Browsing by Author "Mihaylov M."
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item Composites based on acrylonitrile butadiene rubber designed for sealants contacting potable water(2019-01-01) Nikolova S.; Mihaylov M.; Dishovsky N.The present work reports on the preparation and investigation of the properties of composites based on acrylonitrile butadiene rubber (NBR) aimed for production of sealants in water supply networks carrying hot and cold potable water. The studies involve 12 NBR-based composites. A conventional, semi-efficient and efficient sulphurvulcanization system is used for four of the composites. A vulcanizing agent, dicumyl peroxide, was used in the other eight composites. The results obtained show that the type of the vulcanization system used has a significant impact both on the vulcanization characteristics of the investigated rubber compounds and on the mechanical properties of their vulcanizates. The comparison of the results obtained and the requirements of standard EN 681-1:1996 referring to the mechanical properties of the elastomer composites used for production of sealants for pipes carrying hot and cold potable water reveal that composition P-10 is the most suitable for the purpose. The microbiological characteristics of the water in contact with the composites indicate that no bacterial growth occurs in the samples tested as a result of this contact. The latter does not lead to a change of the organoleptic parameters as well. Higher values of heavy metals, nitrates or nitrites are not observed.Item Effect of the modified solid product from waste tyres pyrolysis on the properties of styrene-butadiene rubber based composites(2014-01-01) Delchev N.; Malinova P.; Mihaylov M.; Dishovsky N.Being resistant to moisture, oxygen, ozone, solar radiation, microbiological degradation, etc., waste car tyres and their deposition present a great environmental problem. Pyrolysis is an environment-friendly process for their recycling. This paper presents data referring to the study of the effect of the solid product from waste tyres pyrolysis on the properties of styrene-butadiene rubber (SBR) based composites. It is found that the further modification of the pyrolysis carbon black decreases two times the ash content and six times the zinc oxide concentration in the ash but the curing characteristics of the investigated SBR based compounds remain unaffected. The values of the modulus 100, the tensile strength and Shore A hardness of vulcanizates containing modified pyrolysis carbon black increase, while the elongation at break and the residual elongation decrease slightly. The effects observed are related to the decreased ash content of the pyrolysis carbon black following the modification as well as to the increased silicon oxide concentration in the remaining ash.Item Influence of bis(triethoxysilylpropyl) tetrasulfide amount on the properties of silica-filled epoxidized natural rubber-based composites(2016-07-01) Al-Hartomy O.A.; Al-Ghamdi A.A.; Al Said S.A.F.; Dishovsky N.; Mihaylov M.The aim of the present article is to investigate the influence of the amount of bis(triethoxysilylpropyl) tetrasulfide on the curing characteristics and mechanical and dynamic properties of rubber composites based on epoxidized natural rubber (Epoxyprene 50) filled with 70 phr silica. The obtained results showed that although the interaction between the epoxy groups of epoxidized natural rubber and the silanol groups of silica through hydrogen bonds improves the dispersion of filler in the rubber matrix, the presence of silane coupling agents is necessary to obtain rubber compounds and vulcanizates with good vulcanization characteristics and mechanical and dynamic properties.Item Influence of bis(triethoxysilylpropyl) tetrasulfide amount on the properties of silica-filled epoxidized natural rubber-based composites(2016-07-01) Al-Hartomy O.A.; Al-Ghamdi A.A.; Al Said S.A.F.; Dishovsky N.; Mihaylov M.The aim of the present article is to investigate the influence of the amount of bis(triethoxysilylpropyl) tetrasulfide on the curing characteristics and mechanical and dynamic properties of rubber composites based on epoxidized natural rubber (Epoxyprene 50) filled with 70 phr silica. The obtained results showed that although the interaction between the epoxy groups of epoxidized natural rubber and the silanol groups of silica through hydrogen bonds improves the dispersion of filler in the rubber matrix, the presence of silane coupling agents is necessary to obtain rubber compounds and vulcanizates with good vulcanization characteristics and mechanical and dynamic properties.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 -80Ā°C to -40Ā°C interval. The storage modulus increases with the increasing filler content in the -40Ā°C to +80Ā°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 (Īµā²). Īµā² also increases with temperature increasing. Higher frequency causes a decrease of Īµā² 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 Īµā² values increase up to 102-104. The Īµā² 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 Ā© 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 -80Ā°C to -40Ā°C interval. The storage modulus increases with the increasing filler content in the -40Ā°C to +80Ā°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 (Īµā²). Īµā² also increases with temperature increasing. Higher frequency causes a decrease of Īµā² 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 Īµā² values increase up to 102-104. The Īµā² 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 Ā© 2011 Omar A. Al-Hartomy et al.Item MIXED PEROXIDE/SULFUR VULCANIZATION OF ETHYLENE-PROPYLENE TERPOLYMER BASED COMPOSITES. CURING CHARACTERISTICS, CURING KINETICS AND MECHANICAL PROPERTIES(2022-01-01) Nikolova S.; Mihaylov M.; Dishovsky N.Ethylene propylene diene monomer (EPDM) based composites filled with carbon black were studied to evaluate the effect that a mixed peroxide/sulfur vulcanization system in the absence or presence of the ethylene glycol dimethacrylate (EGDMA) co-agent has on the vulcanization characteristics, the kinetic parameters of the vulcanization process, as well as on the mechanical properties before and after accelerated heat aging. The results obtained show that, implementation of a mixed peroxide/sulfur vulcanization system in the presence of EGDMA as a co-agent is a promising opportunity to expand the fields of application of organic peroxides in rubber industry.Item PERFORMANCE AND TECHNOLOGICAL MODEL FOR PRODUCTION OF SOUND- AND SHOCK-ABSORBING COMPOSITES ON THE BASIS OF WASTE ELATOMERIC MATERIALS(2020-01-01) Dishovsky N.; Delchev N.; Ivanova N.; Mihaylov M.; Malinova P.; Lachev A.The aim of the present work is to investigate the possibilities of using waste sunflower oil as a modifying additive in order to eliminate some disadvantages of polyurethane adhesives used in the production and performance of insulating composites from ground waste rubber vulcanizates. A composition and a technological model for the production of sound- and shock-absorbing composite material have been developed as a result of the present study. A positive effect of the modifying additive on the technological process and the properties of the composite materials has been established. It is attributed to the composition of the waste sunflower oil comprising different types of fatty acids. The conducted tests and the obtained results give grounds to believe that the composite material developed can find applications as a sealing element in railways of rail and tram transport, in construction for sound insulation of buildings, as well as for covering childrenās and sports grounds.Item Zinc resinate's influence on the properties of silica filled composites based on natural rubber(2014-01-01) Todorova N.; Mihaylov M.; Damyankin I.; Dishovsky N.The aim of this study is to investigate the zinc resinate's influence on the rheological, vulcanization, mechanical and dynamic properties of the composites based on silica filled natural rubber, containing bi-functional organosilanes in the presence or absence of zinc oxide. The results obtained demonstrate that the presence of zinc resinate leads to considerable decrease of Mooney viscosity of the rubber compounds investigated. The mixture of zinc oxide and zinc resinate has a strong anti-reversion effect. The reversion absence found in the cure curves results in retaining the mechanical properties of the vulcanizate obtained regardless of the curing duration.