RU2474628C2 - Layered protective material - Google Patents

Abstract

FIELD: textiles, paper.

SUBSTANCE: fibrous absorber of electromagnetic radiation comprises two inner layers of a mixture of dielectric and electrically conducting carbon fibers which are mechanically fastened to each other by needling. Manufacturing of the absorber is carried out from the mixture of dielectric and electrically conducting carbon fibers, in which carbon fiber is used as electrically conducting carbon fibers. Carbon fiber is used with specific insulation resistance from 1.5·10^-3 to 1.0 Ohm cm, and the deviation from the average value of content of carbon fiber in 1 g of the mixture does not exceed 5% by weight. The absorber additionally comprises two outer layers of rubberised fabric. The absorber has the structure of the inner layers of a mixture of dielectric and electrically conducting carbon fibers fixed by piercing with needles with a density of piercing from above of 5÷20 cm^-2, from below of 20÷100 cm^-2. The absorber layers are made of rubberised fabric, on the edges they are tightly stuck to each other or connected by double-faced adhesive tape.

EFFECT: improving hygienic indicators of garments with volumetric unconnected heat retainers, change in thickness of adequately to change in conditions of the ambient environment, and reduction of specific consumption of valuable heat retainer to obtain the specified thermal insulation properties.

3 cl, 2 dwg, 1 tbl, 3 ex

Description

Technical field

The proposal relates to multilayer fibrous materials from various synthetic fibers, intended for the manufacture of absorbers of electromagnetic radiation and thermal insulation. Material and products from it can be used for:

- screening of premises in order to counter technical reconnaissance equipment;

- ensuring electromagnetic compatibility of radio devices;

- reduction in the microwave range of wavelengths of electromagnetic radiation of the reflected signal from various objects;

- reducing the thermal contrast of various objects in the infrared wavelength range of electromagnetic radiation;

- thermal insulation of individual components and assemblies of equipment.

State of the art

Known laminated materials with a metallized surface ("F1 TECH. Jnt. Eguip. Guide Eneergency Serv.", Tunbridge Weels, 1980, 65) and a material with a metallized surface based on viscose fabric for the manufacture of heat-protective clothing ("Close proximity fire suit". Fire Prot, 1982, T.45, No. 536, 21). The metallized surface of the materials is formed by a thin aluminum foil. The materials provide human protection in a certain temperature-time range, however, the protective action time of these materials and their clothes due to rapid heating in the high temperature zone is not enough to carry out fire-fighting operations.

Known laminated material for heat-insulating clothing, consisting of a lower lining fibrous layer made of cotton fabric, an average heat-insulating fibrous layer made of wool felt or batting, and metallized outside an external heat-reflecting fibrous woven layer based on glass fibers (TU 17-08-289 -89). The outer layer of this material is made of ordinary (not hollow) glass fibers. Such a material provides a protective action time of heat-protective clothing made from it at an ambient temperature of + 200 ° C of 3–4 minutes. Such a time of protective action is insufficient to extinguish fires and conduct rescue operations at a number of facilities.

To increase the time of the protective action of clothing without increasing its mass, the material for heat-protective clothing should have high reflectivity, low thermal conductivity, minimal air permeability, high thermal resistance and high heat capacity. The specified technical result is achieved in the material (according to patent application No. 94036696/12, IPC ⁷ A41D 31/00, publ. 06/20/1996), consisting of a lower lining fibrous layer made of cotton fabric, the middle thermal insulation layer of wool felt or batting and metallized on the outside of the external heat-reflective layer of fabric based on hollow glass fibers, 20-40% filled with air. This percentage of filling with air is sufficient to significantly increase the time of the protective effect of the proposed material and the optimal combination of stability properties and manufacturability of the manufacture of hollow fibers. The implementation of the outer layer of hollow fibers in combination with the other specified layers of the proposed material, consisting of monolithic fibers, allows to achieve the optimal combination of its protective properties of low thermal conductivity, high total thermal resistance and high heat capacity. The use of hollow fibers for the manufacture of all fibrous layers leads to a significant decrease in heat capacity and thermal resistance of the material and, as a consequence, to reduce the time of the protective action.

Known layered material for heat-protective clothing, which contains the main layer of low-permeability fabric with air permeability up to 50 l / m ² s, the heat-saving layer is made of synthetic or natural bulk insulation and a gas-permeable lining with air permeability from 50 to 400 l / m ² s. The material provides the microclimate necessary to maintain a comfortable thermal regime of a person (RF patent No. 2129815, IPC ⁶ A41D 13/00, publ. 05/10/1999).

Known layered material, which consists of two non-woven outer layers and the inner frame layer, including homogeneous fibers, and the layers are interconnected by needle piercing (the number of punctures is 120 ÷ 500 per 1 cm ² ). As the skeleton layer, continuous viscose yarns with a linear density of 192 or 380 tex, with a strength of 600-800 cN / tex, laid parallel to each other along non-woven outer layers of viscose stapled fibers with a stapling length of at least 18 mm, are used, the ratio of surface non-woven outer layers and the inner frame layer is (15.5 ÷ 47.0) :( 1 ÷ 4) :( 15.5 ÷ 47.0). The surface density of the nonwoven material is 280-852 g / m ² . The technical result of the claimed solution is to give adjustable strength to the nonwoven material in the longitudinal direction while maintaining high air permeability and improving the processability.

Closest to the claimed is a fibrous absorbent material comprising one or more layers containing synthetic fibers with the addition of from 0.5 to 15 wt.% Of the electrically conductive filler - carbon fiber, which is evenly distributed in a canvas of synthetic fiber, i.e. in a dielectric medium (RF patent 2199806, IPC D04H 1/46, H01Q 17/00, publ. 02.27.2003).

The disadvantages of the known technical solutions are low strength and weather resistance of the material, insufficient protection against heat flux in the temperature range of 40-110 ° C, which limits the use of this absorbing material as thermal masking of objects.

The essence of the proposal

The technical problem to which this invention is directed is to obtain absorbing material with high heat-shielding characteristics in the temperature range of 40-110 ° C, protected from atmospheric factors and operable in the EMP wavelength ranges: 3-14 microns and 0.4-15 cm.

The problem is solved in that the fibrous absorber of electromagnetic radiation, comprising at least two inner layers of a mixture of dielectric and electrically conductive carbon fibers, mechanically bonded to each other by needle piercing, according to the invention is made of a mixture of dielectric and electrically conductive carbon fibers, in which as conductive carbon fibers used carbon fibers having a specific volume electric resistance of 1.5 × 10 ^-3 to 1.0 ohm-cm, a deviation from cFe he values of carbon fiber content in 1 g of the mixture does not exceed 5 wt.%, the absorber further comprises two outer layers of rubberized fabric which is sealed at the edges glued to each other or connected by double-sided adhesive tape.

The inner fibrous layers from a mixture of dielectric and electrically conductive (carbon) fibers are obtained as follows. After preparation of the sample, the components of the carbon fiber are divided into pieces of 0.5 ÷ 1.0 g and laid out on a dielectric fiber. Then, coarse loosening is carried out with the control of the mass of carbon fiber shreds in the fiber mixture, achieving a reduction in their mass to 0.01 g. After that, fine loosening and combing of the mixture is carried out, fixing the structure of the canvas and duplication by pricking with needles.

The problem is solved when coarse loosening leads to a decrease in the mass of shreds of carbon fiber to 0.01 g.

To prepare a mixture of dielectric and electrically conductive (carbon) fibers, 0.5-15 wt.% Carbon fiber is used. The formation of non-woven canvas is carried out from a mixture of fibers with a surface density of 100-150 g / m ² .

The structure of the canvas is fixed and duplication is carried out simultaneously by piercing with needles with a punching density of 5-20 cm ^-2 above, 20-100 cm ^-2 from the bottom.

Puncture of duplicated canvases with needles is carried out through in the direction perpendicular to the plane of the canvas, towards each other.

Duplicate canvases are successively laid on one side of the first canvas. When applying each subsequent layer, a packet of bonded canvases is pierced to the entire thickness. A bundle of bonded fibrous canvases is placed between layers of rubberized fabric that is resistant to weathering, for example, UNKL-AS sheathing fabric (TU 2566-096-00209600) or (UNKL-T TU 2566-068-00209600).

The invention is illustrated by diagrams of the device of the material, the installation diagram for testing the thermal properties of the material and examples of the manufacture of the material.

Figure 1. Fiber absorber device: 1 - two-layer non-woven material; 2 - rubberized fabric.

The device of the absorber is associated with the method of its production. Duplicate fibrous canvases are successively laid on one side of the first canvas. When applying each subsequent layer, a packet of bonded canvases is pierced to the entire thickness. A packet of bonded fibrous canvases is placed between the layers of rubberized fabric.

Figure 2. Installation diagram for measuring brightness temperature:

3 - programmable temperature control unit BTP-78;

4 - thermal chamber TK-500;

5 - cover element;

6 - contact thermometer TK-6 with a thermocouple;

7 - computer thermograph Irtis-2000C.

The measurement of the brightness temperature when testing the heat-shielding properties of the fibrous absorber is as follows. A sample of the absorber is fixed to a heating element heated to a predetermined temperature. As a heating element, the TK-500 heat chamber is used, complete with a programmable block of the BTP-78 temperature regulator. The temperature at the interface — the back of the protective material — the heating element, is controlled by a TK-6 contact thermometer.

The values of the brightness temperature (in the wavelength range of electromagnetic radiation 3-5 microns) of the outer side of the protective material are scanned with a Irtis-2000C portable computer thermograph for a certain time.

When conducting measurements, the following requirements are met:

- temperature of the heating element 100 ° C;

- tight fit of the protective material element to the heating element.

Information confirming the possibility of carrying out the invention

Example 1. A fibrous absorber of electromagnetic radiation, comprising two inner layers of a mixture of dielectric and electrically conductive carbon fibers and two outer layers of rubberized fabric. The inner layers consist of a mixture of staple polyester and carbon fibers. The two outer layers of rubberized fabric are made of UNKL-AS brand sheathing material (TU 2566-096-00209600). A sample of an EMP fiber absorber is prepared as follows. The volumetric electrical resistivity of several samples (batches of material) of staple carbon fibers of the same composition is measured, a batch of fibers with a specified resistance value of 4.0 ± 1.2 · 10-2 Ohm · cm is selected. The components are suspended: staple polyester fiber and carbon fiber in a ratio providing a concentration of carbon fibers in the mixture of 3 wt.%, Respectively. The cut (staple) polyester fiber 0.33 tex has the following parameters: diameter 10 ÷ 15 μm and a length of 3 ÷ 3.5 cm. The cut carbon fiber of the brand "Uglen-9" is characterized by a diameter of 5 ÷ 10 μm and a length of 3 ÷ 3,5 cm.

The polyester fiber is unloaded onto the conveyor belt and the carbon fiber is manually laid out on the polyester fiber in the form of shreds weighing 0.5 ÷ 1.0 g. Coarse loosening of the mixture is carried out at a conveyor speed of 0.2 m / min with control of the mass of shreds of carbon fiber in the volume of the polyester. To control the composition of the mixture during loosening, samples are taken from 15 ÷ 20 shreds and their average weight is determined. The average weight of one shred should not be more than 0.01 g. In case of inconsistency of this parameter, coarse loosening is repeated again. The average coarse loosening time is 20 minutes.

For further separation of the fibrous masses into smaller structural elements and mixing them together, the fibers are loosened in a thin cultivator. After thin loosening, the fiber mixture is fed through the fiber duct to the drive in front of the combing unit. From the drive, the pulp enters the carding machine to separate it into individual fibers and to ensure uniform and uninterrupted supply in a disconnected state to the canvas formation stage. The degree of separation (combing) and mixing of fibers is regulated by changing the speed of rotation of the working bodies of the carding machine (replacing the removable sprockets and pulleys) and the wiring between the main and removable-itching rollers.

In the process of forming a non-woven canvas, the fibers are removed from the removable-casing shaft, transported in suspension in an air stream to the chamber of the aerodynamic attachment to form the canvas and the fibers are deposited on the breathable supporting surface in the form of a fibrous canvas (layer) with a random arrangement of fibers in the material with surface density 100 g / m ² .

The surface density is changed by adjusting the speed of the conveyor belt with constant productivity of the carding machine. After the formation of the canvas, it is duplicated and the structure of the two inner layers of the material is fixed by double-sided piercing with needles on a two-head needle-punched machine of the Okuma brand. The punching density on top is 7 cm ^-2 , on the bottom 22 cm ^-2 .

The combined fibrous layers are placed between the layers of the rubberized fabric of UNKL-T, which are then hermetically glued together along the perimeter of the layered structure.

To evaluate the absorbing properties, a sample of the material is applied to an electrically conductive surface and the reflection coefficient of electromagnetic radiation from a frequency in the range from 3.5 to 37.5 GHz is measured by a standard method. The coefficient of reflection of electromagnetic radiation from frequency in the entire range does not exceed a value equal to 0.1.

A sample of the absorber is fixed to a heating element heated to a temperature of 100 ° C. As a heating element, the TK-500 heat chamber is used, complete with a programmable block of the BTP-78 temperature regulator. The temperature at the interface — the back of the fiber absorber — the heating element, is controlled by a TK-6 contact thermometer.

The values of the brightness temperature (i.e., thermal radiation in the wavelength range of electromagnetic radiation 3-5 microns) of the outer side of the protective material are scanned with a Irtis-2000C portable computer thermograph for a certain time. The results of the determination of heat masking and heat insulating properties are shown in table 1.

Example 2. The fibrous absorber of electromagnetic radiation of example 1, but containing carbon fiber, characterized by a specific volumetric electrical resistance equal to 8.0 ± 1.5 · 10 ^-2 Ohm · cm, and a concentration in the three inner layers of 15 wt.% With a surface density 100 g / m ^{2 is} applied to an electrically conductive surface and the reflection coefficient of electromagnetic radiation from a frequency in the range from 3.5 to 37.5 GHz is measured by a standard method. The coefficient of reflection of electromagnetic radiation from frequency in the entire range does not exceed a value equal to 0.05. The results of the determination of heat masking and heat insulating properties are shown in table 1.

Example 3. The fibrous absorber of electromagnetic radiation according to example 2, but with the outer protective layers of rubberized fabric UNKL-T (TU 2566-068-00209600), which are tightly interconnected around the perimeter of a double-sided adhesive tape on a fabric base brand 3 M 30 mm wide .

The values of the brightness temperature on the outer surface of the fibrous absorber covering the heated element, and the reflection coefficient of electromagnetic radiation by them are shown in table 1.

Table 1 Values of the average brightness temperature of a sample of the external surface of the material in the wavelength range of 3-5 μm when heated from the side of the internal surface * and the reflection coefficient of electromagnetic radiation Time min External surface temperature (T _bright , ° C) Example 1 Example 2 Example 3 one 25.3 25.5 27.6 thirty 32,4 32,7 34.3 60 33.6 33.9 34.5 120 34.9 34.7 35.7 180 34.8 34.7 35.6 Electromagnetic Emissivity 0.1 0.05 0,07 * - During measurements, the temperature of the heated element is 100 ° C, the ambient temperature is 23 ° C, humidity 60%

As follows from table 1, the use of a fibrous absorber can significantly reduce the observed outside temperature luminance temperature of heated objects, while the difference in brightness temperatures on different surfaces of the fibrous absorber lasts a considerable time, and the reflection coefficient of electromagnetic radiation is quite small and amounts to 0.05 ÷ 0.1 .

Claims (3)

1. A fibrous absorber of electromagnetic radiation, comprising at least two inner layers of a mixture of dielectric and electrically conductive carbon fibers, mechanically bonded to each other by needle piercing, characterized in that it is made of a mixture of dielectric and electrically conductive carbon fibers, in which, as the electrically conductive carbon fibers carbon fiber with a specific volumetric electrical resistance of 1.5 · 10 ^-3 to 1.0 Ohm · cm is used, and the deviation from the average carbon content fiber per 1 g of the mixture does not exceed 5 wt.%, and the absorber additionally contains two outer layers of rubberized fabric. 2. The fibrous absorber of electromagnetic radiation according to claim 1, characterized in that the structure of the inner layers of a mixture of dielectric and electrically conductive carbon fibers is fixed by piercing with needles with a punching density of 5 ÷ 20 cm ^-2 above, 20 ÷ 100 cm ^-2 below. 3. The fibrous absorber of electromagnetic radiation according to any one of claims 1 or 2, characterized in that the layers of rubberized fabric at the edges are hermetically glued to each other or connected by a double-sided adhesive tape.

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