Search Results (175)

The photochemistry of 1,3,4-oxadiazoles remains poorly understood, despite their recognized importance in medicinal chemistry and materials science. In this work, we report a detailed matrix-isolation study of 2-amino-5-(4-methoxyphenyl)-1,3,4-oxadiazole, combining low-temperature infrared spectroscopy with broadband UV photolysis and quantum chemical calculations. Theoretical analysis predicts the gas-phase molecule to exist exclusively as the amino tautomer, populating two nearly isoenergetic conformers (anti and syn) defined by the relative orientation of the amino and methoxy groups. Experimental IR spectra of the compound isolated in Ar and Xe matrices at 15 K confirm sole trapping of the amino tautomer. Annealing of the Xe matrix to the highest achievable temperature induced no detectable spectral changes, consistent with the predicted isoenergetic character of the conformers. Upon broadband UV irradiation (λ > 200 nm), the compound undergoes ring opening through N−N and C−O bond cleavages, paralleling the behavior of unsubstituted 1,3,4-oxadiazole system. Isocyanates emerge as the predominant photoproducts from these photochemical pathways. Additionally, spectroscopic evidence supports an alternative reaction pathway involving early-stage amino−imino tautomerization, followed by ring-opening of the imino tautomer through isocyanic acid extrusion, leading to the formation of a nitrilimine intermediate. This reactive species subsequently photorearranges into a carbodiimide via a diazirine-mediated pathway. All photoproducts were unambiguously identified through their distinct IR signatures, supported by quantum chemical calculations and reference data from structurally related systems. These findings provide unprecedented insight into the photochemical behavior of substituted 1,3,4-oxadiazoles and unveil new reaction pathways modulated by substituent effects, expanding the understanding of their photoreactivity. Full article

Biodegradable polymers offer environmental advantages compared to fossil-based alternatives, but they currently lack the stretchability required for demanding applications such as mesh fabrics for woven flexible intermediate bulk container (FIBC) bags and stretch, shrink, and cling films. The goal of this research is to enhance the stretchability of biodegradable blends based on 80% poly(butylene adipate-co-terephthalate) (PBAT) and 20% poly(lactic acid) (PLA) through reactive extrusion. Radical initiator (dicumyl peroxide (DCP)) and chain extenders (maleic anhydride (MA), glycidyl methacrylate (GMA)) were employed to improve the melt strength and elasticity of the extruded films. The reactive blends were initially prepared using a batch mixer and subsequently compounded in a twin-screw extruder. Films were produced via cast extrusion. 0.1% wt. DCP led to a 200% increase in elongation at break and a 44% improvement in tensile strength. Differential scanning calorimetry and scanning electron microscopy revealed enhanced miscibility between components. Shear and complex viscosity increased by 38% and 85%, compared to the neat blend, respectively. Reactive extrusion led to a better dispersion and distribution of the phases. An improved interfacial adhesion between the phases, in addition to higher molecular weight, led to enhanced melt strength and improved stretchability. Full article

Three-dimensional (3D) concrete printing (3DCP) has gained significant attention over the last decade due to its many claimed benefits. The absence of effective real-time quality control mechanisms, however, can lead to inconsistencies in extrusion, compromising the integrity of 3D-printed structures. Although the importance of quality control in 3DCP is broadly acknowledged, research lacks systematic methods. This research investigates the feasibility of using ultrasonic pulse velocity (UPV) as a practical, in situ, real-time monitoring tool for 3DCP. Two different groups of binders were investigated: limestone calcined clay (LC³) and zeolite-based mixes in binary and ternary blends. Filaments of 200 mm were extruded every 5 min, and UPV, pocket hand vane, flow table, and viscometer tests were performed to measure pulse velocity, shear strength, relative deformation, yield stress, and plastic viscosity, respectively, in the fresh state. Once the filaments presented printing defects (e.g., filament tearing, filament width reduction), the tests were concluded, and the open time was recorded. Isothermal calorimetry tests were conducted to obtain the initial heat release and reactivity of the supplementary cementitious materials (SCMs). Results showed a strong correlation (R² = 0.93) between UPV and initial heat release, indicating that early hydration (ettringite formation) influenced UPV and determined printability across different mixes. No correlation was observed between the other tests and hydration kinetics. UPV demonstrated potential as a real-time monitoring tool, provided the mix-specific pulse velocity is established beforehand. Further research is needed to evaluate UPV performance during active printing when there is an active flow through the printer. Full article

Air purification is a key process aimed at removing harmful impurities and providing a safe and comfortable environment for human life and work. This study presents the results of an investigation into the composition, textural, and sorption properties of a multichannel carbon filtering material developed for air purification from biological (infectious) contaminants. The filtering block has a cylindrical shape and is manufactured by extrusion of a plastic composition based on carbonized rice husk with the addition of binding agents, followed by staged thermal treatment (calcination, activation, and demineralization). The filter’s effectiveness is based on the inactivation of pathogenic microorganisms as the air passes through the porous surface of the sorbent, which is modified with broad-spectrum antiseptic agents (active against bacteria, bacilli, fungi, and protozoa). X-ray diffraction analysis revealed the presence of amorphous carbon in a tubostratic structure, with a predominance of sp- and sp²-hybridized carbon atoms not incorporated into regular graphene lattices. IR spectroscopy demonstrated the presence of reactive functional groups characteristic of the developed porous structure of the material, which is capable of selective sorption of antiseptic molecules. SEM surface analysis revealed an amorphous texture with a loose structure and elements in the form of spherical semi-ring formations formed by overlapping carbon plates. An experimental setup was also developed using cylindrical multichannel carbon blocks with a diameter of 48 mm, a length of 120 mm, and 100–120 longitudinal channels with a cross-section of 1 mm². The obtained results confirm the potential of the proposed material for use in air purification and disinfection systems under conditions of elevated biological risk. Full article

Background/Objectives: Triamcinolone acetonide (TA), a poorly water-soluble corticosteroid, presents formulation challenges due to limited membrane permeability. This study aimed to identify suitable drug–polymer–plasticizer systems for TA using combined theoretical and experimental methods. Methods: Using Hansen solubility parameters, seven hot-melt extrusion (HME)-grade polymers and four plasticizers were initially screened for miscibility with TA. Based on Δδt values, four polymers—Eudragit^® L100 (EUD), Parteck^® MXP (PVA), Plasdone^® S-630 (PVPVA), and Aquasolve™ AS-MG (HPMCAS)—along with triethyl citrate (TEC), were selected for experimental evaluation. Differential scanning calorimetry, thermogravimetric analysis, and Fourier transform infrared spectroscopy assessed thermal behavior, miscibility, and chemical compatibility. Results: Amorphous TA content was highest with EUD (81.1%), followed by PVA (67.5%), PVPVA (45.6%), and HPMCAS (8.5%). Thermal incompatibility and TEC evaporation were observed in PVA, PVPVA, and HPMCAS systems. FTIR suggested TEC should be avoided in melt-based formulations with PVA and PVPVA due to PVA degradation and partial TA oxidation. No significant interactions were detected in HPMCAS samples heated to 220 °C, aligning with theoretical predictions. In contrast, the EUD–TEC system showed limited chemical reactivity and maintained TA’s structural integrity. Infrared bands at 1758 and 1802 cm⁻¹ indicated minor anhydride formation above 160 °C with partial TEC evaporation. Conclusions: EUD/TEC were identified as a promising combination for the HME processing of TA. This work supports the rational formulation of stable amorphous systems for thermolabile drugs with poor solubility. Full article

Pretreatment of lignocellulosic biomass remains the primary obstacle to the profitable use of this type of biomass in biorefineries. The challenge lies in the recalcitrance of the lignin-carbohydrate complex to pretreatment, especially the difficulty in removing the lignin to access the carbohydrates (cellulose and hemicellulose). This study had two objectives: (i) to investigate the effect of reactive extrusion on lignocellulosic biomass in terms of delignification percentage and the structural characteristics of the resulting extrudates, and (ii) to propose a novel pretreatment approach involving extrusion technology based on the results of the first objective. Two types of biomasses were used: agricultural residue (corn stover) and forest residue (black spruce chips). By optimizing the extrusion conditions via response surface analysis (RSA), the delignification percentages were significantly improved. For corn stover, the delignification yield increased from 2.3% to 27.4%, while increasing from 1% to 25.3% for black spruce chips. The highest percentages were achieved without the use of sodium hydroxide and for temperatures below 65 °C. Furthermore, the optimized extrudates exhibited important structural changes without any formation of p-cresol, furfural, and 5-hydroxymethylfurfural (HMF) (enzymes and microbial growth-inhibiting compounds). Acetic acid however was detected in corn stover extrudate. The structural changes included the disorganization of the most recalcitrant functional groups, reduction of particle sizes, increase of specific surface areas, and the appearance of microscopic roughness on the particles. Analyzing all the data led to propose a new promising approach to the pretreatment of lignocellulosic biomasses. This approach involves combining extrusion and biodelignification with white rot fungi to improve the enzymatic hydrolysis of carbohydrates. Full article

The increasing global demand for metals, driven by technological progress and the energy transition, has led to an acceleration in the expansion of the mining and metallurgical industry, resulting in an increase in the generation of mine tailings. This waste, which is of heterogeneous composition and has high contaminant potential, represents significant environmental and social challenges, affecting soils, water, and the geotechnical stability of tailings. The accumulation of these mine tailings poses a problem not only in terms of quantity, but also in terms of physicochemical composition, which exacerbates their environmental impact due to the release of heavy metals, affecting ecosystems and nearby communities. This article reviews the potential of geopolymerization and 3D printing as a technological solution for the management of tailings, offering an effective alternative for their reuse as sustainable building materials. Alkaline activation of aluminosilicates facilitates the formation of N–A–S–H and C–A–S–H cementitious structures, thereby providing enhanced mechanical strength and chemical stability. Conversely, 3D printing optimizes structural design and minimizes material consumption, thereby aligning with the principles of a circular eco-economy and facilitating carbon footprint mitigation. The present study sets out to compare different types of tailings and their influence on geopolymer reactivity, workability, and mechanical performance. In order to achieve this, the study analyses factors such as the Si/Al ratio, rheology, and setting. In addition, the impact of alkaline activators, additives, and nanoparticles on the extrusion and interlaminar cohesion of 3D printed geopolymers is evaluated. These are key aspects of their industrial application. A bibliometric analysis was conducted, which revealed the growth of research in this field, highlighting advances in optimized formulations, encapsulation of hazardous waste, CO₂ capture, and self-healing geopolymers. The analysis also identified technical and regulatory challenges to scalability, emphasizing the necessity to standardize methodologies and assess the life cycle of materials. The findings indicated that 3D printing with tailings-derived geopolymers is a viable alternative for sustainable construction, with applications in pavements, prefabricated elements, and materials resistant to extreme environments. This technology not only reduces mining waste but also promotes the circular economy and decarbonization in the construction industry. Full article

The significant waste generated by the fashion industry necessitates sustainable textile recycling strategies. Polyester, made from poly(ethylene terephthalate) (PET), is abundant in post-consumer textiles. Technologies have been developed to convert low-density garment waste into flakes, but the role of color sorting in achieving uniform aesthetics in injection-moldable plastics remains underexplored. This study compares materials extruded from dark color-sorted polyester garment flakes with those from light-color flakes in terms of processability in extrusion and injection molding. The properties examined include melt fluidity, injection molding shrinkage, and mechanical and thermal properties. Commercial chain extenders with anhydride, oxazoline, or epoxide reactive groups were added during extrusion. Interestingly, only dark-colored extruded pellets showed significant degradation, but all the chain extenders allowed melt fluidity to be controlled during reprocessing. The bisoxazoline-based additive was the most promising, due to the highly improved ductility of the samples, regardless of whether they were dark-colored or light-colored. The results indicate significant potential for the industrial recycling of post-consumer textiles and highlight the industrial feasibility of repurposing post-consumer polyester garments. This approach not only supports initiatives of circular economy but also offers a viable solution for managing textile waste, particularly in the fashion industry. Additionally, the suggested recycling route combats the production of microplastics. Full article

Mafic and ultramafic rocks have become a promising approach for atmospheric carbon dioxide (CO₂) reduction, as they are major sources of CO₂-reactive minerals, i.e., olivine, pyroxene, plagioclase, and serpentine. The minerals potentially sequester CO₂ by turning it into a stable solid phase through carbon mineralization in the rock weathering process. However, detailed descriptions and evaluations of the target formations are lacking. This study investigates the mineralogical composition and microtextural characteristics of representative mafic and ultramafic rocks observed in northern Thailand, using a petrographic analysis. The results show that variations in CO₂-reactive mineral assemblages of rocks certainly affect their theoretical CO₂ uptake potential. Ultramafic rocks tend to sequester larger amounts of CO₂ than mafic rocks. The microtextural observation reveals the mineral size ranges of 0.05–5 mm for ultramafic and mafic intrusive rocks and 0.01–2 mm for mafic extrusive and metamorphosed rocks. Reducing the rock size to be equal to the average size of the reactive minerals could be considered one of the practical designs in enhanced rock weathering activities. Understanding the mineralogical and textural characteristics of target rocks thus plays a crucial role in further georesource exploration and engineering designs, supporting climate action strategies on various scales. Full article

The chemical industry faces major challenges despite recent progress in the transition to more environmentally friendly processes. Sustainable industrial chemistry relies on the optimization of protocols and downstream processes such as extraction, purification, and drying. Process intensification, which includes non-conventional techniques and continuous manufacturing, has emerged as a key strategy to improve efficiency and environmental impact. Technologies such as ultrasound, microwaves, mechanochemistry, and reactive extrusion offer improved performance but face scalability and proprietary barriers. Flow chemistry offers additional benefits, including smaller reactors, lower energy consumption (from 40 to 90%), and increased safety through continuous, automated reactions. However, implementing these methods requires overcoming engineering, economic, and regulatory hurdles. Biphasic catalysis and sonochemical activation in liquid–liquid systems are promising approaches for scalable reactions under mild conditions. The pharmaceutical industry, a major source of waste, has shown resistance due to high validation costs and complex regulations. Fortunately, international regulatory institutions have introduced programs to facilitate the introduction of advanced technologies. Future perspectives emphasize the integration of modular, intensified processes with digitalization and smart manufacturing. Collaborative, transdisciplinary research will be crucial for accelerating commercialization and addressing sustainability challenges in chemical production. Full article

Reactive extrusion is a scalable technology for active packaging that promotes food quality and safety. This study investigated the grafting of a methacrylate pyrogallol (PGMC) active agent onto low-density polyethylene (LDPE) through an in situ reactive extrusion process with varying concentrations of PGMC (1, 3, and 5 wt.%). The addition of 5% PGMC increased the tensile strength of pure LDPE from 17.94 MPa to 22.04 MPa. The thermal stability of the samples remained unaffected after PGMC addition, and the grafting process did not interfere with the barrier properties of the LDPE films. Furthermore, 5% PGMC exhibited significant antimicrobial properties, showing 100% and 99.11% reductions in the microbial activity of Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive), respectively. Moreover, the LDPE film with 5% PGMC demonstrated the highest DPPH scavenging effect, reaching up to 85.71%. Therefore, LDPE-g-PGMC films (5%), with antimicrobial and antioxidant properties, have potential applications in non-migratory active packaging. Full article

This study investigated the valorization of industrial lignin for producing biodegradable polybutylene succinate (PBS)–lignin copolymers. PBS was blended with varying lignin contents (0–45 wt. %) and crosslinked/grafted using dicumyl peroxide (DCP). The preparation of the copolymers by reactive extrusion was successful, with mechanical, thermal, and morphological properties comprehensively analyzed. Lignin addition decreased tensile strength but improved stiffness (modulus) and thermal stability. Crosslinking with DCP improved the interfacial adhesion between PBS and lignin, resulting in better flexural performance at moderate lignin levels. Differential scanning calorimetry showed that lignin initially improved the crystallization temperature, but hindered it at higher concentrations due to its rigid, aromatic structure. Scanning electron microscopy analysis showed poor interfacial adhesion in PBS–lignin blends, but the surface morphology improved in crosslinked PBS–lignin copolymers, with less phase separation observed. An optimal lignin concentration appeared to depend on the property of interest. While 30% lignin provided the best improvement in flexural strength, 20% lignin offered a more balanced enhancement for most properties without the severe reduction in tensile strength observed at higher lignin contents. Full article

This work presents a comprehensive review of the evolution in modeling reactive extrusion (REx), tracing developments from early analytical models to advanced computational fluid dynamics (CFD) simulations. Additionally, it highlights the key challenges and future directions in this field. Analytical models to describe the velocity profiles were proposed in the 1950s, involving certain geometrical simplifications. However, numerical models of melt polymeric flow in extruders have proven to be crucial for optimizing screw design and predicting process characteristics. The state-of-the-art CFD models for single and twin-screw extruders design address the impact of geometry (type of mixing elements and geometrical simplifications of CFD geometries), pressure and temperature gradients, and quantification of mixing. Despite the extensive work conducted, modeling reactive extrusion using CFD remains challenging due to the intricate interplay of mixing, heat transfer, chemical reactions, and non-Newtonian fluid behavior under high shear and temperature gradients. These challenges are further intensified by the presence of multiphase flows and the complexity of extruder geometries. Future advancements should enhance simulation accuracy, incorporate multiphase flow models, and utilize real-time sensor data for adaptive modeling approaches. Full article

The present study investigates the entropy generation of chemically reactive micropolar hybrid nanoparticle motion with mass transfer. Magnetic oxide (Fe₃O₄) and copper oxide (CuO) nanoparticles were mixed in water to form a hybrid nanofluid. The governing equations for velocity, concentration, and temperature are transformed into ordinary differential equations along with the boundary conditions. In the fluid region, the heat balance is kept conservative with a source/sink that relies on the temperature. In the case of radiation, there is a differential equation along with several characteristic coefficients that transform hypergeometric and Kummer’s differential equations by a new variable. Furthermore, the results of the current problem can be discussed by implementing a graphical representation with different factors, namely the Brinkman number, porosity parameter, magnetic field, micropolar parameter, thermal radiation, Schmidt number, heat source/sink parameter, and mass transpiration. The results of this study are presented through graphical representations that depict various factors influencing the flow profiles and physical characteristics. The results reveal that an increase in the magnetic field leads to a reduction in velocity and entropy production. Furthermore, temperature and entropy generation rise with a stronger radiation parameter, whereas the Nusselt number experiences a decline. This study has several industrial applications in technology and manufacturing processes, including paper production, polymer extrusion, and the development of specialized materials. Full article

Parabens are widely used in various industries, which are including chemical, pharmaceutical, food, cosmetic, and plastic processing industries. Among these, methyl paraben (MP) serves as an antimicrobial preservative in processed foods, pharmaceuticals, and cosmetics, and it is particularly detected in baby care products. Studies indicate that MP functions as an endocrine-disrupting compound with estrogenic properties, negatively affecting mitochondrial bioenergetics and antioxidant activity in testicular germ cells. However, limited information exists regarding studies on the effects of MP in oocytes. The aim of this study was to investigate the specific mechanism and the toxic effects of MP during oocyte maturation cultured in vitro using a porcine oocyte model. The results indicated that MP (50 μM) inhibited oocyte expansion, significantly reducing the expression of expansion-related genes MAPK1 and ERK1, and decreased the first polar body extrusion significantly as well. ATP levels decreased, reactive oxygen species (ROS) levels remained unchanged, and glutathione (GSH) levels decreased significantly, resulting in an elevated ROS/GSH ratio. The expression of antioxidant genes SOD1 and GPX was significantly decreased. Additionally, a significant decrease in levels of mitochondrial production and biosynthesis protein PGC1α+β, whereas levels of antioxidant-related protein Nrf2 and related gene expression were significantly increased. Autophagy protein LC3B and gene expression significantly decreased, and apoptosis assay indicated a significant increase in levels of caspase3 protein and apoptosis-related genes. These results demonstrated the negative effect of MP on oocyte maturation. In conclusion, our findings indicate that MP disrupts redox balance and induces mitochondrial dysfunction during meiosis in porcine oocytes, resulting in the inhibition of meiotic progression. The present study reveals the mechanism underlying the effects of methyl para-hydroxybenzoate on oocyte maturation. Full article