芳香甲（乙）酯）铵盐的酰胺化与酰亚胺化

用热分析方法得出,由芳香酸甲酯或乙酯与4,4’-二氨基二苯甲烷制备的铵盐的酰胺化,酰亚胺化反应,较芳香酸的铵盐更易进行,反应温度和表观活化能均比四酸铵盐时低。由铵盐生成的聚酰亚胺具有很好的热氧化稳定性。     

测定铵盐酰亚胺化程度的热分析方法

<正> 酰亚胺化的完善程度直接影响聚酰亚胺的耐热性,但现尚无准确判断酰亚胺化程度的可靠方法,以往多采用红外光谱法,根据1380、1780厘米~(-1)(酰亚胺环上C=O基的振动)吸收峰的强度变化研究聚酰胺酸酰亚胺化动力学,并把经高温(如300℃左右)酰亚胺化的样品作为完全环化的“基准”,但并未确定这个“基准”究竟有多少没有环化。也有     

含硫醚结构均苯型聚酰亚胺的合成及表征

以4,4′-二氨基二苯硫醚(SDA)和均苯四酸酐(PMDA)为原料,通过溶液缩聚法-热酰亚胺/化学酰亚胺化的方法制备了一种含硫醚结构均苯型聚酰亚胺.利用高级旋转流变仪建立了在线跟踪反应进程的方法,采用热失重分析仪研究反应条件对热酰亚胺化及化学酰亚胺化法的影响,这些方法的建立为进一步制备高性能的聚酰亚胺提供有效的实验手段.采用小角激光光散射法、红外光谱、元素分析、接触角仪、DSC等方法对聚合物的结构与性能进行表征.结果显示,硫醚结构的引入,可有效改善聚合物薄膜的表面性能,其与铜箔之间的粘附功明显大于传统聚酰亚胺,在无胶挠性线路板应用方面显示出较好的应用前景.所获聚合物的Mw为(6.7±1.6)×104,分解温度均高于560℃;DSC的结果显示所制备的两种酰亚胺化聚合物均具有较高的玻璃化转变温度,相比之下,化学酰亚胺化更有利于获得高酰亚胺化程度的聚合物,产物的玻璃化转变温度也更高.     

Thermal studies of chitin–chitosan derivatives

New poly(azo) amino-chitosan compounds were obtained from the azo coupling reaction of N-benzyl chitosan and diazonium salts. The thermal behavior of these compounds was studied by thermogravimetric analysis (TG), differential thermogravimetric analysis (DTG), TG coupled with a Fourier-transform infrared, and differential scanning calorimetry (DSC). TG/DTG curves of chitin–chitosan polymer showed two thermal events attributed to water loss and decomposition of the polysaccharide after cross-linking reactions. Thermal analysis of the poly(azo) amino-chitosan compounds showed that the decomposition temperatures decreased when compared to the starting chitin–chitosan and N-benzyl chitosan. DSC results showed an agreement with the TG/DTG analyses. Thermal behavior of poly(azo) amino-chitosans suggest that these compounds could be considered as potential thermal sensors.     

Thermal studies on alkaline earth monomethyl violurates

Some alkaline earth monomethyl violurate hexahydrates were prepared in aqueous medium, and characterized on the basis of elemental analysis and IR spectral data. The thermal behaviour of these salts was studied with the aid of TG, DTG and DSC techniques. Heats of dehydration were calculated from DSC curves.     

Kinetic analysis of thermogravimetric data

The potassium, ammonium and thirteen amine salts of hexabromoplatinic acid were obtained and characterized by chemical analysis. The thermal decompositions of these complex salts were studied by derivatograph and differential scanning calorimetry. The natures of the pyrolysis processes are discussed and compared with those obtained for the analogous chlorocomplexes. From the TG curves, kinetic parameters were derived for different stages of the thermal decomposition.

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Zusammenfassung Es wurden die Kalium-, Ammonium- und dreizehn verschiedene Aminsalze von Hexabromoplatinsäure hergestellt und mittels Elementaranalyse charakterisiert. Mittels Derivatographie und DSC wurde die thermische Zersetzung dieser Komplexsalze untersucht. Das Wesen der Pyrolysevorgänge wird besprochen und mit dem der analogen Chlorokomplexe verglichen. Anhand der TG-Kurven wurden für verschiedene Schritte der thermischen Zersetzung kinetische Parameter ermittelt.

     

Structure and properties of polyimide films during a far‐infrared‐induced imidization process

The conversion of poly(amic acid) into polyimide (PI) was achieved with far‐infrared radiation (FIR) and conventional thermal treatments. The structure and properties of PI films during different stages of imidization were studied with Fourier transform infrared spectroscopy, weight‐loss analysis during imidization, tensile property measurements, and dynamic mechanical thermal analysis. The effects of the imidization degree, postimidization, and solvent on the thermal and mechanical properties of PI films were quantitatively investigated. The corresponding structural changes were also examined. The experimental results showed that the imidization process proceeded more quickly and more completely in an FIR oven than in a conventional oven. A prolonged FIR treatment at a lower temperature (25–100 °C) accelerated the imidization process. The tensile stress–strain curves had a fanlike distribution with the development of the FIR imidization process and a fishtail distribution with conventional thermal imidization. During FIR imidization, the best tensile properties were obtained at 340 °C, and thermooxidative degradation occurred at about 420 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2490–2501, 2004     

Comparison of different methods for determining the imidization degree of polyimide fibers

In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree(ID) calculated by TGA was based on the weight loss of each sample, which was caused by the imidization of residual amic acid groups. The results of TGA showed good regularity with the thermal treatment temperature of the PI fibers. For DSC, the ID was calculated based on the area of endothermal peak of each sample. Compared with TGA, DSC showed a relatively higher value because the endothermal peak was reduced by the exothermic re-formation of polyamic acid which may be partially degraded during thermal treatment. The IDs obtained by the FTIR spectra generally showed poorer regularities than those obtained by both TGA and DSC, especially for the results calculated using the 730 cm-1 band. Based on the 1350 cm-1 band, the obtained IDs showed better agreement with the TGA or DSC results. The results obtained by these three methods were compared and analyzed. The ID obtained by TGA showed much more reliability among these three methods.     

Investigation of process of polyimide formation from complexes of diester of benzophenonetetracarboxylic acid with diamines. 1. Investigation of thermal imidization by means of IR spectroscopy

The thermal imidization of complexes of benzophenonetetracarboxylic acid diester with diamines is greatly different from the thermal imidization of the corresponding mechanical mixtures. Preliminary complexation gives a considerably greater degree of completion of the imidization. It is concluded that diffusion processes play a decisive role in the solid-phase thermal imidization of the complexes. On the basis of similar values of the free energy of activation at identical temperatures for complexes with different diamines, it is concluded that the reactivity of the functional groups has little influence on the kinetics of solid-phase imidization of the complex. Alternative schemes are proposed for the formation of polyimides from the complexes, leading to an intermediate mixed-unit prepolymer with amido acid, amido ester, and imide units in the chain.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2462–2468, November, 1989.The authors wish to thank V. V. Shamanin for discussion of the results.     

Characterization of monumental carbonate stones by thermal analysis (TG, DTG and DSC)

Thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC), were found to be suitable instrumental techniques for the study of monumental rocks because they need small amounts of sample and provide extensive qualitative and quantitative information. From DTG curves, the calcite/dolomite ratio in the samples as well as the differences between limestones and dolomites can be quantitatively determined. DSC curves are adequate for the identification of the degradation products in the monumental stones since they are usually salts (sometimes hydrates) which present first-order processes under 600°C. This technique makes it possible to carry out quantitative and semiquantitative analysis of the degradation of monumental rocks since it provides data about its mineralogic composition.     

新的离子型光敏聚酰亚胺

合成了新的复合光敏聚酰胺酸季铵盐，研究了光敏剂、交联剂以及化学结构对感光度的影响，并考察了其热稳定性。结果表明以3，3′，4，4′－联苯四酸二酐－间苯二胺为主链的聚酰胺酸合成的光敏聚酰胺酸季铵盐有较高的感光度，光敏剂米氏酮的含量在3－5％，交联剂2，6－双（4－叠氨苄基）－4－甲基环己酮的含量在8－10％为宜；光敏性叔胺二甲氨基乙醇肉桂叉乙酸酯的含量不可超过8％；由这种复合季铵盐合成的新的光敏聚酰胺酸盐在较低的温度200℃以下就可以完全酰亚胺化，但接近550℃才达到理论失重量。     

A study of the curing behavior of polyamic acid coated on a Cu or Zn layer

ZnO and Cu₂O nanoparticles can be formed through the thermal decomposition of the complex between Zn or Cu with polyamic acid (PAA), accompanying with the formation of polyimide (PI). Transmission electron microscopy (TEM) analysis showed that the formation of ZnO nanoparticles needs a longer curing time than that of Cu₂O. Fourier transform infrared spectroscopy (FT-IR) characterization shows that both Zn and Cu will delay the imidization process of PAA. However, the retarding degree of imidization process is higher for Zn than that of Cu. Further investigation showed the structure of Zn–PAA complex is different from that of Cu–PAA, which is the reason for the difference of initial imidization temperature. Thermogravimetric and differential thermal analysis (TG–DTA) characterization agrees well with the results of FT-IR. Also, the thermal decomposition temperature of the polyimide was changed by the involvement of Zn or Cu during curing.     

Experimental study on optimized composition of mixed carbonate for phase change thermal storage in solar thermal power plant

36 kinds of mixed carbonate molten salts were prepared by mixing potassium carbonate, lithium carbonate, sodium carbonate in accordance with different proportions. The data of melting point and latent heat are measured by the analysis of DSC curves of 36 kinds of salts, which show that the majority of ternary carbonate’s melting points are close at around 400 °C. 24 kinds of eutectic molten salts were selected among 36 kinds of molten salts. With high latent heat, ternary carbonate salt has the potential to be employed for phase change thermal storage. The costs for phase change thermal storage of 24 kinds of carbonate salts are calculated. Finally, 13 kinds of ternary carbonate salts with lower cost for phase change thermal storage are recommended, where there are 6 kinds of mixed carbonates have the considerably larger latent heat of melting.     

Studies on azotetrazolate based high nitrogen content high energy materials potential additives for rocket propellants

This paper reports the synthesis, characterisation and thermolysis studies of a series of azotetrazolate salts, viz., ammonium/guanidinium/triaminoguanidinium [azotetrazolate]. TG-DTA and DSC results of these compounds exhibited their thermal stability up to 180°C. DSC indicated the highest heat release (2804 J g^–1) for guanidinium azotetrazolate salt during exothermic decomposition. FTIR of the decomposition products of azotetrazolate salts showed bands at 3264 and 2358 cm^–1 which may be attributed to gaseous species such as NH₃ and HCN or NH₂CN. The sensitivity data suggests low vulnerability of ammonium and guanidinium salts. In cyclic voltammetric studies all the salts showed similar response in reduction reactions. Triamino guanidinium azotetrazolate (TAGAZ) was incorporated into solid propellant formulations in order to establish the compatibility of this class of compounds. DSC results revealed that it does not have adverse effect on thermal stability of double base matrix. The burning rate data obtained indicated that TAGAZ acts as an efficient energetic additive in composite modified double base (CMDB) propellant formulations in high-pressure region.The authors are grateful to Dr. Haridwar Singh, Outstanding Scientist and Director, HEMRL for constant encouragement to carry out this work. Authors also thankful to Dr. R. S. Satpute, Dr. A. N. Nazare and Dr. C. N. Divekar for their assistance in propellant processing.     

Some observations on the thermal behaviour of curcumin under air and argon atmospheres

The TG, DTG and DTA curves of curcumin(I) have been recorded in static air and inert dynamic argon atmosphere over the range between ambient temperature and 600°–700°C using a Netzsch thermal analyser STA 429. Careful examination of these curves reveals appreciable differences in the behaviour of I under either atmospheres, which are easily recognized by comparing the profiles of their thermal curves, particularly in the melting point, thermalL stability of intermediates, percent weight loss and exothermicity of the chemical processes. Gaschromatographic analysis of volatile pyrolysates trapped during thermal analysis indicates the formation of (CH₃)₂CO, CH₃COH and C₆H₅OCH₂COOH (phenyl oxyacetic acid). However, in static air CO₂ and H₂O were identified as well. X-ray diffractometry reveals the formation of amorphous carbon as a final product in argon and a mixture of amorphous carbon and graphite in air. It seems that the relatively high mass of argon plays an important role in the reactions and stability of intermediates. In either atmospheres curcumin is thermally stable up to 249°C withm.p. of 176.4°–177.5°C. The unique shape of the DTA curve of I could be used forits identification.     

Research on thermal decomposition of trinitrophloroglucinol salts by DSC, TG and DVST

The thermal decomposition of the four nitrogen-rich salts of ammonia (NH₄), aminoguanidine (AG), carbohydrazide (CHZ) and 5-aminotetrazo (ATZ) based on trinitrophloroglucinol (H₃TNPG) was investigated using the differential scanning calorimetry (DSC), thermogravity (TG), and dynamic vacuum stability test (DVST). DSC and TG methods research the complete decomposition, while DVST method researches the very early reaction stage. The peak temperatures of DSC curves are consistent with the temperatures of maximum mass loss rates of TG curves. The apparent activation energies of these H₃TNPG-based salts obtained by DSC and DVST have the same regularity, i.e., (ATZ)(H₂TNPG)·2H₂O < (CHZ)(HTNPG)·0.5H₂O < NH₄(H₂TNPG) < (AG)(H₂TNPG). The thermal stability order is (ATZ)(H₂TNPG)·2H₂O < (CHZ)(HTNPG)·0.5H₂O < (AG)(H₂TNPG) < NH₄(H₂TNPG), which was evaluated by DVST according to the evolved gas amount of thermal decomposition. DVST can monitor the real-time temperature and pressure changes caused by thermal decomposition, dehydration, phase transition and secondary reaction, and also evaluate the thermal stability and kinetics.      

Thermal kinetic studies on the decompositions of cefuroxime lysine in different atmospheres and heating rates

The thermal decomposition of a new antibiotic agent, cefuroxime lysine, was investigated by thermogravimetry analysis/derivative thermogravimetry and differential scanning calorimetry (DSC) methods in anoxic and oxidative environments. The influence of heating rates (including 5, 10, 15, and 20 °C/min) on the thermal behavior of cefuroxime lysine was revealed. By the methods of Kissinger and Flynn–Wall–Ozawa, the thermal kinetic parameters of activation energy and pre-exponential factor for the exothermic processes under non-isothermal conditions were calculated using the analysis of corresponding DSC curves.     

Thermal studies on purine complexes: XII. Thermal behaviour of some metal complexes of hypoxanthine

Some complexes of hypoxanthine with Cu(II), Ag(I), Cd(II), Hg(II), Pd(II), Rh(III) and Pt(IV) have been prepared in ethanolic, aqueous, basic or acid media and characterized on the basis of elemental analysis and IR studies. The thermal behaviour of these compounds has been studied using TG, DTG and DSC techniques. Heats of dehydration, dehalogenation and fusion have been calculated from DSC curves.     

Thermovoltaic detection. III. Thermal decomposition of some amino acids

The thermal dissociation reactions of selected amino acids were studied by thermovoltaic detection (TVD), TG and DSC. All of the TVD curves except L-arginine contained a broad EMF output peak in the 200–300°C temperature range. The leading edges of the peak maxima were reproducible to within ± 1–2% while the trailing edges were reproducible to ± 20% or so. The latter was related to the irreproducible nature of the electrode-decomposition products interface. The TVD curves were not unique in that they yielded thermal analysis curves that were not inherently different from other TA techniques.     

Effect of carbon nanotubes and their dispersion on thermal curing of polyimide precursors

The process of thermal imidization reaction is significant for temperature and time control in the polyimide industry. Here, we report the effect of carbon nanotubes and their states of dispersion on the thermal imidization of the precursor films of polyimide (poly(amic acid)) for the first time. The curing process was followed by measuring Fourier transform-infrared (FT-IR) spectra, fluorescence spectra, thermogravimetric-differential scanning calorimeter (TG-DSC) properties and the refractive indices of films. It was found that by evenly dispersing 1 wt% of carbon nanotubes assisted by a dispersant in the poly(amic acid),the full imidization temperature of the polyimide can be reduced from 300 °C to 250 °C. Different states of distribution of CNTs were observed by light microscopy and scanning electron microscopy, and proved that a better dispersion of carbon nanotubes dramatically enhanced the speed of imidization. Moreover, the DSC results showed that lower decomposition temperature of poly(amic acid) could be obtained with more uniform distribution of carbon nanotubes, which means the process of cyclodehydration of the poly(amic acid) was accelerated.