Electromagnetic interference shielding and physical‐mechanical characteristics of rubber composites filled with manganese‐zinc ferrite and carbon black

In the present work, composite materials were prepared by incorporation of manganese-zinc ferrite, carbon black and combination of ferrite and carbon black into acrylonitrile‐butadiene rubber (NBR). For cross‐linking of composites, standard sulfur‐based curing system was applied. The main goal was to investigate the influence of the fillers on the physical‐mechanical properties of composites. Then, the electromagnetic absorption shielding ability was investigated in the frequency range 1 MHz–3 GHz. The results revealed that composites filled with ferrite provide sufficient absorption shielding performance in the tested frequency range. On the other hand, ferrite behaves as an inactive filler and deteriorates the physical‐mechanical characteristics of composites. Carbon black reinforces the rubber matrix and contributes to the improvement of physical-mechanical properties. However, composites filled with carbon black are not able to absorb electromagnetic radiation in the given frequency range. Finally, the combination of carbon black and ferrite resulted in the modification of both physical‐mechanical characteristics and absorption shielding ability of hybrid composites. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Slovak Research and Development AgencySlovak Research and Development Agency [APVV-19-0091]; Slovak University of Technology in BratislavaAgentúra na Podporu Výskumu a Vývoja, APVV: APVV‐19‐009

Mechanical, thermal, electrical characteristics and emi absorption shielding effectiveness of rubber composites based on ferrite and carbon fillers

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.Slovak Research and Development AgencySlovak Research and Development Agency [APVV-16-0136, APVV-19-0091]Agentúra na Podporu Výskumu a Vývoja, APVV: APVV-16-0136, APVV-19-009

Influence of curing system composition and aging on the performance of rubber magnets based on NBR and EPDM

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.Slovak Research and Development Agency [APVV-16-0136, APVV-19-0091

Combined sulfur and peroxide curing systems applied in cross-linking of rubber magnets

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.Slovak Research and Development AgencySlovak Research and Development Agency [APVV-16-0136, APVV-19-0091

Application of Peroxide Curing Systems in Cross-Linking of Rubber Magnets Based on NBR and Barium Ferrite

Rubber magnetic composites were prepared by incorporation of barium ferrite in constant amount—50 phr into acrylonitrile-butadiene rubber. Dicumyl peroxide as the curing agent was used for cross-linking of rubber magnets alone, or in combination with four different types of co-agents. The main aim was to examine the influence of curing system composition on magnetic and physical-mechanical properties of composites. The cross-link density and the structure of the formed cross-links were investigated too. The results demonstrated that the type and amount of the co-agent had significant influence on cross-link density, which was reflected in typical change of physical-mechanical properties. The tensile strength increased with increasing amount of co-agents, which can be attributed to the improvement of adhesion and compatibility on the interphase filler-rubber due to the presence of co-agents. Magnetic characteristics were found not to be influenced by the curing system composition. The application of peroxide curing systems consisting of organic peroxide and co-agents leads to the preparation of rubber magnets with not only good magnetic properties but also with improved physical-mechanical properties, which could broaden the sphere of their application uses

Rubber magnetic composites cross-linked with peroxide curing systems

Abstract: Styrene–butadiene rubber and acrylonitrile–butadiene rubber as elastomer matrices were filled with barium ferrite in order to prepare rubber magnetic composites. For cross-linking of rubber compounds, peroxide curing systems consisting of dicumyl peroxide as curing agent and four types of low molecular weight organic compounds as co-agents were used. The work was focused on the investigation of different types of co-agents on the cross-linking, physical-mechanical and magnetic properties of the prepared composites. The results revealed that the type and amount of co-agent has no influence on magnetic characteristics of composites. On the other hand, cross-link density and physical-mechanical properties were significantly dependent on the composition of curing system. Co-agents contribute to the improvement of adhesion on the interphase filler-rubber. Considering the type of rubber matrix, higher values of tensile strength exhibited composites based on acrylonitrile–butadiene rubber. As magnetic filler and co-agents are polar materials, their compatibility with polar elastomers like acrylonitrile-butadiene rubber is much higher when compared to no-polar elastomers like styrene–butadiene rubber. © 2019, Pleiades Publishing, Ltd.Slovak Research and Development AgencySlovak Research and Development Agency [APVV-16-0136, APVV-16-0059]; grant agency VEGA project [1/0405/16

Influence of combined sulfur and peroxide curing systems and ageing on the properties of rubber magnets

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 GmbHSlovak Research and Development AgencySlovak Research and Development Agency [APVV-16-0136, APVV-19-0091]Agentúra na Podporu Výskumu a Vývoja, APVV: APVV-16-0136, APVV-19-009

Application of Sulfur and Peroxide Curing Systems for Cross-Linking of Rubber Composites Filled with Calcium Lignosulfonate

Calcium lignosulfonate in different loadings was applied to the rubber matrix based on EPDM. A sulfur curing system, organic peroxide, and a combination of organic peroxide with two coagent types were used for cross-linking of rubber compounds. The work was focused on the investigation of filler content and curing system composition in the curing process, cross-link density, morphology, and physical–mechanical properties of composites. The achieved results demonstrated that the curing parameters of rubber compounds cured with the sulfur system were significantly different from those cured with peroxide systems. There was also an observed different influence of curing systems composition on cross link density, though in all cases, the degree of cross-linking showed a decreasing trend with increasing content of lignosulfonate. The tensile strength of the composites cured with sulfur system and organic peroxide was comparable, regardless of lignosulfonate loading. This points to the application of both curing systems in cross-linking of rubber compounds with biopolymer filler. However, the introduction of coagents in peroxide vulcanization led to the improvement of adhesion and compatibility between the rubber and the filler on the filler–rubber interface. This subsequently resulted in the improvement of the tensile characteristics of composites. The introduction of organic peroxide in combination with coagent seems to be a very simple and efficient way for the preparation of biopolymer-filled composites with applicable physical–mechanical properties

Curing, Properties and EMI Absorption Shielding of Rubber Composites Based on Ferrites and Carbon Fibres

In this work, magnetic soft ferrites, namely manganese–zinc ferrite, nickel–zinc ferrite and combinations of both fillers, were incorporated into acrylonitrile-butadiene rubber to fabricate composite materials. The total content of ferrites was kept constant—300 phr. The second series of composites was fabricated with a similar composition. Moreover, carbon fibres were incorporated into rubber compounds in constant amount—25 phr. The work was focused on investigation of the fillers on absorption shieling performance of the composites, which was investigated within the frequency range 1–6 GHz. Then, the physical–mechanical properties of the composites were evaluated. The achieved results demonstrated that the absorption shielding efficiency of both composite types increased with increasing proportion of nickel–zinc ferrite, which suggests that nickel–zinc ferrite demonstrated better absorption shielding potential. Higher electrical conductivity and higher permittivity of composites filled with carbon fibres and ferrites resulted in their lower absorption shielding performance. Simultaneously, they absorbed electromagnetic radiation at lower frequencies. On the other hand, carbon fibres reinforced the rubber matrix, and subsequent improvement in physical–mechanical properties was recorded