Differential Scanning Calorimetric Techniques Research Articles

An Environmentally Friendly Mineral-Free Tanning of Animal Skins – Sustainable Approach with Plant Resources

An eco-friendly mineral-free process for tanning has been developed in the present investigation, which is based on replenishable plant resources. Significant reduction in total dissolved solids and chlorides compared to conventional tanning method was observed in the new process. Tara and jatropha seed oil were employed for tanning of animal skins. The thermal and morphological characteristics, resistance to fungal and organoleptic properties of the tanned leathers were analyzed by using shrinkage, differential scanning calorimetric and thermo-mechanical analysis techniques. It has been proved that the properties of the tanned leathers are better than that of conventional vegetable tanned and comparable to chrome tanned leathers. The cross section of fibre structure indicates uniform structure and fibre bundles seem to be less dispersed when analyzed through scanning electron microscope. The tanned leathers exhibited better physico-chemical and organoleptic properties. The new tanning system also exhibited cost advantages due to reduction in chemicals consumption and savings due to reduced effluent treatment costs. The developed tanning process reduces the generation of toxic waste compared to mineral tannages, which reduces the environmental impacts. Hence, this techno-commercial study provided a viable and versatile solution for mineral-free tanning for commercially sustainable processing through cleaner process options.

Strontium- and Zinc-Containing Bioactive Glass and Alginates Scaffolds.

With an increasingly elderly population, there is a proportionate increase in bone injuries requiring hospitalization. Clinicians are increasingly adopting tissue-engineering methods for treatment due to limitations in the use of autogenous and autologous grafts. The aim of this study was to synthesize a novel, bioactive, porous, mechanically stable bone graft substitute/scaffold. Strontium- and zinc-containing bioactive glasses were synthesized and used with varying amounts of alginate to form scaffolds. Differential scanning calorimetric analysis (DSC), FTIR, XRD, and NMR techniques were used for the characterization of scaffolds. SEM confirmed the adequate porous structure of the scaffolds required for osteoconductivity. The incorporation of the bioactive glass with alginate has improved the compressive strength of the scaffolds. The bioactivity of the scaffolds was demonstrated by an increase in the pH of the medium after the immersion of the scaffolds in a Tris/HCl buffer and by the formation of orthophosphate precipitate on scaffolds. The scaffolds were able to release calcium, strontium and zinc ions in the Tris/HCl buffer, which would have a positive impact on osteogenesis if tested in vivo.

Investigation of third-order nonlinear optical semi organic potassium bromide malate single crystals for optoelectronic applications

L-Malic acid potassium bromide MAPB, a new semi organic material was synthesized successfully by solution growth method. Single crystal x-ray diffraction analysis reveals the cell parameters of the grown crystal and it crystallized in cubic system. The molecular structure of MAPB was identified by FTIR spectral analysis. The lower cut-off wavelength (λ = 272 nm), optical energy band gap (5049 eV) and Urbach energy (0.2381 eV) of MAPB crystal was determined by using UV–Vis-NIR spectral studies. The single electronic transitional band structure of the material was identified by photoluminescence spectrum. The various morphological formations on the grown crystal were analyzed by scanning electron microscope (SEM) study. The second order nonlinear optical properties of grown MAPB were measured by Kurtz and Perry powder technique. The thermal stability of MAPB crystal was studied by differential scanning calorimetric technique. The relative dielectric property was rigorously analyzed with various temperature ranges. Vickers micro hardness test suggest that the material belongs to soft material category. Z-scan study was employed to analyze the third order non-linear optical characteristics like refractive index (n2), the absorption coefficient (β) and third order susceptibility (χ3).

Synthesis of Chitosan Nanoparticles for Controlled Release of Amiodarone

This work is based on a natural polymer chitosan used in a nanoparticulate drug delivery system for the controlled release of amiodarone along with β-cyclodextrin. Amiodarone-loaded chitosan nanoparticles were prepared using the ionic gelation method aided by sonication. Amiodarone loading on chitosan nanoparticles was done under optimum conditions. For particle characterization; zeta-sizer, UV/Vis, Fourier-transform infrared spectroscopy, X-ray powder diffraction, differential scanning calorimeter and scanning electron microscope techniques were used. In vitro drug release studies of amiodaroneloaded chitosan nanoparticles were performed using the dialysis diffusion technique. Drug loading and release values were determined using UV/Vis spectroscopy. Amiodarone encapsulated in nanoparticles was completely released at the end of 14 days. About 38 % was released at the end of day 1, 44% released at the end of day 3, 50 % released at the end of day 5 followed slow release. Amiodarone-loaded chitosan nanoparticles could serve as a model for controlled delivery of many antiarrhythmic drugs.

Thermoresponsive hydrogels based on renewable resources

ABSTRACTThis work aims to synthesize novel thermoresponsive hydrogels from renewable resources, bacterial cellulose (BC), and castor oil (CO), and to investigate the effect of CO on physical and thermal behaviors of BC/Poly(N‐isopropylacrylamide) (PNIPAM) hydrogels. The structural properties of the hydrogels are analyzed by Fourier‐transform infrared (FTIR) spectroscopy. Differential scanning calorimeter (DSC) technique and thermogravimetric analysis (TGA) are also performed to examine the thermal properties of the hydrogels. The morphological differences of the hydrogels are analyzed by scanning electron microscope (SEM). The thermoresponsive performances of the hydrogels are examined by swelling and deswelling behaviors. The hydrogel with CO is found to be more sensitive to temperature changes than the one without CO. Deswelling study demonstrates 91 and 25% of water loss for hydrogels with and without CO, respectively. The present study shows a novel approach to synthesize thermoresponsive hydrogels with renewable resources for biomedical applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48861.

Low-temperature oxidation reactions of crude oils using TGA–DSC techniques

In this research, combustion behaviour of three crude oils with different °API gravities was analysed. The thermogravimetric analyser (TGA) and differential scanning calorimeter (DSC) experiments were performed using three different heating rates (2, 5, and 10 °C min−1) under air atmosphere. The reaction regions, burn-out temperatures, and peak temperatures were determined accordingly. Two main reaction regions, particularly the low-temperature oxidation (LTO) and high-temperature oxidation (HTO) reactions, were figured out in TGA and DSC curves, which suggested exothermic behaviour. Kinetic parameters of the crude oils were determined using model free methods (Ozawa–Flynn–Wall, OFW, and Kissinger–Akahira–Sunose, KAS), which allows the calculation of kinetic properties at progressive conversion degrees without the requirement of any reaction models and f(α) estimations. The variation in activation energy with respect to the conversion degree pointed out that the LTO reaction stage can be subdivided into three subzones. The results indicated that the activation energies were changing depending on the conversion degree, which is an indication of complex reaction mechanisms. The change in activation energy with respect to conversion degree showed slight variation for heavy crude oil compared with that in light crude oil.

Swift Heavy Ion Irradiated Low-Density Polyethylene: Structural and Optical Investigations

The structural and optical effects of copper (50 MeV) and carbon (70 MeV) ion irradiation of low density polyethylene (LDPE) are described. X-ray diffraction (XRD) and differential scanning calorimetric (DSC) techniques were used to explore the structural behavior, while Fourier transform infrared (FTIR) and UV-visible spectroscopies were used to collect the optical data. Structural parameters, such as interplanar separation, distortion factor, crystallite size and degree of crystallinity, were measured to understand the change in the structural behavior of LDPE caused by the swift heavy ion irradiation. In the irradiated polymeric samples, the formation and growth of new carbon enriched species were revealed by the FTIR and UV-visible analysis, which led to the decrease of their optical bandgap energy with the increase of ion fluence.

Preparation of Nano-Cu-Fe Composite Metal Oxides via a Mechanical Grinding Method and Its Catalytic Performance for the Thermal Decomposition of Ammonium Perchlorate

ABSTRACT In this article, a series of nano-Cu-Fe composite metal oxides (nano CuO/Fe2O3), with different molar ratios of CuO/Fe2O3 (1:2, 1:1, 1:0.5, 1:0.25), were prepared in large-scale by mechanical grinding. The microstructures, surface elements and morphologies of samples are analyzed by X-ray diffraction (XRD), X-ray energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The catalytic effects of nano-Cu-Fe composite metal oxides on the thermal decomposition of ammonium perchlorate (AP) were investigated by thermogravimetric (TG) analysis and differential scanning calorimetric (DSC) techniques. The results show that nano-Cu-Fe composite metal oxides with the molar ratio of CuO/Fe2O3 = 1:2 have the best catalytic effect for AP thermal decomposition as compared to the other nano-Cu-Fe composite metal oxides, the single nano CuO, and nano Fe2O3. Also, the results show that the decomposition temperature of AP has fallen from 441.3°C to 355.3°C, whereas the decomposition heat has risen from 941 to 1749 J/g, which supports the existence of a synergistic effect between CuO and Fe2O3 nanoparticles.

Total salinity elimination during preservation of animal skins: a sustainable approach through benign alternatives.

Use of sodium chloride to preserve animal skins and hides is becoming increasingly untenable due to stringent environmental regulations. In the present research work, a combination of sparingly soluble alkali and water-soluble polymer of ethylene oxide has been used to preserve skins with an objective of total elimination of common salt for preservation. A comprehensive study has been made for evaluating various parameters, such as dehydration and rehydration behaviours of skins, microbial growth, emission loads and physico-chemical characteristics of the cured skin to validate the salt-free preservation system developed. The shrinkage temperature, denaturation temperature and mechanical strength of tanned leather were analysed by using shrinkage, differential scanning calorimetric and thermomechanical analysis techniques. The new curing system has been found to be effective in preserving the skin as indicated by the various parameters studied and the final leather quality. The significant reduction in total solids content such as dissolved solids and suspended solids present in the effluent compared to conventional preservation method is evident from environmental impact assessment studies.

Investigation of (co)-combustion kinetics of biomass, coal and municipal solid wastes

Investigation of thermal behaviors of biomass waste, biochar, coal, municipal solid waste (MSW) and their mixtures were aimed in the present study using both thermogravimetric analysis and differential scanning calorimeter techniques. In fact, this paper intends to interpret the influence of mixtures on activation energy. In this purpose, Coats and Redfern were used. Then, the relative error Δmerror was calculated to quantify the synergism degree. Precisely, it was about 5.34% for biomass/coal, 5.52% for biomass/cardboard, 5.67% for biomass/biochar, 5.93% for biomass/synthetic rubber and 6.05% for biomass/plastic mixtures. This phenomenon was justified by the interaction between C-C bond of biochar, coal and MSW radicals with C-H and C-O bonds of biomass.

Optimization of glass properties by substituting AgI with Ag2S in chalcogenide system

GaSbS–AgI–Ag2S glass system was successfully prepared through the traditional method of vacuum melt quenching. The network structure and physical properties of the system response to the substitution of AgI with Ag2S were investigated by differential scanning calorimeter (DSC), Raman, and electrochemical impedance spectroscopic techniques. The glass transition temperature (Tg), density and hardness of the glass system improved as Ag2S content was increased. The ionic conductivity (room temperature) of the glass system was maintained at the order of ~10−4 S/cm when a high concentration of Ag+ was introduced in the glass matrix. The variation in conductivity originated from structural changes in ionic channels. The optimal glass composition for improving the mechanical and thermal stability and conductivity of solid-state electrolyte materials was inferred from analytical results.

Cure Characteristics and Thermal Behavior of Organic–Inorganic Hybrid Composite as Assessed by DSC, TGA, and DMA Techniques

The current investigation reports the use of a residue from the iron metallurgy namely, “slag” to produce unsaturated polyester composite material-based slag (UPES). The slag has been mechanically treated by crushing and milling prior incorporating in the polymer. The role of the slag as co-curing agent of the polymerization reaction is studied under isothermal and dynamic conditions using differential scanning calorimeter (DSC); consequently, the role of the slag to enhance the thermal stability as well as the heat storage capacity of the UPE is reported. The isothermal cure temperature was varied from 80 to 120 °C, whereas the dynamic scan was run from room temperature to 250 °C at constant heating rate. This allowed us to estimate the degree of cure and cure rate. It has been found that incomplete cure was recorded by DSC for the pristine sample due to vitrification phenomenon. On the other hand, the sample with the slag displayed complete cure at 120 °C indicating that the heat storage capability of the polymer has been improved. The thermal stability of the samples was evaluated by a thermogravimetric analyzer coupled with a DSC unit. The sample containing slag responded better against thermal stimulation which was related to the mineral nature of the slag and the polar–polar interactions between the slag and the matrix. The interactions were attributed to the switch from hydroxyl–hydroxyl interactions to the formation of hydroxyl–slag (oxide). The interactions between the slag and the UPE resin were inspected using attenuated total reflectance infrared spectroscopy. The response of the samples to dynamic stimulation was evaluated by a dynamic mechanical analyzer. The sample containing slag displayed higher elastic moduli and broader tan (α) indicating better damping.

Structural and thermal investigations of CaU(PO4)2; phase diagram study of MO−UO2–P2O5 systems (M = Ca, Sr, Ba)

Structure of monoclinic CaU(PO4)2, synthesized in argon atmosphere at 1473 K, was derived from powder X−ray diffraction (XRD) data using Rietveld refinement method. Thermogravimetric (TG) Curve recorded up to 1573 K in argon atmosphere showed thermal as well as structural stability of CaU(PO4)2. When heated in air, TG curve of CaU(PO4)2 showed weight gain between 1100–1673 K due to oxidation of U(IV) to U(VI). Molar heat capacity of CaU(PO4)2 as well as some ternary alkaline earth phosphates were calculated using differential scanning calorimeter technique. Phase diagrams of pseudo ternary alkaline earth metal−uranium (IV)−phosphates were derived and phase boundaries were established. All the ternary and quaternary compounds used for deriving the phase diagrams were synthesized in an argon atmosphere at 1473 K. X-ray diffraction (XRD) was used as a prime analytical tool to investigate the phase mixtures and draw phase boundaries. Phase diagram of SrO–UO2–P2O5 and BaO–UO2–P2O5 systems confirm the existence two quaternary compounds, (Sr/Ba)U(PO4)2 and (Sr/Ba)7U(PO4)6 in the systems whereas in CaO–UO2–P2O5 system only one quaternary compound, CaU(PO4)2, was identified.

Thermal stability and crystallization kinetics of Ge13In8Se79 chalcogenide glass

ABSTRACTGe-In-Se system, similar to many other chalcogenide glasses, has attracted much attention due to its interesting physical properties and applications. This article reports thermal analysis and estimation of activation energies of the glass transition and amorphous-crystallization transformation of Ge13In8Se79 chalcogenide glass. The kinetic parameters were investigated under a non-isothermal condition at different heating rates (7–40 K/min) using differential scanning calorimetric (DSC) technique. The amorphous nature of the samples was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The activation energy was calculated from DSC data using five isoconversional methods: Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), Tang, Starink, and Vyazovkin. The results confirm that the activation energy of crystallization varies and depends on the degree of crystallization as well as temperature. It was also observed that the transformation from amorphous to the crystalline structure is complex involving different mechanisms of nucleation, diffusion, and growth.

Differential Scanning Calorimetric Study of the Effect of Cholesterol on the Thermotropic Phase Behavior of the Phospholipid 1‐Stearoyl‐2‐Oleoyl‐sn‐Glycero‐3‐Phosphocholine

AbstractUsing the differential scanning calorimetric (DSC) technique, the thermal properties of 1‐stearoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine (SOPC) phospholipid and its mixture with cholesterol (Chol), in the range between 10 and 50 mol.%, were investigated. A considerable modification of the structural conformation and the biophysical properties of the bilayer of the phospholipid system after the Chol incorporation were detected. Concentrations below 30 mol.%, and especially in the range 10–20 mol.%, were found to be optimal in the effective miscibility of SOPC and Chol components. The effective miscibility completeness, mainly in the gel and liquid crystal phases, was indicated. It was discovered that Chol mixed with SOPC slightly shifts its gel (L β) to liquid crystal (L α) phase transition temperature, decreases cooperativity, expressed by the van't Hoff enthalpy, and markedly and progressively reduces the transition enthalpy to almost zero at 50 mol.%. By deep incubation of the cholesteric phospholipid mixture, it was revealed that the endothermic peak associated with laminar crystal to gel phase transition does not exist in conventional pure SOPC bilayer systems.

Copper chromite decorated on nitrogen-doped graphene aerogel as an efficient catalyst for thermal decomposition of ammonium perchlorate particles

In this study, CuCr2O4 spinel (CCO) nanoparticles decorated on three-dimensional graphene networks were synthesized using hydrothermal method followed by a calcination process. The as-prepared material was characterized by different analysis methods and used for catalytic thermal decomposition of ammonium perchlorate particles (AP). For this purpose, CuCr2O4@GA/AP composites were fabricated by solvent/non-solvent (composite processing) and simple mixing methods. The catalytic effect of the as-prepared composites was investigated by differential scanning calorimetric and thermogravimetric (TG) analysis techniques. Owing to the synergistic effect of the spinel-structured copper chromite nanoparticles, high surface area of graphene aerogel and composite processing of AP, the high-temperature decomposition of AP in the presence of 4 mass% CuCr2O4@GA nanocomposite prepared by solvent/non-solvent method was reduced from 432 to 323 °C and the heat released (∆H) from decomposition of AP was increased from 590 to 1760 J g−1.

Glass transition and crystallization kinetics of a new chalcogenide-alkali metal $$\hbox {Se}_{80}\hbox {Te}_{8}(\hbox {NaCl})_{12}$$ Se 80 Te 8 ( NaCl ) 12 alloy

A new chalcogenide-alkali metal alloy of \(\hbox {Se}_{80}\hbox {Te}_{8}(\hbox {NaCl})_{12}\) has been prepared by a melt-quench technique. The crystallized phases due to the thermal annealing are observed by X-ray diffraction of the powdered sample. The glass transition and kinetics of crystallization in the \(\hbox {Se}_{80}\hbox {Te}_{8}(\hbox {NaCl})_{12}\) alloy are studied using the differential scanning calorimetric technique under non-isothermal conditions. The activation energy of the glass transition is evaluated by Kissinger and Mahadevan methods. The crystallization activation energy (\(E_{\mathrm{c}}\)) is calculated by isoconversion Friedman methods. The decrease of \(E_{\mathrm{c}}\) with increasing crystallization conversion is attributed to the complex mechanism of the crystallization process. Based on the shape of the characteristic kinetic function, the crystallization growth is found to be a three-dimensional growth from the bulk nuclei. The results show that the conditions of the Sestak–Berggren model are satisfied for describing the crystallization process of the studied \(\hbox {Se}_{80}\hbox {Te}_{8}(\hbox {NaCl})_{12}\) alloy. The parameters M and N involved in this model are calculated and related to the crystallization process.

Development of Bright Fluorescent Poly(1-vinyl-2-pyrrolidone-co-acrylonitrile) and Its Polysalts with HCl and HNO3: Materials for Solid State Electrical Applications

Herein, we have reported the synthesis, characterization, and ionic conductivity analysis of fluorescent poly(1-vinyl-2-pyrrolidone-co-acrylonitrile) and its salts with 10% HCl and HNO3 in solid state. The synthesized polymers and their polysalts were characterized using Fourier-transformed infrared spectroscopy, UV-visible, Cyclic Voltammetry, Thermogravimetric analysis, Differential Scanning Calorimetric, X-ray diffraction, and spectrofluorometric techniques. The AC conductivities were measured in the frequency ranging from 42 Hz to 1 MHz and temperature from 30°C to 70°C in solid state. Ionic conductivities of the salts of the copolymer with hydrochloric acid and nitric acid were found to be 2.145×10−5 and 2.349×10−5 S cm −1, respectively, which are nearly 1000 times more than that of poly(1-vinyl-2-pyrrolidone-co-acrylonitrile). The activation energies for the copolymer and the polyelectrolytes were found to be 0.454, 0.6288, and 0.659 eV, respectively. The transport number of the copolymers was found to be 0.0278, and that of the polysalts was found to be 0.7596 and 0.7424, respectively. The copolymer showed distinct fluorescent when irradiated with UV light and can be used as acid vapor sensor in solid state.

Intelligent copolymers based on poly (N-isopropilacrylamide). Part ii: Grafts polysaccharide to obtain new biomaterials for biomedical and pharmacological applications

Biopolymers such as polysaccharides are compounds that have functional groups and they are very susceptible to be used in chemical modifications and also allows them to synthesizer of new copolymers (used as graft-like chains). Poly (N-Isopropylacrylamide) PNIPAm, is a thermosensitive synthetic polymer widely used in the preparation of intelligent gels for the biomedical field, but have some limitations in use as biodegradable matrix or scaffolds. In this research wered the synthesis and characterization of copolymers their PNIPAm grafted with the polysaccharides: chitosan (CS) or hyaluronic acid (HA), were performed to obtain new biodegradable and biocompatible biomaterials that conserve the intelligent character (thermosensitivity).The PNIPAm was in first chemically modified with 3-butenoic acid in order to generate carboxyl end groups on the graft-polymer chain (PNIPAm-co-COOH) which serve as anchor points and then covalently graft the polysaccharides. For the specific case of grafting with hyaluronic acid, it was necessary to perform a second modification using piperazine (PIP) and obtain the graft-polymers PNIPAm-co-COO-g-PIP. All this modification process was previously reported (Carrero et al, 2018). In this case, the polysaccharides used as grafts-like chains were: (1) chitosan oligomers obtained by acid degradation and (2) hyaluronic acid. The characterization of all copolymers obtained was follow by infrared spectroscopic (FT-IR); the differential scanning calorimetric (DSC) technique was used to determine the lower critical solution transition temperature (LCST), resulting in the range of 29-34 °C. Its morphology was studied using scanning electron microscopy (SEM), but previously was simulate an inject process, for the reversible gel character presented by these novel copolymers; resulting a high porosity and interconnection between pores (scaffold-like micrometric structures). Hemocompatibility assays were performed on agar/blood systems, showing non cytotoxicity. All these results give these graftcopolymers a high potentiality of use as scaffolds in tissue engineering and also for pharmacological applications.

Thermodynamic investigation of thorium and strontium substituted monazite solid-solution

In this paper, we report synthesis and characterization of thorium and strontium substituted synthetic monazite solid-solutions of general formula La1-xSrx/2Thx/2PO4 (0≤x≤1) using solid-state synthesis route and described the influence of charged coupled (Sr2+, Th4+) substitution in place of La3+ on their thermodynamic stability. High temperature calorimetry has been employed to determine the standard molar enthalpy of formation of La1-xSrx/2Thx/2PO4 (0≤x≤1) compounds. The isobaric molar heat capacities of the compounds were measured employing differential scanning calorimetric technique. Based on these experimental data and the available thermodynamic data for the component oxides, thermodynamic properties of the La1-xSrx/2Thx/2PO4 (0≤x≤1) have been derived. The negative value of excess enthalpy of formation ΔHE indicates that the substitution of La by Sr, Th charge couple in the monazite host structure increases their relative stability. Such strong negative interaction parameter is an indication of short-range cation ordering, which found to be more evident at x = 0.3. Based on the experimental results thermodynamic functions for the solid solutions have been generated.