Search Results (1,064)

Heterogeneous photocatalysis increasingly requires rapid polymer degradation tests relevant to aqueous conditions. In this study, a multi-technique approach was developed to monitor the early-stage photo-oxidation of polyethylene (PE) and polystyrene (PS) microplastics in an aqueous ZnO–TiO₂ suspension under combined ultraviolet A and ultraviolet B (UV-A/B) irradiation. The changes were analyzed by ATR-FTIR and Raman spectroscopy, DSC, and gravimetric measurements. For PE, the carbonyl index increased from 0.0189 to 0.1350 after 12 h, mass loss reached 16.98%, and crystallinity decreased from 32.05% to 25.36% after 8 h. The Raman spectra of PE showed band broadening and intensity redistribution, indicating increasing structural disorder. In contrast, PS showed weaker Raman changes, while FTIR revealed a non-monotonic carbonyl-index response, and DSC showed a 2.2 °C increase in Tg after 12 h. Gravimetric analysis also showed measurable mass loss in PS, reaching 18.62% after 12 h. The results demonstrate that the combined use of ATR-FTIR, Raman, DSC, and gravimetry enables reliable distinction between early oxidation, surface modification, and material erosion in photocatalytically treated microplastics. Full article

In this study, the effect of temperature on thermal-assisted glass delamination was investigated using two treatment conditions differing in the set temperature of the process (100 °C vs. 140 °C). Thermogravimetric Analysis (TGA) confirmed that ethylene-vinyl acetate (EVA) remains thermally stable up to about 280 °C, with degradation onset near 300 °C, ensuring that both treatments operate below decomposition. Differential Scanning Calorimetry (DSC) analysis identified an endothermic transition attributable to the melting of crystalline regions in EVA within the thermal range of 35–65 °C, indicating enhanced polymer chain mobility at elevated temperatures. This endothermic transition corresponds to the melting of polyethylene crystallites within the EVA copolymer and should not be interpreted as a glass transition, since the Tg of EVA is typically located at approximately −30 to −35 °C. Fourier Transform Infrared (FTIR) analysis verified preservation of ester functional groups, confirming the absence of chemical degradation. The morphological analysis performed via Scanning Electron Microscopy (SEM) revealed a clear temperature-dependent morphology of EVA after thermal-assisted delamination. At 140 °C, enhanced polymer softening and viscous flow led to smoother surfaces and more uniform interfacial separation, whereas at 100 °C, limited mobility resulted in heterogeneous, fragmented residues and predominantly cohesive failure. These results highlight that optimizing temperature is key to balancing effective delamination with residue minimization, supporting more sustainable PV recycling. Full article

This study examines how manufacturer-specific additive formulations used to obtain nominally identical black PLA filaments influence the thermal, mechanical, and tribological performance of FDM-printed parts. Five commercial filaments were analyzed under identical processing conditions using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile testing, pin-on-disc measurements, and stereomicroscopy. The filaments exhibited substantial compositional variability, with total additive contents ranging from 2.08 wt.% to 27.82 wt.%. One filament (M5) contained a significant fraction of inorganic fillers, confirmed by SEM/EDX as Ca-, Na- and Mg-based oxides and silicates, identifying it as a PLA-based composite despite being marketed as standard PLA. These differences strongly affected thermal behavior (Tg, Tcc, Tm) and translated directly into the performance of the printed parts. Ultimate tensile strength varied by 88.91% across all filaments (19.38–36.61 MPa), but only by 13% among the four conventional PLA filaments (M1–M4). Tribological performance differed markedly: mean coefficients of friction ranged from 0.246 (M3) to 0.368 (M2), a spread of approximately 50%, with wear-track morphologies reflecting the frictional response. Overall, the results show that PLA filaments cannot be treated as interchangeable materials. Greater transparency and standardized reporting of filament composition are needed to ensure reproducibility and support informed material selection in FDM applications. Full article

Polyfarnesene, a bio-based polymer, was epoxidized in situ using performic acid to investigate oxirane ring formation, stability, and the role of its bottlebrush architecture in the kinetics. The reaction reached a maximum epoxidation degree of ~20% after 6 h but underwent side reactions, producing hydroxyl and formic ester groups. FTIR and ¹H NMR revealed that ring opening began within the first hour, whereas residual unsaturated bonds persisted after prolonged reaction, owing to steric shielding by the polymer’s long C11–C13 side chains. Unlike smaller polydiene homologues, polyfarnesene exhibited slower ring-opening kinetics, retaining approximately 10% of oxirane groups after 20 h. GPC showed minimal molecular weight changes but an increase in polydispersity, confirming structural rearrangements without chain scission or crosslinking. DSC demonstrated that oxirane incorporation increased the T_g; however, side reactions reduced this effect by limiting chain mobility. These findings establish that the spatial constraints imposed by the bottlebrush architecture of polyfarnesene govern the reaction kinetics, restricting epoxidation efficiency and favoring esterification pathways. This interplay provides a basis for designing bio-based polymers with tunable thermal properties. Controlling the reaction environment to suppress side reactions is key to producing high-T_g epoxidized derivatives suitable for rubber technologies and sustainable materials. Full article

Epoxy materials are an important class of thermosets whose properties strongly depend on the used formula, the curing parameters, and many available hardeners. Achieving desired properties such as enhanced thermal stability, extended lifetime, or self-regeneration requires selecting suitable precursors and carefully tuning curing conditions. In this work, a selected biphenyl epoxy precursor was used as a model compound to assess whether using different hardeners could be an effective factor in tailoring the elasticity of cured epoxy networks. We employed two chemically distinct hardeners—4,4′ diaminodiphenylmethane (DDM) and suberic acid—to generate materials with markedly different final properties. For instance, the glass transition temperature T_g varied within a range of over 35 °C. Two complementary experimental techniques were used in this paper to establish the optimal curing parameters: differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS). Both techniques supported tracking of changes in the mixture while curing and enabled determination of T_g in the obtained products. Dielectric relaxation spectroscopy revealed various molecular motions (α, β, and γ-processes) occurring in different phases, especially in glass-forming solids. BDS is therefore a good tool for testing new organic materials. The analytic route used in this work, based on a combination of calorimetric and electrical approaches, enables precise adjustment of the curing parameters to a specific hardener and helps verify the effects of using different hardeners on the elastic properties of the product. This allows the creation and modification of epoxy matrices towards modern materials, such as composites with self-healing properties or enhanced thermal stability. Full article

Poly(lactic acid) (PLA) films containing two different hemp-derived essential oils (EOs), Carmagnola CS (Carm) and Futura 75 (Fut), at 1, 5, and 10% wt were successfully produced via solvent casting for packaging applications. The influence of EO presence, type, and concentration on the chemical, morphological, and thermal properties of the PLA-based films was investigated. In addition, radical-scavenging activity, water transport properties, and antimicrobial performance were evaluated to assess the effect of EOs on the structural and functional characteristics of the resulting packaging materials. FTIR spectroscopy confirmed the successful incorporation of the hemp essential oils Carm and Fut into the polymer matrix, with a concentration-dependent effect that is more pronounced for Fut than for Carm. In the second heating run, evaluated by DSC measurements, both EOs lowered T_g from 60.3 °C (PLA) to 52.0 °C for PLA_10 Carm and 55.1 °C for PLA_10 Fut. The EOs act as plasticizers in the PLA matrix, improving the deformation at break. Gas barrier measurements showed that permeability decreased from 3027 ± 300 Barrer (PLA) to (2499 ± 44) Barrer in PLA_10 Carm and 2623 ± 130 Barrer in PLA_10 Fut, with a corresponding reduction in diffusivity. The barrier improvement factor reached 17% for Carm and 15% for Fut, confirming the enhanced barrier performance of PLA_EOs films. DPPH assays showed that PLA_EOs films retained most of the antioxidant activity of the free oils, with only a 10–15% reduction for PLA_Fut and no significant loss for PLA_Carm after one week. After one month, the activity of Carm in PLA film decreased by 18%, whereas the performance of its free form remained unchanged, confirming the superior and more stable radical scavenging capacity of Carm compared to Fut. Overall, the study demonstrates that hemp essential oils can be effectively integrated into PLA without compromising structural integrity, while preserving antioxidant performance and enhancing water barrier properties, supporting their potential as sustainable active packaging components. Full article

Oxy-fuel combustion is a near-zero emission technology that utilizes high-concentration O₂ in place of air, combined with recycled flue gas, to achieve efficient combustion and enable effective CO₂ capture. In this study, air (21% O₂/79% N₂) was used as the control atmosphere, and rice straw combustion experiments were conducted using thermogravimetric analysis and differential scanning calorimetry and differential scanning calorimetry coupled with mass spectrometry (TG-MS) at heating rates of 10, 20, and 30 °C/min under oxy-fuel conditions of 30% O₂/70% CO₂, 50% O₂/50% CO₂, and 70% O₂/30%CO₂. The combustion behavior, pollutant emissions, reaction kinetics, and underlying mechanisms were systematically evaluated. The results show that CO₂ in oxy-fuel atmospheres exhibits a higher thermal inertia, due to its greater density and specific heat capacity, thereby enhancing flame stability. Oxy-fuel atmospheres reduce the ignition temperature (Tᵢ) and burnout temperature (T_f), shorten the combustion duration, shift DTG and DSC peaks to lower temperatures, and result in sharper peaks along with an increased ignition index (Cᵢ), burnout index (C_b), and comprehensive combustion index (S). Mass spectrometry (MS) analysis reveals that oxy-fuel atmospheres combined with heating rates of 20–30 °C/min suppress O₂ diffusion and thermal NO formation, reducing NO_x emissions by over 75% and simultaneously inhibiting the release of SO₂ and COS. Kinetic analysis using the FWO and Friedman methods shows that the activation energy decreases from 210.5 kJ/mol and 219.1 kJ/mol under air conditions to 110.5 kJ/mol and 114.6 kJ/mol in oxy-fuel atmospheres, representing a reduction in reaction barriers of 47.5% and 47.7%, respectively. The reaction mechanisms were identified as three-dimensional diffusion-controlled processes at heating rates of 20–30 °C/min, and random nucleation followed by growth under high O₂ concentration conditions at a heating rate of 30 °C/min. Optimizing the combustion atmosphere and heating rate enhances the rice straw combustion efficiency and reduces pollutant emissions, thereby providing theoretical support for its clean and efficient utilization. Full article

The chemical and mineral composition, physical and mechanical properties, and pozzolanic activity of ancient bricks from Hubei Province, China were investigated in this study. X-ray diffraction (XRD), thermogravimetric analysis (TG-DSC), X-ray fluorescence analysis (XRF) and scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS) were adopted to characterize the chemical composition, crystalline minerals and microstructure of the ancient bricks. The results show that quartz is the dominant component in most ancient bricks, with a content exceeding 70% in samples BB-2, BB-5, BB-6 and BB-7. Some bricks contain minor non-clay minerals such as calcite, dolomite and albite. On some points in the SEM image, substances such as gypsum, calcite, and quartz can be clearly seen. The calcining temperature of the ancient bricks from Yupan Village, Xiantao City (sample BB-1), does not exceed 600 °C, while that of other samples ranges from 800 to 1100 °C. The compressive strength of most ancient bricks is around 10 MPa, with the highest value of 14.3 MPa (BB-6) and the lowest of 1.2 MPa (BB-3). The apparent density of all samples is approximately 2.2 g/cm³, and the water absorption rate ranges from 6.5% to 23.1%. The pozzolanic activity index of some samples reaches 76% at 28 days, with the 150-year-old sample BB-7 showing the best activity. This study provides a reliable experimental basis for analyzing the weathering resistance and deterioration mechanism of ancient bricks in Hubei Province, offers technical support for the restoration of local ancient buildings, and lays a foundation for the development of antique-style brick craftsmanship. Full article

This study examines the carbonation behavior and CO₂ storage potential of a Ca-rich alkali-activated binder produced entirely from industrial residues-ladle furnace slag (LFS), coal ash (CA), and cement kiln dust (CKD). The system was designed as a one-part alkali-activated material (AAM), with CKD acting as an internal activator, and subjected to ambient curing, water curing, and accelerated CO₂ curing at ambient pressure. Phase evolution, microstructural development, and pore-structure characteristics were investigated using X-ray diffraction, FTIR spectroscopy, DSC–TG analysis, scanning electron microscopy, and X-ray micro-computed tomography, together with measurements of density, water absorption, and compressive strength. Loss-on-ignition measurements combined with chemical analysis were further used to quantify CO₂ uptake and evaluate the degree of carbonation of the binder system. CO₂ curing fundamentally altered the reaction pathway of the binder, shifting it from hydration-dominated to carbonation-controlled phase evolution, leading to the decomposition of calcium-bearing hydrates and complete carbonation of non-hydraulic γ-belite with the formation of vaterite, aragonite, and calcite. These transformations induced pronounced microstructural densification, reflected in a near-doubling of compressive strength (>48 MPa), increased apparent density, reduced water absorption, and simplified pore-network topology. A preliminary carbon footprint assessment indicates that the production of 1 m³ of the developed LFS–CA–CKD concrete generates about 14.36 kg CO₂-eq, while the carbonation process enables significant CO₂ sequestration, resulting in a net negative carbon balance. The results demonstrate that controlled carbonation is an effective post-treatment strategy for waste-derived alkali-activated binders, enabling simultaneous performance enhancement and permanent CO₂ sequestration. Full article

The application of microalloying technology has significantly improved the mechanical properties, oxidation resistance, and corrosion resistance of the Sn-9Zn-xAl-series solder. The effects of Al addition on microstructural evolution and service-related performance of the solders were systematically investigated using a combination of characterization techniques, including scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), differential scanning calorimetry (DSC), tensile testing, spreading testing, thermogravimetry (TG), and potentiodynamic polarization measurements. Microstructural characterization reveals that an optimal content of Al reacts with the Sn-Zn matrix to form AlZnSn intermetallic compounds (IMCs), which effectively refines the Zn-rich precipitates and eutectic lamellar structure. Concomitantly, the formation of second-phase strengthening contributes to a significant enhancement in the tensile strength of the solder alloys. Specifically, the Sn-9Zn-0.8Al solder exhibits a tensile strength of 87 MPa, corresponding to a 37% increment compared to the base Sn-9Zn alloy, whereas the elongation is reduced to 14.1%. Moreover, the in situ-formed Al₂O₃ passive film provides effective protection for the solder matrix, inhibiting oxidation induced by oxygen atoms and corrosion caused by chlorine ions, thereby remarkably improving the oxidation and corrosion resistance of the alloy. Collectively, these findings demonstrate that Al microalloying can substantially enhance the strength, oxidation resistance, and corrosion resistance of Sn-9Zn solder; however, a trade-off between wettability and ductility needs to be carefully considered for practical applications. Full article

The resistance of pathogenic bacteria to antimicrobial agents is currently one of the most significant health challenges. Polymers and nano-polymer composites with antimicrobial properties are widely used, particularly in hospitals, biocompatible implants, and the medical device industry. Syzygium aromaticum (clove) contains several bioactive compounds, including potent antioxidants and antimicrobials, which confer antioxidant, antibacterial, and antiseptic properties. For this purpose, polyvinyl alcohol (PVA) films were produced at three different concentrations using a direct integration method and doped with clove essential oil. The spectral, structural, and thermal properties of the produced films were analyzed, and their antibacterial activity against Klebsiella pneumoniae was tested. Fourier Transform Infrared Spectroscopy (FTIR) results confirm that the structural integrity of the PVA matrix is preserved and that the essential oil is physically trapped within the polymer network. Overall, the Differential Scanning Calorimetry (DSC) results confirm that Syzygium aromaticum essential oil (SAEO) acts as an effective plasticizer in PVA films, significantly modifying the glass transition behavior and enhancing polymer chain mobility in a concentration-dependent manner. The Dynamic Mechanical Analysis (DMA) results, supported by DSC analysis, clearly demonstrate that SAEO acts as an effective plasticizing agent in PVA films by increasing molecular mobility, lowering the glass transition temperature (Tg), and promoting thermally induced deformation. The concentration-dependent increase in the diameter of the inhibition zone of essential-oil-added films showed that their antibacterial efficacy increased as the S. aromaticum essential oil content increased (0.5%, 0.75%, and 1.0%). Additionally, molecular docking was performed to examine interactions between selected virulence proteins of K. pneumoniae and the main components of clove essential oil. As a result, S. aromaticum essential oil conferred antibacterial properties to the polyvinyl alcohol films without significantly altering their transparency and thermal properties. Full article

The performance improvement of mechanical components often relies on heat treatment processes, but these processes inevitably result in oxidation burn-off. The repeated formation and spallation of Fe₂O₃ rich oxide scales lead to substantial iron depletion and surface deterioration. Consequently, environmentally sustainable and economically viable protective coatings are required to suppress oxidation induced burn off. In this work, a TiO₂-MgAl₂O₄ composite coating was synthesized from magnesium slag and applied to Q235 carbon steel to enhance its performance during prolonged high temperature heat treatment. Oxidation tests conducted at 900 °C for 60 min demonstrated that the coating markedly improved the oxidation resistance of carbon steel, with an enhancement of approximately 87% relative to the uncoated specimens. To elucidate the protective mechanism, SEM-EDS, XRD, TG-DSC, and XPS analyses were employed. Based on Wagner Theory, the formation of interfacial phases such as Mg_7.92Al_15.31Fe_0.66O₃₂, which effectively impeded oxygen ion diffusion and thereby enhanced the oxidation resistance during high-temperature exposure. Furthermore, the synergistic effect of aluminum-, magnesium-, and titanium-containing compounds in the coating contributed to suppressing the diffusion of oxygen and iron ions, thus further improving the protective performance. This study provides a systematic theoretical foundation and practical guidance for addressing material loss during high-temperature processing of mechanical components, as well as for promoting the resource utilization of magnesium slag. Full article

This study investigates the adsorption of ibuprofen (IBU) and diclofenac sodium (DS) using bentonite modified with varying amounts (50, 75, and 100% of cation exchange capacity—CEC) of two surfactants: octadecyl(dimethylbenzyl)ammonium (ODMBA) chloride and hexadecyltrimethylammonium (HDTMA) bromide. The resulting organobentonites were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry/thermogravimetric analysis (DSC/TG), and zeta potential analysis. The results indicated that higher surfactant concentrations in organobentonites improved adsorption efficiencies for both drugs, while ODMBA-modified organobentonites exhibited notably larger adsorption capacities than HDTMA-modified samples. The adsorption isotherms fitted well to both the Langmuir and Freundlich models, with a better fit observed for the Freundlich model. The highest adsorption capacities were 102 mg/g for IBU and 160 mg/g for DS on sample OB-100 (organobentonite with 100% of ODMBA). Characterization of samples after drug adsorption, using FTIR, zeta potential and DSC/TG analysis, confirmed drug presence in organobentonites. Adsorption tests of DS in real river water (Danube and Sava rivers) showed that OB-100 demonstrated high removal capacity for DS. The findings suggest that organobentonites are low-cost adsorbents with potential for the removal of pharmaceutical contaminants from real aquatic environments. Full article

In this study, the feasibility of electrospraying as an alternative processing technique for the preparation of composite solid rocket propellants (SRPs) was investigated. The main objective was to improve microstructural homogeneity and interfacial contact between the oxidizer, energetic additive, and metallic fuel without altering the chemical composition of the formulation. Additionally, porous electrosprayed SRP formulations were prepared to examine the influence of controlled porosity on thermal decomposition behavior. The prepared materials were characterized using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM/EDS) to assess microstructural features and component distribution. Thermal decomposition behavior and kinetic parameters were evaluated using simultaneous DSC/TG analysis conducted at multiple heating rates. Safety-related properties were assessed through friction sensitivity testing, while post-decomposition solid residues were analyzed using SEM/EDS and X-ray diffraction. The results show that electrospraying improves structural homogeneity, reduces solid residue formation after thermal decomposition, and decreases apparent activation energy, while maintaining unchanged friction sensitivity. These findings demonstrate the potential of electrospraying as a physical processing route for tailoring the microstructure and thermal behavior of composite solid rocket propellants. Full article

The ultraviolet (UV) copolymers of two monomers, one methacrylic and the other vinyl monomer (styrene, S) were prepared. As methacrylic monomers, citronellyl methacrylate (CM) or geranyl methacrylate (GM) were used. The preparation was proven to contain high solvent- and chemical-resistant copolymers due to their cross-linked structure with the conversion degree of the double bonds above 0.92 for poly(citronellyl methacrylate)/polystyrene (PCM/PS) and above 0.85 for poly(geranyl methacrylate)/polystyrene (PGM/PS) copolymers. The obtained copolymers showed only one glass transition temperature (T_g). Depending on the structure and amount of the used methacrylic monomer, the T_g values were from 0.4 °C to −15.2 °C for PCM/PS copolymers and from −23.2 °C to −50.5 °C for PGM/PS copolymers. The thermogravimetric analysis (TG/DTG) showed a higher thermal stability for PCM/PS (148–187 °C) than for PGM/PS copolymers (119–159 °C) in inert and oxidative atmospheres. The simultaneous thermogravimetric analysis coupled with Fourier Transform Infrared spectroscopy (TG/FTIR) showed that the pyrolysis and oxidative decomposition of the tested copolymers took place according to the radical mechanism. This led to receiving a mixture of low molecular mass organic molecules containing saturated and unsaturated fragments, carbonyl groups, aromatic fragments as well as to CO, CO₂ and H₂O. This indicated the depolymerization process (inert) and further oxidation processes of the initially formed volatiles and/or residues in oxidative conditions. Full article