 MPa (25 atfospheres).

The production of LDPE pipes in Russia is regulated by GOST 18599-2001, according to which they are recommended for the arrangement of:

• cold and hot water supply systems;
• drainage and sewerage communications;
• heating (if there is a system for automatic control of the temperature of the medium);
• industrial transport routes for liquid and gas media;
• wells and systems of irrigation and drainage in agriculture.

In some cases, LDPE pipelines are used as a protective insulating case for laying electrical wires and cables or power embedded foundations when laying technological holes in walls and ceilings during the construction of buildings.

Requirements

The basic rules regarding the material to be disassembled are clearly specified in GOST 16337-77. The most important point is that additives in the original brands should not be used. The choice of this type for a specific task must comply with the instructions of annexes 1 and 2 to the same standard. Both the base grade and the compound blend based on it can be made from three different (including the highest) grades. It is imperative to compose each batch of granules of identical geometric configuration with a size along any axis from 2 to 5 mm.

The share of granules with a size of 5.1-8 mm should account for a maximum of 0.25%. The concentration of particles 1-2 mm in size is normally 0.5%. For PET produced for specialized films, this parameter should be a maximum of 0.25%. Grade 2 material may contain gray and colored granules (maximum 0.1%). Both colored and uncolored products cannot contain granules of any other color; an exception was made only for grade 2, but not more than 0.04%.

The shade must match the officially approved color sample. It is strictly forbidden to have:

• metal inclusions;
• gel accumulations;
• non-melted areas;
• large villi.

For food and medical applications, only polyethylene of the first and highest grades is used, tested for compliance with additional requirements of the ministry of health. GOST also establishes requirements for the acceptance of high-pressure polyethylene. It should only be accepted in lots of at least 1000 kg. In the accompanying quality document, in addition to the batch number, you will have to indicate:

• the official name of the manufacturing enterprise;
• its trademark;
• product category;
• production date;
• net weight;
• the results of the tests performed or an official certificate;
• compliance with additional requirements (if the product is intended for water supply, for medical or food production, for the formation of children's toys).

All standardized indicators are subject to verification, including:

• mass fraction of particles of various fractions;
• mass fraction of gray-colored and oxidized fragments;
• material density;
• nominal fluidity level;
• spread of melt flow within one batch;
• number of inclusions;
• resistance to cracking;
• relative extension;
• the entry of the extracted components;
• susceptibility to thermal-oxidative and light-oxidative obsolescence;
• concentration of volatile components.

TU 2211-145-05766801-2008 developed at OAO Nizhnekamskneftekhim should be considered as exemplary technical conditions. In addition to technical requirements, the document also standardizes the packaging of the shipped product. Samples for test procedures are obtained by injection molding. The melt flow rate is established using an extrusion plastometer according to the ASTM D 1238 method. Flexural modulus testing is carried out according to the ASTM D 790 method.

Storage of HDPE is possible only in closed dry rooms. Direct rays of the sun should not fall there. Packaged or stored outside the packaging, the product must be equally positioned at a minimum height of 0.05 m above the floor.

What can be found in the rules of GOST

The standard itself can always be found in the databases of legal portals or downloaded on the same page. To make it easier to navigate in all the rules describing HDPE polyethylene in it, you should immediately refer to the content of this document.

Document structure

• The relevance of the prescribed rules (dates of adoption and amendments),
• Links to additional necessary legislative acts,
• Decoding of markings with an explanation of the meaning of each position from the 8-digit code,
• Full description of HDPE existing grades with standards for all technical indicators for each grade - in terms of chemical composition and physical and mechanical properties,
• List of permitted additives with their individual properties, separately for gas-phase and suspension types,
• Safety requirements both for the polyethylene composition itself and for the rules for working with the finished product,
• Rules for the acceptance of finished lots of HDPE with a description of the tests carried out and the determination of the grade,
• The issues of correct packaging, safe transportation and non-destructive storage of products,
• Warranties that a polyethylene manufacturer can provide for their goods.

Useful Apps

At the end of the document, as many as 5 appendices are waiting for you, which describe not only the physical and mechanical properties of polyethylene, but also give recommendations for its manufacture and further use:

1. The first appendix gives a label for the first and second grade of each base grade.
2. The second will help you choose the right (and allowed) recipe for additives in the manufacture of products for various purposes:
   • for those in contact with food,
   • intended for children
   • for the manufacture of packaging,
   • pipelines and fittings,
   • medical devices and even prosthetic products.
3. The next page (Appendix No. 3) gives instructions for the use of polyethylene of each of the described brands - both a complete description of the field of application and processing methods.
4. The fourth sheet will be necessary for those who need to dye low-pressure polyethylene in any color: here is given a table of the correspondence of color and substance that will dye HDPE products into it.
5. The last appendix describes all the physical and mechanical characteristics of the grades, from melting points to a list of dielectric properties.

IMPORTANT! GOST is not only instructions for action for manufacturers, but also useful information for consumers. Knowing the standards, you will be able to select products that fully meet your needs and safety rules

Scope of expanded polyethylene sheet

Due to its chemical inertness, resistance to aggressive media, low thermal conductivity, good sound-insulating properties, polyethylene foam is widely used for arranging the interior cladding of yachts, boats, cars.

Polyethylene foam is also used in construction. It is a more effective insulation compared to many materials used for this. So, for example, polyethylene sheet 10mm thick can replace 50mm mineral wool. This explains its popularity when insulating walls and floors in rooms.

Most often, metallized polyethylene foam sheet is used, which, moreover, is also a very light material. It is easy to use, easy to cut and easily attaches to any surface. However, it should be remembered that the metallized side of the sheet should always face the room. In this case, its reflective properties will be maximized.

Good vapor barrier properties make it possible to use a similar material for arranging ceilings in wooden houses. Due to the softness and elasticity of polyethylene foam, as well as the ability to damp small vibrations, it is used as a substrate when laying laminate, parquet, linoleum or underfloor heating. It is also used in the construction of interior partitions.

The same properties make it possible to produce reliable packaging from such a foam material, which ensures safety and protects fragile or expensive items from damage. At the same time, it can serve as a cushioning material that protects objects from damage if a large number of them are packed in one container.

Foamed polyethylene sheets are widely used in instrument making, in the manufacture of household appliances and refrigeration units. Due to a number of valuable properties, polyethylene foam sheet has become an irreplaceable material used in many areas of industry, construction and interior decoration.

Test methods

4.1. Determination of the melt flow rate. The melt flow rate is determined according to GOST 11645-73 at a temperature of 190 ± 0.5 ºC, a standard time of 600 s and a load by brands:

For secondary polyethylene of grades A2, A3, A4 - 21.19N (2.160kgf);

For secondary polyethylene grades A1, B1, B2 - 49.05N (5.0 kgf).

Before testing, the samples are conditioned at a temperature of 20 ± 5 ºC for 3 hours.

4.2. Sample preparation for physical and mechanical tests.

Samples for determining the tensile yield strength and elongation at break are punched out from plates made by pressing.

For this, a combined sample of recycled polyethylene in the amount of 300-400 g. mix thoroughly, condition in accordance with GOST 12423-66 for at least 3 hours. and then plates with a thickness of 1.6 ± 0.1 mm are pressed.

Plates for testing are manufactured in molds in accordance with GOST 12019-66.

To prevent adhesion of recycled polyethylene during pressing to the surface of the mold, you can use gaskets made of cellulose film in accordance with GOST 7730-74 or aluminum foil in accordance with GOST 618-73. It is allowed to use other films that do not affect the test results.

A mold with a sample of secondary polyethylene is installed in a press heated to a temperature of no more than 100ºC.

Then the plates are brought together so that the recycled polyethylene is suppressed by about 0.5 MPa and heated to the pressing temperature. The pressing temperature is selected depending on the grade of recycled polyethylene:

• for grades A1-A4 - 135-160 ºC;
• for grades B1, B2 - 170-190 ºC.

Maintain at this temperature for 8 minutes. Then the specific pressure is increased to 7-10 MPa and kept under pressure for 8 minutes. (based on the calculation of 5 minutes per 1 mm of plate thickness), after which, without decreasing the pressure, cooling is carried out at an average rate of 20-25ºC per minute to a temperature of 40-50ºC.

The temperature of the top and bottom plates must be controlled during the press cycle and kept constant. Temperature fluctuation around the perimeter and between the plates is allowed no more than 2-5 ºC.

The surface of the specimen should be smooth, free from blisters, chips, cracks, pits and other visible defects.

4.3. The tensile yield point and elongation at break are determined according to GOST 11262-80 on type 1 specimens.

It is allowed for grades A1 and A3 to determine the relative elongation by changing the distance between the grips, the calculated value Ɩ 'is taken to be 33 ± 1mm.

The spreading speed of the grips of the tensile testing machine during testing for recycled polyethylene grades A3, A4100 ± 10 mm / min., For other grades 50 ± 5 mm / min.

The tests are carried out at a temperature of 15-30 ºC and a relative humidity of not more than 80%.

4.4. Bulk density is determined according to GOST 11035-64.

4.5. Determination of the mass fraction of volatile substances is carried out in accordance with GOST 26359-84.

4.6. Ash content is determined in accordance with GOST 15973-82, Appendix Clause 1.

4.7. Determination of moisture content is carried out according to OST 63.8-81.

Applications

The presence of extraneous components, including catalysts, determines the widespread use of HDPE for industrial purposes, where strength and strength are considered more important criteria than toxicity and environmental friendliness. Only a small part of the finished product is used to meet household needs.

The scope of use of the material directly depends on the method of processing polyethylene. In accordance with GOST, the following areas are distinguished - extrusion, injection molding, as well as blow molding and rotational molding.

Extrusion

This method involves the production of polyethylene from polymer raw materials by forcing the finished material through the forming cone - the hole of the extruder. The method makes it possible to produce packing bags, conveyor belts and air-bubble belts for packing goods, as well as electrical wires and nets of various types (household, agricultural and construction). There is a wide demand for material for the production of sewage pressure pipes, drainage and gas pipes of different diameters. HDPE retains its characteristics when exposed to temperatures from -60 to +100 degrees.

Injection molding

This method of processing polymer raw materials involves the injection of a melt under high pressure into a mold with its subsequent cooling. In this way, fittings, kitchen attributes, as well as furniture fittings, plastic covers, tare boxes and some types of plumbing are produced.

Blowing out

During processing, heated plastic is injected under pressure into a special cavity shaped like the product to be manufactured. The technology makes it possible to obtain tanks, tubs, cisterns, barrels and all kinds of cosmetic bottles.

Rotational molding

This method of manufacturing polymer products in our country appeared relatively recently. It allows you to make a variety of products according to customer drawings. Rotoforming is used to create children's playgrounds, mobile dry closets, garbage containers, traffic cones and many other products. This area of ​​use of HDPE is considered one of the most promising.

From high-strength polyethylene, you can get the thinnest film, the thickness of which is comparable to tissue paper and does not exceed 7 microns. It can be a good alternative to heat-resistant paper, for example, parchment - unlike the latter, HDPE has good water resistance, exceptional aroma and vapor barrier characteristics.

It is noteworthy that the worn-out items from PVP do not decompose under the influence of external natural factors. That is why the issue of their recycling is especially relevant - such a solution can be not only economically profitable and safe for the environment. The processing of polyethylene in recent years has become one of the most promising areas of the industry.Recyclable materials are widely in demand in the manufacture of plastic containers, dishes and other products that do not require high quality products.

What is the difference between LDPE polyethylene and HDPE, you can find out from the video below.