EVOH film is a random copolymer of ethylene and vinyl alcohol. It is a crystalline polymer that has a molecular structure represented by the following formula:

5-layer films based on a barrier layer are distinguished by excellent processability and excellent barrier properties. The key to this remarkable balance is the combination of proper ethylene-vinyl alcohol copolymerization, carefully selected degree of polymerization, and the unique, patented manufacturing process used to produce EVOH copolymers. These unique polymers are blown in a 5-layer film process, and these films are especially suitable for food, medical, pharmaceutical, cosmetic, agricultural and industrial packaging.

EVOH

EVOH

Product quality takes important place in production, but the packaging of this product is not inferior in importance to the intended result, namely its delivery to the end consumer. Here you need a presentable appearance and reliability during storage and transportation. To solve such problems in the film material creation industry, various types of packaging are being developed that satisfy the most tricky requests of manufacturers. This is possible by combining multiple sequence options and layers of film material.

A major breakthrough in the technology of creating various types packaging with excellent barrier properties is the application EVOH. This material has unique qualities due to its chemical structure: a compound of polyethylene (PE) and polyvinyl alcohol(PVA). At the same time, alcohol is responsible for the barrier properties finished material, and polyethylene makes it susceptible to heat treatment. Since alcohol polymers are susceptible to the negative effects of moisture, polyolefins are added to EVOH on both sides to protect it. And when it burns, only water and CO₂ gas are released, which makes the material easy to recycle.

Also, the uniqueness of EVOH lies in its quality, which in its properties allows not only to replace such expensive materials as metal foil, tin, glass, but also has a number of the following advantages:

has almost no weight;
does not break;
has a high degree of transparency;
Allows heating in the microwave;
has flexible properties (restores shape after deformation);
allows you to give the packaging a presentable, original and unique look due to its flexibility in applying holography and all kinds of printed images;
cannot be subject to corrosion.

Select Valtec 20 (2.0)

Price: 0 65 65 RUB 2029-12-31 RUB.

Main diameter: 16

Nominal pressure: PN 10

Item Type: Pipe

Brand: VALTEC

Manufacturer_: Valtek S.r.l.

Country of origin: CHINA

Warranty period: 7 years

Products webpage: www.valtec.ru

Weight: 0.093 kg

VALTEC PEX-EVOH XL POLYETHYLENE PIPES

Today, the share of low-temperature heating systems in Russian construction is growing. Modern boilers And heating devices are capable of fully heating rooms with a coolant temperature of up to 80 °C. In addition, recently systems have become widespread underfloor heating. The temperature and pressure of the coolant in these systems allow the use of simpler and cheaper materials. That is why there is now a great demand in the Russian market for pipelines made of cross-linked polyethylene. This type of pipeline combines reliability when used in low-temperature heating systems, ease of installation and low cost.

Cross-linked polyethylene pipeline, or PEX pipe as it is called, is practically monolithic structure, the main material of which is molecular cross-linked polyethylene. Conventional polyethylene consists of long hydrocarbon molecules that are not connected to each other in any way and is not suitable for use as the main material for heating pipelines due to its low heat resistance. Molecular cross-linked polyethylene has cross-links between the chains of hydrocarbon molecules, and therefore this material has higher strength and rigidity and, most importantly, higher resistance to temperature influences.

If we talk about metal-polymer pipelines, then this term today covers a fairly broad class of polymer pipelines, the main difference of which from conventional pipelines is the presence of a reinforcing layer of metal, usually aluminum, foil between the inner and outer layers of the polymer. In this case, the same material as in PEX pipes, namely cross-linked polyethylene, can be used as the material of the inner and outer layers. Other materials can also be used - polyethylene (PE, PE-HD), polyethylene with increased temperature resistance (PE-RT), polypropylene (PP-R), etc.

While the characteristics of metal-polymer pipes often depend on the properties of the materials used and the quality of the adhesive layer, the characteristics of PEX pipes, as a rule, depend on the degree of cross-linking of polyethylene, the thickness of the pipeline wall and the method of applying oxygen-impermeable layers.

Cross-linking of polyethylene determines the strength and thermal characteristics of the pipeline. First of all, cross-linking makes it possible to achieve long-term resistance to high temperature and pressure (increases the limit of logarithmic-proportional relaxation). Cross-linking of polyethylene can occur different ways and to varying degrees. There are three main industrial methods for cross-linking polyethylene:

peroxide method (PEX-a) is chemical method crosslinking of polyethylene and consists of crosslinking with organic peroxides and hydroperoxides. The pipeline obtained using this method has a degree of cross-linking of about 75%;
the silane method (PEX-b) is also chemical. When cross-linking using this method, organosilanides are used. The minimum crosslinking coefficient by this method is limited to 65%;
Radiation cross-linking (PEX-c) is carried out using a stream of charged particles. The crosslinking coefficient is about 60%.

VALTEC PEX-EVOH pipelines undergo a complete technological cycle of cross-linking using the silane method (PEX-b) on modern equipment, which ensures uniform cross-linking of polyethylene with a cross-linking degree of 68-70%.

The method of joining pipelines has virtually no effect on physical properties finished pipeline. The properties of the pipeline are mainly affected by the degree of crosslinking. As the degree of crosslinking increases, strength, heat resistance, and resistance to aggressive environments and ultraviolet rays increase. However, along with an increase in the degree of cross-linking, the fragility of the resulting pipeline increases and the flexibility decreases. If you increase the degree of crosslinking of polyethylene to 100%, then its properties will be similar to glass.

Also, crosslinking polyethylene gives the resulting pipeline a “shape memory effect.” Its essence lies in the fact that a previously deformed pipeline, after heating, restores its original shape. This property manifests itself due to the fact that during bending and deformation, molecularly bonded areas are compressed or stretched. After heating, internal stresses arise in places of deformation, due to which the original shape is restored ( rice. 1).

Fracture and shape restoration after heating to 100 °C of the VALTEC PEX-EVOH pipe (crosslinking method - PEX-b)

Fracture and restoration of shape after heating a PEX pipe to 100 °Ca with anti-diffusion layer

Fracture and restoration of shape after heating to 100 °C a PEX-c pipe without an anti-diffusion layer (uncolored cross-linked polyethylene becomes transparent at high temperatures)

Rice. 1. Restoring the shape of pipelines after deformation

On rice. 1 the restoration of pipelines with various methods of stitching after a crease is shown. With all stitching methods, the pipelines regained their original shape. Wrinkles formed on pipelines coated with an anti-diffusion layer after restoration. In these areas, the anti-diffusion layer has peeled away from the PEX layer. This defect practically does not affect the characteristics of the pipeline, since the main bearing capacity The pipeline is identified by a layer of PEX that has been completely restored. A slight peeling of the anti-diffusion layer does not significantly increase the oxygen permeability of the pipeline. A pipeline without an anti-diffusion layer becomes transparent after heating. This effect is inherent in any undyed cross-linked polyethylene.

The shape memory effect is very useful during installation. If a kink, compression or other deformation occurs during pipeline installation, it can be easily eliminated by heating the pipeline to a temperature of 100-120 °C. In addition, when connecting a PEX pipeline to a fitting, deformations also occur in the grooves of the fitting ( rice. 2). When the coolant is supplied and the pipeline is heated, restoring forces arise in these places. Due to these forces, the pipeline fits the fitting more tightly, which increases the reliability of the connection.

Rice. 2. PEX pipe connection VALTEC with press fitting

Rice. 3. Bending a PEX pipe with a diameter of 20 mm to a radius of 100 mm

The choice of the polyethylene crosslinking degree range of 68-70% for VALTEC PEX-EVOH pipelines is due to the optimal ratio of the strength characteristics of the pipeline and its flexibility. For example, a VALTEC PEX pipe can be manually room temperature bend to a radius equal to five pipe diameters ( rice. 3), and when using a pipe bender or jig - to a radius equal to three diameters. A pipeline with more than 70% stitching will have a manual bend radius of at least seven diameters. Greater bending of the pipeline with such a degree of cross-linking can only be achieved by using a construction hair dryer.

It should be noted that PEX pipelines are quite elastic and difficult to bend. After a “cold” bend, the pipe section will take its original shape. However, if you preheat the pipeline and allow it to cool in a fixed position, it will maintain this position. When the pipeline is reheated, the section will return to its original state due to the shape memory effect.

The shape memory effect should not be confused with elastic deformation. In the first case, the original shape is assumed only after heating, and in the second, immediately after removing the deforming forces and only within the limits of elastic deformation (without kinks).

PEX-EVOH pipelines from VALEC can be embedded in building construction both with and without casing. When PEX-EVOH pipes are embedded in a casing, it is possible to replace small sections of pipelines without opening the floor.

The thickness of the pipeline wall directly affects maximum pressure coolant that the pipeline can withstand. VALTEC PEX-EVOH pipes are manufactured with the same wall thickness as that of metal-polymer pipelines - 16 x 2.0, 20 x 2.0 mm. This allows you to use standard press fittings produced for metal-polymer pipelines for pipeline installation.

The disadvantage of PEX material is that it is oxygen permeable. Water in pipelines without oxygen protection becomes saturated with oxygen after a certain time, which can lead to corrosion of system elements. PEX is used to reduce oxygen permeability thin layer made of polyvinylethylene (EVOH). The PEX base layer and the EVOH layer are joined together with glue. It is worth noting that the EVOH layer does not completely prevent oxygen emission, but only reduces oxygen permeability to 0.05-0.1 g/m3 day, which is acceptable for heating systems.

In the VALTEC PEX-EVOH pipe, the anti-diffusion layer is made on the outside, i.e. the pipe has three-layer construction: PEX-glue-EVOH. Five-layer (PEX-glue-EVOH-glue-PEX) pipes are also available on the market (rice. 4).

Rice. 4. Design of five- and three-layerPEX- pipes with an anti-diffusion layer

This design is designed to eliminate the possibility of damage to the EVOH layer. However, tests have shown that a three-layer pipe (with a layer of EVOH applied on the outside) is more reliable than a five-layer pipe. The increased strength of a three-layer pipe is due to the fact that the PEX layer is monolithic over the entire cross-section of the pipe, in contrast to a five-layer pipe, in which the working layer of PEX is interrupted by a layer of EVOH and glue, due to which the internal transverse intermolecular bonds of polyethylene are interrupted. Also, with this design, delamination of the pipe is possible if it overheats. construction hairdryer during bending.

The belief that the outer layer of EVOH in a three-layer construction is susceptible to abrasion is erroneous. The hardness of the EVOH layer is significantly higher than that of the PEX layer, so if properly transported, damage to the outer layer is unlikely.

Pipelines made of cross-linked polyethylene are recommended for use when installing low-temperature heating systems. The use of PEX piping for high temperature heating systems is not prohibited. But here it should be noted that in this case the permissible maximum pressure of the pipeline will be much lower than the rated pressure. In addition, the estimated service life of the pipeline in such a system will be reduced.

Pipeline manufacturers generally set the maximum operating temperature and pressure based on the pipeline's service life of 50 years. When embedding and hidden installation, replacement of these pipelines can be done together with major repairs buildings or premises. More frequent replacement of embedded pipelines will entail large financial costs for alteration of building structures.

But the temperature of the coolant during system operation is different. In summer and during the transition period, the coolant temperature is lower than the calculated one. To assess the applicability of pipelines to a specific temperature conditions in conditions of changing coolant temperature, standards define operating classes. These classes show the shares of the influence of various temperatures from a total of fifty summer term operation.

On rice. 5 a graph is presented showing the duration of the influence of various temperatures on the pipeline during the fourth class of operation (low-temperature radiator heating)

Rice. 5

Therefore, when determining the type of pipeline, one should be guided by the permissible class of operation of a given pipeline, indicated in the pipe passport. PEX pipelines presented on the Russian market are suitable for service classes 1, 2, 3, 4 and ХВ.

Thus, due to its reliability and low cost, pipelines made of cross-linked polyethylene have become increasingly used in the construction of low-temperature heating systems and water supply systems.

Dear readers! Since the publication of this article in the assortment of our company, the practice of using equipment, regulatory documents changes may have occurred. The information offered to you is useful, but is for informational purposes only.

Today, the share of low-temperature heating systems in Russian construction is growing. Modern boilers and heating devices are capable of fully heating rooms with a coolant temperature of up to 80 °C. In addition, underfloor heating systems have become widespread recently. The temperature and pressure of the coolant in these systems allow the use of simpler and cheaper materials. That is why there is now a great demand in the Russian market for pipelines made of cross-linked polyethylene. This type of pipeline combines reliability when used in low-temperature heating systems, ease of installation and low cost.

A cross-linked polyethylene pipeline, or PEX pipe as it is called, is an almost monolithic structure, the main material of which is molecular cross-linked polyethylene. Conventional polyethylene consists of long hydrocarbon molecules that are not connected to each other in any way and is not suitable for use as the main material for heating pipelines due to its low heat resistance. Molecular cross-linked polyethylene has cross-links between chains of hydrocarbon molecules, and therefore this material has higher strength and rigidity and, most importantly, higher resistance to temperature influences.

Cross-linking of polyethylene determines the strength and thermal characteristics of the pipeline. First of all, cross-linking makes it possible to achieve long-term resistance to high temperature and pressure (increases the limit of logarithmic-proportional relaxation). Cross-linking of polyethylene can occur in various ways and to varying degrees. There are three main industrial methods for cross-linking polyethylene:

The peroxide method (PEX-a) is a chemical method for cross-linking polyethylene and involves cross-linking with organic peroxides and hydroperoxides. The pipeline obtained using this method has a degree of cross-linking of about 75%;
the silane method (PEX-b) is also chemical. When cross-linking using this method, organosilanides are used. The minimum crosslinking coefficient by this method is limited to 65%;
Radiation cross-linking (PEX-c) is carried out using a stream of charged particles. The crosslinking coefficient is about 60%.

The method of stitching pipelines has virtually no effect on the physical properties of the finished pipeline. The properties of the pipeline are mainly affected by the degree of crosslinking. As the degree of crosslinking increases, strength, heat resistance, and resistance to aggressive environments and ultraviolet rays increase. However, along with an increase in the degree of cross-linking, the fragility of the resulting pipeline increases and the flexibility decreases. If you increase the degree of crosslinking of polyethylene to 100%, then its properties will be similar to glass.

Fracture and restoration of shape after heating to 100 °C of the VALTEC PEX-EVOH pipe (crosslinking method - PEX-b)

Fracture and restoration of shape after heating a PEX pipe to 100 °Ca with anti-diffusion layer

Fracture and restoration of shape after heating to 100 °C a PEX-c pipe without an anti-diffusion layer (uncolored cross-linked polyethylene becomes transparent at high temperatures)

Rice. 1. Restoring the shape of pipelines after deformation

On rice. 1 the restoration of pipelines with various methods of stitching after a crease is shown. With all stitching methods, the pipelines regained their original shape. Wrinkles formed on pipelines coated with an anti-diffusion layer after restoration. In these areas, the anti-diffusion layer has peeled away from the PEX layer. This defect has virtually no effect on the characteristics of the pipeline, since the main load-bearing capacity of the pipeline is determined by the PEX layer, which has been completely restored. A slight peeling of the anti-diffusion layer does not significantly increase the oxygen permeability of the pipeline. A pipeline without an anti-diffusion layer becomes transparent after heating. This effect is inherent in any undyed cross-linked polyethylene.

The shape memory effect is very useful during installation. If a kink, compression or other deformation occurs during pipeline installation, it can be easily eliminated by heating the pipeline to a temperature of 100–120 °C. In addition, when connecting a PEX pipeline to a fitting, deformations also occur in the grooves of the fitting ( rice. 2). When the coolant is supplied and the pipeline is heated, restoring forces arise in these places. Due to these forces, the pipeline fits the fitting more tightly, which increases the reliability of the connection.

Rice. 2. PEX pipe connection VALTEC with press fitting

Rice. 3. Bending a PEX pipe with a diameter of 20 mm to a radius of 100 mm

The choice of the polyethylene crosslinking degree range of 68–70% for VALTEC PEX-EVOH pipelines is due to the optimal balance between the strength characteristics of the pipeline and its flexibility. For example, a VALTEC PEX pipe can be manually bent at room temperature to a radius equal to five pipe diameters ( rice. 3), and when using a pipe bender or jig - to a radius equal to three diameters. A pipeline with more than 70% stitching will have a manual bend radius of at least seven diameters. Greater bending of the pipeline with such a degree of cross-linking can only be achieved by using a construction hair dryer.

Pipe made of cross-linked polyethylene with an outer diameter of 16 and a wall thickness of 2 mm. Designed for indoor cold and hot water supply systems, low-temperature (up to 80 ° C) heating. Operating classes according to GOST 52134-2003 - 1, 2, 3, 4, ХВ. The pipe design includes a layer of polyvinylethylene (EVOH), which prevents the diffusion of oxygen into the coolant.
Installation of PEX-EVOH polyethylene pipes is carried out using VALTEC press fittings. Estimated service life is 50 years.

The material of VALTEC PEX-EVOH polyethylene pipes is cross-linked polyethylene (PE-X). It is obtained from ordinary polyethylene high density through special processing, which ensures the formation of bulk bonds between linear polymer molecules. This gives the products thermal stability, mechanical strength, high elasticity, increased resistance to ultraviolet radiation. In addition, cross-linked polyethylene pipes are characterized by low roughness inner surface, are not subject to corrosion, do not emit harmful substances into the flow in the operating temperature range, are electrically inert, do not propagate (on the contrary, absorb) noise and vibration, and withstand freezing of liquids without destruction. The estimated service life of such products is 50 years. Polyethylene pipes VALTEC PEX-EVOH are intended for engineering systems, including for heated floors, and technological installations with operating temperature up to 80 °C (at operating pressure 6 bar). It is permissible to briefly heat the transported medium to 95 °C. The pipe design includes a layer of polyvinylethylene (EVOH), which prevents the diffusion of oxygen into the coolant. PEX-EVOH pipes are installed using VALTEC press fittings. The standard size indicates outside diameter and pipe wall thickness. Delivery form: 200 m coils.

Cross-linking of polyethylene determines the strength and thermal characteristics of the pipeline. First of all, cross-linking makes it possible to achieve long-term resistance to high temperature and pressure (increases the limit of logarithmic-proportional relaxation). Cross-linking of polyethylene can occur in various ways and to varying degrees. There are three main industrial methods for cross-linking polyethylene:

The peroxide method (PEX-a) is a chemical method for cross-linking polyethylene and involves cross-linking with organic peroxides and hydroperoxides. The pipeline obtained using this method has a degree of cross-linking of about 75%;
the silane method (PEX-b) is also chemical. When cross-linking using this method, organosilanides are used. The minimum crosslinking coefficient by this method is limited to 65%;
Radiation cross-linking (PEX-c) is carried out using a stream of charged particles. The crosslinking coefficient is about 60%.

VALTEC PEX-EVOH pipelines undergo a complete technological cycle of cross-linking using the silane method (PEX-b) using modern equipment, which ensures uniform cross-linking of polyethylene with a degree of cross-linking of 68-70%.

Fracture and shape restoration after heating to 100 °C of the VALTEC PEX-EVOH pipe (crosslinking method - PEX-b)

Fracture and restoration of shape after heating to 100 °C a PEX-a pipe with an anti-diffusion layer

Fracture and restoration of shape after heating to 100 °C a PEX-c pipe without an anti-diffusion layer (uncolored cross-linked polyethylene becomes transparent at high temperatures)

Rice. 1. Restoring the shape of pipelines after deformation

On rice. 1 the restoration of pipelines with various methods of stitching after a crease is shown. With all stitching methods, the pipelines regained their original shape. Wrinkles formed on pipelines coated with an anti-diffusion layer after restoration. In these areas, the anti-diffusion layer has peeled away from the PEX layer. This defect has virtually no effect on the characteristics of the pipeline, since the main load-bearing capacity of the pipeline is determined by the PEX layer, which has been completely restored. A slight peeling of the anti-diffusion layer does not significantly increase the oxygen permeability of the pipeline. A pipeline without an anti-diffusion layer becomes transparent after heating. This effect is inherent in any undyed cross-linked polyethylene.

Rice. 2. Connection of VALTEC PEX pipe with press fitting

Rice. 3. Bending a PEX pipe with a diameter of 20 mm to a radius of 100 mm

The choice of the polyethylene crosslinking degree range of 68-70% for VALTEC PEX-EVOH pipelines is due to the optimal balance between the strength characteristics of the pipeline and its flexibility. For example, a VALTEC PEX pipe can be manually bent at room temperature to a radius equal to five pipe diameters ( rice. 3), and when using a pipe bender or jig - to a radius equal to three diameters. A pipeline with more than 70% stitching will have a manual bend radius of at least seven diameters. Greater bending of the pipeline with such a degree of cross-linking can only be achieved by using a construction hair dryer.

PEX-EVOH pipelines from VALEC can be embedded into building structures both with and without a casing. When PEX-EVOH pipes are embedded in a casing, it is possible to replace small sections of pipelines without opening the floor.

The thickness of the pipeline wall directly affects the maximum coolant pressure that the pipeline can withstand. VALTEC PEX-EVOH pipes are manufactured with the same wall thickness as that of metal-polymer pipelines - 16 x 2.0, 20 x 2.0 mm. This allows you to use standard press fittings produced for metal-polymer pipelines for pipeline installation.

The disadvantage of PEX material is that it is oxygen permeable. Water in pipelines without oxygen protection becomes saturated with oxygen after a certain time, which can lead to corrosion of system elements. To reduce the oxygen permeability of PEX, a thin layer of polyvinylethylene (EVOH) is used. The PEX base layer and the EVOH layer are joined together with glue. It is worth noting that the EVOH layer does not completely prevent the emission of oxygen, but only reduces oxygen permeability to a value of 0.05-0.1 g/m 3 · day, which is acceptable for heating systems.

In the VALTEC PEX-EVOH pipe, the anti-diffusion layer is made on the outside, i.e. The pipe has a three-layer structure: PEX-adhesive-EVOH. There are also five-layer (PEX-glue-EVOH-glue-PEX) pipes on the market ( rice. 4).

Rice. 4. Design of five- and three-layer PEX pipes with anti-diffusion layer

Pipeline manufacturers generally set the maximum operating temperature and pressure based on the pipeline's service life of 50 years. When grouting and hidden installation, replacement of these pipelines can be done in conjunction with a major overhaul of the building or premises. More frequent replacement of embedded pipelines will entail large financial costs for alteration of building structures.

But the temperature of the coolant during system operation is different. In summer and during the transition period, the coolant temperature is lower than the calculated one. To assess the applicability of pipelines to a certain temperature regime under conditions of changing coolant temperature, standards define operating classes. These classes show the proportion of the influence of various temperatures from the entire fifty-year service life.