Single Mass Loss Research Articles

In-situ oligomerization of lactic acid within broiler skin extracted elastin/collagen matrix for the efficacy of ointment base

Elastin and collagen were isolated from waste broil skin and modified with l-lactic acid oligomer for the efficacy of substituting petroleum based ointment base matrix. Paraffin wax, which is one of the most extensively used petroleum ointment derivative is well known for its incompatibility with the skin. Chronically it clogs the skin pores, which subsequently affects the release of moisture. To mitigate this problem, a novel approach has been followed to synthesize a fully green and biocompatible ointment base matrix. The extracted Elastin and Collagen (which exists naturally in our skin) and lactic acid monomer (commonly known as a part of a body fluid) mixed at different proportion and used to synthesize a lactic acid modified elastin/collagen (OLLA-m-ELN/COL) bioconjugate matrix with lubricating characteristics via in-situ polycondensation reaction. The macromolecular interaction between Amide I group of elastin/collagen and C=O of a lactic acid oligomer was confirmed by FTIR analysis. Organoleptic analysis, spreadability, pH, and viscosity were analyzed. The six-mass loss stages which was observed in the ELN/COL matrix was changed into a single mass loss for the synthesized bioconjugate with improved thermal stability. The thermal stability improvement can be correlated with the formation of secondary macromolecular interaction.

Critical assessment of rapid methods to qualify supplementary cementitious materials for use in concrete

In this study, several tests for supplementary cementitious materials (SCMs) were evaluated to find the best methods to rapidly screen out inert materials, measure overall reactivity, and differentiate between pozzolanicity and latent hydraulicity. The R3 matrix and lime reactivity tests were found to be the most effective at quickly screening out inert materials. However, slow-reacting materials may appear to have low reactivity in both tests and extending the test duration better depicts material reactivity. Additionally, SCMs with higher alumina content perform better in the R3 tests due to the higher heat release and more bound water associated with the formation of calcium aluminate hydrates compared to calcium silicate hydrates, creating reactivity bias when compared to SCMs with lower alumina content. Measuring the calcium hydroxide content of R3 pastes, through thermogravimetric analysis or single point mass loss, can also differentiate between pozzolanic and hydraulic materials.

Spectroscopic characterization andthermal decomposition kinetics of 1,3-dibutyl-imidazolium bromide synthesized through a solvent-free and one-pot method

Imidazolium-based ionic liquids (ILs), as one of the most popular and investigated classes of ILs owing to their outstanding physicochemical features, find applications in different fields over the last decades. Their thermal stability is of paramount importance for their effective use at elevated temperatures. 1,3-dibutyl-imidazolium bromide ([BBIm][Br] is an interesting IL, which may be employed for different purposes. Nevertheless, its thermal stability and decomposition kinetic are scarce. In the present work, 1,3-dibutyl-imidazolium bromide ([BBIm][Br]) is successfully synthesized through a simple, clean, and efficient solvent-free and one-pot ultrasonic method. Its structure was assessed by DSC, FTIR, Raman spectroscopies, µXRF, one-dimensional (1-D) liquid state 1H, 13C, and 15N NMR. The 2-D NMR analyses thoroughly discussed herein corroborated the structure of the cation as well as the alkyl side chains. Its thermal stability and decomposition kinetic were performed with non-isothermal thermogravimetry analysis at different heating rates. The kinetic triplet was determined using isoconversional kinetic methods. It is revealed that [BBIm][Br] undergoes a single step mass loss in the temperature range of 180–380 °C for which the activation energy is 140 kJ/mol. Furthermore, it is proved that the decomposition mechanism that best represents the experimental data is the nth order (Fn) reaction mechanism.

Thermal behavior of naproxen and ketoprofen nonsteroidal anti-inflammatory drugs

Nonsteroidal anti-inflammatory drugs naproxen (NAP) ((+)-(S)-2-(6-methoxynaphthalen-2-yl) propionic acid) and ketoprofen (KET) (RS)-(2-(3-benzoylphenyl)-propionic acid) were investigated by thermoanalytical techniques (TG/DTG/DTA, DSC and hot-stage microscopy) and evolved gas analysis (TG-FTIR) for evaluating their thermal behavior. In air, TG curve of NAP presented one mass loss step followed by the burning of carbonaceous material, with final residue of 1.5%, while in nitrogen, a single mass loss step was observed. After melting, if the sample is submitted to an isotherm it evaporates. According to DSC curve, NAP melts at 153.5 °C (∆Hfus = 31.6 kJ mol−1; ∆Sfus = 73.5 J K−1 mol−1) and recrystallizes in the cooling step. These events were confirmed by hot-stage microscopy. TG-FTIR studies revealed that NAP decomposes by releasing 2-methoxynaphthalene and propionic acid. Ketoprofen TG curves in both atmospheres presented a single mass loss. When the sample was kept under isotherm, after melting, it evaporated. From DSC data, the melting at 93.3 °C (∆Hfus=28.4 kJ mol−1, ∆Sfus = 76.9 J K−1 mol−1) was observed, without crystallization or cooling.

Type I kerogen-rich oil shale from the Democratic Republic of the Congo: mineralogical description and pyrolysis kinetics

The Democratic Republic of the Congo holds important reserves of oil shale which is still under geological status. Herein, the characterization and pyrolysis kinetics of type I kerogen-rich oil shale of the western Central Kongo (CK) were investigated. X-ray diffraction, Fourier-transform infrared spectroscopy and thermal analysis (TG/DTA) showed that CK oil shale exhibits a siliceous mineral matrix with a consistent organic matter rich in aliphatic chains. The pyrolysis behavior of kerogen revealed the presence of a single mass loss between 300 and 550 °C, estimated at 12.5% and attributed to the oil production stage. Non-isothermal kinetics was performed by determining the activation energy using the iterative isoconversional model-free methods and exhibits a constant value with E = 211.5 ± 4.7 kJ mol−1. The most probable kinetic model describing the kerogen pyrolysis mechanism was obtained using the Coats–Redfern and Arrhenius plot methods. The results showed a unique kinetic triplet confirming the nature of kerogen, predominantly type I and reinforcing the previously reported geochemical characteristics of the CK oil shale. Besides, the calculation of thermodynamic parameters (ΔH*, ΔS* and ΔG*) corresponding to the pyrolysis of type I kerogen revealed that the process is non-spontaneous, in agreement with DTA experiments.

Thermal decomposition investigation of paroxetine and sertraline

Antidepressants paroxetine and sertraline both as their hydrochlorides were studied regarding thermal behavior by TG/DTG-DTA, DSC, hot-stage microscopy, X-ray diffraction and coupled TG-FTIR. Paroxetine presented a single mass loss step after dehydration, in nitrogen. However, DTA curve revealed that such degradation actually occurs in three steps, in which HCl, piperidine, fluorobenzene and CO2 are released. In air decomposition took place in a similar way. DSC showed endothermic peaks related to melting and dehydration of paroxetine. During evolved gases analysis it was possible to observe overlapped signals related to HCl and piperidine absorption. Sertraline, on its turn, presented sublimation when slowly heated or alternatively a solid transition from Form II to Form III at c.a. 199 °C followed by two mass losses when heated at higher heating rates. In the first degradation step methylamine is released. The second step is related to the loss of tetraline, dichlorobenzene and HCl, as revealed by TG-FTIR. Based on these data, thermal decomposition mechanisms were proposed for both drugs.

Thermocatalytic cracking kinetics of myristic acid adsorbed on catalysts with different acidity

Mass losses related to the vaporization/decomposition of myristic acid, either pure or adsorbed on SiO2, γ-Al2O3, SiO2-Al2O3 and HZSM-5 catalysts were obtained by non isothermal thermogravimetric analysis from room temperature up to 650°C. The adsorption of myristic acid on catalysts greatly changed the mass loss behavior of myristic acid, suggesting a significant decomposition of this fatty acid during heating as compared to its essentially simple volatilization in absence of catalyst. A model-free kinetic was used to estimate the values of apparent activation energy of the mass losses from experiments performed at heating rates of 3, 7, 10 and 15°Cmin−1. In absence of a catalyst, myristic acid presented a single mass loss event with an activation energy value of ∼87–90kJmol−1. In the case of myristic acid adsorbed on SiO2,γ-Al2O3, SiO2-Al2O3 and HZSM-5 at least two different mass loss events occurred during linear heating, associated to myristic acid volatilization/decomposition. The activation energies calculated for both these events, with the exception of myristic acid adsorbed on silica, exhibited values much higher than 90kJmol−1. The apparent activation energy of the second mass loss events was always higher than that of the first mass loss events. Activation energy of the second mass loss reached a value as high as 190kJmol−1 at which point myristic acid was strongly adsorbed on HZSM-5. Such a high value suggests CC and CH bond ruptures and not only decarboxylation often described as the main reaction path when saturated fatty acids are pyrolyzed.

Thermal analysis and infrared emission spectroscopy of the borate mineral colemanite (CaB3O4(OH)3·H2O)

Colemanite CaB3O4(OH)3·H2O is a secondary borate mineral formed from borax and ulexite in evaporate deposits of alkaline lacustrine sediments. The basic structure of colemanite contains endless chains of interlocking BO2(OH) triangles and BO3(OH) tetrahedrons with the calcium, water and extra hydroxide units interspersed between these chains. We have studied the thermal decomposition of colemanite by using a combination of thermal analysis (TG/DTG) and infrared emission spectroscopy (IES). Thermogravimetric analysis of the colemanite mineral was obtained by using TA Instruments Inc. Q50 high-resolution TGA operating at a 10 °C min−1 ramp with data sample interval of 0.50 s pt−1 from room temperature to 1000 °C in a high-purity flowing nitrogen atmosphere (100 cm3 min−1). Thermogravimetric analysis shows a sharp mass loss at 400.9 °C. Only a single mass loss is observed. IES shows a sharp band at 3610 cm−1 assigned to the stretching vibration of hydroxyl units. Intensity in this band is lost by 350 °C. A broad spectral feature is observed at 3274 cm−1 attributed to water stretching vibrations. Intensity in this band is lost by 300 °C. A combination of thermogravimetry and IES is used to study the thermal stability of the borate mineral colemanite. It is important to characterize the very wide range of borate minerals including colemanite because of the very wide range of applications of boron-containing minerals.

Thermal behavior of the β-blocker propranolol

The thermal behavior of the β-blocker anti-hypertensive drug propranolol was investigated using thermoanalytical techniques TG–DTA, DSC and the evolved gas analysis by TG–FTIR, providing information regarding thermal stability, decomposition steps, melting point and heat of fusion of the compound. The results pointed for the decomposition in a single mass loss step, after melting. DSC data revealed that cold crystallization occurred in heat–cool–heat cycles, around 165 °C. TG–FTIR presented 1-naphthol, isopropylamine and HCl as principal decomposition products. A tentative mechanism for the thermal behavior of propranolol is presented.

Studying the thermal decomposition of carvedilol by coupled TG-FTIR

Thermal analytical behavior of carvedilol (1-(9H-carbazol-4-yloxy)-3-[[2-(2-methoxyphenoxy)ethyl]amine]-2-propanol), a β-blocker antihypertensive drug, has been investigated using thermoanalytical techniques thermogravimetry, derivative thermogravimetry, differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Evolved gas analysis was also performed using thermogravimetry coupled to infrared spectroscopy. Such studies revealed that carvedilol decomposes after melting, releasing 2-methoxyphenol and ammonia in both nitrogen and air atmospheres. In inert atmosphere, the decomposition took place as a single mass loss event without residue at the end of the experiment, while in air, the first step resulted in carbonaceous residue that burnt completely in the second step. DTA and DSC curves demonstrated that the sample melts around 100 °C (ΔH fus = 126.6 J g−1, ΔS fus = 0.32 J K−1 g−1) without recrystallization on cooling. An endothermic event observed previously to the melt has been attributed to concomitant carvedilol forms in the sample. Solid-state decomposition kinetic investigation using the Flynn–Wall–Ozawa approach revealed activation energy of E a = 243 ± 32 kJ mol−1 and Arrhenius pre-exponential factor log A = 22 ± 3 min−1. Finally, a tentative mechanism for carvedilol thermal decomposition is proposed.

Thermocraking of Sunflower Oil over Acid Vermiculite

The catalytic cracking of sunflower oil over vermiculite clay was studied in a thermal analysis system, the process being accompanied by thermogravimetry. The vermiculite was chemically modified by acid leaching and characterized by techniques of XRD, FTIR, SEM and TG. The catalytic test was performed in a thermal analysis system with heating up to 900 °C, with proportion oil/clay = 100. The results of thermogravimetry showed that in the presence of the catalyst, the thermograms present a single mass loss. The test was also performed with the molecular sieve Al-MCM-41 with proportion Si/Al = 25 and 75, with similar results to those presented by vermiculite.

Investigation on the thermal behavior of β-blockers antihypertensives atenolol and nadolol using TG/DTG, DTA, DSC, and TG–FTIR

Thermal behavior of β-blocker antihypertensives nadolol and atenolol was investigated using TG/DTG, DTA, and DSC, under dynamic nitrogen and air atmosphere. Nadolol decomposed in a single mass loss step between 196 and 353 °C, after melting at 128.0 °C. In air, an additional event related to the burning of carbonaceous material was observed. Under nitrogen atenolol decomposed also in a single step from 191.8 to 900 °C. However the DTG revealed that this decomposition splits in two successive events resulting in a residue of 17.2 % at the end of the run, with a melting peak at 153.1 °C. In air, an additional step referent to the burning of carbonaceous residue can be seen. Although both presented melting events, only atenolol crystallized on cooling. Evolved gas analysis by TG–FTIR revealed that nadolol decomposes via terc-butylamine releasing, while atenolol loses ammonia in a nonpreviously reported dimerization reaction after melting with a consecutive isopropylamine releasing. A tentative thermal behavior mechanism is presented for both cases.

Leaf Litter Mixtures Alter Microbial Community Development: Mechanisms for Non-Additive Effects in Litter Decomposition

To what extent microbial community composition can explain variability in ecosystem processes remains an open question in ecology. Microbial decomposer communities can change during litter decomposition due to biotic interactions and shifting substrate availability. Though relative abundance of decomposers may change due to mixing leaf litter, linking these shifts to the non-additive patterns often recorded in mixed species litter decomposition rates has been elusive, and links community composition to ecosystem function. We extracted phospholipid fatty acids (PLFAs) from single species and mixed species leaf litterbags after 10 and 27 months of decomposition in a mixed conifer forest. Total PLFA concentrations were 70% higher on litter mixtures than single litter types after 10 months, but were only 20% higher after 27 months. Similarly, fungal-to-bacterial ratios differed between mixed and single litter types after 10 months of decomposition, but equalized over time. Microbial community composition, as indicated by principal components analyses, differed due to both litter mixing and stage of litter decomposition. PLFA biomarkers a15∶0 and cy17∶0, which indicate gram-positive and gram-negative bacteria respectively, in particular drove these shifts. Total PLFA correlated significantly with single litter mass loss early in decomposition but not at later stages. We conclude that litter mixing alters microbial community development, which can contribute to synergisms in litter decomposition. These findings advance our understanding of how changing forest biodiversity can alter microbial communities and the ecosystem processes they mediate.

Vapor pressure curve determination of α-lipoic acid raw material and capsules by dynamic thermogravimetric method

α-Lipoic acid (ALA) has been described as a potent biological antioxidant and detoxification agent. ALA has become a common ingredient in multivitamin formulas and anti-aging supplements. Vapor pressure determination by thermogravimetric method has been used to characterize drugs and pharmaceutical preparations. The aim of this study was to determinate the vapor pressure of ALA raw materials and capsules using thermogravimetric method. TG curves of ALA were determined by the TA Instruments model SDT Q600 TG/DSC Thermal Analyzer. The TG curves of ALA displayed a single mass loss in the temperature range (from 227.16 to 319.29°C), at a heating rate of 10.0°Cmin−1. ALA showed zero order kinetic reaction for all heating rates (10.0, 20.0, 40.0, 60.0 and 80.0°Cmin−1). The vapor pressure curves were constructed from the Langmuir equation. This work suggests that thermogravimetry can be utilized as a rapid and effective technique for the estimating of ALA vaporization characteristics.

Non‐oxidative Thermal Degradation of Poly(glycidol), Poly(glycidol)‐g‐L‐lactide, and Poly(glycidol)‐g‐glycolide

AbstractThree polymers of pharmaceutical/medical relevance are synthesized: poly(glycidol) (PG), poly(glycidol)‐g‐L‐lactide (PG‐g‐La), and poly(glycidol)‐g‐glycolide (PG‐g‐Gly). Because the thermal stability of these polymers is an essential factor of their processing and practical application, the study focuses on kinetic and mechanistic aspects of non‐oxidative thermal degradation. The study is conducted by combining thermogravimetry, Fourier transform infrared spectroscopy, and isoconversional kinetic analysis. It is found that PG degrades in a single mass loss step, whereas, PG‐g‐La and PG‐g‐Gly in two. It is demonstrated that the first step in degradation of PG‐g‐La and PG‐g‐Gly is associated with decomposition of the pendant groups and the second is due to degradation of the PG backbone.magnified image

Studies on the synthesis and curing of epoxidized novolac vinyl ester resin from renewable resource material

Cardanol-based epoxidized novolac vinyl ester resin (CNEVER) was synthesized by reacting cardanol-based epoxidized novolac (CNE) resin and methacrylic acid (MA) (CNE:MA molar ratio 1:0.9) in presence of triphenylphosphine as catalyst at 90 °C. The CNE resin was prepared by the reaction of cardanol-based novolac-type phenolic (CFN) resin and epichlorohydrin, in basic medium, at 120 °C. The CFN resin was synthesized by reacting cardanol (C) and formaldehyde (F) (C/F ratio = 1:0.7) with p-toluene sulphonic acid (PTSA) as catalyst (0.5 wt.%) at 120 °C for 7 h. The resin products were analyzed by Fourier-transform infra-red (FTIR) and nuclear magnetic resonance (NMR) spectroscopic analysis. The number-average molecular weight of the prepared CNEVER was found to be 859 gmol −1 as determined by gel permeation chromatographic (GPC) analysis. The resin was cured by using the mixture of resin, benzoyl peroxide, and styrene at 120 °C. The CNEVER resin was found to be cured in 60 min at 120 °C. Differential scanning calorimetric (DSC) technique was used to investigate the curing behaviour. Single step mass loss in dynamic thermogravimetric (TG) trace of CNEVER was observed. Thermal stability of the vinyl ester sample containing 40 wt.% styrene was the highest amongst all other prepared systems.

Laminates based on vinyl ester resin and glass fabric: A study on the thermal, mechanical and morphological characteristics

The effects of variation of styrene content on the thermal, mechanical and morphological behaviours of epoxy novolac vinyl ester resin (EVER)/glass fabric laminate have been investigated. The vinyl ester resin matrix was synthesized indigenously using epoxy novolac resin and methacrylic acid catalyzed by triphenylphosphine at a temperature of 85°C in nitrogen atmosphere. Fourier-transform infra-red spectroscopic (FT-IR) analysis was used to see the structural changes during the synthesis of the EVER. Differential scanning calorimetric (DSC) technique was used to investigate the curing behaviour of the EVER matrix. Exothermic peaks (Tp) appeared in the range of 117–127°C for all the samples of epoxy resin and EVERs. Thermal stability of the prepared samples was analyzed by dynamic thermogravimetric runs. The TG/DTG trace of epoxy showed two-step mass loss decomposition behaviour whereas that of vinyl ester resin exhibited a single step mass loss. Mechanical properties such as tensile, flexural and impact strengths of the prepared laminates were determined and it was found cured resin containing 40% styrene showed the best balance of properties and EVER/glass fabric laminates exhibited better properties as compared to the epoxy/glass fabric laminates Dynamic mechanical analyses of the samples were done to determine the viscoelastic properties. Tg decreased significantly with increased styrene concentration due to increase in cross-linking density. Cross-sections of the cured samples, which failed during impact testing, have been critically studied through scanning electron microscopic (SEM) analysis to gain insight into the phase morphology.

Studies on the Kinetics and Mechanism of Thermal Decomposition of Znal-Hydrotalcite-Like Compounds

The thermal decomposition of ZnAl-hydrotalcite-like compounds (ZnAl-HTLcs) was studied using the TG-DTG method. It was shown there was a single mass loss stage of the thermolysis. The kinetics parameters of thermolysis were calculated by the Freeman – Carroll method, and the mechanism function was studied by the Šativa – Šestăk and Achar methods. The value of the apparent activation energy E was ca 180 kJ mol−1, the frequency factor ln( A/s−1) was ca 30 and that reaction order n was equal to about 1.1. The thermal decomposition mechanism function indicated a chemical mechanism and the corresponding function was G(α) = (1 - α)−1 - 1.

Investigation of Pyrolysis Kinetics of Humic Acids from Low Rank Anatolian Coal by Thermal Analysis

Thermogravimetric analysis (TGA) of humic acid samples from low rank Anatolian (east of Turkey, Bingol) coal were investigated under atmospheric pressure. The samples were subjected for the decomposition of organic matter ambient to 800°C at four different heating rates (5, 10, 15, and 20°C min−1). The humic acid samples were started at decomposition between 170–206°C and amount of residues varied 55–60% according to heating rate. Each of samples was showed a single step mass loss. TG/DTG data of samples were analyzed to determine activation energy values by Coats and Redfern method and Arrhenius method. Activation energy values are similar obtained from Coats and Redfern method and Arrhenius method and varied from 25 to 29 kJ mol−1.

Influence of H-ZSM-5, Al-MCM-41 and acid hybrid ZSM-5/MCM-41 on polyethylene decomposition

Thermogravimetry (TG) and mass spectrometry (MS) combined techniques have been used to investigate the thermal degradation and catalytic decomposition of high-density polyethylene (HDPE) over solid acid catalysts as H-ZSM-5, Al-MCM-41 and a hybrid material with a bimodal pore size distribution (H-ZSM-5/Al-MCM-41). The silicon/aluminum ratio of all catalysts is 15. Both thermal and catalytic processes showed total conversion in a single mass loss step. Furthermore, the catalytic conversion presents average reduction of 27.4%, in the onset decomposition temperature. The kinetic parameters were calculated using non-isothermal method. These parameters do not indicate significant differences between the thermal and catalytic processes. Even though, the presence of the catalysts changes the reaction mechanism, from phase boundary controlled reaction to random nucleation mechanism. Important difference in distribution of evolved products was detected when several catalysts were used. However, in all cases the main products were alkanes (C2, C3 and C4), alkenes (C3 and C4), dienes (C4 and C5) and traces of aromatic compounds.