Study on the influence of ageing on chemical and mechanical properties of N,N′-dimethyl-N,N′-diphenylcarbamide stabilized propellants

Double-base propellants undergo chemical, physical and mechanical changes upon ageing, leading to changes in ballistic performance and presenting explosive hazards. This report studies the variation of chemical and mechanical properties of aged N,N′-dimethyl-N,N′-diphenylcarbamide (methyl centralite) stabilized propellants in order to simulate and evaluate the natural ageing throughout the artificial one. Therefore, a comparative study of stabilizer depletion, plasticizers content, heat of combustion and mechanical properties such as storage modulus, loss modulus and damping of naturally and artificially aged propellants has been carried out by the following techniques: high-performance liquid chromatography (HPLC), thermogravimetric analyzer (TG), calorimeter of combustion and dynamic mechanical analyzer (DMA), respectively. The results obtained show that all properties are closely connected. In addition, the determination of stabilizer depletion, plasticizers evaporation, decrease of heat of combustion and mechanical properties are very useful for a better understanding of the decomposition and ageing behaviour of propellants. The HPLC investigation of stabilizer has shown good stability of the propellants. The results obtained for DMA have shown that some considerable changes of the mechanical and viscoelastic properties of the propellants occurred during ageing. These results confirm the results obtained by TG for the reduction of the nitroglycerine amount and the decrease of the heat of combustion.     

GC-MS determination and optimization of extraction of N,N′-dimethyl-N,N′-diphenylcarbamide from building materials

N,N’-dimethyl-N,N’-diphenylcarbamide (centralite) extracted from building materials was quantitated using ion trap GC-MS detection technique. Both linearity and standard deviation of the calibration curve were dependent on the conditions of the mass spectral detection. The most precise calibration has been achieved by quantification of a mass ion not participating in secondary reactions and which is produced via single fragmentation. The best recovery of centralite was obtained after either 30 min of normal extraction with toluene at 60 °C or 10 min of ultrasonic extraction with chloroform at room temperature. Using the latter method resorption processes might cause decrease in efficiency of the recovery at longer extraction time. Received: 3 July 1998 / Revised: 5 November 1998 / Accepted: 26 January 1999     

Solvent extraction of Eu, Th, U and am by N,N′-dimethyl-N,N′-dihexyl-3-thiopentanediamide and thenoyltrifluoroacetone

The diamide, N,N-dimethyl-N,N-dihexyl-3-thiopentanediamide (DMDHTPDA) was synthesized and thested for extraction of Eu(III), Am(III), Th(IV) and U(VI). DMDHTPDA shows a very weak complexation with these metal ions, which can be attributed to the soft base nature of the sulfur atom. None of the cations were extracted into the organic phase when DMDHTPDA alone was present. Synergistic extraction was measured for DMDHTPDA plus thenoyltrifluoroacetone. From the extraction dependencies on pH and extractant concentration, formation of mixed TTA+DMDHTPDA complexes were indicated. Except for the Th(IV) system, the separation and synergistic factors were smaller for the TTA+DMDHTPDA extractant than for the system of TTA+DMDHOPDA (the oxo ether analog of DMDHTPDA).     

Synergic extraction of lanthanide(III) ions with 2-thenoyltrifluoroacetone in the presence of 2,2′-bipyridine or pyridine

The synergic extraction of various tervalent lanthanides (Ln), La, Ce, Nd, Sm, Gd, Tb, Yb and Lu, with 2-thenoyltrifluoroacetone (Htta) in the presence of a bidentate heterocyclic amine, 2,2′-bipyridine (bipy), in benzene was investigated. The synergic enhancement was attributed to the formation of the adducts, Ln(tta)₃(bipy). The synergic extraction of La(III), Sm(III) and Lu(III) with Htta and a unidentate amine, pyridine (py), was also studied and the formation of the adducts, Ln(tta)₃py and Ln(tta)₃(py)₂, was observed. The adduct formation constants, β_s,1 and β_s,2, were determined. The β_s,2 values for py decrease with increasing atomic number of Ln(III), but β_s,1 values for bipy increase with increasing atomic number of Ln(III). The synergic extraction constants and the separation factors in the bipy system were also determined.     

Complexation and extraction studies of lanthanide ions by 1,1′-(3,6,9-Trioxaundecanedionyl)Diphenothiazine

Solid complexes of lanthanide picrates with 1,1′-(3,6,9-trioxaundecanedionyl)diphenothiazine (L), [Ln(pic)₃L] (Ln = La, Nd, Eu, Gd, Er, Y), have been prepared and characterized by elemental analysis, IR and ¹H NMR spectra. The molecular structure of [Er(pic)₃L]·1/2C₂H₅OH shows that five oxygens of L form a ring-like coordination structure. Er(III) is 9-coordinated by L together with the other two unidentate and one bidentate picrate anions, revealing a tri-capped distorted trigonal prism geometry. Solvent extraction of Ln(III) with L has been carried out in a water–nitrobenzene system by use of the multitracer method. The relationship between the complex structure and extractabilities of the ligand is discussed.     

Extraction of trivalent europium and americium by the synergistic mixture of bis-1,2-dicarbollylcobaltate and N,N,N′,N′-tetraoctyl diglycolamide in highly polar 3-nitro-α,α,α-trifluorotoluene solvent

Journal of Radioanalytical and Nuclear Chemistry - The extraction of trivalent europium and americium in the system water—HNO3—3-nitro-α,α,α-trifluorotoluene...     

The structure effect of N,N,N′,N′-alkylamide in the extraction of uranium and thorium

In this paper, nine N,N,N,N-tetraalkyldiamides have been synthesized and the extracting ability for uranium and thorium under different conditions has been studied. All results were compared with those obtained by using tributyl phosphate (TBP) under exactly the same conditions. The extracting ability of thorium and uranium for different N,N,N,N-tetraalkyldiamides is discussed.     

Networks based on aromatic glycidylamines: 1. Effect of curing conditions on the crosslinking of N,N-diglycidylaniline with 4,4′-diaminodiphenylmethane and of N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane with 4,4′-diaminodiphenylmethane

The effect of time and temperature of curing on the conversion of epoxy groups, on the relative change of some other functional groups (–OH, –NH₂, RNH), glass transition temperatureT _g , and equilibrium modulusG _e was investigated for epoxy networks having various initial ratios of N,N-diglycidylaniline to 4,4-diaminodiphenylmethane (DDM) and of networks with various ratio of N,N,N,N-tetraglycidyl-4,4-diaminodiphenylmethane and DDM. Curing conditions were found under which the conversion of minority groups is maximal at the minimal extent of degradation reactions for networks prepared both in the excess of amine and in the excess of epoxide. For networks prepared in the excess of epoxide the degree of the etherification reaction was found to depend on time and temperature.     

Extraction behavior of strontium from nitric acid solution with N,N,N′,N′-Tetraisobutyl diglycolamide

The extraction behaviors of strontium from nitric acid solution were investigated with N,N,N′,N′-tetraisobutyl diglycolamide (TiBDGA). Effects of acidity, diluents, concentration of extractant and temperature on the distribution ratio of strontium (D _Sr) were examined. The stoichiometry of the extracted molecule was Sr²⁺:TiBDGA of 1:3. The apparent extraction equilibrium concentration constant logK _ex was 3.25. The enthalpy change ΔH and entropy change ΔS were ?55.6 kJ mol^-1 and ?124 J mol^-1 K^-1, respectively. The extraction is an exothermic process. Through two strip stages, strontium could be stripped effectively by 0.01 M nitric acid solution.     

Mixed ligand complexes of trivalent lanthanide ions with β-diketones and heterocyclic amines and their use as possible shift reagents

Sixty new complexes of the trivalent lanthanides (except Pm and Lu) and Yttrium of the general formulae, Ln(TFAA)₃o-phen, Ln(TFAA)₃dipy·2H₂O, Ln(dpm)₃im, Ln(dpm)₃pz, and Ln(fod)₃o-phen where TFAA = trifluoroacetyl-acetone-H, dpm = 2,2,6,6-tetramethyl 3,5-heptane dione-H, fod = 1,1,1,2,2,3,3-heptafluoro, 7,7-dimethyl 4,6-octane dione-H, o-phen = 1,10-phenathroline, dipy = 2,2′dipyridyl, im = imidazole and pz = pyrazole, have been synthesised and characterised by elemental analyses, melting points, molar conductance, magnetic susceptibility, thermogravimetric analysis, and IR spectral studies. The trivalent lanthanide ions have a coordination number of ten in the series Ln(TFAA)₃dipy·2H₂O. Their avidity to enhance their coordination number is so great that een in the presence of three such bulky ligands as heptafluorooctane dione the Ln(fod)₃ still coordinates with o-phen. Hexacoordinated trivalent lanthanides act as LIS reagents but it has been observed that even the eight coordinated and very bulky Pr(fod)₃o-phen produces dipolar shifts in the proton resonances of organic moities.     

Preparation,crystal structure and luminescence of lanthanide coordination polymers with 2,2′-dimethyl-4,4′-bipyridine-N,N′-dioxide

Four coordination polymers of the bidentate ligand 2,2′-dimethyl-4,4′-bipyridine-N,N′-dioxide (L), [La(L)(NO₃)₃(H₂O)] _n (1), {[Gd₂(L)₃(NO₃)₆]·6H₂O} _n (2), {[Sm(L)₂(H₂O)₄]·3ClO₄·2L·4H₂O} _n (3) and {[Nd(L)₂(H₂O)₄]·3ClO₄·2L·4H₂O} _n (4) have been synthesized by the diffusing solvent mixture method. Results of X-ray diffraction analysis reveal that 1, with a Ln/L stoichiometry of 1:1, displays a rare 3-D three-fold interpenetrating diamondoid framework, while 2 has a Ln/L stoichiometry of 1:1.5 and exhibits a polycatenane network with a {8²,10} topology and large channels accommodated by water. Complexes 3 and 4, with Ln/L stoichiometry of 1:2, have 3-D two-fold interpenetrating diamondoid structures and large voids. Nonlinear optical property of 2 and luminescence of 3 were also investigated.     

Extraction of americium(III) and europium(III) using a gamma pre-irradiated solution of N,N′-dimethyl-N,N′-dibutyltetradecyl malonamide in n-dodecane modified with N,N′-dihexyloctanamide

The extraction of Am(III) and Eu(III) using a γ-pre-irradiated N,N′-dimethyl-N,N′-dibutyltetradecyl malonamide (DMDBTDMA) modified with N,N′-dihexyloctanamide (DHOA) in n-dodecane (NDD) at 4.5M HNO₃ has been studied as a function of the absorbed dose up to 2×10⁶ Gray. The distribution ratios of Am(III) and Eu(III) were almost constant until a dose of 1×10⁵ Gray and then they decreased gradually up to a dose of 2×10⁶ Gray. The decrease of the distribution ratios of Am(III) and Eu(III) are due to the decreasing concentration of the DMDBTDMA by a γ-pre-irradiation and these results were supported by a determination of the DMDBTDMA concentration with a gas chromatography method. The distribution ratios of Am(III), Eu(III), Ce, Nd and Y with γ-pre-irradiated (DMDBTDMA-DHOA)/NDD have also been studied as a function of the nitric acid concentration and the extraction temperature.     

Syntheses,structures, and luminescent properties of lanthanide complexes with N,N′-bis(p-methoxyphenyl)-3-oxapentanediamide

An amide-type acyclic polyether, N,N′-bis(p-methoxyphenyl)-3-oxapentanediamide (L), and its three lanthanide coordination compounds, [Ln(NO₃)(L)₂(H₂O)₂]?·?(NO₃)₂ [Ln?=?Pr (1), Nd (2), and Dy (3)], have been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis, and X-ray diffraction. Single crystal X-ray structure analyses reveal that 1 and 2 have the same structure and crystallize in the monoclinic crystal system with C2/c space group. The coordination geometry around the central atom is a distorted bicapped square antiprism. Extensive intermolecular hydrogen bonds in 1 and 2 result in 3-D supramolecular networks. Complex 3 exhibits luminescence in the visible region upon excitation with UV-rays.     

Study of the cholesterol extraction capacity of β-cyclodextrin and its derivatives, relationships with their effects on endothelial cell viability and on membrane models

Endothelial cells (HUVEC) were treated with β-cyclodextrin and hydroxypropylated or methylated derivatives solutions in order to quantify their cholesterol extraction capacity. Non-toxic concentrations of cyclodextrins (CDs) were determined following methyl thiazol tetrazolium (MTT) assays, total protein measurements, morphological observations and trypan blue assays. The residual cholesterol content of cells was measured and the extraction power of CDs compared to results obtained by phase solubility diagrams. Cholesterol was extracted with a dose-response relationship, the lowest residual cholesterol content being obtained with β-CD at 10 mM. Low substituted derivatives (Crysmeb^® and hydroxypropyl-β-CD) maintained liposomes integrity (as shown before), were the less cytotoxic and presented the lowest affinity for cholesterol contrary to methylated derivatives with degrees of substitution around 2.     

Study of complexation of alkyl-substituted 2,2′-dipyrrolylmethene with lanthanide salts by electronic spectroscopy

It has been found with the use of electronic spectroscopy that the reaction of alkyl-substituted 2,2′-dipyrrolylmethene with La(III), Pr(III), Sm(III), Dy(III), Ho(III), Er(IIII), and Yb(III) salts leads to the formation of tris(dipyrrolylmethene) complexes. Based on electronic absorption spectroscopy data and formation constants of lanthanide complexes, together with the earlier data, analysis of the nature of M-L bonds in 2,2′-dipyrrolylmethene chelates with p, d, and f elements has been performed. A correlation was found between the complex stability and the polarizing action of the complex-forming ion on the chromophore π system of dipyrrolylmethene, which allows one to classify these heterocyclic ligands with probes highly sensitive to the change in the ratio between the ionic and covalent contributions to coordination interactions.     

Synthesis, transport, and ionophore properties of α,ω-biphosphorylated azapodands: VIII. Solvent extraction of the metal ions with N,N′-bis(dioctylphosphorylmethyl)-1,8-diamino-3,6-dioxaoctane

Liquid extraction from the aqueous solutions of perchloric acid with neutral azapodand extractant N,N′-bis(dioctylphosphorylmethyl)-1,8-diamino-3,6-dioxaoctane has been highly efficient in the cases of uranyl ions and some metals of groups II and III. To estimate the synergic effect of organophosphorus extractants, the neutral extractant was applied in the mixture with an acidic component, bis(pentadecyl)phosphoric acid. The synergic effect has exclusively been observed in the extraction of zinc and cadmium ions.