Experimental and modeling studies of binary organic eutectic systems to be used as stabilizers for nitrate esters-based energetic materials

Four binary mixtures with potential for stabilizing energetic materials have been investigated. The phase diagrams of N-(2-methoxyethyl)-p-nitroaniline þ diphenylamine, N-(2-methoxyethyl)-p-nitroaniline þ N- (2-acetoxyethyl)-p-nitroaniline, N-(2-methoxyethyl)-p-nitroaniline þ 2-nitrodiphenylamine, and N-(2- methoxyethyl)-p-nitroaniline þ 1,3-diethyl-1,3-diphenylurea have been determined by differential scanning calorimetry. All systems display a simple eutectic behavior. Consistency tests have been applied to inspect the quality of the SLE data, showing very satisfactory quality factors. The SLE data have also been correlated by Wilson and NRTL models. The employed equations calculated the equilibrium temperatures with a root mean square deviations varying from 1.37 to 2.29 K. These models have been applied to compute the excess thermodynamic functions as well, giving highly comparable values for a further qualitative and quantitative analysis. The results showa positive deviation fromideality for all the investigated systems due to the dominant effect of the self-association molecules. The XRD studies revealed the existence of weak interactions between the components in the formed eutectics and suggested that they are mechanical systems.The authors are grateful for the financial support of this research from Ecole Militaire Polytechnique (Doctoral Training Program) and Project POCI-01-0145-FEDER-006984 (Ref. FCT UID/EQU/50020/2019) e Associate Laboratory LSRE-LCM e funded by European Regional Development Fund (ERDF) through COMPETE2020 e Programa Operacional Competitividade e Internacionalização (POCI) e and by national funds through FCT e Fundação para a Ciência e a Tecnologia I.P.info:eu-repo/semantics/publishedVersio

Solid + liquid equilibria and molecular structure studies of binary mixtures for nitrate ester's stabilizers: Measurement and modeling

Solid-liquid equilibria (SLE) data for two binary organic mixtures of N-(2-methoxyethyl)-p-nitroaniline+Nethyl- 4-nitroaniline (S1) and N-(2-ethanol)-p-nitroaniline+N-ethyl-4-nitroaniline (S2) have been measured using differential scanning calorimeter to build the corresponding solid-liquid phase diagrams. The quality of the SLE data has been checked by consistency tests, presenting good quality factors for both systems. Simple eutectic behavior has been observed for these systems with the presence of a solid-solid transition for S2. The SLE data have been correlated by means of Wilson, NRTL, and UNIQUAC equations. The used models calculate the equilibrium temperatures very satisfactorily. The best modeling results were obtained using the Wilson equation with a root mean square deviation between experimental and calculated values for S1 and S2 of 1.15 and 1.99, respectively. The Wilson, NRTL, and UNIQUAC equations have also been used to compute excess thermodynamic functions viz. excess Gibbs energy, enthalpy, and entropy. The obtained results demonstrated a moderate positive deviation to ideality for S1, and a strong positive deviation for S2, unveiling the nature of the interactions between the compounds forming each mixture. In addition, microstructural studies have been carried out by FTIR, XRD and optical microscopy. Weak molecular interactions have been shown for the eutectic compositions. Jackson’s roughness parameter was calculated and found to be greater than 2, suggesting the faceted morphology with irregular structures.The authors are grateful for the financial support of this research from Ecole Militaire Polytechnique (Doctoral Training Program) and from Associate Laboratory LSRE-LCM, Instituto Politécnico de Bragança (projectPOCI-01-0145-FEDER-006984) funded by European Regional Development Fund (ERDF) through COMPETE2020 –Programa Operacional Competitividade e Internacionalização (POCI) – and by national funds through FCT - Fundaçãopara a Ciência e a Tecnologia. C.M.S.S. Neves thanks FCT for the postdoctoral grant SFRH/BPD/ 109057/2015.info:eu-repo/semantics/publishedVersio

Solid–Liquid Phase Equilibria, Molecular Interaction and Microstructural Studies on (N-(2-ethanol)-p-nitroaniline + N-(2-acetoxyethyl)-p-nitroaniline) Binary Mixtures

Differential scanning calorimetry (DSC) is used to investigate the thermal properties of N-(2-ethanol)-p-nitroaniline+N-(2-acetoxyethyl)-p-nitroaniline, and their binary systems. The experimental results demonstrate that the studied binary system presents a simple eutectic behavior and the corresponding mole fraction(xeu)ofN-(2-ethanol)p-nitroaniline at the eutectic point is 0.5486, whereas the temperature (Teu) is found to be equal to 363.6 K. The quality of the solid–liquid equilibria (SLE) data has been checked by thermodynamic consistency tests, presenting good quality factor. The SLE data have been correlated by means of Wilson, NRTL, and UNIQUAC equations. The three models describe satisfactorily the phase diagram as the root-mean-square deviations for the equilibrium temperatures vary from 1.25K to 2.07K. Nevertheless, the Wilson model provides the best correlation results. The three equations have also been used to compute excess thermodynamic functions viz. excess Gibbs energy, enthalpy and entropy. The obtained results revealed a sensitive positive deviation to ideality thus demonstrating the nature of the interactions between the compounds forming the mixture. Microstructural studies have been carried out by FTIR, XRD and optical microscopy showing weak molecular interactions for the eutectic mixture.info:eu-repo/semantics/publishedVersio

Effect of amide-based compounds on the combustion characteristics of composite solid rocket propellants

Oxamide (OXA) and azodicarbonamide (ADA) are among the known burning rate suppressants used in composite solid rocket propellants. Much research has been carried out to understand mechanism of suppression but literature about the action of OXA and ADA on the combustion characteristics of propellant is still scarce. Here, a systematic study on coolant-based propellants has been undertaken spanning from thermal analyses of ingredients to a variety of burning processes of the corresponding propellants. Thermal gravimetric analysis and differential thermal analysis on individual coolants are carried out to study their behaviour with temperature. It was noticed that the thermal decomposition of OXA exhibits only endothermic effects, whereas that of ADA presents both endothermic and exothermic effects. Successive experiments on solid propellant looking at burning rate characterization, condensed combustion product collection and visualization, pressure deflagration limit and thermochemical analysis gave a greater insight and enabled better understanding of the action of coolants during combustion. It is proposed that OXA and ADA are acting on both the condensed and gas phases. Also, the nature of coolant is a key parameter, which affects the burning rate pressure index. Increase of agglomerate size and of pressure deflagration limit was obtained in the coolant-based propellants, confirming the trend given in the literature. Keywords: Composite propellant, Ammonium perchlorate, Burning rate suppressant, Combustion characteristic

DSC measurement and prediction of phase diagrams for binary mixtures of energetic materials' stabilizers

International audienceThis study reports the investigation of four binary mixtures of diphenylamine (1)+ N-ethyl-4-nitroaniline (2), ethyl centralite (1) + N-ethyl-4-nitroaniline (2), methyl centralite (1)+ N-ethyl-4-nitroaniline (2) and N-(2-acetoxyethyl)-p-nitroaniline (1) + N-ethyl-4-nitroaniline (2). The liquidus and solidus equilibrium temperatures determined by differential scanning calorimeter (DSC) were used to construct the corresponding solid liquid phase diagrams. On the basis of the DSC results, simple eutectic behaviours for four systems were observed. The experimental results were correlated by means of Wilson and UNIQUAC equations. The root-mean-square deviations of the solubility temperatures for all measured data vary from 0.80 to 4.05 K and depend on the particular model used. The best solubility correlation was obtained with the UNIQUAC model

Physico-chemical properties and thermal stability of microcrystalline cellulose isolated from Alfa fibres

International audienceIn this study, microcrystalline cellulose (Alfa-MCC) was extracted from Alfa fibres using acid hydrolysis method. The molecular weight of the cellulose samples was determined by gel permeation chromatography. The crystallinities were studied by means of X-ray diffraction and solid state cross polarization magic angle spinning C-13 nuclear magnetic resonance spectroscopy, revealing that Alfa-MCC was more crystalline than the native cellulose isolated from Alfa fibres. The morphology of the celluloses was investigated using scanning electron microscopy, showing a compact structure and a rough surface. Furthermore, a good thermal stability was shown for Alfa-MCC. Based on these analyses, Alfa-MCC showed tremendous potential use as composites reinforcing agent, foods stabilizer and pharmaceutical additive

Experimental vapor pressures (from 1 Pa to 100 kPa) of six saturated Fatty Acid Methyl Esters (FAMEs): Methyl hexanoate, methyl octanoate, methyl decanoate, methyl dodecanoate, methyl tetradecanoate and methyl hexadecanoate

International audienceVapor pressures of six saturated Fatty Acid Methyl Esters (FAMEs), methyl hexanoate (or methyl caproate), methyl octanoate (or methyl caprylate), Methyl decanoate (or methyl caprate), methyl dodecanoate (or methyl laurate), methyl tetradecanoate (or methyl myristate), and methyl hexadecanoate (or methyl palmitate) were measured from 1 Pa to 100 kPa and at temperature range between 262 and 453 K using a static apparatus. The experimental data (P-T) were compared with the available literature data

Isothermal Vapor Pressures of Three Binary Systems: n -Tetradecane + Methyl Dodecanoate, Methyl Tetradecanoate, or Methyl Hexadecanoate between 353.15 and 453.15 K

International audienceIsothermal vapor pressures of three binary systems, methyl dodecanoate (1) + n-tetradecane (2); methyl tetradecanoate (1) + n-tetradecane (2); and methyl hexadecanoate (1) + n-tetradecane (2), were measured by means of a static apparatus at temperatures between 353.15 and 453.15 K. The data of the pure components were correlated by the Antoine equation. A maximum azeotropic behavior is observed for the binary mixture, methyl dodecanoate (1) + n-tetradecane (2). The molar excess Gibbs energies GE were deduced from Barker’s method by fitting the experimental points through Redlich–Kister equation. The NRTL and UNIQUAC models were applied to regress the experimental vapor liquid equilibrium (VLE). The investigated systems were successfully represented by the two models