Radar absorbing material

FIELD: physics, nuclear.

SUBSTANCE: invention relates to production of radar absorbing materials which reduce the level of secondary radiation, provide electromagnetic compatibility of onboard equipment, correction of directional patterns of onboard antenna systems during prolonged operation and exposure to aggressive media. Radar absorbing material contains dielectric binder - foamed polyurethane and electroconductive filler which absorbs electromagnetic radiation. The material also contains a polyurethane based protective coating. The electroconductive filler which absorbs electromagnetic radiation used is carbon fibre taken in amount of 0.0003-0.005 vol. % or carbonised fibre taken in amount of 0.003-0.05 vol. %.

EFFECT: good radio properties, moisture resistance, resistance to aggressive media, longer use with low density of the material.

 

The invention relates to the field of radar absorbing materials (PRM)provides a decrease in the level of secondary radiation, electromagnetic compatibility onboard equipment, correction of the directional diagrams of airborne antenna systems for long term use and exposure to aggressive environments.

A known number of absorbing electromagnetic radiation of materials on the basis of magnetic particles with a protective shell particles. For example, in a polymer matrix filler is injected in the form of ferromagnetic particles (iron, carbonyl iron, iron silicides, cobalt, Nickel)coated with a silicone shell, the introduction of which provides resistance RPMS to corrosion when exposed to aggressive environments (U.S. patent No. 5866273, 6486822).

The disadvantages of the known solutions are high density RPM - 2,5-4,0 g/cm3and technically sophisticated technology of applying a protective coating on the magnetic particles of the filler, requiring special equipment.

Known radar absorbing material containing a mixture of particles of crushed foam with cuts threads as absorbing elements impregnated curing glue (U.S. patent No. 6043769).

Known radar absorbing material on the basis of complex polyimide foams with uniform density, including renominalisation it stealth components (particles of iron, ferrite, carbon) (U.S. patent No. 5135959).

The disadvantage of the above technical solutions is a low resistance to moisture and aggressive media, which leads to changes in material properties and reduction of terms of use.

The closest analogue, taken as a prototype, is a radio-absorbing material containing filler particles of carbon technical and polymeric materials - polyurethane foam in the following ratio, wt.%: polyurethane - 82,23-88,47, technical carbon - rest (RF patent No. 2275719).

The defects in the material of the prototype are low radio characteristics, low resistance to moisture and corrosive environments. In addition, the presence of carbon black leads to increased Flammability of the material.

The technical object of the present invention is to improve radio characteristics frequency range (8-13 GHz, increase resistance to moisture and corrosive environments, as well as increased life radio-absorbing material while maintaining the density level of the prototype.

For the technical solution proposed radio-absorbing material comprising the dielectric binder is a polyurethane foam and absorbing electromagnetic radiation conductive filler, while mater is al further comprises a protective coating based on polyurethane.

As the absorbing electromagnetic radiation of electrically conductive filler material contains carbon fiber in the number 0,0003÷0,005 % by volume or carburized fiber in the amount of 0.003÷0,05 %by volume.

The inventive radio-absorbing material was obtained by hot pressing in a closed mold. On lessons from the form element RPMS brush or spray applied 1-2 coats of polyurethane protective coating with a thickness of 100-200 μm.

The best technical result of the claimed invention when used as a component for obtaining polyurethane foam polyester P-2200 (TU 6-05-167-79) and polyisocyanate B-207 (TU 113-03-29-18-83), taken in the ratio 1:(0.7 to 1), and triethanolamine (TU-6-2609-48-91) and emulsifier Penta-483 (TU 2257-008-40245042-99).

Depending on the radio requirements - absorption and frequency range - select the type of filler and its quantity. As filler can be used various carbon fiber, but the most useful within the invention to use carbon fiber Chis-5000 (GOST 2603) or carburized fiber Plan (TU 1-595-19-1022-2007).

It is established that the use of protective coatings allows you to receive radio-absorbing material with high radio performance with up to 15 years and p is a better resistance to moisture and aggressive media 1.7-2.4 times, while maintaining low density RPMS. To produce a protective coating using the same components as for the binder (without emulsifier), which considerably reduces the production process, and can reduce energy and labor for its production.

Examples of implementation

Example 1

In the binder containing the polyester and polyisocyanate in the ratio of 1:1, was injected carbon fiber in the number 0,0003 %by volume, fiber length 5 mm, were mixed until a homogeneous composition was added triethanolamine, emulsifying agent and poured into a heated mold. Pressed element radio-absorbing material was covered with 1 layer of protective coating with a thickness of 100 μm brush method.

Example 2

In the binder containing the polyester and polyisocyanate in the ratio of 1:0.7 and injected carbon fiber in the amount of 0.0005 %by volume, fiber length 3 mm, were mixed until a homogeneous composition was added triethanolamine, emulsifying agent and poured into a heated mold. Pressed element was covered with 2 layers of protective coating thickness of 200 μm by spraying.

Example 3

In the binder containing the polyester and polyisocyanate in the ratio of 1:1, was introduced carburized fiber in the amount of 0.003 %by volume, fiber length 3 mm, were mixed until a homogeneous composition was added triethanolamine, emulsifying agent and poured into a heated mold. Pressed element Pokrywa and 1 layer of protective coating thickness of 200 μm brush method.

Example 4

In the binder containing the polyester and polyisocyanate in the ratio of 1:1, was introduced carburized fiber in the amount of 0.004 %by volume, fiber length of 1 mm, was mixed until a homogeneous composition was added triethanolamine, emulsifying agent and poured into a heated mold. Pressed element was covered with 1 layer of protective coating with a thickness of 150 μm.

The quantitative ratio of the components and properties of the material and the prototype are shown in tables 1 and 2.

Table 1
Name of the componentThe composition, volume %The prototype, vol %
1234
Binder100100100100100
Carburized fiber
Plan
--0.003
L=3 mm
0,004
L=1 mm
-
Carbon is the fiber Chis-5000 0,0003
L=5 mm
0,005
L=3 mm
---
Carbon----0,0001-0,005

Table 2
Name propertiesExamples according to the inventionThe placeholder
1234
The minimum ratio-15-18-16-15-5
reflection, dB, not more than
Density, g/cm30,35-0,40,35-0,40,35-,4 0,35-0,40,4
Life, years10-1510-1510-1510-155
Humidity for 10 days, %3,03,03,53,04,35
Resistance to aggressive
Wednesdays at staying within
30 days, % swelling:
fuel TS-10,360,370,350,360,76
fuel RT 0,340,340,350,340,72
mineral oil MSP0,460,50,480,461,66
synthetic oil IPM-100,360,360,380,371,75

From table 2 it is seen that the proposed material is compared with the prototype advantage over radio characteristics more than 3 times, resistance to moisture - 1.5 times, aggressive media - 2-5 times and life is 2-3 times at the same level density of the material.

The proposed radar absorbing material will reduce the level of secondary radiation, electromagnetic compatibility onboard equipment, correction of the directional diagrams of airborne antenna systems for long term use and exposure to moisture and corrosive environments while reducing energy and labor costs in its production.

Radio-absorbing material comprising the dielectric binder is a polyurethane foam and absorbing electromagnetic radiation electr the filler wire, wherein the material further comprises a protective coating based on polyurethane, and as absorbing electromagnetic radiation conductive filler it contains carbon fiber in the number 0,0003÷0,005% or carburized fiber in the amount of 0.003÷0,05%.



 

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