Differential Scanning Calorimeter Data Research Articles

Simultaneous XRD-DSC identifies correct drug-polymer solubility and miscibility for enantiotropic solid forms

Thermodynamic properties, including solubility and miscibility, which are highly correlated with amorphous solid dispersion physical stability were identified for the complex solid forms of bromopropamide using simultaneous X-ray diffraction (XRD)-differential scanning calorimeter (DSC). The most stable solid form of bromopropamide was crystallized and its crystal structure was solved. The crystallized material was characterized using simultaneous XRD-DSC measurements, which allowed dual analyses of a single sample. Transitions of bromopropamide during heating resulted in observation of the unique diffraction patterns of its different solid forms. The dissolution endpoint (Tend) was measured for various mixtures of bromopropamide and polyvinylpyrrolidone-vinyl acetate random copolymer. The use of XRD-DSC allowed confident and accurate measurements of the Tend for a large range of compositions, assisting in the estimation of drug-polymer solubility and miscibility. Thermodynamic properties identified using combined XRD-DSC were further compared to those obtained using only DSC data. It was found that DSC data in isolation can lead to ambiguity, misinterpretations, and incorrect conclusions, especially for a solid demonstrating multiple, closely related forms.

Polymorphism in 5-methylsalicylic acid: Insights into relative thermal behavior, luminescent properties, crystal structure, and Hirshfeld surface analysis

Polymorphs play an important role in mediating the physical and chemical properties of compounds. Three polymorphs were obtained from different solvents used in crystallization. A new polymorph of 5-methylsalicylic acid (γ-MSA) were obtained from acetic acid. The polymorphs α-MSA and β-MSA crystallized from water, and the mixed solvent containing methanol and water, respectively. The novel morphology of γ-MSA has been characterized by single–crystal X–ray diffraction, IR spectroscopy data, and powder X-ray diffraction. Single-crystal X-ray diffraction analysis shows that γ-MSA belongs to the monoclinic system with the P21/c space group. The parameters are listed as the following: a = 7.2795(5) Å, b = 15.2560(7) Å, c = 6.7170(4) Å, β=100.834(7)°, V = 762.83(8) Å3. In the novel polymorphic structure, classical hydrogen bonds of O–H···O can be obviously observed, through which a supramolecular architecture will be generated. Apart from the classical hydrogen bonds, the weak hydrogen bonds of C–H⋯O can be only found in form γ-MSA. The luminescent maximal are 394, 398 and 406 nm for α-MSA,β-MSA and γ-MSA, respectively. The order of the luminescent maximal peaks is listed as the following: α<β<γ. Single-crystal X-ray diffraction analysis results reveal that the order of the stacking interactions and the dihedral angles occurred between the carboxylic group and phenyl ring presents the following: α<β<γ. The Hirshfeld analysis further confirms that there exists the same sequence of the C···H intercontacts in α-, β- and γ-polymorphs. The contribution of the H···O/O···H close contacts in γ-MSA is the largest among these polymorphs, being confirmed by differential scanning calorimeter (DSC) data, which is in a good agreement with that of melting point. On the basis of analysis of DSC data and the fusion rules, the enthalpies (ΔH) and entropies (ΔS) can be estimated to be 29.5 kJ mol-1 and 69.4 J K-1 mol-1 for α; 31.1 kJ mol-1 and 72.8 J K-1 mol-1 for β, and 35.4 kJ mol-1 and 74.5 J K-1 mol-1 for γ), and these polymorphs are monotropically related. The sequences of melting point, enthalpies and entropies can be proposed: α<β<γ.

Hydrogen isotope effect on thermodynamic and kinetic properties of Pd based ternary alloys: Pd–Ag-M (M = Au, Zr)

Owing to the importance of hydrogen and its isotopes in energy sector, the present study investigates thermodynamic and kinetic hydrogen isotope effects on desorption reaction of newly synthesized Pd-based ternary alloy-hydrides/deuterides viz., Pd0.89Ag0.05M0.06 (M = Au, Zr)–H/D. Alloys were prepared by arc melting method followed by characterization using PXRD, SEM, TXRF and EDX techniques. The effect of hydrogen isotopes on thermodynamics of H2/D2 desorption reaction was investigated by generating pressure-temperature isotherms (PCIs) at various temperatures using a Sieverts' type volumetric apparatus. The PCT diagram of alloys depicts a single plateau which confirms desorption to be a one-step process. Both alloy systems display a normal isotope effect as indicated by higher plateau pressure for deuterides as compared to hydrides. The enthalpy and entropy changes for the desorption reactions were calculated using Van't Hoff equation. The separation factor derived from PCT data indicates that Pd0.89Ag0.05Au0.06 alloy has a significantly high separation factor as compared to other Pd based alloys reported in the literature. To get more insight into this behavior, non-isothermal kinetic analysis of H2/D2 desorption based on Differential Scanning Calorimeter (DSC) data acquired at four different heating rates was conducted and activation energies of desorption were calculated by invoking Kissinger's equation. The activation energies of alloys were found to be lower than that of palladium which explains the high separation factor of alloys as compared to Pd. The desired combination of higher separation factor and lower activation energy makes Pd0.89Ag0.05Au0.06 alloy a promising material for practical application in the separation of hydrogen isotopes via self-displacement gas chromatography (SDGC).

The Investigation of the Production of Salt-Added Polyethylene Oxide/Chitosan Nanofibers.

The influence of different concentrations of salt-added polyethylene oxide (PEO) on the spinnability of chitosan (CS)/PEO + NaCl blends that could be used as a component part of filters for water treatment or nanofiber membranes as well as for medical applications was investigated in this study. The morphological properties of manufactured nanofibers were analyzed as well. It was determined that an increase of PEO concentration resulted mostly in thin and round nanofibers formed during electrospinning, but the manufacturing process became complex, because many wet fibers reached the collector while spinning. Also, it was noticed that the salt was not dissolved completely in the polymer solutions and some crystals were seen in the SEM images of manufactured fiber mats. However, the addition of salt resulted in lower viscosity and better conductivity of solution and fiber mats as well. The opposite effect was observed as the concentration of PEO was increased. The orientation of produced nanofibers as well as their diameter were analyzed with commercially available software. It was determined that the results obtained by software and microscopically are repeatable. The difference among the results of diameter calculated with software and taken by microscope varied from 0% to approximately 12%. The FTIR analyses indicated that alterations in polymer concentrations or the addition of salt did not induce any discernible changes in the chemical composition or nature of the materials under investigation. The sodium chloride present in the solutions enhanced electrical properties and increased conductivity values more than 50 times for PEO solutions and six times for CS/PEO blend solutions, compared to conductivity values of solutions without salt. To assess the thermal characteristics of the PEO/CS blend nanofibers, measurements using a differential scanning calorimeter (DSC) to determine melting (Tm) and crystallization (Tc) temperatures, as well as specific heat capacities were conducted. These parameters were derived from the analysis of endothermic and exothermic peaks observed in the DSC data. It showed that all produced nanofibers were semicrystalline.

The effect of pH and heating on the aggregation behavior and gel properties of beef myosin

Effects of pH and heating on the structure, aggregation, and gelation of beef myosin were evaluated. The results of the changed fluorescence intensity and decreased α-helix content of all treatments demonstrated that protein structure unwound with pH and temperature. Differential scanning calorimeter (DSC) data also proved that protein head denaturation and tail denaturation occurred at 55 °C and 75 °C, respectively. The increment of hydrophobicity and the reduction of sulfhydryl group content indicated that hydrophobic interactions and disulfide bonds were beneficial to protein aggregation at 55 °C. Significantly, the content of active sulfhydryl at pH 6.0 reached its lowest value (15.61 ± 0.67 μmol/g) at 85 °C. In addition, beef myosin aggregation was corroborated by the decreased solubility and increased turbidity of all treatments. The great three-dimensional network structure could be formed at pH 6.0 above 75 °C.

Preparation and characterization of lauric acid-stearic acid/fumed silica/expanded graphite thermally conductive enhanced composites

Fatty acid and fatty acid blend phase change materials (PCM) have issues with easy leakage and low thermal conductivity in thermal storage and exothermic processes. To overcome this issue, a novel low-temperature composite material, Lauric acid - stearic acid - fumed silica - expanded graphite (LA-SA-FS-EG), was fabricated by vacuum impregnation technique using lauric acid-stearic acid (LA-SA) as the phase change material (PCM), fumed silica (FS) as the support material, and expanded graphite (EG) as the thermal conductive material. Leakage tests indicated that the maximum adsorption of LA-SA by fumed silica was 75 wt%. Scanning electron microscopy (SEM) was employed to observe the microscopic morphology of the composites. The crystal structure and chemical composition of the composites were analyzed by X-ray diffraction (XRD) and Fourier infrared spectroscopy (FT-IR). The differential scanning calorimeter (DSC) data indicates that the melting temperatures of LA-SA-FS-EG 3 %, 5 % and 7 % were 33.38 °C, 33.32 °C and 33.13 °C respectively, with melting latent heats of 110.8 J/g, 114.3 J/g and 119.9 J/g, respectively. The thermal conductivity of LA-SA-FS-EG 7 % is improved by 454 % compared to the LA-SA-FS composite without the addition of EG. LA-SA-FS-EG7% composite showed excellent heat storage capacity. LA-SA-FS-EG7% has a 46.1 % increase in heat storage rate and a 59.4 % increase in thermal release rate compared to LA-SA-FS composite. Notably, the LA-SA-FS-EG7% composite retains good thermal properties even after 1000 heating and cooling cycles. Consequently, the LA-SA-FS-EG7% composites produced have potential applications in thermal energy storage and building energy efficiency.

Development of a sorafenib-loaded solid self-nanoemulsifying drug delivery system: Formulation optimization and characterization of enhanced properties.

Sorafenib, marketed under the brand name Nexavar®, is a multiple tyrosine kinase inhibitor drug that has been actively used in the clinical setting for the treatment of several cancers. However, the low solubility and bioavailability of sorafenib constitute a significant barrier to achieving a good therapeutic outcome. We developed a sorafenib-loaded self-nanoemulsifying drug delivery system (SNEDDS) formulation composed of capmul MCM, tween 80, and tetraglycol, and demonstrated that the SNEDDS formulation could improve drug solubility with excellent self-emulsification ability. Moreover, the sorafenib-loaded SNEDDS exhibited anticancer activity against Hep3B and KB cells, which are the most commonly used hepatocellular carcinoma and oral cancer cell lines, respectively. Subsequently, to improve the storage stability and to increase the possibility of commercialization, a solid SNEDDS for sorafenib was further developed through the spray drying method using Aerosil® 200 and PVP K 30. X-ray diffraction and differential scanning calorimeter data showed that the crystallinity of the drug was markedly reduced, and the dissolution rate of the drug was further improved in formulation in simulated gastric and intestinal fluid conditions. In vivo study, the bioavailability of the orally administered formulation increases dramatically compared to the free drug. Our results highlight the use of the solid-SNEDDS formulation to enhance sorafenib's bioavailability and outlines potential translational directions for oral drug development.

The formation mechanism and thermal decomposition kinetics of 2,4,6-trinitroresorcinol in the dinitrobenzene production

2,4,6-Trinitroresorcinol (TNR), one main by-product in the dinitrobenzene (DNB) production process, is self-reactive substance and has led to tragic explosion incidents in China. In this article, the formation mechanism of TNR during the DNB production process was studied employing HPLC and HPLC-MS technique. Thermal decomposition behavior of TNR was also systematically studied by differential scanning calorimeter (DSC). The decomposition kinetics of TNR were investigated employing both iso-conversional (Friedman and Ozawa method) and model-fitting method. The formation mechanism of TNR during the dinitrobenzene (DNB) production is confirmed: The two by-products of dinitrophenol (DNP) and trinitrophenol (TNP) produced in the benzene mononitration stage are further nitrated to form tetranitrophenol (TTNP) in the mononitrobenzene (MNB) nitration stage. Then most of TTNP will be hydrolyzed to form the TNR during the water washing process. The decomposition process of TNR has been proven to follow three consecutive steps (A→B1→B2→B). The former two steps present autocatalytic behavior while the last step obeys N-order reaction model. The accuracy of the developed decomposition model and the obtained model parameters have been demonstrated by the comparison of the simulated and experimental DSC data and the activation energy obtained by both the iso-conversional method and model-fitting method. The same trend of experimental and simulated results about isothermal reaction further verify the building model.

Optoelektronik Uygulamalar için Nb+5 Katkılı Çinko Borat Camların Sentezi ve Optik, Termal ve Yapısal Özelliklerinin Belirlenmesi

Bu çalışmada niyobyum pentaoksit (Nb2O5) katkılı yüksek oranda çinko oksit (ZnO) içeren çinko borat (ZnB) oksit camlar yüksek sıcaklıkta eritme tavlama yöntemi ile başarıyla sentezlenmiştir. Sentezlenen camlara ait yapısal karakterler diferansiyel taramalı kalorimetre (DSC) ve Fourier dönüşümlü kızılötesi spektroskopisi (FTIR) ile belirlenmiştir. DSC verilerine göre camsı geçiş (Tg), kristallenme (Tc), erime (Tm) sıcaklıkları ve termal kararlılıklar (T) belirlenerek Nb2O5 değişimiyle ilgisi açıklanmıştır. DSC verilerine göre Tg, Nb2O5 konsantrasyonunun artışıyla 560oC’den 555oC’ye; Tc, 681oC’den 657oC’ye düşmüştür. Sentezlenen cam numunelerin termal kararlılığı ise Nb2O5 artışıyla 121oC’den 102oC’ye düşmüştür. FTIR verilerine göre borun ve çinkonun yapısal birimleri açıklanmıştır. Borun cam matrisini BO3, BO4 ve borok-sol halka yapısal birimleriyle oluşturduğu, çinkonun ise cam matrisine tetrahedral ZnO4 ve oktahedral ZnO6 yapısal birimleri ile katkıda bulunduğu, niobyumun yapıda düzenleyici görev üstlendiği belirlenmiş-tir. Verilerin değerlendirilmesi sonucunda niyobyumun cam ağında oktahedral NbO6 biriminde bulunduğu gözlenmiştir. Nb2O5’in en belirgin biçimde değiştirdiği özelliklerin başında optik özellikler gelmektedir. Direkt ve indirekt optik bant aralığı, Urbach enerjisi, kırılma indisi üzerinde çalışılmış, geçirgenlik spekt-rumda çok net olmayan kaymalar gözlenmiştir. Optik bant aralığı Nb2O5 artışıyla azaldığı, Urbach enerjisi-nin arttığı belirlenmiştir. Sentezlenen numunelere ait yoğunluk, molar hacim ayrıca incelenmiş ve Nb2O5 konsantrasyonundaki artışın yoğunluk ve molar hacim değerlerini belirgin bir biçimde arttırdığı görülmüştür.

Considering Phase Transformation Heat When Modeling Thermal Process of Polyethylene Pipes Welding

Mathematical modeling of heat process, considering phase transformation heat, is used to develop technology of welding polyethylene pipes with built-in heating elements at low outdoor temperatures.Mathematically, task is to control technological parameters of welding in order to ensure flow of thermal process at low temperatures according to consistent patterns of welding at acceptable temperatures. With this control of thermal process, the need of ensuring certain sizes of supramolecular structures is eliminated, which allows us to simplify accounting for phase transformation heat. Instead of traditionally used crystallization kinetics equation, it is proposed to directly use differential scanning calorimeter (DSC) data to ensure given temperature field dynamics. Since during phase transformation heat is released and absorbed only by crystalline part of polymer material, special role is assigned to function of crystallinity degree. Formula is given for determining the effective heat capacity coefficient used in the shock-capturing method for solving heat conduction problem with phase transition in temperature range, based on temperature dependence on crystallinity degree. The calculation results for pipes with diameter of 63 mm at various ambient temperatures are shown. Significant increase in cooling rate at air temperatures below minus 15 ° C has been shown.

Synergistic Antitumor Effects on Drug-Resistant Breast Cancer of Paclitaxel/Lapatinib Composite Nanocrystals.

Drug resistance presents serious difficulties for cancer treatment. A combination of paclitaxel (PTX) and lapatinib (LAPA) shows potentials in multiple drug resistant cancers in the clinic, but it is almost impossible to deliver these two drugs to the tumor at the same time with the best proportion by simple co-administration of the respective current formualtions for their different pharmacokinetic profiles. Here composite nanocrystals of PTX and LAPA (cNC) were designed with a ratio of 2:1 (w/w), which was their intracellular ratio at the best synergistic efficacy on a drug-resistant cancer cell line (MCF-7/ADR). Such cNC were prepared using a bottom-up method to achieve a nearly spherical appearance and a narrow size distribution of 95.1 ± 2.1 nm. For nanocrystal stabilization, Polyethylene glycol (PEG) coating was introduced into the cNC via polydopamine (PDA) coating in order to get a PEGylated composite nanocrystal (cNC@PDA-PEG) with nanoscale size (170.5 ± 1.4 nm), considerable drug loading (PTX: 21.33 ± 1.48%, LAPA: 10.95 ± 1.24%) and good stability for at least 4 days in plasma-containing buffers. Differential scanning calorimeter (DSC) and XRD data both indicated the different crystalline states of the cNC as well as the cNC@PDA-PEG in comparison with bulk drugs. In vitro release data showed that PTX and LAPA were gradually and completely released from cNC@PDA-PEG in 3 days, while drug release from bulk drugs or cNC was only 30%. cNC@PDA-PEG also showed negligible hemolysis in vitro. Cellular uptake experiments in the MCF-7/ADR cell line showed that the nanocrystals entered the cells in a complete form through endocytosis and then released the drug in the cell. cNC@PDA-PEG inhibits the growth of this drug-resistant cell more effectively than the unmodified version (cNC). In summary, PEGylated PTX and LAPA composite nanocrystals showed the potential for treament of drug-resistant tumors by simultaneously delivering two drugs to tumor cells with the best proportion.

Synthesis, thermal stability and kinetic decomposition of triblock copolymer polypropylene glycol–poly glycidyl nitrate–polypropylene glycol (PPG–PGN–PPG)

An energetic triblock copolymer PPG–PGN–PPG (Mn = 1886 g mol−1) was synthesized for the first time by cationic ring-opening polymerization of propylene oxide with low molecular weight poly glycidyl nitrate (PGN) (Mn = 1061 g mol−1) as a macroinitiator, in the presence of boron trifluoride etherate (BF3·OEt2) as the catalyst. The product obtained in high yield was characterized by FTIR, gel permeation chromatography and 1H and 13C NMR spectroscopy. The thermal properties of the triblock copolymer were characterized by differential scanning calorimeter (DSC). The result approved that the glass transition temperature of the triblock copolymer (Tg = − 58 °C) is lower than PGN (Tg = − 35 °C); also, it was more stable than that of PGN. The effect of heating rates (10, 20, 30 and 40 °C min−1) on the decomposition of the copolymer was evaluated. The decomposition temperature of this compound increased as the heating rate increased. The kinetic parameters such as activation energy and frequency factor for the thermal decomposition of the triblock copolymer were obtained from the DSC and DTG data by non-isothermal methods proposed by the ASTM E696, Flynn–Wall–Ozawa (FWO) and Kissinger methods. The values by the FWO method are in good agreement with ASTM and Kissinger methods.

Thermal Properties of Woven Kenaf/Carbon Fibre-Reinforced Epoxy Hybrid Composite Panels

The effects of carbon fibre hybridisation on the thermal properties of woven kenaf-reinforced epoxy composites were studied. Woven kenaf hybrid composites of different weave designs of plain and satin and fabric counts of5×5and6×6were manually prepared by a vacuum infusion technique. A composite made from 100% carbon fibre was served for a comparison purpose. Thermal properties of pure carbon fibre and hybrid composites were determined by using a thermogravimetric analyser (TGA) and differential scanning calorimeter (DSC). It was found that a hybrid composite with higher kenaf fibre content (fabric count6×6) showed better thermal stability while the highest thermal stability was found in the pure carbon fibre composite. The TG and DTG results showed that the amount of residue decreased in the plain-designed hybrid composite compared to the satin-designed hybrid composite. The DSC data revealed that the presence of woven kenaf increased the decomposition temperature.

Physicochemical and Micromeritics Properties of Ketoprofen-Tartaric Acid Binary System

Physical characteristics of pharmaceutical active ingredients can be modified by molecular structure rearrangement inside its crystal lattice. Cocrystallization involved the formation of new crystal structure from two different crystal components. In its application in the pharmaceutical field, the formation of cocrystals can comprise the interaction between an active ingredient and an inert substance or between two different drugs. This study aimed to synthesize cocrystal from Ketoprofen and Tartaric Acid. Ketoprofen and Tartaric acid were ground with mortar for 10 minutes prior dissolving in methanol at 40°C with continuous stirring. The solution then filtered and evaporated at ambient temperature. The resulting crystal was ground before further characterization. The individual component and cocrystal were characterized using FTIR, Differential Scanning Calorimeter (DSC) and Powder X-Ray Diffractometer (PXRD). The results show that the acquired crystal mass, KET-TAR, is a mixture of a semi-crystalline phase and its non-interacting precursors New phase formation has been confirmed from both PXRD and DSC data. KET-TAR shows greater micromeritics properties compared to Ketoprofen with the value of angle of repose of, bulkiness, Carr’s Index, Haussner’s Ratio and Porosity are 25.3°, 1.8, 16.667, 1.200 and 61.7% consecutively. Overall improvement in micromeritic properties are clearly shown in the results.

Oxidation Behavior of Zr-based Amorphous Alloys at 400˚- 450˚C in Air

&lt;em&gt;&lt;span lang="EN-US"&gt;The study of oxidation behavior of amorphous alloys based on Zirconium with 2 variations in composition was carried out: Zr&lt;sub&gt;64.5&lt;/sub&gt;Cu&lt;sub&gt;17&lt;/sub&gt;Ni&lt;sub&gt;11&lt;/sub&gt;Al&lt;sub&gt;7.5 &lt;/sub&gt;and Zr&lt;sub&gt;69.5&lt;/sub&gt;Cu&lt;sub&gt;12&lt;/sub&gt;Ni&lt;sub&gt;11&lt;/sub&gt;Al&lt;sub&gt;7.5 &lt;/sub&gt;at temperatures of 400 - 450˚C in air. Amorphous Zr-based alloys were thermally characterized using Differential Scanning Calorimeter (DSC) to determine the crystallization temperature and glass transition temperature. The oxidation characterization was carried out using a Thermo gravimetric Analyzer (TGA) at temperatures of 400, 425, and 450˚C for 4 hours in air. The phase analysis of the oxidation product was identified using X-Ra&lt;/span&gt;&lt;span&gt;y Diffaction&lt;/span&gt;&lt;span lang="EN-US"&gt; (XRD). Based on DSC data the crystallization temperature for Zr&lt;sub&gt;64.5&lt;/sub&gt;Cu&lt;sub&gt;17&lt;/sub&gt;Ni&lt;sub&gt;11&lt;/sub&gt;Al&lt;sub&gt;7.5&lt;/sub&gt; and Zr&lt;sub&gt;69.5&lt;/sub&gt;Cu&lt;sub&gt;12&lt;/sub&gt;Ni&lt;sub&gt;11&lt;/sub&gt;Al&lt;sub&gt;7.5 &lt;/sub&gt;is 426 and 442˚C respectively. The oxidation kinetics of the two alloys follow parabolic law and the oxidation rate increases with the addition of temperature. Oxides formed during isothermal oxidation in the Zr&lt;sub&gt;64.5&lt;/sub&gt;Cu&lt;sub&gt;17&lt;/sub&gt;Ni&lt;sub&gt;11&lt;/sub&gt;Al&lt;sub&gt;7.5 &lt;/sub&gt;and Zr&lt;sub&gt;69.5&lt;/sub&gt;Cu&lt;sub&gt;12&lt;/sub&gt;Ni&lt;sub&gt;11&lt;/sub&gt;Al&lt;sub&gt;7.5&lt;/sub&gt; alloys are t-ZrO&lt;sub&gt;2&lt;/sub&gt; (tetragonal) as the dominant phase and ZrO&lt;sub&gt;2&lt;/sub&gt; (monoclinic) and CuO as the minor phase. The intermetallic phase is also formed in both samples, t-Zr&lt;sub&gt;2&lt;/sub&gt;Ni and Zr&lt;sub&gt;2&lt;/sub&gt;Cu.&lt;/span&gt;&lt;/em&gt;

Photosensitization of optical band gap modified polyvinyl alcohol films with hybrid AgAlO2 nanoparticles

Silver doped aluminium oxide (AgAlO2) nanoparticles (NPs) have been synthesized by sol gel combustion method. The size and morphology of the synthesized NPs have been confirmed by high-resolution transition electron microscopy (HRTEM), and results indicate the size of the particles is around 8–14 nm with spherical in shape. A series of polyvinyl alcohol (PVA) nanocomposites (NCs) have been fabricated with varying amounts viz., 0.5, 1.0, 1.5, 2.0 and 2.5 wt% of AgAlO2 NPs using solvent intercalation technique. The intensity of crystalline peaks of NC films was reduced, and a slight shift in the peak position was observed in XRD profiles, which depicts the changes in microcrystalline behaviors of the NCs. The morphological behaviors of PVA/AgAlO2 films have been established by scanning electron microscope and atomic force microscopy. The physical interactions between the components in NCs have been evaluated by Fourier transfer infrared spectroscopy. Differential scanning calorimeter data showed a reduction in glass transition temperature (Tg) from 72 °C for PVA to 64 °C for PVA/2.5 wt% NPs. The optical constants of NCs have been evaluated from UV–Visible spectra. The obtained results reveal that band gap energy (Eg) reduces from 4.9 to 2.8 eV and refractive index increases from 1.5 to 2.4 with an increase in AgAlO2 NPs content from 0 to 2.5 wt% in PVA matrix respectively. The current–voltage (I–V) data exhibit non-ohmic behaviors at higher potential voltage region (> 6 V) for NC films.

LCST phase transition kinetics of aqueous poly(N-isopropylacrylamide) solution

Abstract LCST phase transition kinetics of aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions was studied by using non-isothermal differential scanning calorimeter (DSC) and isothermal dynamic light scattering (DLS) techniques. The DSC data obtained from 5 and 10 wt% PNIPAM solutions were used in isoconversional kinetics analysis. The resultant large activation energy (Eα) and pre-exponential factor indicated that the phase transition occurred by cooperatively breaking multiple hydrogen bonds. Eα decreased with increasing temperature approximately in a hyperbola form. Theoretical nucleation and growth models were used to adequately describe the temperature dependent Eα. Furthermore, the phase transition process obeyed Avrami–Erofeev nucleation and growth models. As to the 0.05 wt% PNIPAM solution using the isothermal DLS technique, the reaction rate constant was determined at different temperatures, and the Avrami–Arofeev nucleation and growth models adopted to predict the phase transition process.

Simulation approach to decomposition kinetics and thermal hazards of hexamethylenetetramine

The thermal stability of HMT under dynamic, isothermal and adiabatic conditions was investigated using differential scanning calorimeter (DSC) and accelerating rate calorimeter (ARC), respectively. It is found from the dynamic DSC results that the exothermic decomposition reaction appears immediately after endothermic peak, a coupling phenomenon of heat absorption and generation, and the endothermic peak and exothermic peak were indentified at about 277–289 and 279–296 °C (Tpeak) with the heating rates 1, 2, 4 and 8 °C min−1. The ARC results reveal that the initial decomposition temperature of HMT is about 236.55 °C, and the total gas production in decomposition process is 6.9 mol kg−1. Based on the isothermal DSC and ARC data, some kinetic parameters have been determined using thermal safety software. The simulation results show that the exothermic decomposition process of HMT can be expressed by an autocatalytic reaction mechanism. There is also a good agreement between the kinetic model and kinetic parameters simulated based on the isothermal DSC and ARC data. Thermal hazards of HMT can be evaluated by carrying out thermal explosion simulations, which were based on kinetic models (Isothermal DSC and ARC) to predict several thermal hazard indicators, such as TD24, TD8, TCL, SADT, ET and CT so that we can optimize the conditions of transportation and storage for chemical, also minimizing industrial disasters.

Synthesis, characterization and thermal decomposition performance of polyaminofullerene nitrate

A novel fullerene nitrate derivative, polyaminofullerene nitrate, with high nitrogen content was synthesized using bromofullerene Th-C60Br24 as a starting material. The composition of the obtained product was determined as C60(NH2)24·13HNO3 by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The thermal decomposition of C60(NH2)24·13HNO3 was observed by differential thermal analysis and thermogravimetric analysis with infrared spectroscopy. The results show C60(NH2)24·13HNO3 proceeded with a one-step exothermic reaction at 425 K. Kinetics parameters of the thermal decomposition C60(NH2)24·13HNO3 were obtained from the differential scanning calorimeter data, and the reaction mechanism was found in Mampel power model. Our work prepared a novel fullerene derivative by a facile method, and it has potential application in explosives and propellants additives.

Thermal, spectroscopic and structural characterization of isostructural phase transition in 4-hydroxybenzaldehyde

ABSTRACTPolycrystalline samples of 4-hydroxybenzaldehyde (4-HOBAL) were investigated using differential scanning calorimeter (DSC), Raman spectroscopy and X-ray powder diffraction. The DSC data indicated that 4-HOBAL on heating undergoes a polymorphic transformation from polymorph I to polymorph II. The polymorph II formed remains metastable at ambient condition and transforms to polymorph I when annealed at ambient temperature for more than seven days. The structural information of polymorphs I and II obtained using its X-ray powder diffraction patterns indicated that 4-HOBAL undergoes an isostructural phase transition from polymorph I (monoclinic, P21/c) to polymorph II (monoclinic, P21/c). Raman data suggest that this structural change is associated with some change in its molecular interactions. Thus, in 4-HOBAL the polymorphic phase transformation (II to I) even though energetically favoured is kinetically hindered.