Browsing by Author "Al-Solamy F."
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Item Dielectric and microwave properties of siloxane rubber/carbon black nanocomposites and their correlation(2011-01-01) Al-Hartomy O.A.; Al-Solamy F.; Al-Ghamdi A.; Dishovsky N.; Iliev V.; El-Tantawy F.In this paper, the dielectric and microwave properties of carbon black/siloxane rubber-based nanocomposites have been investigated in the frequency range from 1 GHz till 12GHz according to the content of carbon black and the frequency. It has been established that the increasing frequency and filler content lead to an increase in the relative permittivity and tangent of dielectric loss angle. At higher filler content, the effects become more pronounced, especially those upon dielectric loss. It has been also established that there are two well-distinguished areas in all dependences of microwave properties on frequency and filler content increasing. The first is between 1 and 8 GHz wherein the reflection and attenuation of microwaves do not change considerably with frequency and filler content alternation while shielding effectiveness worsens. The second area is between 8 and 12 GHz wherein the reflection and attenuation of microwaves increase drastically with the increasing frequency and filler content. Shielding effectiveness improves, too. It has been established that in all cases the degree of correlation between dielectric and microwave properties evaluated on the basis of the coefficients of correlation calculation is perfect. Copyright © 2011 Omar A. Al-Hartomy et al.Item Influence of carbon black structure and specific surface area on the mechanical and dielectric properties of filled rubber composites(2011-01-01) Al-Hartomy O.A.; Al-Solamy F.; Al-Ghamdi A.; Dishovsky N.; Ivanov M.; Mihaylov M.; El-Tantawy F.Natural rubber based composites have been prepared using various amounts of two fillers: conventional Corax N220 carbon black or electrically conductive carbon black Printex XE-2B which has a very high specific surface area. The composites have been studied by dynamic mechanical thermal analysis, dielectric thermal analysis and SEM. It has been established that all vulcanizates investigated are in the glass state in the -80°C to -40°C interval. The storage modulus increases with the increasing filler content in the -40°C to +80°C interval when the vulcanizates are in the highly elastic state. DETA shows that the increase in filler content leads to an increase in the dielectric permittivity (ε′). ε′ also increases with temperature increasing. Higher frequency causes a decrease of ε′ values which becomes more pronounced with the increasing filler content. Obviously, when the content of Printex XE-2B carbon black in the vulcanizates is higher than 7.5 phr, the percolation threshold is reached and the ε′ values increase up to 102-104. The ε′ values for the vulcanizates comprising 20 and 50 phr Corax N220 carbon black are measurable with those for the vulcanizates comprising 5 and 10 phr Printex XE-2B carbon black respectively. The results obtained could be explained by the difference in the structure and specific surface area of the two types of carbon black - Printex XE-2B and Corax N220. Copyright © 2011 Omar A. Al-Hartomy et al.Item Influence of carbon black structure and specific surface area on the mechanical and dielectric properties of filled rubber composites(2011-01-01) Al-Hartomy O.A.; Al-Solamy F.; Al-Ghamdi A.; Dishovsky N.; Ivanov M.; Mihaylov M.; El-Tantawy F.Natural rubber based composites have been prepared using various amounts of two fillers: conventional Corax N220 carbon black or electrically conductive carbon black Printex XE-2B which has a very high specific surface area. The composites have been studied by dynamic mechanical thermal analysis, dielectric thermal analysis and SEM. It has been established that all vulcanizates investigated are in the glass state in the -80°C to -40°C interval. The storage modulus increases with the increasing filler content in the -40°C to +80°C interval when the vulcanizates are in the highly elastic state. DETA shows that the increase in filler content leads to an increase in the dielectric permittivity (ε′). ε′ also increases with temperature increasing. Higher frequency causes a decrease of ε′ values which becomes more pronounced with the increasing filler content. Obviously, when the content of Printex XE-2B carbon black in the vulcanizates is higher than 7.5 phr, the percolation threshold is reached and the ε′ values increase up to 102-104. The ε′ values for the vulcanizates comprising 20 and 50 phr Corax N220 carbon black are measurable with those for the vulcanizates comprising 5 and 10 phr Printex XE-2B carbon black respectively. The results obtained could be explained by the difference in the structure and specific surface area of the two types of carbon black - Printex XE-2B and Corax N220. Copyright © 2011 Omar A. Al-Hartomy et al.Item Microwave properties of natural rubber based composites containing carbon black-magnetite hybrid fillers(2018-04-25) Al-Ghamdi A.; Al-Hartomy O.; Al-Solamy F.; Dishovsky N.; Malinova P.; Shtarkova R.The paper presents the synthesis and characterization of a carbon black-magnetite hybrid filler. The complex study on the structure of the filler has shown the magnetite phase to be distributed both over the surface (inter-aggregately) and inside (intra-aggregately) the carbon black particles, thus forming a true hybrid material. The results from the investigations on the mechanical and microwave properties of natural rubber-based composites filled with the new hybrid filler have been also reported. They have been compared to those of a composite comprising the physical mixture of carbon black and magnetite (at the same ratio as in the hybrid filler). The determined microwave characteristics of the composite comprising the hybrid filler obtained reveal the possibility for its use in manufacturing elastomer-based microwave absorbers.