Browsing by Author "Nikolova S."

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    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.
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    Crystal Structure of N-(2-Benzoyl-4,5-dimethoxyphenethyl)-2-phenylacetamide
    (2022-06-01) Marinova P.; Nikolova S.; Dołęga A.; Ahmedova A.
    The crystal structure of N-(2-benzoyl-4,5-dimethoxyphenethyl)-2-phenylacetamide indi-cates that the compound crystallizes in the monoclinic C2/c space group with eight molecules in the unit cell. The heteroatoms from the amide group form a chain of intermolecular N-H ··· O hydrogen bonds propagating along the b axis. The carbonyl group from the benzoyl substituent participates in short contacts with two H-atoms from the ethyl or phenyl groups.
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    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.
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    Synthesis of N-[1-(2-Acetyl-4,5-dimethoxyphenyl)propan-2-yl]benzamide and Its Copper(II) Complex
    (2023-01-01) Marinova P.; Nikolova S.; Tsoneva S.
    Abstract: This paper represents a convenient method for the synthesis of N-[1-(2-acetyl-4,5-dimethoxyphenyl)propan-2-yl]benzamide and its Cu(II) complex. In silico analysis predicted spasmolytic activity for the compound. Based on the in silico calculations, the importance of the predicted ketoamide, and our previous experiments, we synthesized the ketoamide via ortho-acylation of N-[1-(3,4-dimethoxyphenyl)propan-2-yl]benzamide with acetic anhydride in polyphosphoric acid. We applied the title ketoamide in reaction with Cu(II) varying the solvents. We found that the reaction leads to the formation of a coordination compound when the ligand dissolved in DMSO reacts with a water solution of CuCl2 in an alkaline environment in a molar ratio M : L : OH– = 1 : 2 : 2. The structures of the new compounds are discussed based on their melting points, IR, 1H, 13C NMR and Raman spectral data.