The effects of solvent properties and temperature on the solid–liquid equilibrium of 2-bromodibenzofuran (NSC 1735) were investigated for the first time in terms of temperature, solvent polarity, hydrogen bonding donor and acceptor tendency, as well as cohesive energy density. Firstly, the equilibrium solubility of 2-bromodibenzofuran in 12 mono-solvents, such as alcohol, ketone, nitrile and ester, was determined by gravimetric method ranging from 278.15 ∼ 343.15 K. The values of the mole fraction solubility of NSC 1735 in all the selected solvents increased with increasing temperature. Moreover, the statistical correlations between temperature and solubility were described by the modified Apelblat equation, λh equation, Van’t Hoff equation, and NRTL model. The calculated ARD% values show that the correlation results agree well with the experimental date and the modified Apelblat equation receives the best regression performance. Solvent polarity and cohesive energy density mainly determine the solubility of NSC 1735 in various solvents. Thermodynamic studies of dissolution have shown that the dissolution of NSC 1735 in selected solvents.is endothermic and enthalpy driven. The change of dissolution enthalpy is the main contributor to the molar Gibbs free energy during the dissolution process.
Guanjun Liu,Fan Yang,Wenbo Liu,Weicheng Jiao,Xiaodong He,Rongguo Wang
High gas barrier polyethylene (PE) composites containing non-oxidized graphene flakes (GFs) were fabricated through solution blending. GFs were synthesized through ultrasonic-assisted electrochemical exfoliation of graphite. Then, GFs were functionalized via directly inducing PE molecular crystallization along their surface under proper temperature and PE/GFs ratio. The composites with only 0.5 wt% GFs gave a helium leak rate of 6.29 × 10 −8 Pa m 3 /s at 0.6 MPa, outperforming pure PE with a decrease of 83.4%. In addition, the interface interaction between PE and GFs is very weak, and the cohesive energy is only 0.1448 J m −2 . Therefore, at high GFs concentrations (>0.5 wt%), the continuous weak interfaces between the GFs interconnected networks and PE will reduce the effective diffusion path to a certain extent, leading to the reduction of gas barrier efficiency. In general, this method offers great promise for barrier materials that can be utilized in lightweight high-pressure gas storage vessels.
La Shi,Li Ren,Yang Li,Xiaolong Fu,Saiqin Meng,Jiangning Wang
In this study, the crosslinking structures of nitrate ester plasticized polyether (NEPE) binders were constructed by a computational procedure. Based on the final crosslinking models, the glass transition temperatures, mechanical properties, and thermal expansion coefficients of polyethylene glycol400/multi-functional isocyanate (PEG400/N-100), polyethylene glycol400/toluene diisocyanate (PEG400/HDI), polyethylene glycol400/hexamethylene diisocyanate (PEG400/TDI) and polyethylene glycol400/isophorone diisocyanate (PEG400/IPDI) models were simulated by molecular dynamics, and could be confirmed by experiments. Then the bond-length distributions, conformation properties and cohesive energy densities were used to analyze in detail how the different cured structures influenced the mechanical and thermal properties. Furthermore, the radial distribution function, mean square radius of gyration, volume shrinkage and fraction free volume were calculated, which could directly explain the relationships between the intermolecular chains and macroscopical properties of the NEPE binders. Lastly, PEG400/N-100 and PEG400/HDI systems were chosen for the experiments. The dynamic mechanical analysis results explained that PEG400-HDI showed better flexibility and its Tg value was 45 °C lower than that of PEG400-N100. The mechanical properties illustrated that the ultimate tensile strength and Young's modulus of PEG400/N-100 were both to an extent higher than that of PEG400/HDI in the temperature range of −40 °C to 50 °C, according to the results provided by a universal tensile test machine. The experimental results were in good agreement with the simulation analysis. This work can help us to have an efficient comprehension on the crosslinking structures and micro-property relationships of the NEPE binders and act as a guidance for designing applicable polyurethanes in propellant applications.
危险品化学品经营许可证（带存储）