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Two types of composites based on natural rubber (NR) and strontium ferrite were tested in this study. Composites of the first type were prepared by incorporation of strontium ferrite in the concentration range ranging from 0 to 100 phr (parts per hundred rubber) into pure NR based rubber matrix, while with those of the second type, strontium ferrite was dosed in the same concentration level into NR based rubber batch with constant amount of carbon black — 25 phr. For rubber matrices cross-linking, a standard sulfur based curing system was used. This work is focused on the effect of magnetic filler content on physico-mechanical, magnetic and thermo-physical properties of composite materials. Subsequently, the cross-link density and the structure of the formed sulfidic cross-links were examined. The results showed that the cross-link density of both types of composites increased with the increasing content of magnetic filler, while the structure of the sulfidic cross-links was almost not influenced by the amount of strontium ferrite. Tensile strength of rubber composites with pure rubber matrix was slightly improved by the incorporation of ferrite, while in case of composites based on a carbon black batch, the incorporation of magnetic filler resulted in the decrease of this characteristic. The presence of magnetic filler in both types of composites leads to a significant increase of the remanent magnetic induction. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In the present work, rubber magnetic composites were prepared by incorporation of strontium ferrite into rubber matrices based on natural rubber (NR) and acrylonitrile butadiene rubber (NBR). The sulfur and peroxide curing systems were introduced in cross-linking of rubber matrices. The research was aimed at the evaluation of magnetic filler content and type of curing system on the cross-link density, physical–mechanical and magnetic properties of prepared composites. The relationship between the composition of elastomers and cross-link structure within the rubber matrices, formed by applying different curing systems, was under investigation through strain–stress behavior of tested materials. The achieved results showed that ferrite behaves as a reinforcing filler in peroxide-cured composites based on NR, and in both, sulfur as well as peroxide-cured composites based on NBR. The results also demonstrated that the cross-linking degree and the type of cross-link structure as well as the composition of rubber matrices, to a large extent, influence the property spectrum of tested composite systems. [ABSTRACT FROM AUTHOR]

In the present work, rubber magnetic composites were prepared by incorporation of strontium ferrite into rubber matrices based on natural rubber (NR) and acrylonitrile-butadiene rubber (NBR). Sulphur, peroxide and mixed sulphur/peroxide curing systems were introduced in cross-linking of rubber matrices. The aim was to investigate the influence of curing system composition on physical-mechanical, thermo-physical and magnetic properties of prepared rubber composites and the curing process. Then, the determination of cross-link density and the structure of cross-links were under consideration. The achieved results showed that all investigated parameters were changed depending on the composition of curing system, but also on the type of rubber matrix. While the tensile strength of composites based on NR increased with increasing amount of sulphur in mixed curing systems, in case of composites based on NBR, the highest value of tensile strength reached the value of the sample cured with equivalent ratio of sulphur and peroxide. On the other hand, thermo-physical and magnetic characteristics were found not to be dependent on the curing system composition. The results revealed that not only the composition of curing system, but also the type of rubber matrix plays an important role when preparing the final materials. [ABSTRACT FROM AUTHOR]

Rubber magnetic composites were prepared by incorporation of unmodified and surface modified strontium ferrite into rubber matrices based on NBR and NBR/PVC. Strontium ferrite was dosed to the rubber matrices in concentration scale ranging from 0 to 100 phr. The main goal was to investigate the influence of the type of ferrite on the curing process, physical-mechanical and magnetic properties of composites. The mutual interactions between the filler and rubber matrices were investigated by determination of cross-link density and SEM analysis. The incorporation of magnetic fillers leads to the increase of cross-link density and remanent magnetic induction of composites. Moreover, the improvement of physical-mechanical properties was achieved in dependence on the content of magnetic fillers. Surface modification of ferrite contributed to the enhancement of adhesion on the interphase filler-rubber. It can be stated that ferrite exhibits reinforcing effect in the composite materials and this reinforcing behavior was emphasized with the increase in polarity of the rubber matrix. [ABSTRACT FROM AUTHOR]

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Rubber magnetic composites were prepared by incorporation of strontium ferrites in natural rubber-based elastomer matrix. The work was aimed at the evaluation of magnetic filler influence on physical-mechanical, magnetic and thermal properties of prepared composites. The study was also dedicated to the investigation of microstructure and evaluation of interactions between strontium ferrites and natural rubber. The observed parameters are dependent on the type of ferrite and on the content of applied ferrite, too. Surface modification of ferrite leads to the improvement of interfacial conditions and adhesion between the rubber matrix and the magnetic filler. [ABSTRACT FROM AUTHOR]

Abstract: Elastomeric magnetic composites are materials with ferromagnetic fillers as one of the constituents and rubber blend as polymer matrix. Ferrites, as commonly used magnetic fillers, might be able to influence the long-term stability of rubber materials, mainly if they are applied in high concentrations. Therefore, the thermo-oxidative and ozone stability of ferrite as well as ferrite and carbon black filled composites based on natural and butadiene rubber were studied by oven ageing and thermogravimetric analysis. The results revealed that ferrite alone also ferrite in combinations with carbon black influences the properties of evaluated materials in various ways. But the thermo-oxidative stability of prepared composites seems not to be influenced by the amount of ferrite even in case of high magnetic filler contents. From thermogravimetric curves it became evident that the thermal degradation of prepared materials also was not influenced by the doping content of ferrite. The ozone ageing tests demonstrated that the influence of ferrite on the ozone stability of natural rubber as well as butadiene rubber based composites was ambiguous. In case of natural rubber based composites filled with combinations of ferrite and carbon black, it can be stated that the more carbon black rubber materials contain, the better is the resistance against ozone degradation. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Elastomeric magnetic composites were prepared by incorporation of strontium ferrite into polymer matrices based on natural as well as butadiene rubber. Besides the rubber and ferrite, or the combinations of ferrite and carbon black (in case of natural rubber), the model rubber compounds contained only ingredients which support curing process. The study was dedicated to the observation of fillers dispersion degree in the rubber matrices and investigation of physical-mechanical and magnetic properties of prepared composites. The results indicate that the dispersion degree of ferrite in the rubber matrices is not very high, but it can be positively influenced by the addition of carbon black. Despite of the fact that ferrite exhibits only low reinforcing effect on cross-linked elastomeric materials, physical-mechanical properties can be also positively influenced by the mutual change in combinations of both fillers (ferrite and carbon black). The prepared materials seem to have suitable magnetic and elastic properties. [ABSTRACT FROM AUTHOR]