Search Results (12)

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

This study investigates the effectiveness of citric acid as a salt crystallization inhibitor aimed at improving the durability and mechanical performance of concrete exposed to marine environments. The goal is to evaluate whether the addition of citric acid can mitigate the deterioration of concrete caused by salt crystallization during wet–dry cycles and simulated wave impacts. The novelty of this work lies in the experimental demonstration that a simple and environmentally friendly organic compound can effectively reduce salt-induced damage in marine-exposed concrete. Concrete samples were subjected to repeated wet–dry cycles and simulated marine wave impacts to assess changes in their physical and elastic properties. Variations in P-wave and S-wave velocities, Young’s modulus, and the effects of salt crystallization within the concrete matrix were evaluated through acoustic measurements. Results show that citric acid significantly reduces internal cracking, stiffness loss, and salt accumulation, leading to enhanced structural integrity and greater resistance to environmental stressors. These findings highlight the potential of citric acid as a sustainable additive for improving the long-term durability and mechanical stability of concrete structures in marine environments. Full article

Using common corn stalks as raw materials, a functional dense-structured carbon microsphere with good elastic deformation and certain rigid support was modified from biomass through a step-by-step hydrothermal method. The composition, thermal stability, fluid-loss reduction performance, and reservoir protection performance of the modified carbon microspheres were studied. Research indicates that after hydrothermal treatment, under the multi-level structural action of a small amount of proteins in corn stalks, the naturally occurring cellulose, polysaccharide organic compounds, and part of the ash in the stalks are adsorbed and encapsulated within the long-chain network structure formed by proteins and cellulose. By attaching silicate nanoparticles with certain rigidity from the ash to the relatively stable chair-type structure in cellulose, functional dense-structured carbon microspheres were ultimately prepared. These carbon microspheres could still effectively reduce fluid loss at 200 °C. The permeability recovery value of the cores treated with modified biomass carbon microspheres during flowback reached as high as 88%, which was much higher than that of the biomass itself. With the dense network-like chain structure supplemented by small-molecule aldehydes and silicate ash, the subsequent invasion of drilling fluid was successfully prevented, and a good sealing effect was maintained even under high-temperature and high-pressure conditions. Moreover, since this functional dense-structured carbon microsphere achieved sealing through a physical mechanism, it did not cause damage to the formation, showing a promising application prospect. Full article

Betulinic acid (BA) is a natural pentacyclic triterpene with diverse biological activities. However, its low water solubility limits its pharmaceutical application. The conversion of pharmaceutically active molecules into ionic liquids (ILs) is a promising strategy to improve their physicochemical properties, stability, and/or potency. Here, we report the synthesis and characterization of 15 novel ILs containing a cation ethyl ester of a polar, non-polar, or charged amino acid [AAOEt] and an anion BA. Except for [ValOEt][BA], we observed preserved or up to 2-fold enhanced cytotoxicity toward hormone-dependent breast cancer cells MCF-7. The estimated IC50 (72 h) values within the series varied between 4.8 and 25.7 µM. We found that the most cytotoxic IL, [LysOEt][BA]₂, reduced clonogenic efficiency to 20% compared to that of BA. In addition, we evaluated the effect of a 72 h treatment with BA or [LysOEt][BA]₂, the most cytotoxic compound, on the thermodynamic behavior of MCF-7 cells. Based on our data, we suggest that the charged amino acid lysine included in the novel ILs provokes cytotoxicity by a mechanism involving alteration in membrane lipid organization, which could be accompanied by modulation of the visco–elastic properties of the cytoplasm. Full article

One of the key characteristics of pharmaceutical substances is their solubility in pharmaceutically relevant media. This characteristic reflects the quality of the drug and the rate at which the pharmaceutical substance is released from its dosage form. Reduced efficacy and difficulties in the medical use of pharmaceutical substances are often associated with their low solubility in aqueous solutions. It is worth noting that about 40% of pharmaceuticals are practically insoluble, given that 85% are intended for oral administration, which is the simplest and most convenient form. The encapsulation of drug substances can solve this problem. The modern pharmaceutical industry uses molecular containers such as cyclodextrins for this purpose. The incorporation of the target component occurs on a host–guest basis and is driven by weak intermolecular interactions, the nature of which is not yet fully understood. Encapsulation has been shown to promote stability during storage, improve palatability, enhance pharmacological activity and bioavailability, reduce side effects, and, most importantly, increase the solubility of these substances. Our study presents the synthesis of the nimesulide inclusion complex in β-, γ-cyclodextrin cavity. The experimental results were confirmed using TLC, HPLC, UV- and IR spectroscopy, and X-ray diffraction analysis. The theoretical justification of the stability of the β-cyclodextrin/nimesulide complex was performed via one of the most innovative methods, the molecular dynamics method, using NAMD V2.14 and Gaussian 09W software with a simulation step of 2 femtoseconds and a duration of 5 nanoseconds. A modified CHARMM36 force field was used as the MD force field. The ability to enhance drug solubility and maintain drug stability is a promising area in the field of pharmaceutical chemistry. Full article

The food and beverage industry is constantly evolving, and consumers are increasingly searching for premium products that not only offer health benefits but a pleasant taste. A viable strategy to accomplish this is through the altering of sensory profiles through encapsulation of compounds with unique flavors. We used this approach here to examine how brewing in the presence of yeast cells encapsulated in alginate affected the sensory profile of beer wort. Initial tests were conducted for various combinations of sodium alginate and calcium chloride concentrations. Mechanical properties (i.e., breaking force and elasticity) and stability of the encapsulates were then considered to select the most reliable encapsulating formulation to conduct the corresponding alcoholic fermentations. Yeast cells were then encapsulated using 3% (w/v) alginate and 0.1 M calcium chloride as a reticulating agent. Fourteen-day fermentations with this encapsulating formulation involved a Pilsen malt-based wort and four S. cerevisiae strains, three commercially available and one locally isolated. The obtained beer was aged in an amber glass container for two weeks at 4 °C. The color, turbidity, taste, and flavor profile were measured and compared to similar commercially available products. Cell growth was monitored concurrently with fermentation, and the concentrations of ethanol, sugars, and organic acids in the samples were determined via high-performance liquid chromatography (HPLC). It was observed that encapsulation caused significant differences in the sensory profile between strains, as evidenced by marked changes in the astringency, geraniol, and capric acid aroma production. Three repeated batch experiments under the same conditions revealed that cell viability and mechanical properties decreased substantially, which might limit the reusability of encapsulates. In terms of ethanol production and substrate consumption, it was also observed that encapsulation improved the performance of the locally isolated strain. Full article

To avoid fungal spreading in the bloodstream and internal organs, many research efforts concentrate on finding appropriate candidiasis treatment from the initial stage. This paper proposes chitosan-based physically or chemically cross-linked hydrogels aimed to provide sustained release of micronized nystatin (NYSm) antifungal drug, known for its large activity spectrum. Nystatin was demonstrated itself to provide hydrodynamic/mechanic stability to the chitosan hydrogel through hydrophobic interactions and H-bonds. For chemical cross-linking of the succinylated chitosan, a non-toxic diepoxy-functionalized siloxane compound was used. The chemical structure and composition of the hydrogels, also their morphology, were evidenced by infrared spectroscopy (FTIR), by energy dispersive X-ray (EDX) analysis and by scanning electron microscopy (SEM), respectively. The hydrogels presented mechanical properties which mimic those of the soft tissues (elastic moduli < 1 MPa), necessary to ensure matrix accommodation and bioadhesion. Maximum swelling capacities were reached by the hydrogels with higher succinic anhydride content at both pH 7.4 (429%) and pH 4.2 (471%), while higher amounts of nystatin released in the simulative immersion media (57% in acidic pH and 51% in pH 7.4) occurred from the physical cross-linked hydrogel. The release mechanism by non-swellable matrix diffusion and the susceptibility of three Candida strains make all the hydrogel formulations effective for NYSm local delivery and for combating fungal infections. Full article

In order to improve the performance of soft plantation wood, an environmentally friendly wood modifier was developed. First, using urea and melamine as crosslinking agents, the glucose-urea-melamine resin (MUG) was prepared with glucose under the catalysis of inorganic acid and metal ions. Then MUG, sodium silicate, and distilled water were mixed and stirred at 40 °C to prepare MUG resin/sodium silicate compound modifier (G₂₀S₁₀, G₁₀S₂₀, the subscript number represents the mass percentage of the component in the solution.). Then plantation poplar wood (Populus tomentosa) was impregnated and modified with them. Their physical and mechanical properties were tested and compared with those of the wood treated with sodium silicate of 20% mass fraction (S₂₀). Infrared analysis showed that the amino resin characteristic structure (CO-NH-) existed in MUG, and the absorption peak of the furan ring (C=C) appeared. Compared with S₂₀ modified wood, the shrinkage degree of G₁₀S₂₀ or G₂₀S₁₀ modified wood is reduced, their moisture absorption is decreased, and their dimensional stability is improved. MUG resin/sodium silicate compound modifier can effectively enhance the wood’s density, modulus of elasticity, modulus of rupture, and compression strength. SEM analysis showed that there were columnar and granular solid substances attached to the cell wall, cell lumen, intercellular space, and vessel of G₂₀S₁₀ modified wood. EDX showed that the number of Si elements on the cell wall was significantly increased compared with the control, indicating that the modifier effectively entered the wood cell wall. The G₂₀S₁₀ can greatly improve the wood’s physical and mechanical properties through an organic–inorganic compound synergistic effect. It is a green, non-formaldehyde, low cost wood modifier with broad application prospects. Full article

Functionalization of protein-based materials by incorporation of organic and inorganic compounds has emerged as an active research area due to their improved properties and diversified applications. The present review provides an overview of the functionalization of protein-based materials by incorporating TiO₂ nanoparticles. Their effects on technological (mechanical, thermal, adsorptive, gas-barrier, and water-related) and functional (antimicrobial, photodegradation, ultraviolet (UV)-protective, wound-healing, and biocompatibility) properties are also discussed. In general, protein–TiO₂ hybrid materials are biodegradable and exhibit improved tensile strength, elasticity, thermal stability, oxygen and water resistance in a TiO₂ concentration-dependent response. Nonetheless, they showed enhanced antimicrobial and UV-protective effects with good biocompatibility on different cell lines. The main applications of protein–TiO₂ are focused on the development of eco-friendly and active packaging materials, biomedical (tissue engineering, bone regeneration, biosensors, implantable human motion devices, and wound-healing membranes), food preservation (meat, fruits, and fish oil), pharmaceutical (empty capsule shell), environmental remediation (removal and degradation of diverse water pollutants), anti-corrosion, and textiles. According to the evidence, protein–TiO₂ hybrid composites exhibited potential applications; however, standardized protocols for their preparation are needed for industrial-scale implementation. Full article

The aim of this study was to develop new sulfur-copolymer concrete composites using waste compounds that have good mechanical characteristics and show a resistance to biocorrosion. The comonomers used to synthesize the sulfur–organic copolymers were—90 wt. % sulfur; 5 wt. % dicyclopentadiene (DCPD); 5 wt. % organic monomers, styrene (SDS), 1-decene (SDD), turpentine (SDT), and furfural (SDF). The concrete composites based on sulfur–organic copolymers were filled with aggregates, sand, gravel, as well as additives and industrial waste such as fly ash or phosphogypsum. The sulfur–organic copolymers were found to be chemically stable (softening temperature, thermal stability, melting temperature, amount of recrystallized sulfur, and shore D hardness). Partial replacement of DCPD with other organic comonomers did not change the thermal stability markedly but did make the copolymers more elastic. However, the materials became significantly stiffer after repeated melting. All the tested copolymers were found to be resistant to microbial corrosion. The highest resistance was exhibited by the SDS-containing polymer, while the SDF polymer exhibited the greatest change due to the activity of the microorganisms (FTIR analysis and sulfur crystallization). The concrete composites with sulfur–organic copolymers containing DCPD, SDS, SDF, fly ash, and phosphogypsum were mechanically resistant to compression and stretching, had low water absorbance, and were resistant to factors, such as temperature and salt. Resistance to freezing and thawing (150 cycles) was not confirmed. The concrete composites with sulfur–organic copolymers showed resistance to bacterial growth and acid activity during 8 weeks of incubation with microorganisms. No significant structural changes were observed in the SDS composites after incubation with bacteria, whereas composites containing SDF showed slight changes (FTIR and microscopic analysis). The concrete composite containing sulfur, DCPD, SDS, sand, gravel, and fly ash was the most resistant to microbiological corrosion, based on the metabolic activity of the bacteria and the production of ergosterol by the molds after eight weeks of incubation. It was found that Thiobacillus thioparus was the first of the acidifying bacteria to colonize the sulfur concrete, decreasing the pH of the environment. The molds Penicillium chrysogenum, Aspergillus versicolor and Cladosporium herbarum were able to grow on the surface of the tested composites only in the presence of an organic carbon source (glucose). During incubation, they produced organic acids and acidified the environment. However, no morphological changes in the concretes were observed suggesting that sulfur–organic copolymers containing styrene could be used as engineering materials or be applied as binders in sulfur-concretes. Full article

Natural rubber/butadiene rubber (NR/BR) blends are widely used in industrial areas for absorbing vibrations and shocks because of their excellent elastic stability. However, when an industrial-equipment surface is exposed to sunlight and oxygen over a long period of time, the rubber hardens. As a result, the tensile properties of the rubber material and the behavior of the strain-energy density function are changed, greatly reducing the performance of the rubber product. However, only a few experimental studies on the aging characteristics of NR/BR blends are available, and it is difficult to find a study that analyzes the organic relationship of the changes in the mechanical (stress–strain curves, strain-energy density, etc.) and chemical (cross-linked structure, crosslink density, etc.) properties. In this study, a swelling test was performed on an aged rubber compound, and the result was substituted into the Flory–Rehner equation to obtain the quantitative crosslink density. The results revealed a linear relationship between the strain-energy density (SED) and the crosslink density (CLD) when the cross-linked structure increase was represented by a parallel spring model. Finally, the relationship between the strain-energy density and the crosslink density was summarized as a formula, and a method for predicting the aging behavior of NR/BR blends using the crosslink density was proposed. Full article

A polyethylene/wood-fiber composite loaded with nano-ZnO was prepared by a facile hot-press method and was used for the photocatalytic degradation of organic compounds as well as for microwave absorption. ZnO nanoparticles with an average size of 29 nm and polyethylene (PE) powders were dispersed on the wood fibers’ surface through a viscous cationic polyacrylamide (CPAM) solution. The reflection loss (RL) value of the resulting composite was −21 dB, with a thickness of 3.5 mm in the frequency of 17.17 GHz. The PE/ZnO/wood-fiber (PZW) composite exhibited superior photocatalytic activity (84% methyl orange degradation within 300 min) under UV light irradiation. ZnO nanoparticels (NPs) increased the storage modulus of the PZW composite, and the damping factor was transferred to the higher temperature region. The PZW composite exhibited the maximum flexural strength of 58 MPa and a modulus of elasticity (MOE) of 9625 MPa. Meanwhile, it also displayed dimensional stability (thickness swelling value of 9%). Full article