Search Results (574)

Silicone food contact materials (FCMs) pose potential health risks due to the migration of siloxanes. This study presents a comprehensive migration profiling of 35 siloxanes (cyclic D3–D22 and linear L2–L14) from 30 silicone FCMs, with migration tests rigorously conducted under worst-case intended-use scenarios to ensure conservative and reliable exposure estimates. Methodological innovations include an expanded analytical scope, age-stratified exposure assessment across seven age groups, and a multi-tiered risk evaluation framework. The results reveal that migration behaviors were affected by simulant polarity, siloxane solubility, and silicone thermal stability. The risk evaluation framework integrates aggregate migration limits for total cyclic (D3–D13) and total cyclic plus linear siloxanes (D3–D13, L3–L13), complemented by individual siloxane assessment via Risk Quotient (RQ) and Threshold of Toxicological Concern (TTC) approaches. While the total migration of cyclic siloxanes exceeded the proposed action limit of 12 mg/kg for adults in several samples and 2 mg/kg for children in most samples, granular assessment revealed divergent risks: Cyclic D4 and D5 showed negligible risk (RQ < 5). In contrast, D3 migration posed a potential concern (RQ > 5), especially for individuals aged >13 years. Notably, the estimated exposures to 14 siloxanes with low molecular weight (<1000 Da), including highly prevalent D6 and L12 with detection frequency >90%, exceeded the TTC threshold across all age groups, highlighting unaddressed risks that are not captured by aggregate action limits. This work underscores the need for substance-specific, age-specific risk evaluations and regulatory updates for silicone FCMs. Full article

In this study, polysiloxane-containing polyimide (si-PI) composite coatings containing hexagonal boron nitride (hBN) particles of four different sizes and at different contents were prepared, and their mechanical and tribological properties were investigated. The coatings were deposited on steel substrates via dip coating and cured at 160 °C. Their tribological properties were measured using reciprocating sliding tests under unlubricated conditions against a steel ball. The composite coatings containing nano-hBN with the smallest mean primary particle size of 0.05 μm exhibited the lowest wear. Subsequently, coatings containing 1–15 wt% nano-hBN were prepared to examine the effect of filler content. The results showed that the coatings with low nano-hBN contents (1–2 wt%) had relatively high friction coefficients and significantly reduced wear on both the coating and the counterpart. Cross-sectional scanning electron microscopy (SEM) observations revealed that dispersed small hBN aggregates suppress crack propagation through dispersion strengthening. Coatings with low nano-hBN contents (1–2 wt%) also exhibited sufficient electrical insulation. However, as the hBN content increased further, hBN agglomeration was promoted, weakening the crack-propagation suppression effect and increasing wear. These findings indicate that low-content nano-hBN/si-PI composite coatings are promising electrical erosion-resistant coatings for the outer rings of the bearings used in electric vehicle motors. Full article

Selenium nanoparticles (SeNPs) represent promising bioactive agents due to their reduced toxicity and multifunctional biological properties. In this study, SeNPs were synthesized via an eco-friendly phytosynthesis approach using Curcuma longa extract, yielding curcumin-functionalized selenium nanoparticles (cur–SeNPs). The composites (cur–SeNPs), either in native extract form or isolated, were incorporated into siloxane hybrid matrices prepared by the sol–gel method from tetraethyl orthosilicate: dimethyldimethoxysilane precursors, with polyvinylpyrrolidone (PVP) as a structural modifier. The host matrices were differentiated by the ratios between the precursors of the siloxane network, 3:1 for CS0–CS4, respectively, 1:1 for CS5, modified with PVP in the case of CS2 and CS3. These were loaded with cur–SeNPs–T in the cases of CS1, CS2, CS5 or with cur–SeNPs for CS3 and CS4. FTIR, XRD, SEM, and EDX analyses confirmed the formation of amorphous siloxane networks with well-dispersed SeNPs (up to ~12 wt%). PVP incorporation generated ordered mesoporous structures, increasing total pore volume sixfold and enlarging the average pore diameter to 9.26 nm. Studies about selenium ion release demonstrate that mesoporosity significantly enhances diffusion-controlled release. Antimicrobial assays against Staphylococcus aureus, Escherichia coli, and Candida albicans reveal a synergistic effect between curcuminoids and SeNPs, particularly in matrices with higher nanoparticle loading. The sol–gel technique for obtaining hybrid materials is very versatile regarding the supports on which the resulting materials or the compounds hosted in these host networks can be deposited. The dynamics of the development of hybrid materials is also reflected in the multitude of applications in various fields such as bio-medical, electronics, agriculture or food. Results obtained in this work highlight the potential of the developed systems for antimicrobial coatings on glass substrates and targeted delivery applications. Full article

Developing environmentally friendly, multifunctional waterproof and breathable membranes (WBMs) has attracted extensive attention and is of great significance but remains challenging. Herein, an environmentally friendly and multifunctional waterborne polyurethane WBM with self-healing and self-cleaning properties is developed in two steps. Firstly, by using polydimethylsiloxane (PDMS) as a hydrophobicity giver and tannic acid (TA) as a crosslinker, a dual-modified waterborne polyurethane (PTWPU) is prepared, which has high surface hydrophobicity due to the surface enrichment of siloxane segments and self-healing performance from the formation of a dynamic phenolic carbamate network. Secondly, by incorporating titanium dioxide (TiO₂) photocatalyst nanoparticles to increase internal porosity and establish hydrophilic pathways, a multifunctional waterborne polyurethane WBM (TPTWPU) is developed. This membrane features further enhanced surface hydrophobicity from generated micro-roughness and effective self-cleaning performance, because TA acts as an electron trap to promote the photocatalytic activity of TiO₂. The TPTWPU membrane shows good hydrophobicity (water contact angle of 115.3°) and satisfactory moisture permeability of 135.0 g/(m²·24 h), which is 61.2% higher than unmodified membranes. Furthermore, it exhibits efficient self-healing, with a recovery rate exceeding 80% within 2 h. This feasible strategy will provide guidance for materials design in multifunctional coatings for textiles and leather. Full article

The development of high-performance polymers exhibiting both low dielectric constant (D_k) and low dielectric loss (D_f) at high frequencies is highly desirable yet challenging for applications in microelectronics and wireless communication technologies. In this work, a series of siloxane-containing poly(ester imide)s (SiPEIs) are designed and synthesized via a two-step polymerization route, using 1,4-phenylene bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate) (TAHQ) as the dianhydride monomer, and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (DMS) together with 4,4′-diaminodiphenyl ether (ODA) as the diamine comonomers. Although the introduction of short siloxane segments lowers the glass transition temperature (T_g) and the tensile strength of the resulting PEIs, they still remain at a relatively high level. Liquid crystalline phase behavior is observed at lower temperature for the siloxane-containing PEIs. Meanwhile, the hydrophobicity and the high-frequency dielectric performance is effectively improved with increasing siloxane content. Notably, SiPEI-20, prepared with 20 mol% DMS, displays an outstanding integrated performance. It exhibits a T_g of 200 °C, a D_k of 2.87 and a D_f of 0.00155 at 10 GHz, as well as an adhesive strength of 0.85 N·mm⁻¹ on copper foil. Overall, this work provides a feasible strategy by incorporating siloxane into the PEI backbone, enabling the synergistic enhancement of high-frequency dielectric properties (simultaneous reduction in D_k and D_f) and adhesion to copper foil. Full article

In this article operational problems associated with the use of landfill biogas as an alternative fuel in cogeneration systems, with particular emphasis on micro-installations based on the Perkins 4008-30 TRS2 combustion engine are presented. Such installations are commonly used in cogeneration systems, whose importance in obtaining stable electric and thermal energy is growing, especially when taking into account the additional reduction in environmental impact through biogas combustion. Reducing emissions of biogas, which consists of approximately 60% methane and approximately 35% carbon dioxide, directly reduces emissions of a greenhouse gas (GHG) with a high global warming potential (GWP). In this study the characteristics of the landfill, the biogas purification system, the measurement system and the energy balance of the entire process, biogas production → electric energy → thermal energy, are presented and the importance of this type of installation in the context of a low-carbon economy is discussed. Attention is also drawn to the operational problems of the cogeneration system, which led to its failure, requiring comprehensive repairs of the internal combustion engine. Full article

Natural laccases are a widely reported option for pollutant degradation; however, their widespread application is severely restricted by high production costs, limited storage stability, and rapid inactivation at the neutral pH typical of wastewater treatment plants. To overcome these limitations, we rationally designed manganese-based nanozymes (Mn-APTES/1MeIm) that mimic natural metal–histidine coordination within a protective siloxane network. Optimization via Response Surface Methodology produced two variants, Mn-APTES/1MeIm-6 and Mn-APTES/1MeIm-7, revealing distinct synthesis mechanisms: catalytic activity at pH 6 is driven by synthesis temperature, whereas activity at pH 7 is controlled by the APTES:1MeIm molar ratio. TEM and XRD analysis confirmed a delaminated aminoclay architecture composed of electron-transparent nanosheets, while FTIR verified Mn–N coordination through characteristic blue shifts. The optimized nanozymes retained robust activity, exhibiting maximum reaction velocities of 4.331 µM min⁻¹ (Mn-APTES/1MeIm-6) and 1.71 µM min⁻¹ (Mn-APTES/1MeIm-7), whereas Trametes versicolor laccase was practically inactive. Practically, Mn-APTES/1MeIm-6 achieved 75% degradation of oxytetracycline in 120 min without detectable manganese leaching, significantly outperforming the natural enzyme (<13%). These findings present a robust, pH-stable alternative for sustainable environmental remediation. Full article

Oily substances (oils, greases, lubricants, etc.) are among the most persistent pollutants for water. They mix with water to form emulsions that contaminate large volumes. Therefore, this project evaluated the use of porous systems (polyurethane foam) modified with polydimethylsiloxane-modified silica (SiO₂/DMS) hybrid ceramics as filtration membranes at the laboratory scale for vegetable oil. The polyurethane foam was modified using sol solutions with various SiO₂/PDMS ratios obtained via the sol–gel method. Tetraethyl-orthosilicate (TEOS) was used as the silica precursor. Three different polydimethylsiloxane chains were employed as the organic fragment: polydimethylsiloxane hydroxyl terminated (DMS-CH₃), aminopropyl-terminated polydimethylsiloxane (DMS-N), and copolymer polydiphenylsiloxane-polydimethylsiloxane hydroxyl terminated (PDS). The siloxane chain was added at a concentration of 20–40% w/w. The modification of the porous system was determined using different characterization techniques, including infrared spectroscopy, which was used to observe the main functional groups. Optical microscopy and SEM were used to identify the hybrid ceramic deposited into the pore structure of the polyurethane sponge. Contact angle measurements revealed the hydrophobic character of the modified material. The removal capacity was evaluated by using vegetable oil as a representative oily contaminant, with values ranging from 43.42 to 96.78 g of oil per gram of adsorbent. In the case of gasoline, removal capacities between 27 and 54 g were observed. This study demonstrated the influence of hydrophobicity on vegetable oil removal, confirming that higher hydrophobicity leads to greater adsorption capacity. Nevertheless, the use of a viscous contaminant introduced challenges in the extraction process from the PS/SiO₂-DMS system. Despite this limitation, the material maintained adequate removal performance for up to five reuse cycles. On the other hand, the removal capacity depends on the amount of polysiloxane chain in the ceramic, as well as the functional group, exhibiting the following behavior: DMS-N < DMS-CH₃ < PDS. This study demonstrates that hydrophobicity is a key property for enhancing the removal capacity of oily substances. Moreover, the control of intermolecular interactions further strengthens this effect, as evidenced in the PS/SiO₂–PDS system. Full article

Octa(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane (8F-POSS) was synthesized via a vertex-capping method and incorporated into natural rubber (NR) and deproteinized natural rubber (DPNR) to fabricate inorganic–organic vulcanizates. Curing characteristics, crosslink density, and the filler–rubber interaction parameter (α) were evaluated. We found that 8F-POSS retarded vulcanization kinetics but eventually enhanced network integrity. Two-dimensional infrared (2D-IR) spectroscopy indicated a hydrogen-bond shielding effect between siloxane cages and protein hydroxyl groups in NR. This interaction governed morphology development: proteins in NR acted as compatibilizers to improve initial POSS dispersion, though at high loadings they compromised reinforcement efficiency (α fell from 18.12 to 9.04). In contrast, DPNR vulcanizates showed stronger direct filler–rubber interactions, with higher α values (25.66–35.58) and a more constrained physical network. Despite a denser physical network, the 8F-POSS cages increased fractional free volume and promoted interfacial frictional slippage, leading to a synergistic “reinforcement–dissipation” effect. As a consequence, 8F-POSS/DPNR vulcanizates exhibited an enhanced damping performance (e.g., a loss factor of 1.26) alongside a depressed Tg, reduced equilibrium swelling in oil from 324% to 147%, high hydrophobicity (water contact angle above 120°), and distinctive multi-stage thermal stability. These findings demonstrate a strategy to manipulate the protein network in NR using nanoscale hybrid fillers for the design of high-performance vulcanizates. Full article

In this work, we report the synthesis and evaluation of a bioink based on marine collagen, chitosan, and silica-doped hydroxyapatite (HA–SiO₂) for extrusion-based 3D bioprinting. FTIR spectroscopy confirmed amide (I–III) and phosphate/siloxane signals, TGA showed initial dehydration and degradation stages compatible with the process’s thermal handling, and SEM revealed an interconnected porous microstructure. Rheologically, the ink exhibited elastic dominance (G′ > G″) within the linear range and pseudoplastic, shear-thinning behavior—consistent with pneumatic extrusion. Process evaluation on a BIO X printer (14 G nozzle, low print speeds, moderate pressure, cartridge at 37 °C to 45 °C, and a cooled build platform) enabled deposition of strands with local shape retention. However, filament continuity was limited and line width varied, indicating only preliminary printability and a narrow operating window. Overall, physicochemical, microstructural, and rheological evidence supports the formulation’s viability as a starting point for scaffold fabrication. Full article

This article presents the concept of using a functionalised siloxane compound HOL9 with amphiphilic properties as a coating for cement composites to enhance their antifouling properties against algae. The biological properties of the compound were assessed based on its ability to inhibit chlorophyll fluorescence intensity, which is used as an indicator of photosynthetic activity and biofilm development. The greatest decrease in algal photosynthetic activity was observed for a 10% aqueous solution of HOL9 applied by painting. In these conditions, the maximum ^chlFI value decreased by 97.6%. In addition, the impact of the protective coating containing HOL9 on the fundamental physical and mechanical characteristics of the cement composite, along with its resilience to frost cycling, was thoroughly investigated. The coating applied by immersion demonstrated a 50.7% strength loss after 150 freeze–thaw cycles, while the coating applied by painting exhibited a 43.8% loss. In comparison, the control samples experienced a 42.8% strength reduction. It has been demonstrated that the method of application, the modifier concentration, and the type of solvent can have a substantial impact on the protective properties of concrete. The most marked inhibition of algae photosynthetic activity was observed with a 10% aqueous solution applied by painting. Full article

Background/Objectives: Volatile organic compounds (VOCs) have emerged as promising non-invasive biomarkers for assessing metabolic and reproductive health. In the context of assisted reproductive techniques (ARTs), the volatilomic composition of follicular fluid (FF) may reflect the biochemical environment surrounding the oocyte, influencing fertilization success and embryo development. This study aimed to characterize the volatilomic profile of FF in women undergoing ARTs and to explore associations between specific VOCs and female fertilization-related parameters (FFRPs). Methods: A total of 54 Caucasian women aged 19–39 years, enrolled between October 2015 and July 2019, were recruited at the Assisted Reproduction Laboratory of the Local Health Unit of Cova da Beira, Covilhã. FF samples were analyzed via gas chromatography–mass spectrometry (GC–MS) in scan mode, identifying 136 VOCs, of which 72 were selected based on prevalence. Sixteen FFRPs were evaluated, including age, body mass index (BMI), smoking habits, infertility factor, oocyte yield, embryo quality, β-hCG levels, country of birth, and reproductive history. Associations between VOCs and FFRPs were assessed using the Chi-square (χ²) test. Results: Significant correlations (p ≤ 0.05) were identified between 45 VOCs and 11 FFRPs. The detected compounds comprised alkanes, siloxanes, aromatics, alcohols, ketones, aldehydes, carboxylic acids and esters, fatty acid derivatives, epoxides, acrylates, nitriles, and sterols. Several VOCs were associated with more than one FFRP, indicating overlapping metabolic pathways that may influence reproductive performance. Conclusions: The volatilomic profile of FF demonstrates significant variability linked to individual reproductive and metabolic factors. VOC analysis may provide novel insights into follicular physiology, representing a promising approach for identifying potential biomarkers of infertility and ART outcomes. Full article

MQ copolymers, consisting of monofunctional (M) and tetrafunctional (Q) siloxane units, are versatile materials used as additives, adhesives, and in composite materials. Functional groups, such as vinyl substituents, in M-units allow for the tailoring of properties for specific applications. This study aimed to synthesize vinyl-containing MQ copolymers (M^VinMQ) via a controlled, chlorine-free method to explore the regulation of their composition and properties. The results demonstrated precise control over the copolymer architecture, with hydroxyl content and molecular weight increasing alongside the Q-unit fraction. All obtained copolymers exhibited high thermal stability, with 5% mass loss occurring above 295 °C in air and 365 °C in argon. Fractionation data supported a molecular composite model consisting of an inorganic core and an organic shell. Polycondensation in an active medium is an effective method for the directed synthesis of structurally tunable M^VinMQ copolymers, offering a versatile platform for developing functional hybrid materials, modifiers, and cross-linking agents. Full article

The aim of this work is to develop structurally enhanced and highly hydrophobic polyurethane (PU) foams for the efficient remediation of liquid organic pollutants. For this purpose, PU foams were modified with renewable activated biochar derived from marine algae (AC) and a hydrophobic polydimethylsiloxane (PDMS) coating, producing four systems: pristine PU, PU-AC, PU/PDMS, and the hybrid PU-AC/PDMS composite. The study evaluates how AC incorporation and PDMS surface functionalization influence the microstructure, chemical composition, wettability, thermal stability, and sorption behavior of the foams. SEM images revealed progressive reductions in pore size from 420 ± 80 μm (PU) to 360 ± 85 μm (PU-AC/PDMS), with AC introducing heterogeneity while PDMS preserved open-cell morphology. FTIR confirmed the presence of urethane linkages, carbonaceous structures, and PDMS siloxane groups. Surface hydrophobicity increased markedly from 88.53° (PU) to 148.25° (PU-AC/PDMS). TGA results showed that PDMS improved thermal stability through silica-rich char formation, whereas AC slightly lowered degradation onset. Sorption tests using petroleum-derived oils and hydrophobic organic liquids demonstrated a consistent performance hierarchy (PU < PU/PDMS < PU-AC < PU-AC/PDMS). The ternary composite achieved the highest uptake capacities, reaching 44–56 g/g for oils and up to 35 g/g for hydrophobic solvents, while maintaining reusability. These findings demonstrate that combining activated biochar with PDMS significantly enhances the functional properties of PU foams, offering an efficient and sustainable material for oil–water separation and organic pollutant remediation. Full article

Quercetin’s therapeutic potential is limited by its poor water solubility and rapid degradation. Natural clay minerals such as kaolinite present sustainable platforms for drug delivery, yet the molecular mechanisms of drug encapsulation are not fully understood. Specifically, the role of kaolinite’s structural polarity, its hydrophilic aluminol (001) and hydrophobic siloxane (00-1) basal surfaces, in selective drug adsorption remains unexplored. This study combines Monte Carlo sampling and Density Functional Theory (DFT) to provide the first quantitative, atomistic comparison of quercetin adsorption on both kaolinite surfaces. The results demonstrate a pronounced polarity-driven selectivity. Strong, exothermic adsorption (−206.65 kJ mol⁻¹) occurs on the hydrophilic (001) surface, stabilized by a network of five hydrogen bonds. In contrast, the hydrophobic (00-1) surface exhibits significantly weaker sorption (−147.16 kJ mol⁻¹), dominated by van der Waals interactions. Charge-transfer analysis shows that the hydrophilic (001) surface exhibits a net charge transfer of −0.198 e, approximately 2.4 times greater than that of the hydrophobic (00-1) surface (−0.083 e), consistent with differential electron density maps and partial density of states. By linking hydrogen bonding and charge transfer to adsorption energy, these results elucidate how surface polarity dictates drug encapsulation. This work establishes a predictive framework for designing kaolinite-based nanocarriers with optimized stability, bioavailability, and controlled release, guiding the development of sustainable drug delivery systems. It is noted that this DFT study models adsorption at 0 K using periodic slab models in a vacuum. Full article