Thermochimica Acta最新文献

Transition metal nanomaterials are widely applied as flame retardants in materials. Herein, an oxidation-mediated strategy was developed for temporally controlling the in situ growth of Fe(OH)₃ nanoparticles on wool/nylon (W/N) fabrics. The formed particles exhibit homogeneous dispersion on the surface of W/N fabrics, with an average particle diameter of about 60 nm. These Fe(OH)₃ nanoparticles can simultaneously enhance both the flame retardancy (the limiting oxygen index increased by 18.8 % and passed the UL-94 burning test of V-0 rating) and mechanical performance (the tensile strength increased by 9.13 %) of the W/N fabrics. Meanwhile, the obtained W/N fabrics exhibit remarkable smoke-suppressant properties, demonstrating a reduction of 76.4 % and 65.5 % in smoke production rate and total smoke production, respectively, compared to the pure W/N fabrics. Furthermore, the prepared W/N fabrics exhibit good durability. This innovative strategy may be also extended for synthesizing other nanomaterials and pave a new path to develop high-performance flame-retardant materials.

Phase change materials (PCMs) can improve thermal comfort of occupants acting as thermal energy storage systems. During their service life, PCMs undergo many phase change transitions. However, there is a lack of feasible and cost-effective techniques to evaluate the effect of thermal cycling on the long-term stability and performance of PCMs, which can influence their selection and restrict a broader acceptance of these materials by the construction sector. This study developed a novel accelerated thermal cycling multi-technique to assess the stability and reliability of PCMs under dynamic thermal conditions. All investigated PCMs showed remarkable stability in terms of phase change temperature and latent heat energy even after undergoing 10,000 thermal cycles. The Thermogravimetric Analysis (TGA) results underscore the suitability of these PCMs for built environments, with minimal mass loss at lower temperatures (below 150 °C). The Fourier Transform Infrared spectroscopy (FT-IR) and ¹H Nuclear Magnetic Resonance (NMR) results revelled no molecular changes induced by thermal cycling. The novel accelerated thermal cycling technique provides more accurate results than thermal cycling using Differential Scanning Calorimetry (DSC) only, overcoming the issues of contamination and subcooling of smaller samples in DSC measurements.

In this study, high-pressure differential scanning calorimetry (HP-DSC) was used to examine the curing process of a peroxide-cured silicone rubber (SR) system under compressed CO₂ to investigate the influence of pressure and CO₂ on the curing process. We found that the curing reaction occurred in two parts, described as cure separation, because of the dual effect of CO₂ pressure and solvation at 6 MPa CO₂. Consequently, peak fitting was used to calculate the kinetic parameters of the two-part reaction at 6 MPa CO₂. Results indicate that pressure and CO₂ exerted a combined effect on the curing reaction. In particular, pressure and CO₂ solvation effects changed with varying conversion rates and CO₂ pressures. This study provides an effective analysis methodology and an accurate kinetic model for characterizing and predicting high-pressure cure kinetics and unexpected cure separation in a peroxide-cured SR system under compressed CO₂.

Replacing antimony trioxide (ATO) in flame retardant formulations is an urgent task due to its toxicity. There are indications that calcium hypophosphite (CaP) may be a promising replacement. This study investigates the decomposition, fire behavior, and smoke release of brominated flame-retarded acrylonitrile butadiene styrene (ABS) under various fire scenarios like ignition, developing fire and smoldering, while replacing ATO with CaP and CaP/talc. Adding 4 wt.-% of talc to CaP formulations showed beneficial effects on flammability due to changes in the viscosity and barrier properties. Synergism between 8 wt.-% talc and CaP improved the protective layer in the developing fire scenario, resulting in a ∼60 % decrease in the peak of heat release rate and reduction of ∼21 % in total smoke production (ref. ABS+Br+ATO). With a conventional index of toxicity (CIT) of below 0.75, ABS+Br+CaP passes the highest requirements according to EN 45545-2. Overall, the CaP/talc materials improve flame retardancy, show less smoke emission under forced flaming conditions, and prevent chronic intoxication and environmental pollution through smoke particles contaminated with antimony.

The purpose of this study was to determine the quantitative and qualitative effects of the form of natural phenolic compounds (NPCs) on the decomposition of polylactide (PLA) under different measurement conditions. For this purpose, thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), and pyrolysis-combustion flow calorimetry (PCFC) analyses were carried out not only on individual raw materials like calcium lignosulfonate (BX), tannic acid (TA), BX chemically modified with TA (BMT), but also on PLA/BX, PLA/TA, and PLA/BMT composites with 3, 6, and 9 wt.% of filler. Moreover, the work checked whether to obtain satisfactory results it is necessary to carry out chemical modification lasting many hours, or whether simple physical mixing of ingredients (TABX) is enough, e.g. in proportions 1:2, 2:4, 3:6. The results of these analyses showed that TA is neither a good flame retardant nor a highly swelling material, but when combined with BX physically or chemically, it can produce an interesting synergistic effect. This work proves that chemically obtained BMT hybrid material allows to reduce flammability by 30 % compared to PLA which cannot be achieved by physically mixing these components in a polymer melt. On the other hand, the addition of TABX is sufficient to achieve a good thermal stabilization effect under processing conditions.

Metal ion-nucleic acid interactions are important for their contribution in structure formation and their potential applications in nanotechnology. Hg²⁺ and Ag⁺ bind to T–T and CC mismatched base pairs, respectively, at the center of duplex DNA to form T–Hg–T and C–Ag–C. Although primer-extension by DNA polymerases with Hg²⁺ incorporated thymidine 5′-triphosphate to form T–Hg–T, the same reaction with Ag⁺ did not incorporate deoxycytidine 5′-triphosphate to form C–Ag–C. Here, isothermal titration calorimetric analyses to examine the effect of CC position in duplex DNA on Ag⁺ binding demonstrated that Ag⁺ did not bind to the terminal CC base pair in duplex, but it bound to the central CC base pair in duplex at 1:1 molar ratio with 9 × 10⁵ M^–1 binding constant. Ag⁺ did not bind to the terminal and central C–A, C–G, and C–T base pairs in duplex. These findings are useful for developing efficient metal-mediated base pair formation in nanotechnology.

N-ethyl-2,2-diisopropylbutylamide (WS-27) is a new cooling agent with a soothing, long-lasting cooling effect, widely used in personal care and cosmetic products. The dissolution behavior of WS-27 in fourteen mono solvents (methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, methyl acetate, ethyl acetate, isopropyl acetate, propyl acetate, butyl acetate, dichloromethane, cyclohexanone, and acetone) was measured using a dynamic laser monitoring method from 263.15 K to 298.15 K under 101.6 ± 1.2 kPa. In these selected solvents, the solubility of WS-27 increased with increasing temperature. The van't Hoff equation, λh equation, modified Apelblat equation, Wilson model, and NRTL (non-random two-liquid) model were applied to correlate the experimental solubility data of WS-27, and the modified Apelblat equation showed the best-fitting results. In addition, the intermolecular interactions and solvent effect were analyzed using the Hirshfeld surface analysis, molecular electrostatic potential surface analysis, and KAT-LSER model analysis to understand the dissolution behavior of WS-27. The results indicate that the solubility of WS-27 is influenced by multiple factors, and there can be other factors as well. These fundamental data can provide essential information for the crystallization and purification process of WS-27.

The present paper proposes the isoconversional approach to a quantitative assessment of the reactivity in elementary and complex reactions studied by thermal methods under non-isothermal conditions. The focus is on the processes studied at a constant heating rate as the most common mode used in thermal analysis. The accuracy of the proposed approach is tested on simulated data for elementary reactions, whereas its practical application is demonstrated on few experimental examples. The effect of experimental uncertainties on the precision of the introduced reactivity factors is also considered.

Here we report on kinetic analysis of thermal degradation of polymer blends based on incremental isoconversional method coupled with mathematical deconvolution of thermogravimetric curves based on Fraser–Suzuki peak function. The measured kinetic envelope was decomposed into contributions approximately corresponding to degradation of each constituent of a polymer blend. Kinetic parameters from isoconversional analysis were further used for estimating the effect of blending on thermal stability of the constituents. Compared to routinely used parameters such as degradation onset temperature or DTG-peak temperature, the deconvolution analysis allows to determine stability of all components in a mixture regardless of their relative content. Here we also show that deconvolution analysis can be carried out directly on integral α(T) curves, thus bypassing the work with differential data dα/dt. Isoconversional analysis of deconvoluted α(T) curves allows to calculate various parameters for assessing the potentially accelerating or inhibiting effect on thermal degradation, for example, by means of decomposition half-time t_0.5. The results can be made more robust by utilizing relative criteria for stability such as t_0.5(blend)/t_0.5(neat polymer). Using this approach, detrimental effect of PHBV and PBAT on thermal stability of PLA above 300 °C was confirmed. On the other hand, stability of PHBV in both binary and ternary mixtures was improved compared to neat polymer.