Search Results
Abstract
The synergism of lithium bromide and antimony trioxide on the flame-retardancy of a cotton fabric (woven, plain 150 g m2) has been investigated in this study. The impregnations of cotton fabric with suitable individual additives and/or their appropriate admixed formulation were carried out. The flammability test has also been fulfilled using described procedure, in the earlier published articles. Their outcomes comply with thermogravimetry’s data. Moreover the latest mentioned outcomes support the catalytic effect of this synergism. Explanation of the data could be in favor of existing flame-retardation’s theories. Ultimately this synergism is in compliance with the green chemistry and economical viewpoints.
have synergistic, and/or antagonistic effects. Actually an additional effect is the sum of the effects of the mixed components taken independently. Synergism means that the observed effect is greater than individual efficiency of each additive, on the
Evaluation of the residual stability of polyurethane automotive coatings by DSC
Equivalence of Xenotest and desert weathering tests and the synergism of stabilizers
Abstract
Degradation of poly(ester-urethanes), poly(ether-urethanes) and poly(acrylic-urethanes), as a base for automotive paintings in interior applications, has been studied by DSC. The samples were clearcoat and black-pigmented paints, unstabilized and stabilized with HALS Tinuvin 292, UV absorber Tinuvin 1130 and antioxidant Hostanox O3, exposed to weathering in Xenotest and in Arizona desert. From the dependences of oxidation onset temperature on the heating rate, the kinetic parameters enabling to calculate the oxidation induction time for a chosen temperature have been obtained. From the values of oxidation induction time, the protection factors of the additives and the residual stability of the polymer after an ageing stress has been evaluated. It has been shown that the equivalence between the two methods of weathering depends on the polymer composition. A new criterion for the evaluation of synergism/antagonism of additives in the stabilizing mixture has been proposed.
Abstract
The synergism of the crown ethers (CE) dicyclohexano-18-crown-6 (DC18C6), dibenzo-18-crown-6 (DB18C6) and 18-crown-6 (18C6) has been investigated in the thenoyl trifluoroacetone (HTTA) extraction of americium(III) in benzene medium from an aqueous phase of ionic strength 0.5 and pH 3.50 at room temperature (23°C). The extracted synergistic species have the general formula Am(TTA)3 · CE except for DC18C6 in which case the species Am(TTA)3·2CE was also observed at high CE concentrations. The order of synergism was found to be DC18C6>DB18C6>18C6, which is the order of the basicity of CE as indicated by their ability to extract hydrogen ions from nitric acid solutions.
Synergism with amides
I. Synergistic extraction of uranyl ion with thenoyltrifluoroacetone and some aliphatic amides
Abstract
Synergistic extraction of uranyl ion with 2-thenoyltrifluoroacetone (HTTA) and aliphatic amides with varying basicities, viz. dibutyl hexanamide (DBHA), dibutyloctanamide (DBOA) or dibutyldecanamide (DBDA) has been studied at various fixed temperatures of 20, 30, 40 and 50±0.1°C. Results indicate that the equilibrium constants of the organic phase addition reaction (Ks) with these amides follow their order of basicity (Kh) viz. DBHA (0.09)<0.10) H DBOA (0.13) with log Ks values of 4.91, 4.99 and 5.02, respectively. These values are much higher than those with TBP (3.8) or sulfoxides (
4) as donors. This may be attributed to the existence of a resonance form of the amide, which has higher electron density on the carbonyl oxygen. The thermodynamic parameters associated with these systems evaluated by the temperature coefficient method indicate that the organic phase addition reaction with all the three amides is stabilized by both enthalpy and entropy changes as against UO
2
2+
/HTTA/TBP system, where only the enthalpy change contributes to the stabilization.
Synergism with amides
II. Synergistic extraction of uranylion with 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (HPMBP) and some aliphatic amides
Abstract
Synergistic extraction of uranyl ion with 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (HPMBP) and N,N
-dibutyl derivatives of hexanamide (DBHA), octanamide (DBOA) and decanamide (DBDA) has been studied at various fixed temperatures of 20, 30, 40 and (50±0.1)°C. Results indicate that the equilibrium constants of the organic phase addition reaction (log Ks) with these amides follow their order of basicity (Kh) viz. 4.01 (DBHA, Kh=0.09)<4.05 (DBOA, Kh=0.1)<4.09 (DBDA, Kh=0.13). These values of log Ks (
4) are lower than those (5) of HTTA system with these amides, which may perhaps be attributed to the effect of steric hindrance exerted by the uranyl pyrazolone ohelate to the incoming rigid amide molecule. High negative 
H and negative S values for this system indicate the organic phase reaction to be an addition and not a substitution.
Abstract
The extraction of Be(II) from sulphuric acid solutions by binary mixtures particularly that of the sodium salt of di-(2-ethyl hexyl)-phosphoric acid (NaDEHP) and tributyl phosphate (TBP), has been described. The dependence of extraction on acidity, diluent type and solvents concentration was thoroughly examined. The possible extraction mechanism is discussed in the light of results obtained.
Abstract
Extraction chromatographic supports (XAD-7) impregnated with binary mixtures of cobalt dicarbollide and one of the two phosphororganic extractants (dibutyl-N,N-diethylcarbamoylmethyl phosphonate, DBDECMP, or octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide, (CMPO) were prepared using methanolic solutions of the extractants and subsequent evaporation of methanol at room temperature. The molar ratios (x) in isomolar series of the two extractants were 0, 0.25, 0.5, 0.75, and 1. The sorbents were used for investigating Eu capture from 0.1 and 1M HNO3 solutions under static conditions (24 hours shaking, 2 cm3 aqueous phase with 0.2 g sorbent, Eu initial concentrations 3·10–9, 0.0001, 0.001, 0.01 and 0.1M). The sorbents containing mixtures of extractants corresponding to the interpolated value x=0.45 (phosphororg./dicarb.) exhibited the highest values of the distribution ratios of Eu. A synergic effect of three orders of magnitude for low concentrations of Eu was observed. A tentative determination is given of the nature and the equilibrium constants of the chemical reactions assumed.
Abstract
Synergistic extraction of hexavalent uranium and plutonium as well as trivalent americium was studied in HNO3 with thenoyl, trifluoro-acetone (HTTA)/1-phenyl, 3-methyl, 4-benzoyl pyrazolone-5 (HPMBP) in combination with neutral donors viz, DPSO, TBP, TOPO (mono-functional) and DBDECMP, DHDECMP, CMPO (bi-functional) with wide basicity range using benzene as dileunt. A linear correlation was observed when the equilibrium constant log Ks for the organic phase synergistic reaction of both U(VI) and Pu(VI) with either of the chelating agents HTTA or HPMBP was plotted vs. the basicity (log Kh) of the donor (both mono- and bi-functional) indicating bi-functional donors also behave as mono-functional. This was supported by the thermodynamic data (
G
0,
H
0,
S
0) obtained for these systems. The organic phase adduct formation reactions were identified for the above systems from the thermodynamic data. In the Am(III) HTTA system log K
s
values of bi-functional donors were found to be very high and deviate from the linear plot (log K
s
vs. log K
h
) obtained for mono-functional donors, indicating that they function as bi-functional for the Am(III)/HTTA system studied. This was supported by high +ve
S
0 values obtained for this system.
Abstract
Synergism is observed in the extraction of uranium(VI) by the binary mixture of Aliquat 336 and PC 88A (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) from 0.5–6M HNO3 solution showing a maximum at 3M. In H2SO4 medium, antagonism at lower acidity and slight synergism at higher acid concentrations have been observed. Synergism occurs in the extraction of Am(III) from nitrate solutions when a mixture of Aliquat 336 and TOPO is used.
