Elastomeric radio-absorbing material for protection against electromagnetic radiation of radio frequency range

Abstract

FIELD: radio-absorbing materials.SUBSTANCE: elastomeric radio-absorbing material for protection against electromagnetic radiation of the radio frequency range includes the following components, in wt.%: butadiene-styrene rubber 19-20; electrically conductive carbon black UM-76 45-47; mineral oil 23-25; ethylene vinyl acetate 3-4; unexpanded polymer microspheres 4-4.5%; sulfur 0.92-0.97; thiuram D 0.92-0.97; zinc white 0.83-0.87.EFFECT: creation of an elastomeric radio-absorbing material of the lowest possible density with improved radio-absorbing properties in the radio frequency range of 0.8-14 GHz, high physical and mechanical characteristics (elasticity and strength) and increased manufacturability in production.1 cl, 2 tbl

Description

[0001] The invention relates to the field of radio-absorbing materials, namely to elastomeric radio-absorbing composite materials for ensuring the protection of technical equipment, buildings, and premises from the harmful effects of electromagnetic fields in the radio frequency range, aimed at minimizing the impact of electromagnetic radiation on personnel in various industries and services.

[0002] Radio absorbing materials (RAM) based on a polymer binder, which serves as a matrix for the uniform distribution of radio-absorbing fillers within the material, are widely known. Most commonly used radio-absorbing fillers are electrically conductive (technical carbon, graphite, metal particles, carbon fiber) and magnetic (carbonyl iron, ferrites, magnetite, etc.) fillers.

[0003] The most widely used matrices for radio-absorbing materials are epoxy resin, polyurethane, silicone rubber, PVC plastisols, etc.

[0004] Currently, along with other requirements, radar absorbing materials also have to be lightweight, have a high degree of strength, elasticity and flexibility to protect curved surfaces with reduced material density.

[0005] A known RPM is based on polyurethane foam containing carbon black as a radio-absorbing filler [1]. This material has an uncertain reflection coefficient and low strength.

[0006] A known RPM is based on an epoxy compound containing granulated carbon black as a radio-absorbing filler [2]. The disadvantages of the material are low elasticity and rigidity.

[0007] A known RPM is based on ethylene-propylene rubber, containing a functional filler – a mixture of UFM-4HD carbon fiber and metal scale [3]. This material has a number of important qualities: it has radio-absorbing properties in the ultra-high-frequency (UHF) range, is self-adhesive, and is easy to install. Disadvantages of this known solution include poor physical and mechanical properties (strength, elasticity) and unstable radio-absorbing properties.

[0008] A known radio-absorbing material (RAM) is based on polyaluminochromophosphate and an electromagnetic radiation-absorbing filler, including hollow glass microspheres, carbon black (grade P366E), and dispersed carbon fiber [4]. The material absorbs electromagnetic radiation over a wide frequency range from 6 to 40 GHz; however, its disadvantages include low elasticity and rigidity. This limits the use of this radio-absorbing material in products and objects requiring increased elastic properties.

[0009] The closest to the proposed radio-absorbing material is a radio-absorbing material for protection against electromagnetic radiation, including butadiene-styrene oil-filled rubber grade SKS-30ARKM15, electrically conductive carbon black UM-76 TU 20.13.21-002-94724566-2022, sevilen grade 11808-340, mineral oil, sulfur, thiuram D, stearic acid, zinc white [5].

[0010] The disadvantages of this radio-absorbing material are its high density, which increases the weight of finished products and limits its use in the manufacture of protective clothing, as well as insufficient elasticity and radio-absorbing properties in the frequency range of 0.8-14 GHz.

[0011] The technical objective of the invention is to develop a lightweight elastomeric radio-absorbing material that has a lower density compared to the prototype, providing higher radio-absorbing properties in the frequency range of 0.8-14 GHz, as well as higher physical and mechanical properties (elasticity and strength).

[0012] The technical result of the invention is the production of an elastomeric radio-absorbing material of reduced density with increased radio-absorbing properties in the radio frequency range of 0.8-14 GHz, increased elasticity and strength, as well as improved manufacturability in production.

[0013] The said technical result is achieved due to the fact that the elastomeric radio-absorbing material for protection against electromagnetic radiation of the radio frequency range, including butadiene-styrene rubber as a polymer base, mineral oil as a plasticizer, sulfur as a vulcanizing agent, thiuram D as a vulcanization accelerator, zinc white as a vulcanization activator, sevilen as a technological additive, a functional filler, electrically conductive carbon black UM-76, according to the invention the material additionally contains a technological foaming additive in the form of polymer non-expanded microspheres in the following ratio of components, mass %:

[0014] Styrene butadiene rubber 19-20 Carbon black conductive UM-76 45-47 Mineral oil 23-25 Sevilen 3-4 Unexpanded polymer microspheres 4-4,5 Sulfur 0,92-0,97 Thiuram D 0,92-0,97 Zinc white 0,83-0,87

[0015] Introducing ingredients above or below the specified range will result in deterioration of the performance of the radar absorbing material.

[0016] The radar absorbing material was obtained using styrene-butadiene rubber of the SKS-30ARKM15 grade GOST 11138-2019 as a polymer base. The choice of rubber was due to its dielectric properties, good processability, high physical and mechanical properties of rubbers based on it, and the availability of rubber compared to other synthetic rubbers. High elasticity and strength of the proposed material is ensured by the introduction of a vulcanizing group into the composition of the radar absorbing material in the form of sulfur GOST 127.4-93 as a vulcanizing agent, thiuram D GOST 740-76 as a vulcanization accelerator, zinc white GOST 202-84 as vulcanization activators; mineral oil grade I-20A GOST 20799-2022 as a plasticizer and Sevilen grade 11808-340 TU 20.16.10-211-00203335-2017 as a technological additive.

[0017] The UM-76 carbon black conductive grade TU 20.13.21-002-94724566-2022 was used as a functional filler. The distinctive features of UM-76 carbon black are: high particle dispersion (average particle size 24.7 nm) and high surface area (290 ± 30 m 2 / g), which contribute to the formation of a developed conductive spatial structure and the achievement of enhanced radio-absorbing properties. Unexpanded polymer microspheres DU175 according to the manufacturer's specification Crerax Science and Technology Co. were used as a foaming technological additive to reduce the density. Distinctive properties of the microspheres are the particle size in the unexpanded state (18-25 μm), the true density after expansion (less than 15 kg / m 3), which helps reduce the overall weight of the composite material after vulcanization, while the polymer base of the microspheres increases elasticity and processability. The microspheres expand during vulcanization of the elastomer material at 140°C for 3 minutes, and the formation of micropores during expansion contributes to the material's heterogeneous structure, resulting in increased radar absorption properties.

[0018] The combined use of available ingredients in an optimal quantitative ratio allows for the desired technical result to be achieved: an elastomeric radio-absorbing material with reduced density, improved radio-absorbing properties in the radio frequency range of 0.8-14 GHz, enhanced physical and mechanical properties, and improved manufacturing processability.

[0019] The applicant's analysis of the prior art revealed that there are no existing analogues characterized by sets of features identical to all the features of the claimed radar-absorbing material. Consequently, the claimed technical solution meets the patentability requirement of "novelty."

[0020] A study of other technical solutions in this field reveals that technical conductive carbon is used as a functional filler in specific ratios with a polymer binder based on styrene-butadiene rubber. To enhance the materials' radio-absorbing properties, up to 50% of technical carbon is added to their composition. Moreover, the density of the material with a high content of functional filler is quite high. The introduction of non-expanded polymer microspheres allows for a reduction in the material's density. The claimed combination of essential features exhibits new properties that enable a change in the quantitative measure of the technical result, namely, a reduction in the density of the radio-absorbing material compared to the known prototype while simultaneously increasing the absorption coefficient of electromagnetic radiation in the frequency range of 0.8-14 GHz and its physical and mechanical properties.This significantly expands the scope of application of the new material and allows us to conclude that the invention meets the patentability requirement of “inventive step”.

[0021] When electromagnetic radiation of the radio frequency range interacts with the proposed radio-absorbing material, absorption of radiation occurs as a result of its conversion into thermal energy due to dielectric losses and conductivity losses, and scattering of radiation due to the structural heterogeneity of the material.

[0022] All components included in the radio-absorbing material are products produced in industrial volumes.

[0023] The production and processing of compositions are carried out on standard equipment and do not cause any difficulties.

[0024] The compound is manufactured in a rubber mixer by mechanically mixing all components and formed into sheets half the specified size using roller or extrusion equipment. Vulcanization of the elastomer material is carried out in molds using a hydraulic vulcanization press at a mold pressure of 15 MPa and a temperature of 140°C for 3 minutes. A foaming additive doubles the thickness of the finished product to the required size, thereby reducing the consumption of the starting material.

[0025] Taking into account the above, the invention meets the patentability requirement of “industrial applicability”.

[0026] Measurements of the physical and mechanical properties of the radar-absorbing material were conducted using standard methods for polymer composite materials. Tensile strength and elongation at break were determined according to GOST 270-75 "Rubber. Method for Determining Tensile Elastic Strength Properties."

[0027] Measurements of the electromagnetic radiation attenuation parameters of the radio-absorbing material were carried out in the frequency range from 0.8 GHz to 14 GHz on 2 mm samples using a test bench including PKh-0860 and PKh-1015 electromagnetic radiation sources, an Arinst SSATG R3 spectrum analyzer, and a P3-34 electromagnetic field meter. The efficiency of electromagnetic radiation attenuation by the radio-absorbing material was determined by the radiation absorption coefficient (dB).

[0028] The compositions of the radio-absorbing material are given in Table 1.

[0029] Table 1

[0030] Elastomeric radio-absorbing material

[0031] Item No. Components Composition of the material composition, mass% 1 2 3 4 5 Prototype 1 Styrene butadiene rubber 22 21 20 19 18 22 2 Conductive soot UM-76 40 43 45 47 50 45 3 Unexpanded polymer microspheres 3 3,5 4 4,5 5 - 4 Sevilen 2 3 3 4 5 3 5 Mineral oil 29,81 26,54 25,19 22,83 19,45 26,48 6 Stearic acid - - - - - 0,33 7 Sulfur 1,1 1,02 0,97 0,92 0,88 1,1 8 Thiuram D 1,1 1,02 0,97 0,92 0,88 1,1 9 Zinc white 0,99 0,92 0,87 0,83 0,79 0,99

[0032] Technical characteristics of the radio-absorbing material are given in Table 2.

[0033] Table 2

[0034] Item No. Characteristics Compositions of the material composition 1 2 3 4 5 Prototype 1 Absorption coefficient in a thickness of 2 mm, dB, at a frequency of 0.8-6 GHz 8-14 GHz 12 15 13 20 16 23 15 22 12 19 14 22 2 Tensile strength, MPa 3,3 3,5 3,8 3,5 3,2 3,3 3 Relative elongation at break, % 150 155 175 160 135 160 4 Density, g / cm3 0,8 0,8 0,6 0,55 0,5 1,23 5 Weight of 1 m2, kg 1,6 1,6 1,2 1,1 1,0 2,46

[0035] The radio-absorbing material specified in Examples 3 and 4 has optimal radio-absorbing and physical-mechanical characteristics. As can be seen from the data provided in Table 2, the proposed elastomeric radio-absorbing material has a number of advantages in comparison with the prototype:

[0036] - reduced material density (not more than 0.6 g / cm 3 ) and, accordingly, the mass of 1 m3 reduced by 50%. 2 finished products, which significantly increases the technical and economic efficiency of finished product production;

[0037] - reduced amount of source material to achieve the specified thickness after vulcanization, due to the foaming additive (non-expanded polymer microspheres), which saves component consumption and optimizes production costs;

[0038] - an unexpected result is an increase in the absorption coefficient of electromagnetic radiation in the radio frequency range of 0.8-14 GHz (up to 23 dB) and an improvement in the physical and mechanical properties of relative elongation at break (175%) and tensile strength (3.8 MPa).

[0039] The proposed elastomeric radar-absorbing material was tested under industrial conditions. Tests confirmed the expected properties and improved manufacturing processability of the finished product by reducing the vulcanization temperature and shortening the vulcanization time, which saves energy consumption and optimizes production costs.

[0040] By reducing the density and mass per square meter, the scope of application of the radio-absorbing material with microspheres is expanded, and it becomes possible to use the material for the production of protective clothing with improved radio-absorbing properties and physical and mechanical properties inherent in the prototype.

[0041] The listed features distinguish the proposed technical solution from the prototype and determine the compliance of this solution with the requirements of the invention.

[0042] Literature

[0043] 1. Patent RU No. 2275719 dated 09 / 06 / 2004.

[0044] 2. Patent RU No. 2417491 dated 04 / 26 / 2010.

[0045] 3. Patent RU No. 2798073 dated November 21, 2022.

[0046] 4. Patent RU No. 2762691 dated 04 / 05 / 2021.

[0047] 5. Patent RU No. 2846079 dated March 17, 2025.

Claims

An elastomeric radio-absorbing material for protection against electromagnetic radiation of the radio frequency range, including butadiene-styrene rubber as a polymer base, mineral oil as a plasticizer, sulfur as a vulcanizing agent, thiuram D as a vulcanization accelerator, zinc white as a vulcanization activator, sevilen as a technological additive, a functional filler, electrically conductive carbon black UM-76, characterized in that the material additionally contains a technological foaming additive in the form of polymer non-expanded microspheres in the following ratio of components, wt.%: Styrene butadiene rubber 19-20 Carbon black conductive UM-76 45-47 Mineral oil 23-25 Sevilen 3-4 Unexpanded polymer microspheres 4-4,5 Sulfur 0,92-0,97 Thiuram D 0,92-0,97 Zinc white 0,83-0,87