evoh anti-diffusion layer. VALTEC, VALTEC polymer pipe PEX-b, with anti-diffusion layer EVOH, 16 (2.0). Specifications of SP Slide PEX-EVOH pipe

18.10.2019

SP Slide XLPE pipes with a PEX-b/EVOH barrier layer are designed for use in radiator heating, plumbing and underfloor heating systems.

SP Slide pipes made of cross-linked polyethylene are produced at the Metzerplas plant (Israel).

SP Slide XLPE pipes with a PEX-b/EVOH barrier layer offer a number of advantages.

The EVOH barrier layer prevents oxygen from entering the piping system. Heating and water supply elements are not subject to corrosion. The inner layer of pipes is resistant to abrasion. The ideally smooth inner surface of the wall does not contribute to the deposition of hardness salts, scale, scale, etc.

SP Slide pipes made of cross-linked PEX-EVOH polyethylene are environmentally friendly in use, due to the absence of toxic and physiologically harmful emissions.

Also, SP Slide pipes made of PEX-EVOH cross-linked polyethylene are quieter in use, unlike metal ones.

The SP Slide PEX-EVOH pipe consists of three layers: cross-linked polyethylene, an outer anti-diffusion layer and an adhesive composition connecting them.

The structure of polyethylene is not homogeneous. It contains amorphous and "crystalline" zones. Crosslinking occurs most effectively in amorphous zones, starting from a temperature of +125°C.

Crosslinking also occurs in "crystalline" zones. When cooling, the cross-linking process continues in the finished pipes in air and accelerates in hot water. The minimum percentage of cross-linked molecules (crosslink) set by the PEX-B pipe standard is 65%.

Pipes with a small percentage of crosslinking (less than 60%) are not recommended for installation in radiator heating systems.

Specifications of SP Slide PEX-EVOH pipe

Outer diameter - 20 mm
Wall thickness - 2.0 mm
Bay length - 100/200 m
Scope - water heated floor
Service life - up to 50 years
Operating temperature maximum - 95 ° C
Working pressure - 10 bar
Oxygen diffusion per day - 0 mg/m3
Emergency mode temperature, (max 1 hour) - 100 о С
The degree of cross-linking - 65-85%
Thermal conductivity coefficient - 1.2-1.4x10 -4 W / m * K
Linear elongation at a temperature of 95 ° C - 3% per 1m
Thermal conductivity coefficient - 0.32 W / m * s
Volume 1 p.m. pipes - 0.201 l

Select Valtec 20 (2.0)

Price: 0 65 65 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 PIPES

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

Cross-linked polyethylene pipeline, or, as it is called, PEX-pipe, is an almost monolithic structure, the main material of which is molecularly cross-linked polyethylene. Ordinary polyethylene consists of long hydrocarbon molecules that are not connected to each other in any way and are not suitable for use as the main material for heating pipelines due to low thermal stability. Molecularly 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 effects.

Speaking of metal polymer pipes piping, then this term is currently accepted as a fairly extensive 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 polymer layers. 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 of 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 barrier layers.

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

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

Pipelines VALTEC PEX-EVOH pass hollow technological cycle cross-linking by the silane method (PEX-b) on modern equipment, due to which uniform cross-linking of polyethylene with a cross-linking degree of 68-70% is ensured.

The method of sewing pipelines practically does not affect physical properties finished pipeline. The properties of the pipeline are mainly affected by the degree of crosslinking. With an increase in the degree of crosslinking, strength, heat resistance, resistance to aggressive media and ultraviolet rays increase. However, along with an increase in the degree of crosslinking, the brittleness increases and the flexibility of the resulting pipeline decreases. If you bring the degree of crosslinking of polyethylene to 100%, then in its properties it will be similar to glass.

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

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

Fracture and restoration of shape after heating up to 100 ° C pipes made of PEX-a with anti-diffusion layer

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

Rice. 1. Restoring the shape of pipelines after deformation

On the rice. one the restoration of pipelines with various methods of stitching after a break is shown. With all methods of stitching, the pipelines restored their original shape. On pipelines coated with an anti-diffusion layer, folds formed after restoration. In these places, the anti-diffusion layer has delaminated from the PEX layer. This defect practically does not affect the characteristics of the pipeline, since the main bearing capacity of the pipeline is determined by the PEX layer, which has completely recovered. Slight delamination of the anti-diffusion layer slightly increases the oxygen permeability of the pipeline. A pipeline without an anti-diffusion layer becomes transparent after heating. This effect is inherent in any uncolored cross-linked polyethylene.

The shape memory effect is very useful in editing. If during the installation of the pipeline a fracture, squeezing or other deformation is formed, then it is 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 efforts, 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 range of polyethylene crosslinking degree 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 conductor - to a radius equal to three diameters. A pipeline with more than 70% crosslinking will have a manual bend radius of at least seven diameters. Greater bending of the pipeline with such a degree of crosslinking can only be achieved using a building hair dryer.

It should be noted that PEX pipelines are quite elastic and difficult to bend. After a "cold" bend, the pipe segment will take its original shape. However, if the pipeline is preheated and allowed to cool in a fixed position, it will retain this position. When the pipeline is reheated, the segment 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 initial form is taken only after heating, and in the second, immediately after the removal of the deforming forces and only within the limits of elastic deformation (without kinks).

VALEC PEX-EVOH pipelines can be embedded in building construction both with and without casing. When embedding PEX-EVOH pipes 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 metal-polymer pipelines - 16 x 2.0, 20 x 2.0 mm. This allows the use of standard press fittings for pipeline installation, which are produced for metal-polymer pipelines.

The disadvantage of PEX material is that it is oxygen permeable. Water in pipelines without protection from oxygen becomes saturated with oxygen after a certain time, which can lead to corrosion of the 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 glued together. It should be noted that the EVOH layer does not completely prevent oxygen emission, but only reduces oxygen permeability to a value of 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 a three-layer structure: PEX-adhesive-EVOH. There are also five-layer (PEX-adhesive-EVOH-adhesive-PEX) pipes on the market (rice. 4).

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

This design is designed to prevent damage to the EVOH layer. However, tests have shown that a three-layer pipe (with an EVOH layer on the outside) is more reliable than a five-layer one. The increased strength of the 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 the five-layer pipe, in which the working PEX layer is interrupted by the EVOH layer and glue, which breaks the internal cross-linking intermolecular polyethylene bonds. Also, with this design, it is possible to bundle the pipe when it is overheated by a building hair dryer during bending.

The notion that the outer layer of EVOH in a three-layer construction is subject to abrasion is erroneous. The hardness of the EVOH layer is significantly higher than that of the PEX layer, so damage to the outer layer is unlikely if handled correctly.

Pipelines made of cross-linked polyethylene are recommended for use in the construction of 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 passport one. 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 service life of the pipeline - 50 years. With monolithic and hidden laying, the replacement of these pipelines can be carried out together with the overhaul of the building or premises. More frequent replacement of monolithic pipelines will entail large financial costs for the alteration of building structures.

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

On the rice. 5 a graph is presented showing the duration of the influence of various temperatures on the pipeline in 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 operating class of this pipeline, indicated in the pipe passport. PEX pipelines on the Russian market are suitable for service classes 1, 2, 3, 4 and XB.

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

Dear readers! Since the publication of this article, changes may have occurred in the assortment of our company, the practice of using equipment, and regulatory documents. 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 able to fully heat rooms with a coolant temperature of up to 80 ° C. In addition, floor heating systems have become widespread in recent years. The temperature and pressure of the coolant in these systems allow the use of simpler and cheaper materials. That is why in the Russian market there is now a great demand 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, as it is called, PEX-pipe, is an almost monolithic structure, the main material of which is molecularly cross-linked polyethylene. Ordinary polyethylene consists of long hydrocarbon molecules that are not connected to each other in any way and are not suitable for use as the main material for heating pipelines due to low thermal stability. Molecularly 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 effects.

If we talk about metal-polymer pipelines, then under this term today a fairly extensive class of polymer pipelines is accepted, 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 polymer layers. 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 of increased temperature resistance (PE-RT), polypropylene (PP-R), etc.

Polyethylene crosslinking 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 logarithmically proportional relaxation). Crosslinking of polyethylene can occur in various ways and to varying degrees. There are three main industrial methods for crosslinking polyethylene:

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

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

The method of sewing pipelines practically does not affect the physical properties of the finished pipeline. The properties of the pipeline are mainly affected by the degree of crosslinking. With an increase in the degree of crosslinking, strength, heat resistance, resistance to aggressive media and ultraviolet rays increase. However, along with an increase in the degree of crosslinking, the brittleness increases and the flexibility of the resulting pipeline decreases. If you bring the degree of crosslinking of polyethylene to 100%, then in its properties it will be similar to glass.

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

Fracture and restoration of shape after heating up to 100 ° C pipes made of PEX-a with anti-diffusion layer

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

Rice. 1. Restoring the shape of pipelines after deformation

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 cross-link 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 bent at room temperature to a radius equal to five pipe diameters ( rice. 3), and when using a pipe bender or conductor - to a radius equal to three diameters. A pipeline with more than 70% crosslinking will have a manual bend radius of at least seven diameters. Greater bending of the pipeline with such a degree of crosslinking can only be achieved using a building hair dryer.

Today, there are many solutions for heating systems on the market, however, when choosing, it is not always possible to determine which technical characteristics are decisive and what you need to pay attention to in the first place.

In order for the system to work for a long time and without interruption, one should carefully study not only its components, but also the material from which they are made. The metal components of heating systems (steel radiators, sections of steel lines, etc.) tend to wear out quickly, which can be prevented by the oxygen barrier of the pipes in the system.

Having installed a heating system, the buyer expects that it will last 10, 20, 30 years. But after some time, rust usually forms on its elements, which leads to damage, heat loss and, as a result, disruption of the entire system. The process of corrosion formation is based on chemical reaction oxidation: the steel that makes up the components of the system corrodes due to constant contact with oxygen dissolved in water. To prevent such contact, and therefore premature wear of the systems, a barrier in the heat transfer pipe is needed to provide maximum oxygen tightness.

Often, to prevent the diffusion of oxygen into the coolant, the pipes are reinforced with fiberglass. However, fiberglass is not able to provide high oxygen impermeability, which has been confirmed by numerous tests. According to the requirements of SP 60.13330.2012 "Heating, ventilation and air conditioning", the oxygen permeability of heating systems made of polymer pipes should be no more than 0.1 g / (m3 / day). The anti-diffusion layer EVOH (a copolymer of ethylene and vinyl alcohol) allows to minimize the contact of the coolant and oxygen. It is he who will allow the pipes to last much longer, save them appearance and ensure the smooth operation of the entire system.

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

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

EVOH

EVOH

Product quality occupies an 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 industry for the creation of film material, various types of packaging are being developed that satisfy the most tricky requests of manufacturers. This is possible by combining multiple sequences and layers of film material.

A big breakthrough in technology various kinds packaging with excellent barrier properties is the application EVOH. This material has unique qualities due to its chemical structure: a combination of polyethylene (PE) and polyvinyl alcohol (PVA). At the same time, alcohol is responsible for the barrier properties of the finished material, and polyethylene makes it amenable to heat treatment. Because alcohol polymers are susceptible to negative impact moisture, then polyolefins are attached 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, by its properties, allows not only to replace such expensive materials as metal foil, tin, glass, but also has whole line the following benefits:

almost no weight;
does not beat;
has a high degree of transparency;
allows heating in the microwave;
has flexible properties (restores shape after deformation);
allows you to give the package a presentable, original and unique look due to the susceptibility to the application of holography and all kinds of printing images;
cannot be corroded.