聚乙烯醇/纳米纤维素复合膜的渗透汽化性能及结构表征

将聚乙烯醇/纳米纤维素(PVA/NCC)复合膜应用于乙醇-水混合溶液的渗透汽化脱水过程,探讨了纳米纤维素对膜的溶胀性能、机械性能和渗透汽化性能的影响; 利用原子力显微镜(AFM)探测了纳米纤维素的形貌特征; 采用傅里叶变换红外光谱仪(FTIR)、扫描电镜(SEM)、差示扫描量热仪(DSC)和热重分析仪(TGA)对膜结构...     

Study of some volatile compounds evolved from the thermal decomposition of atenolol

Simultaneous thermogravimetry–differential scanning calorimetry (TG–DSC) and coupled thermogravimetry–infrared spectroscopy (TG–FTIR) analyses were used to study the antihypertensive drug atenolol. The TG–DSC curves provided information concerning the thermal stability and decomposition profiles of the compound. From the TG–FTIR coupled techniques, it was possible to identify ammonia and isopropylamine as possible volatile compounds released during the thermal decomposition of the drug.     

Thermal degradation behavior of cellulose fibers partially esterified with some long chain organic acids

The thermal degradation behavior of cellulose fibers and some fibrous cellulose esters with partial degree of substitution has been studied by thermogravimetry analysis (TG) and differential scanning calorimetry (DSC). Cellulose esters were prepared by heterogeneous esterification in Py/TsCl with unsaturated or saturated long chain organic acids [undecylenic (C₁₁), undecanoic (C₁₁), oleic (C₁₈) and stearic (C₁₈)]. The thermal degradation of cellulose fibers follows a one-step process. The thermal stability of cellulose esters is inferior to that of unmodified cellulose fibers and the thermograms show a two-step degradation process, probably controlled by crosslinking reactions, which occur during thermal decomposition. Exothermic peaks in the DSC thermograms are also an indication of such reactions. Kinetic parameters such as the activation energy E, order of decomposition n, and frequency factor Z were obtained following the Friedman method. The cellulose sample followed first order of decomposition, however for cellulose esters higher orders were observed.     

Dehydration studies of Co(II), Cu(II) and Zn(II) methanesulfonates

The dehydration process of Co(II), Cu(II) and Zn(II) methanesulfonates was studied by thermogravimetry/derivative thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC) techniques in dynamic N₂ atmosphere. The TG/DTG curves show that all of them contain four crystallization water molecules, which are lost in two steps. The peak temperature and dehydration enthalpies ΔH were measured from DSC curves for each compound. The effect of procedural variables on the TG and DSC curves was investigated. In this work, the procedural variables included heating rate, Al pan state (unsealed and sealed) and sample mass.     

Characterization of venlafaxine hydrochloride and compatibility studies with pharmaceutical excipients

The thermal analytical study of venlafaxine hydrochloride, a third generation antidepressant, was investigated using thermogravimetry (TG) and differential scanning calorimetry (DSC). The DSC curves have shown a sharp endothermic event at 211 °C and TG demonstrated a single stage of mass loss between 254 and 283 °C. Solid-state characterization was carried out by DRIFT, SEM, and XRPD demonstrating the drug physicochemical properties including crystallinity. Drug-excipient compatibility studies investigated by DSC have shown a possible physical interaction of the drug with magnesium stearate, microcrystalline cellulose and starch. Nevertheless, these results where not confirmed by DRIFT and SEM analyses.     

Thermal degradation of polymers: Part XXV—Synthesis, polymerisation and thermal characterisation of m-acetamidostyrene and m-acetoxystyrene homopolymers

m-Acetoxystyrene and m-acetamidostyrene have been synthesised and homopolymerised using 2,2′-azoisobutyronitrile as free radical initiator. The resulting polymers have been characterised by a variety of methods including thermogravimetry (TG) and differential scanning calorimetry (DSC). Glass transition temperatures have been measured for samples of different molecular weight.

TG and DSC have been used to compare the degradation behaviour of poly(m-acetoxystyrene) and poly(m-acetamidostyrene) with polystyrene in air and nitrogen atmospheres.     

Application of thermal analysis to the study of antituberculosis drugs–excipient compatibility

First-line drugs (rifampicin, RIF; isoniazid, INH; ethambutol, ETA; and pyrazinamide, PZA) recommended in conventional treatment of tuberculosis were analyzed in 1:1 w/w binary mixtures with microcrystalline cellulose MC 101 (CEL) and lactose supertab^® (LAC) by differential scanning calorimetry (DSC), thermogravimetry (TG), differential thermal analysis (DTA), and Fourier transformed infrared analysis (FTIR) as part of development of fixed dose combination (FDC) tablets. Evidence of interaction between drug and pharmaceutical excipients was supposed when peaks disappearance or shifting were observed on DTA and DSC curves, as well as decreasing of decomposition temperature onset and TG profiles, comparing to pure species data submitted to the same conditions. LAC was showed to interact with RIF (absence of drug fusion and recrystallization events on DSC/DTA curves); INH (thermal events of the mixtures different from those observed for drug and excipient pure in DSC/DTA curves); PZA (decrease on drug fusion peak in DSC/DTA curves), and ETA (shift on drug onset fusion and absence of pure LAC events on DSC/DTA curves). In all cases, an important decrease on the temperature of drug decomposition was verified for the mixtures (TG analysis). However, FTIR analysis showed good correlation between theoretical and experimental drug-LAC spectra except for INH–LAC mixture, evidencing high incompatibility between these two species and suggesting that those interactions with PZA and RIF were thermally induced. No evidence of incompatibilities in CEL mixtures was observed to any of the four-studied drugs.     

Thermal characterization of bacterial cellulose–phosphate composite membranes

Cellulose–phosphate composite membranes have been prepared from bacterial cellulose membranes (BC) and sodium polyphosphate solution. The structure and thermal behavior of the new composites were evaluated by X-ray diffraction (XRD), ³¹P-nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetry (TG) and thermomechanical analysis (TMA). From XRD analyses the Iα and Iβ cellulose crystalline phases were identified together with crystalline sodium phosphate that covers the cellulose microfibrils as revealed by SEM. ³¹P NMR spectra show peaks assigned to Q⁰ and Q¹ phosphate structures to be compared to the Q² units that characterize the precursor polyphosphate. Glass transition temperature, T _g, obtained from TMA curves and thermal stability obtained from TG and DSC measurements, were observed to be dependent on the phosphate content.     

N,N′-dichloro-bis[2,4,6-trichlorophenyl]urea (CC2) and suspending agents used for the preparation of decontamination formulation against chemical warfare agents

N,N′-dichloro-bis[2,4,6-trichlorophenyl]urea, known as CC2, is used as a reactive chemical decontaminant of mustard agents. The present study was undertaken to establish the compatibility of CC2 with a number of commonly used suspending agents, using thermoanalytical techniques viz., thermogravimetry (TG) and differential scanning calorimetry (DSC) with the support of Fourier transform infrared spectroscopy (FTIR). The results demonstrated the applicability of TG and DSC as a fast screening tool for analysing the compatibility of drug with excipients at the early stages of a preformulation process. Methylcellulose, hydroxypropylcellulose, and betaine were found to be compatible with CC2.     

Selecting polymers for medical devices based on thermal analytical methods

This biomaterials overview for selecting polymers for medical devices focuses on polymer materials, properties and performance. An improved understanding of thermoplastics and thermoset properties is accomplished by thermal analysis for device applications. The medical applications and requirements as well as the oxidative and mechanical stability of currently used polymers in devices are discussed. The tools used to aid the ranking of the thermoplastics and thermosets are differential scanning calorimetry (DSC), thermogravimetry (TG), thermal mechanical analysis (TMA) and dynamic mechanical analysis (DMA) as well as a number of key ASTM polymer tests. This paper will spotlight the thermal and mechanical characterization of the bio-compatible polymers e.g., olefins, nylon, polyacetals, polyvinyl chloride and polyesters.     

β-环糊精共聚物及其金属配合物的制备与性能

合成了顺丁烯二酸酐酯化β-环糊精与苯乙烯的共聚物及其金属配合物。 利用红外、紫外、元素分析、差示扫描量热法及热失重分析法对其进行了结构表征和性能测试。 这种含有β-环糊精的共聚物金属配合物作为脲酶抑制剂,对大豆脲酶催化尿素水解的抑制效果显著,其铜金属配合物为4 g/L时,抑制率达96.67%。     

Thermal and surface study of phenolic resin from cashew nut shell liquid cured by plasma treatment

In this study, phenolic resins from cashew nut shell liquid (CNSL) were applied as coating on Carbon Steel 1020 samples and successfully cured by plasma treatment or with hexamethylenetetramine (HMTA). The crosslinked samples were characterized by thermal analysis using thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), and atomic force microscopy (AFM) techniques in order to evaluate the thermal stability of these samples, as well as understand and study the curing process. TG/DTG curves showed that the thermal stability of the HMTA-cured resin was slightly higher than the resin treated by plasma. According to the DSC curves, HMTA-cured resin and plasma-treated resin exhibited only transition temperatures, so both resins were predominantly amorphous. Images generated by AFM provided qualitative evaluation of the resin surfaces, demonstrating that the coating surface with best homogeneity was cured by plasma treatment.     

Thermotropic phase behaviour of mixed liposomes of archaeal diether and conventional diester lipids

During preformulation studies of pharmaceutical solid dosage forms, thermal analysis techniques are very useful to detect physical or chemical incompatibilities between the drug and adjuvants of interest that might interfere with efficacy and safety of the final drug product. Differential scanning calorimetry (DSC) and thermogravimetry (TG) are useful tools for this purpose. The aim of this study was to investigate the thermoanalytical behavior of olanzapine (OLZ) when mixed with several excipients commonly used in solid dosage forms such as microcrystalline cellulose, croscarmellose, dicalcium phosphate dihydrate (DCPD), lactose, magnesium stearate, and povidone. Following DSC and TG analyses, powder X-ray diffraction tests were carried out. Thermoanalytical methods showed evidence of interaction between OLZ and magnesium stearate, lactose, and povidone. These results can be useful during the selection of excipients for pharmaceutical formulation development.     

Thermal characterization of the poultry fat biodiesel

Chemical composition of oils and fats used in the biodiesel synthesis can influence in processing and storage conditions, due to the presence of unsaturated fatty acids. An important point is the study of the biodiesel thermal stability to evaluate its quality using thermal analysis methods. In this study the thermal stabilities of the poultry fat and of their ethyl (BEF) and methyl (BMF) biodiesels were determined with the use of thermogravimetry (TG/DTG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC), in different atmospheres. The TG/DTG curves of the poultry fat in synthetic air presented three decomposition steps while only one step was observed in nitrogen (N₂) atmosphere. The DSC results indicated four exothermic enthalpic transitions in synthetic air and an endothermic transitions in N₂ atmosphere attributed to the combustion process and to the volatilization and/or decomposition of the fatty acids, respectively. For both biodiesels the TG/DTG curves in air indicated two mass loss steps. In the DSC curves four exothermic transitions were observed in synthetic air besides an endothermic one in N₂ atmosphere.     

纤维素在离子液体[AMMor]Cl/[AMIM]Cl混合溶剂中的溶解性能

研究了纤维素在混配离子液体N-甲基-N-烯丙基吗啉氯盐[AMMor]Cl/3-甲基-1-烯丙基咪唑氯盐[AMIM]Cl中的溶解性能, 结果表明, [AMMor]Cl/[AMIM]Cl混配溶剂能有效溶解天然纤维素, 且在相同条件下, 溶解能力要优于离子液体[AMIM]Cl; 随着溶解温度的升高, 溶解时间大大缩短. 利用FTIR, XRD和TGA方法分析了再生纤维素的化学结构和热稳定性, 结果表明, 未经活化的纤维素可直接溶于[AMMor]Cl/[AMIM]Cl而不发生其它衍生化反应, 且天然纤维素在该溶剂体系中纤维素聚合度下降较小.     

Compatibility study between ibuprofen and excipients in their physical mixtures

The thermal techniques of analysis were used to assess the compatibility between ibuprofen (IB) and some excipients used in the development of extended released formulations. This study is a part of a systematic study undertaken to find and optimizes a general method of detecting the drug–excipient interactions, with the aim of predicting rapidly and assuring the long-term stability of pharmaceutical product and speeding up its marketing. The thermal properties of IB and its physical association as binary mixtures with some common excipients were evaluated by thermogravimetry/derivative thermogravimetry (TG/DTG) and differential scanning calorimetry. FT-IR spectroscopy and X-ray powder diffraction (XRPD) were used as complementary techniques to adequately implement and assist in interpretation of the thermal results. Based on their frequent use in preformulations nine different excipients: starch; microcrystalline cellulose (PH 101 and PH 102); colloidal silicon dioxide; lactose (monohydrate and anhydre); polyvinylpyrrolidone; magnesium stearate and talc were blended with IB. The samples were prepared by mixing the analyte and excipients in a proportion of 1:1 (w:w). The TG/DSC curves of the IB have shown a single stage of mass loss between 175 and 290 °C, respectively, an endothermic peak at 78.5 °C, which corresponds to the melting (literature T _m = 75–78 °C).     

Glass transition temperature and thermal decomposition of cellulose powder

Cellulose powder and cellulose pellets obtained by pressing the microcrystalline powder were studied using differential scanning calorimetry (DSC), differential thermal analysis (DTA), and thermal gravimetry (TG). The TG method enabled the assessment of water content in the investigated samples. The glass phase transition in cellulose was studied using the DSC method, both in heating and cooling runs, in a wide temperature range from −100 to 180 °C. It is shown that the DSC cooling runs are more suitable for the glass phase transition visualisation than the heating runs. The discrepancy between glass phase transition temperature T _g found using DSC and predictions by Kaelbe’s approach are observed for “dry” (7 and 5.3% water content) cellulose. This could be explained by strong interactions between cellulose chains appearing when the water concentration decreases. The T _g measurements vs. moisture content may be used for cellulose crystallinity index determination.     

Complexes of cobalt(II), nickel(II) and copper(II) with the benzenedicarboxylic acids. Thermal properties

The thermal properties of the complexes of phthalic, isophthalic and terephthalic acid with cobalt(II), nickel(II) and copper(II) are determined by thermogravimetry (TG), differential thermogravimetry (DTG) and differential scanning calorimetry (DSC).The thermal stability of the anhydrous compounds gives, for the metal ions, a sequence Co > Ni > Cu.The thermal stability series as a function of the ligand for each metal is terephthalate > isophthalate > phthalate.     

Effect of cerium, holmium and samarium ions on the thermal and structural properties of the HZSM-12 zeolite

The study of the incorporation of rare earth elements as additives in Y zeolites is a very interesting field of research, mainly by its potential application as additives in catalytic cracking process. In this work was studied the thermal and structural properties of cerium, holmium and samarium supported on HZSM-12 zeolite. The obtained materials were characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), nitrogen adsorption, thermogravimetry (TG/DTG), differential scanning calorimetry (DSC) and differential thermal analysis (DTA). TG/DSC/DTA analyses showed that the dehydration temperatures of RE/HZSM-12 zeolites (RE=Ce, Ho, Sm) increase in relation to pure HZSM-12. The acid properties were investigated by pyridine thermo desorption via TG. The results showed two events of mass loss attributed to elimination of pyridine adsorbed on the weak+medium acid sites and on the strong acid sites.     

Evaluation of thermal stability of enalapril maleate tablets using thermogravimetry and differential scanning calorimetry

Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used in order to evaluate the thermal stability of an enalapril maleate formulation packaged in two types of packaging, polyvinyl chloride/aluminum blister and aluminum strip. Enalapril and the excipients employed in the formulation were also evaluated by TG and DSC. Tablets were analyzed before and after storage in an acclimatized room at 40 °C and relative humidity of 75 % for 90 days. The DSC and TG results were compared with the results of dosage of enalapril and related compounds obtained by high-performance liquid chromatography. These results indicate an occurrence of chemical interaction between enalapril maleate and the excipients during its storage. After storage, it was observed that the enalapril content reduced and the predominant degradation product was diketopiperazine for both types of packaging. The predominance of diketopiperazine could be related to the absence of sodium bicarbonate in the tablets, alkalinizing agent employed in the thermal stabilization of the drug.