Search Results (2,189)

Phosphorus-modified poly(vinyl alcohol) (PVA) has recently gained increasing attention as a functional polymeric matrix suitable for gel-based systems, owing to its biocompatibility, film-forming ability, and capacity to develop semi-interpenetrating networks. In this work, PVA was chemically modified through the nucleophilic substitution of its hydroxyl groups with the chloride groups of phenyl dichlorophosphate, following a literature-reported method carried out in N,N-dimethylformamide (DMF) as reaction medium, resulting in phosphorus-containing PVA networks (PVA-OP3). Hybrid gel-like films were then prepared by incorporating titanium dioxide nanoparticles (TiO₂ NPs), known for their antimicrobial activity, low toxicity, and high stability. The resulting composites were structurally, morphologically, and thermally characterized using FTIR, SEM, and thermogravimetric analysis. The incorporation of TiO₂ NPs significantly improved the thermal stability, with T₅% increasing from 240 °C for neat PVA-OP3 to 288 °C for the optimal composite, increased the char residue from 4.5% for the neat polymer to 30.1% for PVA-OP3/TiO₂-4, and enhanced antimicrobial activity against both Gram-positive and Gram-negative bacteria. These findings demonstrate that PVA-OP3/TiO₂ hybrid films possess promising potential as advanced biomaterials for biomedical, protective, and environmental applications. Full article

Most polymeric plastics used as food packaging are obtained from petroleum or made with non-biodegradable synthetic molecules, which slowly degrade and leach into the environment, resulting in the accumulation of microplastics along the trophic chains. To mitigate these impacts, biodegradable packaging derived from agro-industrial biomass residues has emerged as a promising alternative. In this study, bio-based methylcellulose films reinforced with cellulose nanocrystals (CNCs) extracted from low-quality coffee beans were developed and fully characterized. The extracted CNCs presented a needle-like morphology, with an average height of 7.27 nm and a length of 221.34 nm, with 65.75% crystallinity, were stable at pH 7–8, and presented thermogravimetric mass loss of 8.0%. Methylcellulose films containing 0.6% w/w of CNC were produced by casting and characterized in terms of thermal, mechanical, and optical properties. Notably, the incorporation of CNCs resulted in significantly more flexible and less rigid films, as evidenced by the higher elongation at break (57.90%) and lower Young’s modulus (0.0015 GPa) compared to neat methylcellulose film. The tensile strength was not affected (p > 0.05). Additionally, the MCNC 0.6% films effectively blocked UV light in the 200–300 nm range without compromising transparency. Altogether, these findings underscore the MCNC 0.6% film as a flexible, biodegradable packaging material suitable for food industry application. Full article

This research successfully developed novel hydrogels composed of methacrylated dextran and inulin for targeted drug delivery in colorectal cancer therapy. The formulation exploits the natural degradation of both biopolymers by the large intestine’s microflora. A key achievement was the development of a room-temperature free radical polymerization synthesis method. The study thoroughly investigated how varying inulin content (10 and 20 wt%) influenced the hydrogels’ properties. The formulation with 20 wt% inulin exhibited the highest swelling ability at both pH 3 and pH 6, and consequently the lowest elastic modulus, measured by a newly established technique for granulated hydrogels. Using uracil as a model drug, in situ incorporated, confirmed that the greatest drug release occurs in the colorectal region for the neat dextran-based hydrogel, triggered by specific microbial enzymes. Notably, the addition of inulin did not enhance biodegradation-driven drug release in combination with dextran; instead, inulin primarily acted as a protective component against premature hydrolysis in the gastric medium. These findings strongly confirm that the targeted action is predominantly governed by the dextran component. The synthesized hydrogels, particularly the dextran-only formulation, therefore show strong potential as effective carriers for colon-targeted drug delivery. The primary objective of this study was to evaluate the feasibility of modified and unmodified dextran and inulin as biodegradable carriers for enzyme-triggered, colon-targeted drug delivery. Full article

Erosion of the leading edge is one of the most severe forms of damage in wind turbine blades, particularly in offshore wind farms. This degradation, mainly caused by rain, sand, and airborne particles through droplet impingement wear, significantly decreases blade aerodynamic efficiency and power output. Since blades, typically made of fiber-reinforced polymer composites, are the most expensive components of a turbine, developing protective coatings is essential. In this study, polyurethane (PU) composite coatings reinforced with titanium dioxide (TiO₂) particles were added on glass fiber substrates by spray coating. The incorporation of TiO₂ improved the mechanical and electrochemical performance of the PU coatings. FTIR and XRD confirmed that low TiO₂ loadings (1 and 3 wt%) were well dispersed within the PU matrix due to hydrogen bonding between TiO₂ –OH groups and PU –NH groups. The PU/TiO₂ 3% coating exhibited ~61% lower corrosion current density (I_corr) compared to neat PU, indicating superior corrosion resistance. Furthermore, uniform TiO₂ dispersion resulted in statistically significant improvements (p < 0.05) in hardness, yield strength, elastic modulus, and adhesion strength. Overall, the PU/TiO₂ coatings, particularly at 3 wt% loading, show strong potential as protective materials for wind turbine blades, given their enhanced mechanical integrity and corrosion resistance. Full article

Delamination remains a critical failure mode in carbon fiber-reinforced polymer (CFRP) composites, particularly under cyclic loading in aerospace and automotive applications. This study explores whether nanoscale reinforcement with graphene-based materials can enhance delamination resistance and identifies the most effective nanofiller type. Two distinct graphene nanospecies—reduced graphene oxide (rGO) and carboxyl-functionalized graphene nanoplatelets (HDPlas)—were incorporated at 0.5 wt% into CFRP laminates and tested under static and fatigue mode I loading using double cantilever beam (DCB) tests. Both nanofillers enhanced interlaminar fracture toughness compared to the neat composite: rGO improved the energy release rate by 36%, while HDPlas achieved a remarkable 67% enhancement. Fatigue testing showed even stronger effects, with the fatigue threshold energy release rate rising by 24% for rGO and 67% for HDPlas, leading to a fivefold increase in fatigue life for HDPlas-modified laminates. A compliance calibration method enabled continuous monitoring of crack growth over one million cycles. Fractography analysis using scanning electron microscopy revealed that both nanofillers activated crack bifurcation, enhancing energy dissipation. However, the HDPlas system further exhibited extensive nanoparticle pull-out, creating a more tortuous crack path and superior resistance to crack initiation and growth under cyclic loading. Full article

Humidity monitoring is essential in industrial and scientific scenarios, yet remains challenging for compact EMI (electromagnetic interference)-immune sensors with high sensitivity and robust stability. A novel fiber Bragg grating (FBG) humidity sensor was developed, which incorporated LiCl@UIO-66 microfillers within a poly(N-isopropylacrylamide) (PNIPAM) hydrogel matrix. Structural characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared (FTIR) spectroscopy confirms that LiCl is confined or nanodispersed within intact UIO-66, and that interfacial ion–dipole/hydrogen-bonding exists between the composite and water. Systematic variation in coating time (30–720 min) reveals monotonic growth of the total wavelength shift with diminishing returns. A coating time of 4 h was found to yield a wavelength shift of approximately 0.38–0.40 nm, representing about 82% of the maximum shift observed at 12 h, while maintaining good quasi-linearity and favorable kinetics. Calibration demonstrates sensitivities of 6.7 pm/%RH for LiCl@UIO-66_33 and 10.6 pm/%RH for LiCl@UIO-66_51 over ~0–95%RH. Stepwise tests show response times t90 of ≈14 min for both composites, versus ≈30 min for UIO-66 and ≈55 min for neat PNIPAM. Long-term measurements on the 51 wt.% device are stable over the first ~20 days, with only slow drift thereafter, and repeated humidity cycling is reversible. The wavelength decreases monotonically during drying while settling time increases toward low RH. The synergy of hydrogel–MOF–salt underpins high sensitivity, accelerated transport, and practical stability, offering a scalable route to high-performance optical humidity sensing. Full article

Biocomposites based on natural fibres represent a promising solution for the circular economy. The aim of this study was to develop and characterise a biodegradable composite based on sheep wool from herds raised in the Kyrgyz Republic and polylactide (PLA 4032D). Composite samples with a wool–PLA ratio of 50:50 were fabricated by thermoforming at a temperature of 168 °C for 30 s (n = 10). Mechanical properties tests were performed (PN-EN ISO 604—compression tests), for impact resistance (Charpy method), differential scanning calorimetry (DSC), and measurements of density and thermal conductivity. Biodegradation samples were subjected to enriched soil conditions for 6 weeks in two variants (with and without irrigation). The results showed that the addition of sheep wool to the PLA matrix significantly increased compressive strength (23.56 ± 5.23 MPa) and impact energy absorption (226.2 ± 23.8 kJ/m²) compared to neat PLA. After biodegradation, a 59% reduction in compressive strength was observed while maintaining an increase in fracture energy, suggesting a change in the failure mechanism. The density (0.27 ± 0.02 g/cm³) and the thermal conductivity (0.127 W/m·K) comparable to polymer foams indicate potential for thermal insulation applications. Microscopy and DSC analysis confirmed complete biodegradation under soil conditions. The developed biocomposite from Kyrgyz sheep wool demonstrates the potential for valorisation of local fibrous waste for biodegradable materials with functional insulation properties. Full article

Pediatric inflammatory bowel disease (pIBD), comprising ulcerative colitis (UC) and Crohn’s disease (CD), involves complex mechanisms that include non-coding RNAs (ncRNAs), such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), alongside enzymes regulating serotonin metabolism. Tryptophan hydroxylase 1 (TPH1) and monoamine oxidase A (MAOA) play critical roles in serotonin turnover and may contribute to intestinal inflammation. We investigated the expression of TPH1, MAOA, hsa-miR-194-5p, hsa-miR-1276, and the lncRNA Nuclear Enriched Abundant Transcript 1 (NEAT1) in intestinal tissue biopsies and peripheral blood from pIBD patients and controls. TPH1 was significantly elevated in the inflamed transverse colon (p = 0.034), whereas MAOA was reduced in the ileum (p = 0.041) and descending colon (p = 0.001), with further decreases in inflamed ileum (p < 0.001), ascending (p = 0.008), and descending colon (p = 0.001). Subgroup analysis revealed decreased MAOA in the ascending colon of UC patients (p = 0.011). hsa-miR-194-5p was upregulated in the transverse colon (p = 0.015), inflamed transverse (p = 0.013) and descending colon (p = 0.015), and in blood of UC patients (p = 0.01). NEAT1 expression increased in the ascending colon (p = 0.042) but decreased in the ileum (p = 0.006). Correlation analysis showed strong positive associations between TPH1 and NEAT1 in the ileum (r = 0.945, p < 0.01) and transverse colon (r = 0.609, p < 0.01). These results highlight region-specific dysregulation of serotonin-related genes and ncRNAs in pIBD, with the TPH1/miR-194-5p/NEAT1 axis potentially contributing to disease pathophysiology and warranting further mechanistic investigation. Full article

Polymer matrix composites (PMCs) have been prepared having a polyethersulfone (PES) matrix loaded with polytetrafluoroethylene (PTFE) particles coated with negative thermal expansion zirconium tungstate (ZT) with an aim to reduce the thermal mismatch stresses at the PES/PTFE interfaces and, thus, reduce wear rate when sliding against a ball bearing AISI 52100 steel counterpart at elevated temperatures. The zirconium tungsten particles were synthesized using thermal decomposition from hydrothermally prepared precursors. The PMCs have been obtained using compression molding at 370 °C and contained, according to XRD, only the hexagonal α-ZrW₂O₈ phase. Wear testing was carried out at 25, 120, and 180 °C using a ball-on-disk scheme at 5 N and 0.3 m/s. The resulting wear tracks’ radial profiles were registered by means of profilometry, which was then used for calculating the wear rate. It was shown that both wear rate and friction reduced in testing the PES/PTFE/ZT samples at 180 °C compared to those of PES/PTFE containing only neat PTFE particles. Wear mechanism transitions have been observed from low-temperature generation of the tribological layer by the PTFE smearing to flow and abrasion wear at high temperatures. Full article

The present study explores the comparative influence of reduced graphene oxide (rGO), silver nanowires (AgNWs), and their hybrid rGO–AgNWs on the electromagnetic interference (EMI) shielding performance of polyaniline (PANI)-based flexible films prepared using a polycaprolactone (PCL) matrix. The nanocomposites were synthesized through in situ oxidative polymerization of aniline in the presence of individual or hybrid fillers, followed by their dispersion in the PCL matrix and casting of the corresponding films. Morphological and structural characterization (SEM, Raman, and FTIR spectroscopy) confirmed a uniform PANI coating on both rGO sheets and AgNWs, forming hierarchical 3D conductive networks. Thermal (TGA) and thermomechanical (TMA) analyses revealed enhanced thermal stability and stiffness across all composite systems, driven by strong interfacial interactions and restricted polymer chain mobility. Tmax increased from 437.9 °C for neat PCL to 487.9 °C for PANI/PCL, 480.6 °C for PANI/rGO/PCL, 499.4 °C for PANI/AgNWs/PCL and 495.0 °C for the hybrid PANI/rGO–AgNWs/PCL film. The gradual decrease in contact angle following the order PANI/AgNWs/PCL < PANI/rGO–AgNWs/PCL < PANI/rGO/PCL < PANI/PCL < PCL clearly indicates a systematic increase in surface polarity and surface energy with the incorporation of conductive nanofillers. Electrical conductivity reached 60.8 S cm⁻¹ for PANI/rGO/PCL, gradually decreasing to 27.4 S cm⁻¹ for PANI/AgNWs/PCL and 22.1 S cm⁻¹ for the quaternary hybrid film. The EMI shielding effectiveness (SET) measurements in the X-band (8–12 GHz) demonstrated that the PANI/rGO/PCL film exhibited the highest attenuation (~7.2 dB). In contrast, the incorporation of AgNWs partially disrupted the conductive network, reducing SE to ~5–6 dB. The findings highlight the distinct and synergistic roles of 1D and 2D fillers in modulating the electrical, thermal, and mechanical properties of biodegradable polymer films, offering a sustainable route toward lightweight, flexible EMI shielding materials. Full article

Background: Soft actuation relies on materials that are lightweight, flexible, and responsive to external stimuli. In biomedical applications, miniaturization and biocompatibility are key requirements for developing smart devices. Thermoplastic polyurethane (TPU) is particularly attractive due to its elasticity, processability, and biocompatibility; however, an improvement in its shape-recovery performance would significantly enhance its suitability for actuation systems. This study aims to develop TPU-based shape memory polymer (SMP) composites with improved functional behavior for biomedical applications. Methods: TPU was modified with aluminum nanoparticles (AlNPs) and multi-walled carbon nanotubes (MWCNTs), incorporated individually (1 wt.% and 3 wt.%) and in hybrid combinations (MWCNT:AlNP ratios of 2:1, 5:1, and 10:1). Samples were produced by compression molding and characterized through thermal, mechanical, electrical, and shape-recovery tests, supported by morphological analysis. Results: AlNPs moderately improved thermal conductivity, while MWCNTs significantly enhanced electrical conductivity and doubled the recovery force compared with neat TPU. Hybrid composites showed intermediate properties, with the 5:1 MWCNT:AlNP ratio offering the best balance between recovery force and activation speed. Conclusions: The synergistic combination of MWCNTs and AlNPs effectively enhances TPU’s multifunctional behavior, demonstrating strong potential for soft actuation in biomedical devices. Full article

The impact of zinc oxide (ZnO) nanoparticles on the dispersion, rheological behaviour, and mechanical properties of epoxy-based composites was investigated. Through experimental examinations, we found that 100 nm ZnO with a 4 wt.% content, when incorporated into epoxy, demonstrated homogeneous dispersion. Conversely, an increase in ZnO nanoparticle content led to particle agglomeration within the composite’s core. Rheology tests revealed that the 4 wt.% ZnO/epoxy mixture exhibited the lowest shear stress value, surpassing even the neat epoxy. Additionally, theoretical models were employed to evaluate the stress–strain properties of the ZnO/epoxy with the hollow glass fibre composite system. The study demonstrates the critical role of ZnO nanoparticle content in achieving dispersion and mechanical strength without the need for chemical solvents or surface modifications. Furthermore, variations in ZnO content within the composite resulted in a differing Young’s Modulus and UV absorbability, highlighting the importance of nanoparticle concentration in determining material properties. The study also delves into the effects of core diameter, length of hollow glass fibres (HGF), and adhesive layer thickness on stress transfer and strain deformation mechanisms within the composite system. Full article

This study develops biodegradable chitosan (CS) films plasticized with natural deep eutectic solvents (NaDES) composed of choline chloride and glycolic acid (1:3 molar ratio). The same NaDES served as an effective extraction medium for bioactive compounds from hawthorn (Crataegus monogyna), which were incorporated into the chitosan matrix to enhance functionality. CS films with 44–70 wt% NaDES were evaluated, and the 50 wt% formulation exhibited the optimal mechanical and barrier performance. Upon extract incorporation, this film showed marked decreases in Young’s modulus (131→30 MPa) and tensile strength (24→12 MPa), relative to the extract-free counterparts, indicating enhanced flexibility. Stress–strain analyses confirmed a progressive reduction in stiffness with increasing NaDES content, evidencing its plasticizing effect. FTIR analysis revealed extensive hydrogen-bonding between CS and NaDES, alongside successful integration of polyphenolics extracted from hawthorn. Morphological analysis showed smooth, dense, homogeneous surfaces. Films exhibited strong UV absorption, with extract-loaded samples extending into the UVA and visible ranges, enhancing light-barrier properties. The presence of polyphenolic compounds enhanced the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity to nearly twice that of the neat CS films. These combined mechanical, optical, and antioxidant properties highlight the potential of these NaDES-based chitosan films for sustainable active packaging. Full article

Objective. To determine how bamboo loadings (2.5–5 wt%) and compatibilization with PBAT-g-MAH (BP-1, 10 wt%) affect melt flow and early-time mineralization of PLA biocomposites under near-ambient soil–compost conditions (ASTM D5988), while using PBAT-g-GMA (BP-2) only as a melt-flow screening reference. Methods. Melt flow index (MFI, ASTM D1238, 2.16 kg; 190/210/230 °C) was first measured for neat PLA and PLA/BP-1/BP-2 blends to select a printable matrix. PLA/10BP-1 composites containing 2.5–5 wt% bamboo were then compounded, extruded as bars for biodegradation tests, and validated by FFF printing. Biodegradation was quantified from titrimetric CO₂ evolution in soil–compost reactors at 21 ± 2 °C and pH ≈ 7 (triplicate specimens plus triplicate blanks; mean ± SD and endpoint statistics). ATR-FTIR was used to support mechanistic interpretation. Results. BP-1 markedly increased MFI relative to neat PLA, whereas BP-2 remained close to the neat matrix, consistent with epoxy-driven coupling that can raise viscosity. Under ambient burial, all materials exhibited very low mineralization over 0–23 days; PLA/10BP-1/2.5B and PLA/10BP-1/5B showed a slight increase in net CO₂ evolution compared with neat PLA, but the differences remained modest and within the experimental uncertainty, reflecting a balance between bamboo’s pro-hydrolytic effect and the sealing action of PBAT-g-MAH compatibilization. Significance. The data delineate a printing–degradation window in which PLA/10BP-1 with 2.5–5 wt% bamboo combines easy processing and short-term durability while preserving industrial compostability at end-of-life. Full article

Graphene nanoplatelets (GNPs) are efficient nanofillers for improving the mechanical and thermal properties of epoxy resins due to their high stiffness, aspect ratio, and interfacial reinforcement ability. This study employs a three-factor, three-level Box–Behnken Design (BBD) to investigate the combined effect of GNP content (0.5–3.5 wt.%), hardener concentration (9–17 phr), and post-curing temperature (30–120 °C) on DGEBA/TETA epoxy nanocomposites. Mechanical, thermal, dynamic mechanical, and morphological characterizations (flexural testing, DMA, TGA, DSC, FTIR, SEM, TEM, and AFM) established structure–property correlations. The optimized formulation (2.0 wt.% GNP, 9 phr hardener, and 120 °C post-curing) exhibited superior reinforcement, with flexural strength of 322.0 ± 12.8 MPa, flexural modulus of 9.7 ± 0.5 GPa, and strain at break of 4.4 ± 0.2%, corresponding to increases of 197%, 155%, and 91% compared with neat epoxy. DMA confirmed a rise in storage modulus from 2.9 to 7.5 GPa and a Tg of 143 °C, while TGA showed a 15 °C improvement in thermal stability. Statistical analysis identified post-curing temperature as the dominant factor governing Tg, stiffness, and thermal stability, with synergistic contributions from GNP content and hardener concentration to the overall network performance. These results surpass those of GO- and CNT-based systems, demonstrating the superior efficiency of GNPs under optimized conditions. The proposed approach provides a robust pathway for developing epoxy nanocomposites with low filler content and enhanced multifunctional performance. Full article