Journal of Thermal Analysis and Calorimetry最新文献

The study investigates the horizontal fuel size effect on free-burning fires for PMMA plates and wood cribs. The fuel size effect on mass burning flux and flame behavior is mainly discussed and compared with typical pool fires. For the PMMA plate and liquid pool, when the fuel size is small (< 10 cm), either the 3D sidewall burning of PMMA or the container wall heated by flame can promote the burning flux at the horizontal projection area. As the fuel size increases, these side wall burning or heating effects decrease, causing the drop in burning flux with fuel scale for both the PMMA plate and liquid pool. For small-scale wood cribs, fire cannot self-sustain due to the large airflow cooling. With the increase in wood crib size, the burning rate first remains constant and then gradually increases, driven by the enhanced internal radiation. As the fuel size increases above 20–30 cm, the flame radiation dominates the burning flux for all fuel types. Fire dynamics simulator (FDS) was adopted to simulate the horizontal size effect by setting a varied fire source (horizontal projection) area. First, the flame geometry and heat release rate (HRR) of simulations were validated against experimental results. Subsequently, the validated fire model generates cases covering a broad range of fire scales. Finally, a new correlation of flame height with the fire heat release rate and fuel size is proposed, and its prediction capability is validated in the numerical fire modeling. This study quantifies the size effect on the burning rate for common solid fuels and provides valuable information for the numerical modeling of multi-scale fires.

The search for sustainable polymers to replace those of fossil origin has been constant. Poli (lactic acid) (PLA) is one of the alternatives since it is a biodegradable and ecofriendly polymer. This work intended to aggregate zinc oxide (ZnO) and zirconium phosphate (ZrP) as a tentative to improve PLA crystallization and ultraviolet light stability. To easy the incorporation of ZnO in the ZrP the last one was pre-expanded with Jeffamine and following melting extruded PLA composites were prepared. X-ray fluorescence spectroscopy (EDX) showed that incorporation of ZnO (around 50%) in the host filler was successful. Carbonyl absorbance ratio revealed some PLA degraded during the processing. This ratio also increased by exposure to ultraviolet lamps, but ZnO showed best stabilization in the PLA/E-A/ZrP/ZnO. X-rays diffraction revealed that fillers pre-expanded with Jeffamine promoted better dispersion but some reduction on the PLA thermal stability was noticed. Fillers promoted a slight increment of the PLA glass transition temperature. The precursor PLA presented a unique melting peak and low degree of crystallinity (around 4%). Either by compression or by extrusion, PLA lonely and in the composites presented two melting peaks identified as α’ and α crystalline arrangements and an increase of crystallinity degree was achieved. The material addresses potential application as sustainable alternative for packaging industry.

In this paper, the non-isothermal co-pyrolysis of walnut shell (WS), Enteromorpha clathrata (EN), and their blends (WEB) was studied using a thermogravimetric analyzer (TGA). For all the samples, three different decomposition stages were identified by the thermogravimetric analysis. At the same temperature, the mass loss of WEB was always stable between the values of WS and EN. In addition, different heating rates resulted in different TG–DTG profiles. The interaction between WS and EN showed a gradual enhancement with temperature increase, and the most significant interaction was generated when the blending proportion of WS and EN was 7:3. The Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and masterplots methods were used to determine the kinetic triplets. The results show that for different blending ratios, the effective activation energies of WS and EN co-pyrolysis vary from 86.21 to 247.86 kJ mol⁻¹ when the conversion rate is 0.2–0.8. The most appropriate mechanism for the pyrolysis of 70WS30EN is g(α)=[-ln(1-α)]^1/2 with kinetic parameters: apparent activation energy 86.21 kJ mol^-1 and pre-exponential factor 8.99 × 10¹⁶ s⁻¹. The findings in this paper provide a reference for further research on the co-pyrolysis of aquatic and terrestrial biomass.

A tris(DOPO-grafted piperazine)-triazine phosphoramide (DOPO-TPT) was synthesized, and its structure was well characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. DOPO-TPT was used as a flame retardant additive to modify the epoxy resin to obtain a series of flame retardant epoxy thermosets. The effects of DOPO-TPT on the thermomechanical properties, thermal stability and flame retardancy of the resulting epoxy thermosets were investigated. The results showed that when the addition of DOPO-TPT was 5 mass% (phosphorus content was 0.47 mass%), the limiting oxygen index of the epoxy thermoset reached 30.0%, and it passed the UL-94 V-0 classification. Compared with unmodified epoxy resin, the maximum heat release rate and total heat release of EP/DOPO-TPT-5.0 decreased by 28% and 20%, respectively. Additionally, the presence of DOPO-TPT did not deteriorate the thermomechanical properties of the resulting epoxy thermosets. TG-FTIR test confirmed that the incorporation of DOPO-TPT could significantly inhibit the release of gaseous products. The char layer analysis results showed that DOPO-TPT had good catalytic charring performance, which was conducive to decreasing the escape of combustible gas during combustion, thus improving the flame retardancy.

Biochar-based composite phase change materials (PCMs) are gaining popularity in thermal energy storage (TES) applications. Organic PCMs derived from fatty acids are favored for their affordability and variable melting temperatures based on carbon chain length. Understanding the interaction between different carbon-length fatty acid PCMs and porous biochar is crucial for optimizing thermal performance. Thus, this study explored the interaction between PCMs of decanoic acid (DA) and octadecanoic acid (OA) with banana peel (BP) biochar. Experimental results showed that shorter carbon chain of DA enhanced thermal properties and surface compactness compared to OA. BP-DA had higher loading efficiency and PCMs ratio, resulting in superior thermal cycle endurance and latent heat ratio. The molecular dynamics suggest that longer carbon chains affect the mean square displacement (MSD) curves, reducing the self-diffusion coefficients of BP-DA. This is due to DA’s high loading rate, which occupies more space within BP biochar structure, thus limiting its diffusion capacity. Enhanced hydrogen bonding constrained DA’s thermal motion during phase transition, restricting atom mobility within BP. With temperature elevations, BP-DA exhibits lesser fractional free volume than BP-OA, due to lower molecular mass. This research highlights how carbon chain length influences composite PCMs performance, offering insights for efficient TES system design.

A polymer nanocomposite based on sulfonated polyphenylene oxide with amino-functionalized mesoporous silica was designed, synthesized, and tested as a new material for proton exchange membrane (PEM preparation. Characterization of the intermediate and final products of synthesis was realized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and thermal analysis. Broadband Dielectric Spectroscopy (BDS) was used to determine dielectric properties including ionic conductivity. Thermogravimetric analysis has provided important information regarding the composition and thermal stability of the three compounds, subject to thermal degradation: 1) the amino-silica with cetyltrimethylammonium bromide (CTAB) template inside the pores (MS-NH₂ I), 2) the mesoporous amino-silica after removing the template (MS-NH₂ II) and 3) the polymer nanocomposite (sPPO-MS-NH₂). The thermal decomposition of the composite samples occurs in three stages: in the first, up to 150 °C, water and organic solvents were lost; the second stage, between 200-300 °C, was due to breaking the organic functionalities (-NH₂, amino and -SO₃H, sulfonic acid), and the third stage, above 400 °C was due to polymer chain degradation. The final residue at 700 °C reflects the contribution of inorganic silica. The proton conductivity, for polymeric (sPPO) and composite (sPPO-MS-NH₂) membranes was determined from BDS dates, both in dry and hydrated states. For dried samples, the higher values of proton conductivities were: 0.16 mS cm⁻¹ (sPPO, 70 °C) and 0.03 mS cm⁻¹ (sPPO-MS-NH₂, 120 °C), and the higher values of proton conductivity increased for the hydrated samples with two orders of magnitude: 36.5 mS cm⁻¹ (sPPO, 40 °C) and 22.4 mS cm⁻¹ (sPPO-MS-NH₂, 50 °C). However, the proton conductivity is still dependent on the hydration state, even for the composite membrane.

Coal spontaneous combustion (CSC) events pose hazards to miners, infrastructure, and the environment. To mitigate some of the risk of CSC, this study explored the influence of airflow rate (AFR), oxygen concentration (OxyC), and heating rate (HR) on CSC. A temperature programmed experiment was used to examine a coal sample under different AFRs, OxyCs, and HRs. The characteristic temperature was determined using index gas growth rate analysis, and the characteristic parameters were shown. The apparent activation energy (E_a) of the sample was computed by the Arrhenius equation, and variance analysis was employed to quantitatively characterise the impact of different environmental factors on the characteristic parameters of the coal samples. The experimental results show that the critical temperature of the coal samples ranges between 65 and 75 °C, and the cracking temperature ranges between 115 and 130 °C, dividing the low-temperature oxidation process of coal into three stages: before the critical temperature, between the critical temperature and the cracking temperature, and after the cracking temperature. An AFR of 120 mL min⁻¹ was identified as the optimal level; exceeding or falling below this value inhibits the coal-oxygen reaction. Increasing OxyC and reducing HR improves coal oxidation. Compared to the same samples under AFR and HR conditions, the E_a of coal under oxygen conditions is lower, ranging between 20 and 35 kJ mol⁻¹, while under AFR and HR conditions, the E_a is not less than 30 kJ mol⁻¹, indicating a stronger tendency for spontaneous combustion under oxygen conditions. AFR substantially affects the oxygen consumption rate, CH₄, and exothermic intensity at all stages, with a partial η² of 0.6. Before the critical temperature, OxyC has the greatest impact on CO₂; between the critical temperature and the cracking temperature, OxyC has the greatest impact on CO; and after the cracking temperature, OxyC has the greatest impact on CO, CO₂, C₂H₄, and C₂H₆, with partial η² values of 0.51, 0.59, 0.278, and 0.45, respectively.

Green and facile route was employed for development of smart flame-retardant, antibacterial and reinforced textile fabric's coatings. The multifunctional coatings were fabricated from sustainable chitosan functionalized via one pot method with α-aminophosphonates with different groups (methyl and phenyl groups). Phenyl- and methyl-based α-aminophosphonates were grafted on chitosan chains individually. Additionally, magnetic chitosan-Fe₃O₄ nanoparticles functionalized α-aminophosphonates-based phenyl moiety were also prepared. Moreover, tetra-n-butylammonium hexafluorophosphate was also dispersed in coating dispersion. The different prepared functionated chitosan was then exploited as efficient flame-retardant, reinforced and antibacterial-based multifunctional coatings for cotton fabrics. Different mass loadings of methyl- and phenyl-based functionalized chitosan and magnetic chitosan were dispersed in chitosan solution and then coated on cotton surface. The influence of mass loading and different side groups was studied. Flammability, tensile strength and antibacterial properties of developed cotton fabrics were evaluated. The flammability of coated cotton fabrics was strongly improved achieving reduction in rate of burning by 48% compared to uncoated one. This is in addition to LOI value of 23.5% compared to 18% for uncoated fabric. This is due to the influence of organic phosphate in coating layer which stimulates the formation of protective char layer. The tensile strength of coated fabrics was improved recording 29% enhancement compared to uncoated one. Moreover, the developed coating layer strongly inhibits the growth of well-known bacterial strains Escherichia coli and Staphylococcus aureus, achieving clear antibacterial inhibition zones of 16.7 and 23.6 mm, respectively. Additionally, the flame retardancy mechanism was proposed and elucidated.

This study is aimed at investigating the crystallization kinetics of two structurally related polymers, Nylon 6,6 (PA66) and Nylon 11 (PA11), by differential scanning calorimetry (DSC) in the scope of a logistic-based model using a model fitting approach. By this method, the values of the rate parameters for each specific temperature are obtained from fitting all points of the crystallization exotherm that were accurately recorded at that temperature. This method differs from Arrhenius-based model fitting approaches, in which the initial and final parts of the exotherm do not usually match the shape of Arrhenius-based models and are therefore discarded for fitting. Furthermore, in other kinetic approaches that fall outside the scope of this article, kinetic parameters are typically obtained from specific points in the crystallization exotherm, and good fits cannot generally be obtained nor is that the goal of those approaches. The DSC curves of both polymers obtained at different temperatures are analysed to determine the crystallization kinetics. One of the most insightful parameters of the model is the crystallization rate. Its dependence on temperature is analysed for both polymers and compared to others. The other parameters can also help to better understand some of the crystallization features of these polymers. In addition, the information retrieved from this study can be useful to adjust processing conditions.