Search Results (329)

Hybrid silica xerogels functionalised with chlorinated organosilanes combine tunable porosity and surface chemistry, rendering them attractive for applications in sensing, membrane technology, and photonics. This study quantitatively investigates the thermal decomposition kinetics of organochlorinated xerogels and correlates with volatile compounds previously identified via Thermogravimetric Analysis (TGA) coupled to Fourier-Transform Infrared Spectroscopy (FT–IR) and Gas Chromatography coupled with Mass Spectrometry (GC–MS). The xerogels were synthesised via the sol–gel process using organochlorinated alkoxysilane precursors and yielded highly condensed nanostructures in which the precursor nature strongly influences the morphology and textural properties. In this study, the molar percentage of the organochlorinated compounds was fixed at 10%. Standard N₂ adsorption-desorption isotherm at 77 K revealed that increasing the precursor content systematically decreased the specific surface area and pore volume of the materials while promoting the formation of periodic domains, which are observed even at low organosilane molar percentages. Thermal characterisation via TGA/FT–IR/GC–MS revealed at least two main decomposition stages, with thermal stability following the order of 4–chlorophenyl > chloromethyl > 3–chloropropyl > 2–chloroethyl. This study focuses on kinetic and mechanistic insights in the thermal decomposition process through the Flynn–Wall–Ozawa isoconversional method and Criado master plots, using TGA/Differential Scanning Calorimetry (DSC) measurements under nitrogen at multiple heating rates (5, 10, 20, 30, and 40 K min⁻¹), which revealed activation energies ranging from 53 to 290 kJ mol⁻¹. Demonstrating that the chlorinated organosilane precursor directly controls both the textural properties and thermal behaviour of the resulting silica materials, with aromatic groups providing superior thermal stability compared to aliphatic chains. These quantitative kinetic insights provide a predictive framework for designing thermally stable hybrid materials while ensuring safe processing conditions to prevent hazardous volatile release. Full article

In this study, the potential use of Epsom salt production waste as a supplementary cementitious material was investigated. This acidic waste was neutralized with lime milk and used to replace up to 25 wt.% of Portland cement. The following research methods were employed: XRD, XRF, SEM, DSC-TG, and isothermal calorimetry. The waste neutralization process was found to proceed consistently, producing a neutral material (pH = 7.5) composed of amorphous silicon compounds with a negligible impurity of crystalline antigorite. Consequently, this material exhibits very high pozzolanic activity. The neutralized Epsom salt production waste accelerates the early hydration of Portland cement and promotes an intense pozzolanic reaction. This new material is a highly effective supplementary cementitious material, capable of replacing up to 25 wt.% of Portland cement without reducing its strength class. Full article

The crystallization behavior of the bioactive silicate glass “1d” was analyzed using non-isothermal conditions through differential scanning calorimetry (DSC). The plots carried out at different heating rates showed only one crystallization peak. The activation energy for crystallization was calculated through the equations proposed in the Kissinger and Matusita–Sakka models. The Johnson–Mehl–Avrami coefficient (n) was estimated by applying Ozawa and Augis–Bennet methods, resulting in a two-dimensional crystal growth. Crystalline phases which developed during high-temperature treatment were analyzed by X-ray diffraction and scanning electron microscopy. The activation energy for viscous flow was estimated to be 513 kJ/mol, which is lower than the activation energy for crystallization (539 kJ/mol). The Malek test highlighted that the crystallization process was more complex than a simple nucleation-growth mechanism. The sinterability parameter and Hruby coefficient showed the high stability of 1d glass against crystallization, which makes this bioactive material highly appealing for producing well-sintered products of biomedical interest, such as bioactive porous scaffolds for bone regeneration. Full article

A comprehensive investigation was conducted focusing on two series of poly(lactic acid) (PLA)-based nanocomposites filled with small amounts (0.5 and 1.0%) of metal (Ag/Cu) nanoparticles (NPs). Our work aimed to synthesize PLA/Ag nanocomposites via in situ ring-opening polymerization (ROP), and for comparison purposes, the same materials were also prepared via solution casting followed by melt mixing. PLA/Cu nanocomposites were also prepared via melt extrusion. Gel permeation chromatography (GPC) and intrinsic viscosity measurements [η] showed that the incorporation of Ag nanoparticles (AgNPs) resulted in a decrease in the molecular weight of the PLA matrix, indicating a direct effect of the AgNPs on its macromolecular structure. Fourier-transform infrared spectroscopy (FTIR) revealed no significant changes in the characteristic peaks of the nanocomposites, except for an in situ sample containing 1.0 wt% of AgNPs, where slight interactions in the C=O region were detected. Differential scanning calorimetry (DSC) analysis confirmed the semi-crystalline nature of the materials. Glass transition temperature was strongly affected by the presence of NPs in the case of the in situ-based samples. Melt crystallized studies suggested potential indirect polymer–NP interactions, while isothermal melt crystallization experiments confirmed the nucleation ability of the NPs. The mechanical performance was assessed via tensile and flexural measurements, revealing that the in situ-based samples exhibited remarkable flexibility. Moreover, during the three-point bending tests, none of the in situ nanocomposite samples broke. In this context, next-generation PLA-based nanocomposites have been proposed for advanced applications, including flexible printed electronics. Full article

Fluoride contamination in groundwater is a pressing environmental and public health issue, with chronic exposure linked to skeletal and dental fluorosis. Here, we report the synthesis of magnesium oxide nanoparticles via a controlled co-precipitation method employing dimethylformamide (DMF) as solvent and either ammonium hydroxide (MgO-1) or ammonium carbonate (MgO-2) as precipitating agents. The resulting materials were comprehensively characterized using thermogravimetric analysis (TGA/DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS). Additionally, BET surface area and porosity analyses revealed mesoporous structures, with MgO-1 showing a slightly higher surface area (14.12 m² g⁻¹) than MgO-2 (13.87 m² g⁻¹). Both MgO-1 and MgO-2 exhibited high crystallinity, nanoscale particle sizes (81.6 nm and 128.1 nm, respectively), and distinct morphological features. Batch adsorption studies revealed maximum fluoride uptake capacities of 117.6 mg/g (MgO-1) and 94.5 mg/g (MgO-2) at neutral pH, with MgO-1 exhibiting superior performance due to its smaller particle size and higher specific surface area. Fluoride removal remained above 98% between pH 3–9, confirming stability across a wide pH range, with a minor decline at pH 11 due to OH⁻ competition. Adsorption equilibrium data were best described by the Temkin isotherm model, suggesting heterogeneous surface interactions and an exothermic process, while kinetic analyses indicated pseudo-second-order behavior for MgO-1 and pseudo-first-order for MgO-2. Both materials maintained high fluoride selectivity in the presence of competing anions and successfully reduced fluoride in tap water from 2.11 mg/L to below the WHO limits without altering water hardness. These findings underscore the potential of engineered MgO nanomaterials as efficient, selective, and sustainable adsorbents for water defluoridation, offering a promising pathway toward scalable remediation technologies in fluoride-affected regions. Full article

The local segmental mobility of polymer chains in polydimethylsiloxane (PDMS) plays a critical role in determining the material’s behaviour. Incorporation of zeolite particles can modify these local dynamics, which is crucial as they affect the overall performance of the resulting composite material with potential for various industrial applications. The aim of this study was to investigate the influence of zeolite addition on the local dynamic behaviour of PDMS chain segments in PDMS–zeolite composites. To investigate the effect of zeolite morphology and loading on the segmental dynamics and phase behaviour of PDMS, Zeolite A (with cubic and spherical morphologies) and Zeolite X were incorporated into the PDMS matrix at 20, 30, and 40 wt%. The electron spin resonance (ESR)-spin probe method was used to study molecular dynamics, while the thermal behaviour was analysed using differential scanning calorimetry (DSC). ESR results revealed that the presence of zeolites increases the isothermal crystallisation rate affecting segmental mobility in the amorphous phase below the crystallisation temperature. This effect was found to depend more strongly on zeolite morphology than on filler content. DSC measurements showed no change in glass transition temperature with the addition of zeolite; however, shifts in cold crystallisation and melting behaviour were observed, indicating changes in crystal structure and its degree of perfection. These findings suggest that zeolites act as heterogeneous nucleation agents, with their structural properties playing a critical role in the crystallisation behaviour of PDMS. Full article

This study aimed to solve two problems of polyethylene terephthalate (PET) films, namely, their slow crystallization rate and insufficient thermal stability, by using polyethylene naphthalate (PEN) as a modifier to prepare PET-PEN blends with varying PEN contents (0%, 0.9%, 1.8%, and 9%). Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and other methods were used to systematically investigate the effects of the PEN content and cooling rate (5–40 °C/min) on the non-isothermal crystallization behavior and kinetics of the blends. The results indicate that PET and PEN exhibit excellent compatibility. As the PEN content increases, the glass transition temperature (T_g) of the blend increases, while the melting point (T_m) and relative crystallinity decrease. PEN exerts an effect on the crystallization temperature (T_c)—“heterogeneous nucleation—diffusion control—steric hindrance effect”. The cold crystallization behavior depends on the PEN content and cooling rate. Samples with PEN content did not exhibit cold crystallization at low cooling rates. The observed non-isothermal crystallization kinetics show that PEN transforms the growth dimension of PET crystals from three-dimensional to two-dimensional, significantly reducing the absolute values of the crystallization rate constant (Z_c) and crystallization activation energy (ΔE). ΔE tends to stabilize when the PEN content reaches or exceeds 1.8%. In summary, PEN achieves precise control of PET non-isothermal crystallization through the mechanism of “heterogeneous nucleation—diffusion control—steric hindrance effect”. The research results provide theoretical support for the optimization of processing technology for PET-PEN blend films in high-end fields such as food packaging and electronic insulation. Full article

This study provides a comprehensive quantitative comparison of three structurally distinct epoxy prepolymers—cycloaliphatic, novolac, and bis-aromatic (BADGE)—cured with a single hardener, methyl nadic anhydride (MNA), and catalyzed by 1-methylimidazole under strictly identical stoichiometric and thermal conditions. Each formulation was optimized in terms of epoxy/anhydride ratio and catalyst concentration to ensure meaningful cross-comparison under representative cure conditions. A multi-technique approach combining differential scanning calorimetry (DSC), dynamic rheometry, and thermogravimetric analysis (TGA) was employed to jointly assess cure kinetics, network build-up, and long-term thermal stability. DSC analyses provided reaction enthalpies and glass transition temperatures (Tg) ranging from 145 °C (BADGE-MNA) to 253 °C (cycloaliphatic ECy-MNA) after stabilization of the curing reaction under the chosen thermal protocol, enabling experimental fine-tuning of stoichiometry beyond the theoretical 1:1 ratio. Isothermal rheology revealed gel times of approximately 14 s for novolac, 16 s for BADGE, and 20 s for the cycloaliphatic system at 200 °C, defining a clear hierarchy of reactivity (Novolac > BADGE > ECy). Post-cure thermomechanical performance and thermal aging resistance (100 h at 250 °C) were assessed via rheometry and TGA under both dynamic and isothermal conditions. They demonstrated that the novolac-based resin retained approximately 93.7% of its initial mass, confirming its outstanding thermo-oxidative stability. The three systems exhibited distinct trade-offs between reactivity and thermal resistance: the novolac resin showed superior thermal endurance but, owing to its highly aromatic and rigid structure, limited flowability, while the cycloaliphatic resin exhibited greater molecular mobility and longer pot life but reduced stability. Overall, this work provides a comprehensive and quantitatively consistent benchmark, consolidating stoichiometric control, DSC and rheological reactivity, Tg evolution, thermomechanical stability, and degradation behavior within a single unified experimental framework. The results offer reliable reference data for modeling, formulation, and possible use of epoxy–anhydride thermosets at temperatures above 200 °C. Full article

A depth study of optical, isothermal crystallization and mechanical properties was conducted on a series of poly(lactic acid) (PLA) nanocomposites based on lignin/multi-walled carbon nanotubes (MWCNTs) hybrid nanomaterial. The preparation was performed via solution casting followed by melt mixing. For comparison reasons, a group of PLA/lignin polymeric materials were prepared. Infrared spectroscopy (FTIR) did not reveal any significant impact on the main peaks of the nanocomposites by the incorporation of the additives. The optical properties were strongly affected by the content of the additive, as long as the thermal transitions parameters as evaluated from the differential scanning calorimetry (DSC) show important differences between cold and melt crystallization. X-ray diffraction (XRD) showed the semicrystalline behavior of the materials, while during isothermal crystallization experiments, the hybrid conductive nanomaterial acted as nucleation agent by promoting crystallization. Under evaluation of the mechanical properties, Young’s modulus tensile parameter increased significantly while the content of the hybrid nanomaterial increased, and the bending experiments of the materials with low content of the additives did not break. Thus, these substrates could be promising candidates for engineering applications, such as printed electronics. Full article

The accurate determination of the equilibrium moisture content (EMC) of gel-related powdery samples requires strictly controlled conditions and a long time period. In this study, the adsorption and desorption isotherms of two fructooligosaccharide (FOS) powders and three inulin powders were determined using a dynamic moisture sorption analyzer at 0.1–0.9 water activity (a_w) and 20–35 °C, respectively. The adsorption and desorption isotherms all exhibited type IIa sigmoidal curves; the desorptive isotherm was smooth, the FOS adsorption curves had three inflection points, and the inulin adsorption curves had five inflection points. Large hysteresis between the adsorption and desorption isotherms occurred at 0.1–0.7 a_w for FOS and 0.1–0.6 a_w for inulin. Seven equations, Boquet, Ferro–Fontan, Guggenheim–Anderson–de Boer (GAB), Generalized D’Arcy and Watt (GDW), modified GAB (MGAB), Peleg, and our developed Polynomial, were found to fit the isotherms of the FOS and inulin samples; for adsorption, the best equations were Ferro–Fontan and GDW, and for desorption, the best equations were Polynomial and MGAB. The GDW and MGAB equations could not distinguish the effect of temperature on the isotherms, while the Polynomial equation could. The mean adsorptive monolayer moisture content (M₀) values in FOS and inulin samples were predicted as 7.29% and 7.94% wet basis, respectively. The heat of moisture sorption of FOS and inulin approached that of pure water at about 32.5% and 22.5% wet basis (w.b.) moisture content (MC), respectively. Fourier Transform Infrared Spectroscopy (FTIR) showed that the peaks in inulin with absorbance values above 0.52 and in FOS with absorbance values above 0.35 were at 1020, 1084, and 337 cm⁻¹; these could represent the amorphous structure (primary alcohol C-OH), C-O group, and hydroxyl functional group, respectively. Microscopic structure analysis showed that inulin powder particles were more round-shaped and adhered together, resulting in hygroscopic and sticky characteristics, with a maximum equilibrium moisture content (EMC) of 34% w.b. In contrast, the FOS powders exhibited irregular amorphous particles and a maximum EMC of 60% w.b. As hydrogels, 3–10% FOS or inulin addition reduced the peak, trough, final, breakdown, and setback viscosities of rice starch pasting, but increased the peak time and pasting temperature. FOS addition gave stronger reduction in the setback viscosity and in amylose retrogradation of rice starch pasting than inulin addition. The differential scanning calorimeter (DSC) showed 3–10% FOS addition reduced the amylopectin aging of retrograded paste of rice starch, but 5–7% inulin addition tended to reduce. These results suggest that FOS and inulin have strong hygroscopic properties and can be used to maintain the freshness of starch-based foods. These data can be used for drying, storage, and functional food design of FOS and inulin products. Full article

The rheological behavior and low-temperature curing kinetics of poly(ethylene glycol fumarate)–acrylic acid systems initiated by benzoyl peroxide/N,N-dimethylaniline have been investigated for the first time with a focus on the development of thermosetting binders with controllable properties. It has been established that both composition and temperature have a significant effect on rheological behavior and kinetic parameters. Rheological studies revealed non-Newtonian flow behavior and thixotropic properties, while oscillatory tests demonstrated structural transformations during curing. Increasing the temperature was found to accelerate gelation, whereas a higher polyester content retarded the process, which is crucial for controlling the pot life of the reactive mixture. DSC analysis indicated that isothermal curing at 30–40 °C can be satisfactorily described by the Kamal autocatalytic model, whereas at 20 °C, at later stages, and at higher polyester contents, diffusion control becomes significant. The thermal behavior of cured systems was investigated using thermogravimetry. Calculations using the isoconversional Kissinger–Akahira–Sunose and Friedman methods confirmed an increase in the apparent activation energy for thermal decomposition, suggesting a stabilizing effect of poly(ethylene glycol fumarate) in the polymer structure. The studied systems are characterized by controllable kinetics, tunable viscosity, and high thermal stability, making them promising thermosetting binders for applications in composites, construction, paints and coatings, and adhesives. Full article

For the first time, the kinetics of isothermal curing and thermal degradation of polyethylene glycol maleate (pEGM)–based systems and their composites with mineral fillers were investigated in the presence of a benzoyl peroxide/N,N-Dimethylaniline redox-initiating system. DSC analysis revealed that the curing process at 20 °C can be described by the modified Kamal autocatalytic model; the critical degree of conversion (α_c) decreases with increasing content of the unsaturated polyester pEGM and in the presence of fillers. In particular, for unfilled systems, α_c was 0.77 for pEGM45 and 0.60 for pEGM60. TGA results demonstrated that higher pEGM content and the incorporation of fillers lead to increased thermal stability and residual mass, along with a reduction in the maximum decomposition rate (dTGₘₐₓ). Calculations using the Kissinger–Akahira–Sunose and Friedman methods also confirmed an increase in the activation energy of thermal degradation (E_a): E_KAS was 419 kJ/mol for pEGM45 and 470 kJ/mol for pEGM60, with the highest values observed for pEGM60 systems with fillers (496 kJ/mol for SiO₂ and 514 kJ/mol for CaCO₃). Rheological studies employing three-interval thixotropy tests revealed the onset of thixotropic behavior upon filler addition and an increase in structure recovery after deformation of up to 56%. These findings underscore the potential of pEGM-based systems for low-temperature curing and for the design of composite materials with improved thermal resistance. Full article

This work evaluates the CO₂-adsorption relevance and cycling stability of graphene oxide–silica (GO-SiO₂) and reduced graphene oxide–silica (rGO-SiO₂) gels after amine functionalization, demonstrating high-capacity retention under repeated adsorption–desorption cycles: rGO-SiO₂-APTMS retains ≈96.3% of its initial uptake after 50 cycles, while GO-SiO₂-APTMS retains ≈90.0%. The use of surfactants to control the organization of inorganic and organic molecules has enabled the development of ordered mesostructures, such as mesoporous silica and organic/inorganic nanocomposites. Owing to the outstanding properties of graphene and its derivatives, synthesizing mesostructures intercalated between graphene sheets offers nanocomposites with novel morphologies and enhanced functionalities. In this study, GO-SiO₂ and rGO-SiO₂ gels were synthesized and characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TG), mass spectrometry (MS), N₂ adsorption–desorption isotherms, and transmission electron microscopy (TEM). The resulting materials exhibit a laminar architecture, with mesoporous silica domains grown between graphene-based layers; the silica contents are 83.6% and 87.6%, and the specific surface areas reach 446 and 710 m²·g⁻¹, respectively. The laminar architecture is retained regardless of the surfactant-removal route; however, in GO-SiO₂ obtained by solvent extraction, a fraction of the surfactant remains partially trapped. Together with their high surface area, hierarchical porosity, and amenability to surface functionalization, these features establish amine-grafted graphene–silica gels, particularly rGO-SiO₂-APTMS, as promising CO₂-capture adsorbents. Full article

Background/Objectives: In the past two decades, the primary therapeutic use of sildenafil has shifted significantly, from the treatment of angina to managing erectile dysfunction, and since the early 2000s it has been used in the treatment of pulmonary hypertension, particularly pulmonary arterial hypertension. Sildenafil is used as a citrate salt; after oral administration, it presents an absorption of ~90% and an absolute bioavailability of 38%, due to the first-pass effect, such that it belongs to class II of the Biopharmaceutics Classification System. Currently, studies are seeking to obtain new pharmaceutical formulations with an optimized biopharmaceutical profile. In this study, an inclusion complex of sildenafil citrate and 2-hydroxypropyl-beta-cyclodextrin in a molar ratio of 1:1 was obtained and its pharmaceutical compatibility with six pharmaceutical excipients was assessed. For three of these excipients, the presence of chemical interactions with sildenafil citrate has been presented in the literature, and for the other three, compatibility has not been evaluated. Methods: To certify the stoichiometry of the obtained inclusion complex molecular modeling, Job’s method and the Benesi–Hildebrand method were employed. Furthermore, we have described the inclusion complex and the obtained binary mixtures via ATR-FTIR and thermal (TG/DTG and DSC) analysis. Results: The results indicated a lack of chemical interactions between the inclusion complex and the six pharmaceutical excipients at ambient temperature (confirmed by ATR–FTIR investigations) and the presence of chemical interactions between the inclusion complex and three of the excipients when the mixture was heated under non-isothermal conditions (TG/DTG and DSC investigations). Conclusions: This study describes the inclusion complex between sildenafil citrate and 2-hydroxypropyl-beta-cyclodextrin in a molar ratio of 1:1 and its compatibility with several pharmaceutical excipients, results with further applications in the preformulation stage of novel delivery systems. Full article

Pharmaceutical contaminants such as ibuprofen are increasingly detected in water sources due to widespread use and insufficient removal by conventional treatment processes. Given its persistence and adverse effects on human health and aquatic ecosystems, efficient removal technologies are needed. This study reports the synthesis of a Mg/Al-layered double hydroxide (LDH) hybridized with carbon quantum dots (CQDs) via in situ co-precipitation to enhance adsorptive performance. The hybrid (LDH-CQD) was characterized by FTIR, XRD, DSC, TGA-DTG, SEM-EDS, BET, and pH in the point of zero charge (pH_PZC) analysis. Results indicated a marked increase in surface area (2.89 to 66.9 m²/g), a shift in surface charge behavior (pHpzc from 8.57 to 6.21), and improved porosity. Adsorption experiments using ibuprofen as a model contaminant revealed superior performance of the hybrid compared to pristine Mg/Al-LDH, with a maximum capacity of 22.13 mg·g⁻¹ (% Removal = 88.53%) at 25 ppm, and in lower concentrations (5 and 10 ppm), the hybrid showed 100% removal. Kinetic modeling followed a pseudo-second-order mechanism, and the isotherm was the SIPS model (maximum adsorption capacity = 24.150 mg.g⁻¹). These findings highlight the potential of LDH-CQD hybrid as efficient and tunable adsorbents for removing emerging pharmaceutical pollutants from aqueous media. Full article