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991.
Wen Jin Liu Zhi Bin Xu Ke Jian Cui Min Xue Zi Hui Meng Xiao Chuan Huang Zhong Xue Ge Zhi Hui Lin Guang Ming Qin 《Propellants, Explosives, Pyrotechnics》2015,40(5):645-651
Two intermediates, 1,5‐dinitroso‐3,7‐dinitro‐1,3,5,7‐tetraazacyclooctane (DNDS) and 1‐nitroso‐3,5,7‐trinitro‐1,3,5,7‐tetraazacyclooctane (MNX), were isolated and characterized in the synthesis of 1,3,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX) from the nitrolysis of 3,7‐dinitro‐1,3,5,7‐tetraazabicyclo[3,3,1]nonane (DPT) for the first time. When the nitrolysis of DPT was slowed down, two intermediates were detected with HPLC. It was proposed that electrophilic NO2+ and NO+ from HNO3 and N2O4 might attack nitrogen atoms at positions 3 and 7 of DPT to form the cations of the intermediates, then nucleophilic H2O attacked the bridge carbon atoms of DPT to produce the intermediates, which were oxidized to form HMX. 相似文献
992.
以PPP项目利益相关方的关系演化为研究对象,在分析PPP项目现状的基础上,分析并提出PPP项目利益相关方关系演化的外部环境变化、利益均衡分配、信任水平和惯性约束等因素。通过调查问卷,运用结构方程模型,对动力因素与PPP项目利益相关方关系演化之间关系的概念模型以及潜变量之间的相互作用等进行验证和修正,从而得出动力因素与关系演化相互作用的路径以及路径系数,以验证PPP项目利益相关方关系演化动力的整体结构关系。为PPP项目进行有效的关系治理提供依据,推动PPP项目的可持续发展。 相似文献
993.
994.
以4-[3,5-双(4-氨基苯氧基)苯氧基]邻苯二甲腈和3,3′,4,4′-联苯四甲酸二酐为原料,经聚酰胺酸热酰亚胺化制备含氰基的聚酰亚胺(CN-BP-PI)薄膜。采用傅里叶变换红外光谱、热重分析、差示扫描量热法对CN-BP-PI薄膜进行了分析。采用动态热重法研究了CN-BP-PI的分解动力学,用积分法结合常见固相热分解反应动力学函数来判断热分解的动力学函数。由Ozawa,KAS,Kissinger,Achar,Coats-Redfern,MacCallum-Tanner,van Krevelen方程求热分解反应的动力学参数。转化率为0.2~0.8时所得CN-BP-PI在氮气中热分解反应的表观活化能为119.68~215.61 kJ/mol,平均活化能为136.35 kJ/mol,指前因子平均值为8.52×107 s-1。 相似文献
995.
996.
从尿素生产作业现场危险源和尿素生产作业过程危险源两方面,对尿素装置生产安全状况进行分析,提出相应的尿素生产作业危险源的防范对策。 相似文献
997.
Nonisothermal crystallization behaviors of biodegradable double crystalline poly(butylene succinate)‐poly(ethylene glycol) multiblock copolymers 下载免费PDF全文
Nonisothermal crystallization behaviors of both poly(butylene succinate) (PBS) and poly(ethylene glycol) (PEG) segments within PBS‐PEG (PBSEG) multiblock copolymers were investigated by differential scanning calorimetry (DSC). The nonisothermal crystallization kinetics of both PBS and PEG segments were analyzed by Avrami, Ozawa, and Mo methods. The results showed that both of Avrami and Mo methods were successful to describe the nonisothermal crystallization kinetics of PBS and PEG segments. The results of crystallization kinetics indicated that the crystallization rate of PBS segment decreased with PBS segment content and/or LPBS, while that of PEG segment decreased with Mn,PEG or FPEG. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40940. 相似文献
998.
Ultraviolet‐crosslinked hydrogel sustained‐release hydrophobic antibiotics with long‐term antibacterial activity and limited cytotoxicity 下载免费PDF全文
To prolong erythromycin (EM) release and prevent the side effects of EM, a Pluronic F‐127 diacrylate macromer (PF127) was synthesized and then self‐assembled into micelles with their hydrophobic cores loaded with EM. The EM‐loaded micelles were mixed with a photoinitiator to form the EM/PF127 hydrogels rapidly under a low‐intensity UV light. Afterward, the hydrogel properties, antibacterial performance, and cytotoxicity of this novel hybrid hydrogel were investigated. The results show that the EM/PF127 hydrogel had a rapid gelation time. The sustained release of EM reduced its side effects. With controlled antibacterial activity, the use of EM would be safer and more efficient. What is more, the EM/PF127 hydrogel showed a slight cytotoxicity, and this suggests great potential application as antibacterial hydrogels in the prevention of postoperative infection. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40438. 相似文献
999.
Poly(vinylidene fluoride) (PVDF) based nanocomposites with different surface-functionalized multi-walled carbon nanotubes (MWCNTs) were prepared by melt mixing in a small scale compounder. With the incorporation of commercial functionalized MWCNTs, the β-phase in PVDF can be directly achieved from melt cooling, as verified by results of Fourier transform infrared spectrum and X-ray diffraction. Interestingly, nanocomposites with amino group functionalized MWCNTs showed the highest percentage of β-phase (17.4%) formation in PVDF, followed by those with hydroxyl groups (11.6%) and unmodified MWCNTs (9.4%). However, the nanocomposites containing MWCNTs with carboxyl groups which were thought to be able to well interact with the dipoles on PVDF chains have the lowest amount of β-phase, i.e. 4.7%. The analysis on the mechanism of the influence of surface functionalization of MWCNTs on the formation of β-phase in PVDF shows that the combined effects of the dispersion of MWCNTs and the nanotube–polymer interactions account for the formation of the β-phase in PVDF. 相似文献
1000.
Shouwen Shi Dan Liu Dazhi Liu Patrick Tae Carrie Y. Gao Lei Yan Ke An Xu Chen 《Polymer Engineering and Science》2014,54(10):2215-2221
In this study, mechanical tensile stress–strain response and microstructure changes of proton exchange membranes (PEM) in immersed conditions are studied. The effects of water pretreatment and immersion time on stress–strain responses of Nafion®?212 membranes are discussed. It is found that in the water immersion it took 24 h for the membrane to reach saturation equilibrium. Compared with dry membrane, immersed Nafion membrane shows a lower stress level at 30°C, but a higher stress level at 70°C. In situ small angle neutron scattering (SANS) experiments show that with the increase of temperature and water uptake, domains of the membrane become ordered and stay stable at around 60°C. Based on the observation, the relationship between the microstructure and mechanical properties is explained. POLYM. ENG. SCI. 54:2215–2221, 2014. © 2013 Society of Plastics Engineers 相似文献