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Manganese–zinc ferrite, nickel-zinc ferrite and the combination of both fillers were used for fabrication of composites. Then, carbon black was applied in combination with ferrites in the second type of composites. The main goal was to investigate the influence of fillers on absorption shielding efficiency and physical–mechanical properties of composites. It was revealed that incorporation of ferrites into rubber matrix leads to fabrication of composites that are able to absorb electromagnetic radiation. The higher was the amount of nickel-zinc ferrite in fillers combinations, the higher was the absorption shielding performance of composites. The results showed that nickel-zinc ferrite demonstrated better absorption shielding potential. The absorption shielding efficiency of composites filled with carbon black and ferrites was lower when compared to equivalent composites filled only with ferrites, which can be attributed to higher electrical conductivity of composites due to the presence of carbon black. On the other side, the incorporation of carbon black caused the improvement in physical–mechanical properties of composites, mainly the enhancement of the tensile strength, modulus and hardness. [ABSTRACT FROM AUTHOR]

The work is focused on the investigation of the effect of dicumyl peroxide as curing agent and zinc dimethacrylate as co-agent on morphology, cross-linking and properties of rubber vulcanizates, in which the amount of zinc dimethacrylate was kept constant and amount of peroxide was varied. The cross-link density of vulcanizates increased proportionally to the amount of dicumyl peroxide. The highest dependence of cross-link density on peroxide content exhibited vulcanizates based on butadiene rubber and styrene-butadiene rubber due to their highest reactivity with free radicals. Relative low reactivity of radicals is characteristic of natural rubber, acrylonitrile-butadiene rubber, ethylene propylene diene monomer rubber, which supports higher conversion rate and in-situ polymerization of zinc dimethacrylate. Poor dispersion of zinc dimethacrylate in natural rubber has also negative effect on dimethacrylate conversion. High viscosity of ethylene propylene diene monomer rubber in contrast facilitates dispersion of zinc dimethacrylate in the rubber matrix and increases its conversion. Low relative reactivity of free radicals with acrylonitrile-butadiene rubber together with good dispersion of polar zinc dimethacrylate in polar rubber provides in-situ polymerization of zinc dimethacrylate. [ABSTRACT FROM AUTHOR]

The work is focused on the investigation of the influence of the amount of co-agent on cross-linking and properties of rubber compounds. The in-situ radical polymerization of zinc dimethacrylate occurs during the curing process of rubber compounds with organic peroxide. Polymerized zinc dimethacrylate tends to form different types of chemical and physical linkages within the rubber matrices. As the amount of dimethacrylate ranged from 10 to 50 phr, the conversion of zinc dimethacrylate remained low. Residual zinc dimethacrylate formed micro-dispersion in the rubber matrix. The dispersion and distribution of zinc dimethacrylate in the rubber depends on the viscosity of matrix, shear stress and polarity of the matrix. Despite low conversion of zinc dimethacrylate, the application of co-agent resulted in the increase of cross-link density and improvement of physical-mechanical properties of vulcanizates. [ABSTRACT FROM AUTHOR]

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. [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]

Vulcanisation is a process of transforming a plastic rubber compound into a highly elastic product by forming a three-dimensional cross-linked network structure in the rubber matrix. Many systems have been developed to vulcanise rubber compounds, among which sulphur and peroxide curing systems remain the most desirable. The application of sulphur systems leads to the forming of sulphidic cross-links between elastomer chains, while carbon–carbon bonds are formed in peroxidecuring. Both vulcanisation systems provide certain benefits to the cross-linked rubber articles, but also some disadvantages. The present work seeks to provide an overview on both vulcanisation systems; their composition, possibilities of their application, reaction mechanisms, structure of the cross-links formed and the main feature of the final cross-linked materials – vulcanisates. [ABSTRACT FROM AUTHOR]