硝酸舍他康唑的热分解机理及动力学

采用热重法(TG)、差示扫描量热法(DSC)测定了硝酸舍他康唑(STCZ)在氮气氛和空气氛中的热分解过程,结果表明STCZ的热分解过程是一个三阶段过程。运用量子化学GAMESS软件计算了STCZ分子的键级,测定了STCZ及其在热分解过程中不同阶段残留物的红外光谱,推断了STCZ的热分解机理,起始步骤是硝酸的分解。根据不同升温速率下的热重曲线计算得到STCZ第一阶段热分解反应的动力学参数,在氮气中,表观活化能Ea=222.2 kJ.mol-1,指前因子A=4.467×1024min-1,在空气中,表观活化能Ea=177.2 kJ.mol-1,指前因子A=1.738×1019min-1。推算了不同使用温度下STCZ的预期寿命。     

镁铜合金储氢材料的制备及对高氯酸铵热分解过程的影响

采用置换-扩散法制备了镁铜合金储氢材料(Mg2Cu-H), 并对其结构进行了表征. 结果表明, Mg2Cu经过氢化得到的镁铜合金储氢材料不是单一晶相, 而是MgCu2和MgH2的混合物. 用热分析法(DSC)研究了镁铜合金储氢材料对固体火箭推进剂常用氧化剂——高氯酸铵(AP)热分解过程的影响. 结果表明, 镁铜合金储氢材料可以显著促进AP的热分解过程, 加快热分解速率, 降低高温热分解温度, 使DSC表观分解热明显增大. Mg2Cu-H对AP热分解过程的促进作用明显强于Mg2Cu. 随着加入量增加, 镁铜合金储氢材料对AP热分解的催化促进作用增强. 探讨了镁铜合金储氢材料促进AP热分解过程的作用机制.     

聚缩水甘油硝酸酯的热安定性和相容性研究

采用DSC、TG热分析方法研究了聚缩水甘油硝酸酯(PolyGLYN)的热安定性和与1,3,5-三硝基-1,3,5-三氮杂环己烷(RDX)间的相容性.结果表明,PolyGLYN在100℃以前较为稳定.当加热速率趋于零时PolyGLYN的热分解峰温为196.4℃,由Ozawa法计算的热分解表观活化能为182.0 kJ·mol-1,分别比RDX的低15.1℃和高22.2 kJ·mol-1.PolyGLYN热稳定性与RDX接近,两者之间的相容性较好.     

差示扫描量热法研究丙烯腈-衣康酸共聚物的热稳定化

应用差示扫描量热法(DSC)研究了衣康酸(IA)、气氛、升温速率对丙烯腈-衣康酸共聚物[P(AN-IA)]热稳定化的影响. IA能够显著降低放热峰起始温度、放热量和放热速率. P(AN-IA)共聚物的放热峰起始温度受气氛影响不大, 却随着IA含量的增加而明显降低, 表明在热稳定化过程中它可能首先以离子机理发生氰基环化反应, 再发生氧化反应. 提高升温速率会导致放热峰向高温偏移和放热速率加快. 采用Kissinger法计算了不同IA含量共聚物的热稳定化活化能, 结果表明IA可以有效降低活化能.     

含能配位聚合物[Cu(tza)2]n的晶体结构、热分析、感度和催化性能

以碱式碳酸铜和四氮唑乙酸在水中反应制备得到四唑乙酸铜(II)含能配位聚合物, 并培养出单晶. 运用元素分析, FT-IR分析和X-射线单晶衍射对标题配合物的组成和结构进行了全面的表征. 采用差示扫描量热分析(DSC)和热重-微分热重分析(TG-DTG)研究了标题配合物的热分解过程, 表明标题配合物的热分解主要包含三个放热峰. 用Kissinger和Ozawa-Doyle法对标题配合物的第一放热分解过程进行了动力学研究, 计算得到其活化能为356.1 kJ/mol. 对配合物的撞击、摩擦、火焰感度和5s爆发点测试表明该配合物具有一定的感度, 有望作为含能材料应用于相关领域. 同时研究了标题配合物对RDX热分解的影响, 结果表明: 标题配合物可以使RDX的放热分解峰的温度提前16.4 ℃,分解速度加快, 对RDX具有良好的催化作用.     

PPESK/PES共混物热性能及动态机械性能研究

采用熔融共混法制备了不同重量比例的新型含二氮杂萘酮结构聚芳醚砜酮(PPESK)与聚醚砜(PES)共混物.利用热失重(TGA)及动态热机械仪(DMTA)对该共混物的热性能及动态机械性能进行了研究.研究结果表明,在氮气氛围中,PPESK热分解分为两步反应进行,反应级数n=1,说明PPESK在氮气氛围中的热分解反应类型与β(升温速率)无关而与材料物性有关;采用Ozawa方法得出在15%热失重前,热分解活化能的平均值为240 kJ/mol;随着升温速率的提高,PPESK热降解速率有减缓趋势.在280℃以前,PPESK储能模量值随温度变化较小,保持在较高值,温度在280~330℃之间,储能模量值降低幅度突变.另外,PPESK中加入PES会降低其储能模量值及其热稳定性.     

热重-傅立叶变换红外光谱联用法研究超支化聚氨酯/丙烯酸酯的热性能及热分解机理

采用热重分析仪(TG)和差示扫描量热仪(DSC)对自制的超支化聚氨酯(HPU)和UV固化超支化聚氨酯丙烯酸酯(HPUA)在不同气氛下的热失重行为和玻璃化转变温度(Tg)进行分析,在此基础上,结合热重红外联用仪(TG-FTIR)探究了HPU和HPUA的热分解机理。热重分析结果表明:HPU和HPUA在氮气气氛下具有相似的热分解行为,均有3段热分解温度;在空气气氛下的热分解与氮气气氛下的热分解相比,其分解行为相似,但前者的分解更迅速。DSC分析表明:接入丙烯酸羟乙酯(HEA)后,HPUA的Tg明显低于HPU。热红联用对热分解机理的分析表明:空气气氛下的分解比氮气气氛下更迅速,降解更完全。HPU的3段热分解分别为:醇的降解、氨基甲酸酯键的降解、脲基键的降解;HPUA的3段热分解分别为:丙烯酸羟乙酯的降解、氨基甲酸酯键的降解、脲基键的降解。     

基于TGA-FTIR联用技术研究ABS树脂的热氧降解行为

采用热失重-傅立叶变换红外光谱(TGA-FTIR)联用技术研究了空气气氛下ABS树脂的热稳定性及热氧降解失重情况。研究了ABS在4个不同升温速率下的失重情况;采用TGA-FTIR联用技术对10℃/min等速升温下ABS失重过程的逸出气体进行分析;采用热分解动力学方法分析ABS的热氧降解过程,计算热分解活化能。结果表明,ABS的TGA曲线有两个失重区间:第一区间是ABS的急剧氧化降解过程,活化能(Ea)为191.8~262.8 kJ.mol-1,第二区间是成炭产物的氧化,Ea约为139.7 kJ.mol-1;升温速率越小,ABS热氧降解速率越慢,交联成炭产物越多,有利于抑制ABS的降解;由FTIR测试和Ea变化发现,热氧降解反应为多步复杂反应,初期时氧化反应和氧化断链同时进行,并以氧化断链反应为主,随着分子链上产生的双键增多发生交联反应,失重率大于80%时开始炭化反应,最终交联炭层发生氧化反应生成CO2。     

二水草酸亚铁热分解反应动力学

用原位XRD技术和热重法分析了二水草酸亚铁的热分解过程, 并进行了动力学研究. 通过结合主曲线法和统计方法判定了热分解过程的动力学模型函数, 并求算了动力学参数. 在静态自产气氛下, 二水草酸亚铁脱水反应遵循随机成核与核增长模型, 草酸亚铁热分解生成氧化铁遵循相界面控制动力学模型. 结果表明, 该方法可以准确、可靠地判定非等温热分解反应的动力学模型函数,并求算动力学参数.     

双硫脲银配合物(Cl^-)红外光谱及热分解机理的研究

用红外光谱,差热分析、热重量分析研究了AgCl.2CS(NH2)2络合物的热分解,提出络合物的热分解机理,它包括在温度210-230℃的范围内硫脲基转变为NH4NCS同分异构体.计算了热分解反应的表观活化能和指前因子.     

Terbium-sensitized fluorescence method for the determination of pazufloxacin mesilate and its application.

A simple, rapid and highly sensitive fluorometric method for the determination of pazufloxacin mesilate (PZFX) is described. It is based on the formation of the complex [Tb(PZFX)2](3+), which shows the intensive characteristic bands of Tb3+. Optimum conditions for the determination were investigated. Under the optimum experimental condition, the fluorescence intensity responds linearly to the PZFX concentration in the range of 2.0 x 10(-8) - 5.0 x 10(-6) mol/l with a detection limit of 6.2 x 10(-9) mol/l. The method has been successfully applied to the determination of PZFX in urine and serum samples.     

Preparation of poly(butylene-co-ε-caprolactone carbonate) and their use as drug carriers for a controlled delivery system

Poly(butylene-co-ε-caprolactone carbonate) (PBCCL) was successfully synthesized via terpolymerization of carbon dioxide, 1,2-butylene oxide (BO), and ε-caprolactone (ε-CL). ε-CL was inserted into the backbone of BO-CO₂. The glass transition temperature (T_g) and the decomposition temperature (T_d) of PBCCL were much higher than those of poly(butylene carbonate) (PBC). The degradation rate of PBCCL was higher than that of PBC in a pH 7.4 phosphate-buffered solution. ε-CL offered an ester structural unit that gave the terpolymers remarkable degradability. PBC and PBCCL microcapsules containing a hydrophilic antibiotic drug pazufloxacin mesilate (PZFX) were elaborated by solvent evaporation method based on the formation of double W/O/W emulsion. Microcapsules were characterized in terms of the morphology, size, amount of encapsulated, and encapsulation efficiency. The results showed that the microcapsules had smooth and spherical surfaces, and the mean diameter of the microcapsules was in the range of 0.5–1 μm. Of all, 87.90% drug encapsulation efficiency has been achieved for microcapsules of 38.21% drug loading. In vitro drug release of these microcapsules was performed in a pH 7.4 phosphate-buffered solution. The release profiles were investigated from the measurement of PZFX presented in the release medium at various intervals. The release profiles of PZFX from PBC and PBCL microcapsules were found to be biphasic with a burst release followed by a gradual release phase. The release rate of PZFX from the microcapsules increased with increasing the content of ε-CL inserted into the copolymers. It showed that the release profiles of PZFX were highly polymer-dependent. © 2007 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 45: 2152–2160, 2007     

Molecularly imprinted on-line solid-phase extraction combined with chemiluminescence for the determination of pazufloxacin mesilate

A novel molecularly imprinted polymer solid-phase extraction (MISPE) with flow-injection chemiluminescence (CL) was developed for the determination of pazufloxacin mesilate (PZFX). The molecularly imprinted polymer (MIP) was synthesized by using PZFX as the imprinting molecule. A glass tube packed the particles of the MIP was employed as MISPE micro-column, which was connected into the sampling loop of the eight-way injection valve for on-line selective preconcentration and extraction of PZFX. The eluent of acetonitrile:acetic acid (9:1, v:v) was used as carrier for eluting the adsorbed PZFX to react with the mixture of cerium(IV) and sodium sulfite in the flow cell to produce strong CL. The relative intensity of CL was linear to PZFX concentration in the range from 2.5 × 10⁻⁹ to 2.5 × 10⁻⁷ g mL⁻¹. The limit of detection was 7 × 10⁻¹⁰ g mL⁻¹ (3 σ) and the relative standard deviation for 5 × 10⁻⁸ g mL⁻¹of PZFX solution was 3.7% (n = 7). This method has been applied to the determination of PZFX in human urine.     

Oxygen concentration and modeling thermal decomposition of a high‐performance material: A case study of polyimide (Cirlex)

Kinetic decomposition models for the thermal decomposition of a high‐performance polymeric material (Polyimide, PI) were determined from specific techniques. Experimental data from thermogravimetric analysis (TGA) and previously elucidated decomposition mechanism were combined with numerical simulating tool to establish a comprehensive kinetic model for the decomposition of PI under three atmospheres: nitrogen, 2% oxygen, and synthetic air. Multistaged kinetic models with subsequent and competitive reactions were established by taking into consideration the different types of reactions that may be occurring during the thermal decomposition of the material (chain scission, thermo‐oxidation, char formation). The decomposition products and decomposition mechanism of PI which was established in our previous report allowed for the elucidation of the kinetic decomposition models. A three‐staged kinetic thermal decomposition pathway was a good fit to model the thermal decomposition of PI under nitrogen. The kinetic model involved an autocatalytic type of reaction followed by successive nth order reactions. Such types of models were set up for the evaluation of the kinetics of the thermal decomposition of PI under 2% oxygen and in air, leading to models with satisfactory fidelity.     

司他夫定的热分解机理及动力学

采用TG-DTG-DSC测定司他夫定（STVD）在N2气和空气气氛中的热分解过程及其在热分解过程中不同阶段残留物的红外光谱,运用量子化学GAMESS软件计算STVD分子的键级,探讨了STVD的热分解机理。 采用Ozawa方法计算STVD各阶段热分解反应动力学参数,采用Dakin方程推算了不同使用温度下STVD的预期寿命。结果表明,STVD的热分解过程是一个三阶段过程,起始热分解步骤是联接胸腺嘧啶环与五元环的C-N键的断裂。 在N2气中,第一阶段热分解温度范围为139~173 ℃,失重21.2%,反应活化能Ea=168.9 kJ/mol,指前因子A=2.884×1019 min-1;第二阶段热分解温度范围为173~313 ℃,失重56.2%,Ea=96.4 kJ/mol,A=2.884×108 min-1;第三阶段分解速率缓慢,至880 ℃仍有10.9%残重。 在空气中,第一阶段热分解温度范围为139~166 ℃,失重19.1%,Ea=168.1 kJ/mol,A=2.188×1019 min-1;第二阶段热分解温度范围为166~314 ℃,失重53.9%,Ea=154.9 kJ/mol,A=8.913×1013 min-1;第三阶段热分解温度范围314~550 ℃,失重27%,Ea=116.9 kJ/mol,A=3.548×108 min-1。 STVD在常温下具有较好的热稳定性。     

纳米NdCoO3催化高氯酸铵热分解的DSC/TG-MS研究

采用微乳液法制备了立方晶系的NdCoO3纳米晶.利用DSC/TG-MS研究了NdCoO3对AP热分解的催化作用.结果表明,在NdCoO3的催化作用下,AP的热分解反应峰值温度下降了113℃,表观分解反应热从655 J·g-1增加到1 363 J·g-1,分解的气相产物主要有NH3,H2O,O2,HCl,N2O,NO,NO2和Cl2.在金属氧化物表面吸附生成超氧化离子(O2-)和氧离子(O-,O2-),这是加速AP分解反应的主要原因.加入NdCoO3催化AP热分解,由于对氨的氧化深度不同而导致分解放热量的增加.     

N-(苯乙酰氨基)-N’-(α-萘乙酰基)硫脲的热解机理及热动力学研究

采用热重法(TG)和微分热重法(DTG)对合成的新型酰氨基硫脲类化合物——N-(苯乙酰氨基)-N’-(α-萘乙酰基)硫脲进行了热稳定性研究, 在25～600 ℃范围内有两次失重过程. 通过量子化学方法计算了分子的Mayer键级, 据此计算结果和热重分析结果提出了其热解机理. 并运用Kissinger和Ozawa等方法计算了其热解动力学参数. 得到第一阶段热解动力学方程为: dα/dt＝541.5exp(－38350/RT)(1－α)2.58; 第二阶段热解动力学方程为: dα/dt＝505.2exp(－64810/RT)• (1－α)2.12.     

Investigations on poly(vinyl chloride). IV. Effects of metal chlorides on the thermal decomposition of poly(vinyl chloride)

The effects of various metal oxides upon the thermal decomposition of poly(vinyl chloride) (PVC) were previously reported. In this work, 23 metal chlorides were investigated to determine their effects on the thermal decomposition of PVC by pyrolysis–gas chromatography at 500°C. Each metal chloride exhibits influences on the course of thermal decomposition of PVC almost similar to the corresponding metal oxide except for a few elements; the metal chlorides from acidic metal oxides accelerate the thermal decomposition of PVC, but the metal chlorides from basic metal oxides do not. On comparing the effects of metal oxides and metal chlorides on the thermal decomposition of PVC, most metal chlorides were found to accelerate the thermal decomposition of PVC more than the corresponding metal oxides, owing to ease of addition of the chlorine atoms released from metal chloride to the dehydrochlorinated chains. It is concluded from these results that the thermal decomposition of PVC containing metal salts is markedly influenced by the ease with which chlorine atoms are released from the corresponding metal chloride.     

Spectroscopic and thermal properties of FeHg(SCN)4

The preparation and characterization of iron mercury thiocyanate, FeHg(SCN)₄ (abbreviated as FMTC) are described. The spectroscopic properties were characterized by X-ray powder diffraction (XRPD), infrared, Raman and UV-Vis-NIR transmission spectra. The thermal stability and thermal decomposition of FMTC were investigated by means of thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The intermediates and final products of the thermal decomposition were identified by X-ray powder diffraction at room temperature.