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Rubber magnetic composites were fabricated by incorporation of strontium ferrite in constant loading level in ethylene propylene diene monomer rubber and acrylonitrile butadiene rubber. Different curing additives based on peroxide, sulfur and combined sulfur/peroxide systems were introduced for cross-linking of rubber matrices. Both sulfur and peroxide curing systems lead to the formation of cross-links with different length and structure, which subsequently results in different properties of rubber products. Moreover, due to various bonding energies of the formed cross-links, rubber articles exhibit different propensity to degradation factors as to thermo-oxidative aging. Therefore, the work was aimed at the investigation of curing system composition and aging on cross-link density and properties of rubber magnetic composites. The achieved results point out to close correlation between cross-link density and physical-mechanical characteristics with exception of tensile strength, which showed increasing tendency with increasing amount of peroxide in combined vulcanization systems. It can be stated that no significant changes in physical-mechanical and magnetic properties were recorded during aging.

Composites based on acrylonitrile-butadiene rubber, carbon nanotubes, and manganese-zinc ferrite were fabricated and tested for electromagnetic interference (EMI) absorption shielding. First, carbon nanotubes and ferrite were solely used for the preparation of rubber composites. Then, carbon nanotubes were combined with magnetic filler and incorporated into the rubber matrix. The results revealed that carbon nanotubes act as reinforcing filler and significantly enhance the physical-mechanical properties of composites. The presence of carbon nanotubes in the rubber matrix also results in an outstanding increase in electrical conductivity and permittivity of composite materials, as a consequence of which the EMI absorption shielding was poor in the tested frequency range of 1 MHz to 3 GHz. On the other hand, ferrite-filled composites are able to efficiently absorb electromagnetic radiation emitted from various electronic and radiation sources. However, the tensile strength of the composites showed a decreasing trend with increasing content of ferrite. The combination of carbon nanotubes with manganese-zinc ferrite resulted in an improvement in the physical-mechanical properties of hybrid composites. As the permittivity of hybrid composites was still much higher in comparison with those filled only with ferrite, only the composite filled with 5 phr of carbon nanotubes and 100 phr of ferrite showed a slight EMI absorption shielding ability over the tested frequency range.

In this work, rubber composites were fabricated by incorporation of manganese-zinc ferrite alone and in combination with carbon-based fillers into acrylonitrile-butadiene rubber. Electromagnetic parameters and electromagnetic interference (EMI) absorption shielding effectiveness of composite materials were examined in the frequency range 1 MHz–3 GHz. The influence of ferrite and fillers combination on thermal characteristics and mechanical properties of composites was investigated as well. The results revealed that ferrite imparts absorption shielding efficiency to the composites in tested frequency range. The absorption shielding effectiveness and absorption maxima of ferrite filled composites shifted to lower frequencies with increasing content of magnetic filler. The combination of carbon black and ferrite also resulted in the fabrication of efficient EMI shields. However, the EMI absorption shielding effectiveness was lower, which can be ascribed to higher electrical conductivity and higher permittivity of those materials. The highest conductivity and permittivity of composites filled with combination of carbon nanotubes and ferrite was responsible for the lowest absorption shielding effectiveness within the examined frequency range. The results also demonstrated that combination of ferrite with carbon-based fillers resulted in the enhancement of thermal conductivity and improvement of mechanical properties. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

In the current study, manganese-zinc ferrite in a concentration scale ranging from 100 to 500 phr was incorporated into acrylonitrile-butadiene rubber having the constant amount of carbon black (20 phr) or carbon nanotubes (5 phr). The work was focused on the investigation of fillers combination on curing process, physical-mechanical, and dynamic characteristics of composites. The electromagnetic interference absorption shielding efficiency of composites was subsequently investigated at low frequencies. The results revealed that composites filled with a combination of ferrite and CB are able to efficiently shield electromagnetic radiation in the tested frequency range 1 MHz to 3 GHz, while electromagnetic interference absorption shielding performance of CNT/ferrite composites was insufficient. The reason can be attributed to the outstanding increase of electrical conductivity of composites filled with combination of ferrite and CNT. As the best absorption shielding material can be considered the CB/ferrite composite containing 100 phr of ferrite, as it exhibited the widest absorption frequency bandwidth at return loss of −10 and −20 dB. The presence of ferrite in composites resulted in the decrease of cross-link density, modification of curing characteristics and physical-mechanical properties, and no significant influence on glass transition temperature. © 2021 John Wiley & Sons Ltd.

Strontium ferrite in constant loading is incorporated into acrylonitrile butadiene rubber in order to prepare rubber magnetic composites. Sulfur, peroxide and combined sulfur/peroxide curing systems are applied for cross-linking of rubber composites. The work is focused on the investigation of curing system composition and thermo-oxidative ageing on cross-link density, physical-mechanical and magnetic properties of rubber magnets. The results revealed that the cross-link density and the structure of the formed cross-links within the rubber matrices affect the property spectrum of vulcanizates. © 2021 Wiley-VCH GmbH

In the present work, barium ferrite in constant loading was dosed to the rubber matrices based on NR, SBR and NBR. Sulfur, peroxide and mixed sulfur and peroxide curing systems were applied for cross-linking of rubber magnetic composites. The application of sulfur or peroxide curing system leads to the formation of different types of linkages between rubber chain segments. As the structure of the formed cross-links plays a significant role in determining the final properties of rubber articles, the main aim of the work was to use the combination of curing systems in order to suppress the disadvantages of both systems and possibly to highlight their benefits. The results showed that composition of curing system has considerable influence on cross-link density of composites, which was subsequently reflected in typical change of physical-mechanical properties and glass transition temperature. The tensile strength was improved with increasing amount of peroxide curing system. The reason can be attributed to the presence of co-agent zinc methacrylate, which exhibits strong adhesion to magnetic filler and thus it contributes to the improvement of compatibility and homogeneity on the interphase filler–rubber. On the hand, there was observed no influence of curing system composition or type of rubber matrix on magnetic characteristics of composites. © The Author(s) 2020.

Rubber magnetic composites based on acrylonitrile butadiene rubber and strontium ferrite were cured with standard sulfur-based vulcanization systems as well as an organic peroxide. Zinc methacrylate (ZDMA) as a coagent was applied in both sulfur and peroxide vulcanization of rubber magnets. The aim was to evaluate the influence of ZDMA on curing characteristics and cross-link density of the prepared materials. Subsequently, physical-mechanical and magnetic properties were investigated. The results showed that ZDMA takes an active part in the cross-linking process of composites cured with an organic peroxide. Due to the presence of free radicals formed from peroxide decomposition, molecules of ZDMA polymerize into the nanostructures which can be physically adsorbed or chemically grafted onto rubber chains. Moreover, owing to zinc ions, ZDMA exhibits strong adhesion to ferrite filler and thus it contributes to the improvement of adhesion between the rubber and the filler on the interphase. The overall reinforcement of rubber magnetic composites was subsequently achieved. In the case of rubber magnets cured with the sulfur-based system, ZDMA acts as a conventional filler with a slight reinforcing effect due to the lack of free radicals required for its polymerization.