Calorimetric Curves Research Articles

Structural build-up, hydration and strength development of cement-based materials with accelerators

Fast structural build-up and strength development of fresh/hardened cement-based materials are always desired in many scenarios, where accelerators are often used. In this paper, the hydration, structural build-up and strength development of cement pates with different accelerators were investigated. The growth of static yield stress was used to characterize the structural build-up of fresh cement paste with 1% nano silica. Calorimetric curves, zeta potential and conductivity of pastes and strength development of mortars were also measured. Results showed that accelerators promote the reaction of C3S or C3A at different stages and in different mechanisms. Mechanical efficiency of C-S-H determined by growth of elastic modulus or yield stress over cumulated hydration heat may give wrong ranking on the efficiency of C-S-H. Apart from formation of C-S-H gel, structural build-up may originate from other sources.

The influence of inorganic admixtures on early cement hydration from the point of view of thermodynamics

Calcium salt and other inorganic chemicals have long been used as the accelerators of cement hydration; however, the underlying mechanism remains to be resolved. In this contribution, thermodynamic analysis of cement systems with calcium chloride (0.06 M and 0.12 M), potassium hydroxide (0.28 M and 0.56 M) and hydrochloric acid (0.09 M and 0.18 M) were combined with quantitative analysis of the calorimetric curves of these systems. Calorimetric tests show that calcium chloride and hydrochloric acid would increase hydration rate, whereas lower dosage of potassium hydroxide would decrease hydration rate. Thermodynamic analyses show that in all the systems, the chemical driving force of C3S dissolution keeps increasing whereas that of calcium silicate hydrates (C-S-H) precipitation keeps decreasing, indicating that the dissolution of C3S could be the limiting step of cement hydration. This is further confirmed by the facts that the chemical driving force of tricalcium silicate (C3S) dissolution is positively related to both the intensity of the silicate peak and the occurring time of the silicate peak time, and that the chemical driving force of C3S dissolution is negatively related to the length of induction period. Furthermore, the calcium concentration of pore solution is positively related to the chemical driving force of C3S dissolution, implying that calcium concentration could play a critical role in regulating effect of inorganic admixtures. This work finds the crucial role of C3S dissolution in early cement hydration and also provides new insight into the effect of inorganic chemicals on cement hydration and the mechanism of cement hydration.

Structural, thermal and broadband NIR emission properties of Nd3+/Pr3+/Ag NPs co-doped tellurite glass

Nd3+/Pr3+ co-doped tellurite glasses containing metallic Ag NPs were synthesized by melt-quenching and heat-treating techniques. The amorphous structural nature, fundamental vibrational units and good thermal stability of the prepared tellurite glasses were confirmed by X-ray diffraction (XRD) pattern, Raman spectrum and differential scanning calorimeter (DSC) curve, respectively. The precipitated Ag NPs in a glass matrix with an average diameter ∼5 nm were revealed by transmission electron microscopy (TEM) image, and the radiative property of Nd3+ and Pr3+ ions was evaluated from the absorption spectrum by Judd-Ofelt theory. Under the excitation of 488 nm Xenon lamp, two broadband near-infrared emissions covering 800-1100 nm and 1250-1650 nm ranges were observed from the fluorescence spectrum. The former originated from the transitions of Pr3+:3P1,0→1G4, Pr3+:1D2→3F4,3, Nd3+:4F3/2→4I11/2 and Nd3+:4F3/2→4I9/2, while the latter was contributed by the Pr3+:1G4→3H5, Pr3+:1D2→1G4, Pr3+:3F3→3H4 and Nd3+:4F3/2→4I13/2 transitions. With the introduction of Ag NPs, the emission intensity of two broadband near-infrared emissions was further enhanced, in which the peak emission intensity of 1250-1650 nm band was increased by about 56% and the FWHM is up to 250 nm. The obtained results indicate that Nd3+/Pr3+/Ag NPs co-doped tellurite glass has great potential in realizing ultra-broadband near-infrared emission covering O-, E- and S-bands simultaneously.

Broadband flat near-infrared emission from tellurite glass doped with Tm3+, Er3+ and Ag NPs

Tellurite glasses doped with trivalent Tm3+, Er3+ ions and metal Ag nanoparticles (NPs) were synthesized by single-step melt-quenching technique, and the near-infrared photoluminescence property was investigated. Differential scanning calorimeter (DSC) curve, X-ray diffraction (XRD) pattern, transmission electron microscopy (TEM) image, absorption spectrum, emission spectrum and fluorescence decay curve were measured. The good thermal stability and amorphous state nature of the as-prepared tellurite glasses were demonstrated by the DSC curve and XRD pattern, respectively. Absorption spectrum disclosed the electronic transitions in the ultraviolet to near-infrared spectral range and was further used to evaluate the potential in near-infrared band luminescence by the calculations of spontaneous radiative transition parameters and gain cross-sections of Tm3+(Er3+) ions. Under the excitation of 808 nm laser diode (LD), a broadband flat near-infrared emission with FWHM of approximately 160 nm was obtained in the Tm3+/Er3+ doped tellurite glass. This broadband flat near-infrared emission, originating from the spectral overlapping of Tm3+:3H4→3F4 transition (~1.47 µm) and Er3+:4I13/2 → 4I15/2 transition (~1.53 µm), was located in the 1350–1650 nm region and covered the E + S + C + L-bands simultaneously. With the precipitation of Ag NPs having diameter in the 10–20 nm range evidenced by TEM image in the Tm3+/Er3+ doped tellurite glass, the peak luminescent intensity increased by about 45%, which is attributed to the increased local electric field and the possible energy transfer from the Ag species to Tm3+(Er3+) ions. The obtained results demonstrate that Tm3+/Er3+/Ag NPs doped tellurite glass is prospective for broadband optical amplifiers, broadband lighting sources and so on.

Assessment of packing, flowability, hydration kinetics, and strength of blended cements with illitic calcined shale

The effects of two illitic calcined shales as supplementary cementitious materials (SCMs) on the performance of ordinary Portland cement (OPC)-based pastes and mortars were investigated. The packing density of blended cement pastes and mortars were predicted with compressible packing model (CPM). The water film thickness (WFT) and flowability were calculated and measured. Early hydration was described by calorimetric curves and the hydration microstructure was identified by X-ray diffraction (XRD), differential thermal analysis (DSC/TG), and pore size distribution (MIP). The compressive strength was tested at 2, 7, 28, and 90 days. The results showed that the partial replacement of OPC by illitic calcined shale decreased the packing density and the flowability of cement pastes but this does not occur for standard mortars. For blended cements, the hydration products were similar to that corresponding to OPC, the pozzolanic reaction contributed from 28 days to the densifying of solid structure and it was also noticed the pore size refinement that improved the compressive strength at later age.

Kinetic analysis of hydrothermal carbonization using high-pressure differential scanning calorimetry applied to biomass

Assessing kinetic parameters of hydrothermal carbonization still requires several tests and time-consuming analyses, usually relying on few data points. With a view to containing the experimental effort and testing the accuracy of models based on continuum curves, high-pressure differential scanning calorimetry was used for the first time to assess the heat release profile, the overall enthalpy change, and the kinetic parameters of a hydrothermal carbonization process in two substrates: digestate and sludge. The process-related thermal effect was established from the difference between the calorimetric curves for the unreacted samples during a first run and for the reacted samples obtained through a second run. The parameters of a kinetic model built on the Arrhenius reaction were adjusted on the basis of the calorimetric curves, adopting an nth-order and an autocatalytic reaction model. Activation energy values of 139.16 and 161.68 kJ/mol, pre-exponential factors around 2.15 × 1011 and 2.52 × 1014 s−1, reaction orders of about 2.68 and 2.46, and R2 values of 0.86 and 0.94 were obtained for digestate and sludge, respectively. Results were consistent with the available literature. Autocatalysis was negligible for both substrates, so the process could be modeled effectively as a single Arrhenius nth-order reaction with significant loss of precision. Coupled with more traditional approaches, this newly-proposed method may pave the way to describing the set of reactions taking place during hydrothermal carbonization by means of their enthalpy values, improving our knowledge of the process’s chemistry and kinetics.

Aging mechanism of hot-poured sealants for asphalt pavement under natural environmental exposure

ABSTRACT Extended exposure of crack sealant to the natural environment causes a gradual degradation of its properties owing to aging with complex mechanisms. Two types of sealants were directly exposed to natural environment to investigate the aging effects on the sealant properties. In comparison with the original sealant, the surface of the aged sealant gradually hardened, embrittled, and darkened, while numerous cracks with different depths and widths appeared during aging. Fourier transform infrared spectroscopy, confocal laser scanning microscopy, differential scanning calorimetry, and three conventional properties of sealants were employed to discuss the micro- and macro-performance differences and mechanism before and after three-month-aging. Experimental programme results show that age-conditioned sealants cause a clear increase in sulphoxide and carbonyl compared with the unconditioned ones. During the aging process, the polymer particles degraded, and the base asphalt in the sealant has undergone fateful aging. The endothermic peak values of sealants in the differential scanning calorimetric curves become wide, particularly two endothermic peaks are observed after aging. This phenomenon suggests that the sealant properties become unstable after aging. Cone penetration dramatically declines while the softening point increases after aging. The two sealants are in the glass state under the low-temperature tensile test environment after aging.

Formation of octahedron-shaped ZnFe2O4/SiO2 with yolk–shell structure

In this study, octahedron-shaped ZnFe2O4/SiO2 was fabricated using a facile solvothermal method by adding hollow SiO2 spheres to the reaction system. The experimental results indicated that the octahedron-shaped ZnFe2O4/SiO2 with a yolk–shell structure was only synthesized at a high heating rate (2.0 °C/min). A sample fabricated at a low heating rate (0.25 °C/min) did not form a yolk–shell structure. Calorimetry was conducted to investigate the mechanism associated with the formation of the yolk–shell structure. Several intermediates were obtained based on the as-measured calorimetric curve, which were characterized by transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction, Fourier transform-infrared spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that Fe3+ and Zn2+ first entered the hollow core of the SiO2 spheres through the mesoporous shell, before α-(Fe,Zn)OOH and α-Fe2O3 were formed in the core and outer surfaces of the hollow SiO2 spheres at a heating rate of 2.0 °C/min α-Fe2O3 had an octahedral shape. Finally, α-Fe2O3 was converted into the octahedron-shaped ZnFe2O4. The hollow SiO2 spheres were simultaneously changed into nanosheets, which induced the formation of the yolk–shell structure.

Impact of physical and physicochemical properties of supplementary cementitious materials on structural build-up of cement-based pastes

Understanding the structural build-up is relevant to new technologies that require workability control, such as 3D concrete printing. The effect of supplementary cementitious materials (SCM) particle size (i.e. specific surface area and particle density) and physicochemical behavior (i.e., chemical reactivity and surface potential) and their interactions with the primary mixture parameters (i.e., water to cement ratio, cement reactivity and SCM replacement) on the structural build up of cementitious paste were studied. The growth of static yield stress with time was used to characterize the structural build up of cementitious pastes. Calorimetric curves were also measured. Results showed that the effect of SCM on structural build up is governed by their particle density and surface potential. The structural build up can be raised by increasing the number of contact points (governed by particle density and w/c), the growth rate of C-S-H bridges (governed by surface potential), or the reactivity of cement.

Broadband and flat near-infrared emission from Er3+/Tm3+ codoped tellurite glass for amplifier applications

E r 3 + / T m 3 + codoped tellurite glasses have been synthesized using the melt-quenching technique; they are characterized by measurements of absorption spectrum, luminescence spectrum, fluorescence decay, Raman spectrum, and differential scanning calorimeter curve. Under the excitation of an 808 nm laser diode (LD), an extremely flat and broadband near-infrared emission with the full width at half-maximum of ∼ 160 n m has been obtained in tellurite glass doped with optimized E r 3 + − T m 3 + concentrations. This broadband and flat fluorescence emission is located in the region of 1350–1650 nm and covered the E, S, C, and L bands, which originate from the spectral overlapping of 1.53 µm band emission of E r 3 + : 4 I 13 / 2 → 4 I 15 / 2 transition and 1.47 µm band emission of T m 3 + : 3 H 4 → 3 F 4 transition. The Judd-Ofelt theory was applied to the absorption spectrum, and the radiative properties such as transition probability, branching ratio, and radiative lifetime of E r 3 + and T m 3 + ions have been determined to evaluate the potential luminescence characteristics. The time-resolved fluorescence decay of E r 3 + and T m 3 + ions demonstrated the existence of energy transfers between them, and the energy transfer micromechanism was further investigated quantitatively. The results indicate that tellurite glass codoped with appropriate amounts of E r 3 + − T m 3 + ions is promising for applications in broadband optical fibers and photonic devices.

Novel Eudragit® -based polymeric nanoparticles for sustained release of simvastatin

This paper reports on the development of nanoparticles aiming at the in vitro controlled release of simvastatin (SVT). The nanoparticles were prepared by the nanoprecipitation method with polymers Eudragit® FS30D (EDGFS) or Eudragit® NE30D (EDGNE). EDGFS+SVT nanoparticles showed mean size of 148.8 nm and entrapment efficiency of 76.4%, whereas EDGNE+SVT nanoparticles showed mean size of 105.0 nm and entrapment efficiency of 103.2%. Infrared absorption spectra demonstrated that SVT incorporated into the polymer matrix, especially EDGNE. Similarly, the differential scanning calorimeter (DSC) curve presented no endothermic peak of fusion, indicating that the system is amorphous and the drug is not in the crystalline state. The maintenance of SVT in the amorphous state may favors its solubilization in the target release sites. In the in vitro dissolution assay, the SVT incorporated into the EDGFS+SVT nanoparticles showed a rapid initial release, which may be related to the pH of the dissolution medium used. Regarding the EDGNE+SVT nanoparticles, the in vitro release occurred in a bimodal behavior, i.e., an initial “burst” followed by a sustained delivery, with the kinetics of drug release following Baker-Lonsdale’s mathematical model. All these features suggest the nanoparticulate system’s potential to modulate SVT delivery and enhance its bioavailability.

Voltage induced phase transition of polyethene glycol composite film filled with VO<sub>2</sub> nanoparticles

In this paper, the voltage induced metal-insulator phase transition (MIT) of polyethene glycol (PEG) composite film is investigated based on VO<sub>2</sub> nanoparticles prepared by the hydrothermal method and vacuum annealing process. High purity VO<sub>2</sub> (B) nanoparticles are obtained after being treated in a hydrothermal reactor at 180 ℃ for 12 h by using vanadium pentoxide (V<sub>2</sub>O<sub>5</sub>) and oxalic acid (H<sub>2</sub>C<sub>2</sub>O<sub>4</sub>·2H<sub>2</sub>O) as raw materials. The X-ray diffraction (XRD) pattern shows that the prepared nano-powders are free of impurities, and the scanning electron microscope (SEM) pictures confirm that the micro-morphology is of a band-shaped nano-structure. Next, these products are heated in a vacuum quartz tube at 500 ℃ for different times. The XRD and differential scanning calorimeter (DSC) curves of the annealed samples prove that the VO<sub>2</sub> (M) with MIT performance is successfully prepared. And the content of M phase in the sample increases with preparation time increasing. When the annealing time is longer than 60 min, all the samples are converted into materials with M phase. The SEM images show that the average length of the nano-powders decreases with the annealing time increasing from 10 min to 300 min. Then PEG coating containing VO<sub>2</sub> (M) nanoparticles is applied between two electrodes with a pitch of 1 mm on printed circuit board (PCB). The <i>V</i>-<i>I</i> test is carried out after a 20 kΩ resistor has been connected in the circuit. The results display repeatable non-linear <i>V</i>-<i>I</i> curves indicating that the composite film undergoes an MIT phase transition under voltage. After it is activated for the first test, the MIT voltage and non-linear coefficient increase exponentially as the length of VO<sub>2</sub> decreases. Besides, it is also found that the voltage across the material is maintained at around 10 V after the resistance has changed suddenly, which is similar to the behavior of diode clamping voltage. We believe that the phase transition voltage and non-linear coefficient of the VO<sub>2</sub> composite film are influenced by the intra-particle potential barrier and the inter-layer potential barrier. The longer the average length of the nanoparticles, the higher the potential barrier between the interfaces in the conductive channels is, and thus increasing the phase transition voltage and phase transition coefficient. The activation phenomenon of the thin film is caused by reducing the barrier between particles during the first test. Furthermore, the results can prove that the electric field is the determinant of the phase transition during the VO<sub>2</sub> composite film electrical field induced MIT of the VO<sub>2</sub> composite film. However, after the phase transition, Joule heat plays a significant role in maintaining the low resistance state.

Influencia de la deformación previa sobre el endurecimiento por precipitación en una aleación de Cu-Ni-Si

Los efectos de la deformación previa sobre los procesos de precipitación en una aleación de Cu-2,8 Ni-1,4 Si (at.%) fueron estudiados utilizando calorimetría diferencial de barrido (DSC), microscopía electrónica de transmisión (TEM) y medidas de microdureza. Las curvas calorimétricas muestran la presencia de una reacción exotérmica atribuido a la formación de precipitados de δ-Ni2Si en la matriz de cobre, lo cual fue confirmado mediante TEM. Además, sse puede observar que la temperatura del máximo del pico de DSC decrece con el aumento de la deformación previa a los tratamientos de envejecimiento. Las energías de activación calculadas para la precipitación de δ-Ni2Si, mediante el método de Kissinger, resultaron similares a aquellas calculadas mediante una función de Arrhenius, a partir del máximo de endurecimiento de la matriz debido al tratamiento de envejecimiento (saturación de la dureza durante el envejecimiento isotérmico). El análisis de las medidas de microdureza en conjunto con las curvas calorimétricas y las micrografías TEM permiten corroborar, por una parte que la formación de la fase δ-Ni2Si, durante los tratamientos de envejecimiento, son los responsables del endurecimiento de la matriz de cobre, y por otra que la deformación previa al tratamiento de envejecimiento inhibe parcialmente la formación de los precipitados.

2.0-µm and 4.1-µm mid-infrared broadband emission enhancement in Ho3+/Yb3+ co-doped tellurite–germanate glasses

Ho3+/Yb3+ co-doped tellurite–germanate glasses with lower phonon energy (771 cm−1) were prepared by conventional melt-quenching method. The prepared samples were characterized by emission spectra, differential scanning calorimeter (DSC) curve, X-ray diffraction (XRD) pattern, and Raman spectra. The DSC curve shows that the sample has a good thermal stability, in which the ΔT is 202 °C. Compared to the recently reported tellurite glasses, the ΔT was increased by approximately 24%. Under the 980 nm laser excitation, it was found that the full width at half maximum (FWHM) of the sample at 2.0 µm was 190 nm. Compared with the reported glasses for this type, the value was effectively improved. Meanwhile, the FWHM of the sample at 4.1 µm was 285 nm, which has not been reported yet. This indicates that Ho3+/Yb3+ co-doped tellurite–germanate glass has a great application prospect in mid-infrared broadband fiber amplifiers.

Nucleus density and crystallization behavior of isotactic polypropylene nucleated with different α/β compound nucleating agents

Different compound nucleating agents consisting of a highly efficient novel α-nucleating agent N,N’-bis(benzoyl) sebacic acid dihydrazide and three typical β-nucleating agents N,N-dicyclohexylterephthalamide, rare earth compound (WBG-II) and calcium pimelate were incorporated into isotactic polypropylene (iPP), and the isothermal crystallization behavior of iPP nucleated with these compound nucleating agents was investigated by differential scanning calorimetry. Based on the classical Avrami theory and the calorimetric curves under isothermal conditions, the crystallization half-time and the Avrami index can be calculated. The results demonstrate that addition of these nucleating agents reduced the crystallization half-time and speed up the crystallization process of iPP. In addition, the nucleus density of pure and nucleated iPP was further calculated from the Lamberti model and the results illustrate that the nucleus density of iPP after addition of different compound nucleating agents was increased greatly and it was several orders of magnitude higher than that of pure iPP.

One-step synthesis of methyl eugenol/Schiff base mesoporous silica nanoparticles sustained-release performance with high lure efficiency

The mesoporous silica nanoparticles (MSN) was modified by salicylaldimine, furfuralimine, and benzaldehyde imine, respectively, denoted as Sal-MSN, Fur-MSN, and Ben-MSN for methyl eugenol (Me) delivery by one-step method. The results confirmed that Me was successfully adsorbed by Schiff base mesoporous silica, which maintained regular hexagonal pore structure. Me is distributed in amorphous state in the pores of the mesoporous silica indicated by differential scanning calorimeter (DSC) curves. Schiff base modification strengthened the interaction between Me and mesoporous silica, leading to its higher sustained-release performance and the disappearance of sudden release in sustained-release performance comparing with Me-MSN before Schiff base modification. Me and Me-MSN were most consistent with the First-order kinetic and logistic equation, respectively. After Schiff base modification, Me-Sal-MSN, Me-Fur-MSN, and Me-Ben-MSN were most consistent with Korsmeryer–Peppas kinetic equation. Therefore, the difference of Me concentration was no longer the main control factor of sustained-release system after Schiff base modification. In the attraction of Bactrocera dorsalis test, the lure efficiency for per unit Me for Me-MSN, Me-Sal-MSN, Me-Fur-MSN, and Me-Ben-MSN equal to 2.83, 3.31, 3.32, 4.24 times of pure Me. After Schiff base modification, the samples showed higher lure efficiency due to their ideal sustained-release performance without sudden release. In short, the lure efficiency of Me was improved by the Schiff base mesoporous silica sustained-release system, in the meanwhile its service life was also prolonged.

Early hydration calorimetric study of the sewage sludge incinerated waste streams Portland cement-based binders: technological implications

The research study forms a part of the “Management of municipal water waste treatment plants potential by-products of sewage sludge ash type, as active or non-active additions to Portland cement-based binders” project’s outcomes (H2020-MSCA-IF-2016-746830). Based on the applied techniques characteristics (non-isothermal and non-adiabatic differential micro-calorimeter, SEM/EDS and XRF analysis), this study comprises the very first stage for a sustainable conversion of each of the considered 190114 and 190107* waste streams into a value-added by-product for specific constructive applications. Provided technical requirements regarding the designed cementitious products handling and suggested industrial application are focused on the early performance of the tested for quality and consistency, pastes, mortars and concretes. In detail, the obtained physical–chemical parameters show substantial differences of the original waste streams regarding their technological origin, seasonability and geographical localisation. Consequently, the calorimetric curves exhibit diverse early chemistry of the produced cements, showing the considerable variations in mineral nature (siliceous, aluminous) or hydraulic factor contents (reactive silica, SiO2r−, and reactive alumina, Al2O3r−) of the observed pozzolanic activities. Setting retarding phenomenon and shrinkage reducing effects are also carefully discussed. All the calorimetric and pozzolanic activity related data is contrasted with two other reference materials, fly ash and granulated blast furnace slag, standard behaviour.

Characterization of Bio-fiber from Pongamiapinnata L. Bark as Possible Reinforcement of Polymer Composites

ABSTRACT The suitability of Pongamia pinnata L .bark fiber (PPF) as polymer reinforcement was identified first time in this article. Chemical analysis, X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) analysis exemplified the presence of cellulose, hemicelluloses, and lignin in PPF. Higher cellulose (62.34 wt.%), crystalline index (45.31%) and low hemicellulose (14.57 wt. %), density (1345 kg/m3), and crystalline size (5.43 nm) of PPF were beneficial for reinforcement. PPF is thermally stable up to 210°C which is acknowledged from the Thermogravimetric and Differential Scanning Calorimeter curves. Surface roughness parameters of PF were identified through the Atomic Force Microscope. Comparatively lower density (1345 kg/m3) and higher tensile Strength (322 Mpa) of PPF have proved that it is an appropriate reinforcement to fabricate the eco-friendly bio-composites.

Effect of microfluidization on cholesterol, thermal properties and in vitro and in vivo protein digestibility of milk

There is very scarce literature about effect of microfluidization on milk cholesterol level. In the present work, cattle and buffalo milk was passed through microfluidizer at different pressure (2500, 15000, 22000 and 30000 psi). HPLC analysis revealed that microfluidization at 22000 psi pressure was more effective in reducing (p < 0.05) cholesterol level in the cow and buffalo milk by 42% and 46%, respectively. Microfluidization significantly (p < 0.05) improved melting property of fat, stability of proteins and lactose asanalyzed by Differential Scanning Calorimeter curves. Further, microfluidization significantly improved in vitro trypsin and in vivo (Wistar rats) digestibility of milk proteins compared to non-microfluidized one. Results of the present study clearly evinced that microfluidization has remarkable positive effects on milk. Results hold significance and are highly relevant to the dairy industry and manufacturers of infant food and nutraceuticals as microfluidized milk can be used as a raw ingredient for processing different novel products offering low cholesterol and beneficial functional properties.

Thermal Behavior Analysis of Two Synthesized Flavor Precursors of N‐alkylpyrrole Derivatives

To expand the library of pyrrole‐containing flavor precursors, two new flavor precursors—methyl N‐benzyl‐2‐methyl‐5‐formylpyrrole‐3‐carboxylate (NBMF) and methyl N‐butyl‐2‐methyl‐5‐formylpyrrole‐3‐carboxylate (NUMF)—were synthesized by cyclization, oxidation, and alkylation reactions. Thermogravimetry (TG), differential scanning calorimeter, and pyrolysis–gas chromatography/mass spectrometry were utilized to analyze the thermal degradation behavior and thermal degradation products of NBMF and NUMF. The TG‐DTG curve indicated that the maximum mass loss rates of NBMF and NUMF appear at 310 and 268°C, respectively. The largest peaks of NBMF and NUMF showed by the differential scanning calorimeter curve were 315 and 274°C, respectively. Pyrolysis–gas chromatography/mass spectrometry detected small molecule fragrance compounds appeared during thermal degradation, such as 2‐methylpyrrole, 1‐methylpyrrole‐2‐carboxylic acid methyl ester, limonene, and methyl formate. Finally, the thermal degradation mechanism of NBMF and NUMF was discussed, which provided a theoretical basis for their application in tobacco flavoring additives.