Abstract:Results on surface conductivity of cotton fibres dyed with reactive dyes have been reported. In general the surface conductivity values were higher in alkaline pH, but lower in acidic pH as compared to the neutral pH. This observation has been attributed to the contribution of the functional groups present on the dye molecule reacted with the fibre. Results on the surface conductivity of fibres dyed with mono-and bifunctional reactive dyes suggest that dyes react with the hydroxyl groups of the fibre, and that the bifunctional dye molecule forms a crosslink between two cellulosic chains.
SynopsisAcrylic acid (AA), acrylonitrile (AN), and acrylamide (AM) were grafted onto polyformaldehyde (PF) fibers employing y-ray irradiation as well as benzoyl peroxide initiation. The nature of the graft copolymer obtained from a given monomer was dependent on the type of method used for the grafting reactions. This was reflected in the various characteristics of the grafted PF fibers such as moisture regain and dyeability to disperse, direct, basic, and acid dyes. The extent of grafting was dependent on time, concentration of the initiator, concentration of monomer, and irradiation dose. The grafting reaction with all the three monomers and both methods of grafting studied followed first-order kinetics. The rate constant values for grafting with AA, AN, and AM were 0.493, 0.576, and 0.420 hr-l, respectively for the irradiation method and 0.385,0.385, and 0.346 hr-l, respectively, for the benzoyl peroxide initiation technique. The increase in the moisture regain was directly proportional to the amount of graft in the fiber. Acrylic acid grafted P F fibers were rendered hydrophilic to the highest extent (7.9% M.R. for 42% graft), while AM-grafted fibers were rendered so to the lowest extent (7.23% M.R. for 76.5% graft). Considerable improvement in dyeability of P F fibers was observed as a result of grafting. In general, dyeability was proportional to the amount of graft introduced in the fibers. The AA-grafted P F fibers gave a six-to sevenfold increase in disperse dye content when the irradiation method was followed and a four-to fivefold improvement when the chemical method was used during the grafting reaction. The AA-grafted and AM-grafted P F fibers show considerable affinity toward direct cotton dyes. The two substrates could also be dyed with fiber-reactive dyes in deep fast shades, the AM-grafted P F fibers giving deeper shades as a result of higher reactivity imparted to the substrate by the NH2 group of the graft copolymer. The AA-and AN-grafted P F fibers could be dyed in intense deep shades with cationic dyes. Similarly, AM-grafted substrates gave bright deep shades with acid dyes. Infrared studies, used to analyze the grafted P F fibers, indicated the presence of -COOH, -CN, and -NH2 groups introduced in the fiber structure as a result of grafting with AA, AN, and AM. INTRODUCTIONSakurada and coworkers1>2 carried out graft copolymerization of styrene onto poly(oxymethy1ene) fibers (Delrin and Celon) using irradiation and observed that the extent of grafting was higher at higher dose rates but could not obtain improvement in thermal stability or resistance to strong alkalis or mineral acids. Eguchi and O k a~a ,~ however, claimed good thermal stability of the graft copolymer when the poly(oxymethy1ene) copolymers were grafted with vinyl compounds using the irradiation technique. The grafted copolymers when spun into filaments had improved bulkiness, crimp stability, and dyeability. Although the Japanese workers have carried out grafting on polyformaldehyde [poly(oxymethylene)] fiber, there is no wor...
One of the major drawbacks in Lithium-air batteries is the sluggish kinetics of the oxygen reduction reaction (ORR). In this context, better performances can be achieved by adopting a suitable electrocatalyst, such as MnO2. Herein, we tried to design nano-MnO2 tuning the final ORR electroactivity by tailoring the doping agent (Co or Fe) and its content (2% or 5% molar ratios). Staircase-linear sweep voltammetries (S-LSV) were performed to investigate the nanopowders electrocatalytic behavior in organic solvent (propylene carbonate, PC and 0.15 M LiNO3 as electrolyte). Two percent Co-doped MnO2 revealed to be the best-performing sample in terms of ORR onset shift (of ~130 mV with respect to bare glassy carbon electrode), due to its great lattice defectivity and presence of the highly electroactive γ polymorph (by X-ray diffraction analyses, XRPD and infrared spectroscopy, FTIR). 5% Co together with 2% Fe could also be promising, since they exhibited fewer diffusive limitations, mainly due to their peculiar pore distribution (by Brunauer–Emmett-Teller, BET) that disfavored the cathode clogging. Particularly, a too-high Fe content led to iron segregation (by energy dispersive X-ray spectroscopy, EDX, X-ray photoelectron spectroscopy, XPS and FTIR) provoking a decrease of the electroactive sites, with negative consequences for the ORR.
SynopsisElectrokinetic properties, namely, zeta potential (0, surface charge density ( u ) , and surface conductivity (K,) of polyformaldehyde fibers [poly(oxymethylene) fibers] have been studied in the presence of direct dyes, with or without surfactants and an electrolyte. The anionic dyes increased the negative zeta potential of fibers. The increase in [was found to be a function of concentration and basicity of the dye in the streaming solution. Thus, the tetrabasic dye gave higher value of negative {than the equivalent concentration of the dibasic dye. The cationic surfactant brought about a decrease in negative {, giving a point of inflection, while the anionic surfactant increased it. The nonionic surfactant brought about a certain reduction in negative 1; but failed to give a point of inflection. In the presence of a direct dye, the cationic surfactant brought about considerable reduction in negative [to give a point of inflection. The presence of an electrolyte in the streaming dye solution progressively lowered the negative [. In general, u increased with the increase in the concentration of either a dye or an electrolyte in the presence of a given concentration of the dye in the streaming solution. Results on K, indicated that the surface conductivity of the fibers is a function of concentration of dye, surfactant, and electrolyte. It was, however, observed to be independent of the nature of the surfactant. Although both the dibasic and tetrabasic direct dyes brought about an increase in K,, the extent of increase was dependent upon the basicity of the molecules.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.