Polymers

Citation: Garrido-Miranda, K.A.; Gonzalez, M.E.; Hernandez-Montelongo, J.; Jaramillo, A.; Oñate, A.; Burgos-Díaz, C.; Manso-Silvan, M. Poly (3-hydroxybutyrate)/Clay/Essential Oils Bionanocomposites Incorporating Biochar: Thermo-Mechanical and Antioxidant Properties. Polymers 2025, 17, 1157. https://doi. Abstract: The use of biodegradable active materials is being explored as a strategy to reduce food loss and waste. The aim is to extend the shelf life of food and to ensure biodegradation when these materials are discarded. The utilization of biodegradable polymers remains limited due to their inherent properties and cost-effectiveness. An alternative approach involves the fabrication of bionanocomposites, which offer a potential solution to address these challenges. Therefore, this study investigates the production of a polyhydroxybutyrate/biochar/clay/essential oil (Tepa:Eugenol) bionanocomposite with antioxidant and antimicrobial properties. The morphological, physicochemical, and antioxidant properties of the materials were evaluated in comparison to those of the original PHB. The materials obtained showed a porous surface with cavities, associated with the presence of biochar. It was also determined that it presented an intercalated-exfoliated morphology by XRD. Thermal properties showed minor improvements over those of PHB, indicating that the components did not substantially influence properties such as crystal-lization temperature, decomposition temperature, or degree of crystallinity; the melting temperature decreased up to 11%. In addition, the PHB/biochar_7/MMT-OM_3/EO_3 bionanocomposites showed a tendency toward hydrophobicity and the highest elastic modulus with respect to PHB. Finally, all essential-oil-loaded bionanocomposites exhibited excellent antioxidant properties against DPPH and ABTS radicals. The results highlight the potential of these bionanocomposites for the development of antioxidant active packaging.

Dendrobium is a famous edible and medicinal plants, and polysaccharides are their main bioactive components. Polysaccharides from five species, namely, DO (Dendrobium officinale Kimura et Migo), DH (Dendrobium huoshanense C. Z. Tang et S. J. Cheng), DNL (Dendrobium nobile Lindl.), DFH (Dendrobium fimbriatum Hook.), and DCL (Dendrobium chrysanthum Lindl.), were compared based on molecular weight (Mw), monosaccharide composition, and glycosidic bond types. The results showed that Dendrobium polysaccharides (DPs) contain relatively simple compositional monosaccharides and mainly consist of mannose (Man) and glucose (Glc), along with small amounts of arabinose (Ara), xylose (Xyl), and galactose (Gal). The Am/Ag (the ratio of Man to Glc) values in DO, DH, and DNL polysaccharides were 3.23, 3.81, and 3.88, while those in DFH and DCL were 0.45 and 0.81. DPs are mainly composed of →4)Manp(1→ and →4)Glcp(1→, but their molar ratios were different. →4)Manp(1→ and →4)Glcp(1→ ratios were 2.85, 2.92, 1.50, 1.45, and 1.05 in DO, DH, DNL, DFH, and DCL, respectively. Hierarchical cluster analysis (HCA) showed that there were significant differences in structural information, especially in glycosidic bond types and proportions. DH, DO, and DCL were clustered into different groups based on glycosidic bond types and proportions, respectively. Moreover, the five species of Dendrobium could significantly inhibit NO production and apoptosis induced by LPS in RAW 264.7, especially DH. The results of a correlation analysis of structure and anti-inflammatory activity showed that polysaccharides with a high →4)Manp(1→/→4)Glcp(1→ ratio and a molecular weight distribution between 3.343 × 105 Da and 13.540 × 105 Da had better anti-inflammatory activity. The results indicated that the quality evaluation of Dendrobium in clinical applications should investigate molecular weight and the composition of the glycoside bond types and proportions to ensure the consistency of curative effects.

The objective of this study was to evaluate how high-energy milling affects the structural, thermal, and morphological properties of brewer’s spent grain fibers over time. The researchers determined the chemical composition of the samples using TAPPI techniques, particle size analysis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The samples displayed distinct morphologies and particle sizes depending on the treatment duration. The sample treated for 120 min (T120) showed the smallest particle size (19.4 µm). FTIR spectra revealed that the mechanical treatment strongly disrupted the structure of hemicellulose. The thermal stability of the samples decreased because of the applied treatment. Mechanical milling also fully eliminated the crystalline structure of cellulose in the samples. These findings indicate that high-energy milling holds strong potential as a pre-treatment method for the valorization of lignocellulosic residues.

Designing conducting polymers with novel structures is essential for electrochemical energy storage devices. Here, copolymers of s-triazine and o-aminophenol are electropolymerized from an aqueous solution onto a carbon cloth substrate using the galvanostatic method. The poly(s-triazine-co-o-aminophenol) (PT-co-oAP) is characterized, and its charge storage properties are investigated in 1 M H2SO4 and in 1 M ZnSO4. At 1 A g−1, the specific capacities of PT-co-oAP reach 101.3 mAh g−1 and 84.4 mAh g−1 in 1 M H2SO4 and in 1 M ZnSO4, respectively. The specific capacity of PT-co-oAP maintains 90.3% of its initial value after cycling at 10 A g−1 for 2000 cycles in 1 M H2SO4. The high specific capacity achieved originates from abundant surface active sites, facile ion diffusion, with optimized active site structure achieved by forming copolymer. The charge storage mechanism involves the redox processes of amino/imino groups and hydroxyl/carbonyl groups in the copolymer, together with the insertion of cations. Two electrode devices using two PT-co-oAP and aqueous 1 M H2SO4 are assembled, and the maximum energy density reaches 63 Wh kg−1 at 0.5 A g−1 with a power density of 540 W kg−1. The capacity retention of the device after 3000 cycles at 10 A g−1 reaches 81.2%.

Bacterial cellulose (BC) is a highly pure and crystalline cellulose produced via bacterial fermentation. However, due to its chemical structure made of strong hydrogen bonds and its high molecular weight, BC can neither be melted nor dissolved by common solvents. Therefore, processing BC implies the use of very strong, often toxic and dangerous chemicals. In this study, we proved a green method to produce electrospun BC fibers by testing different ionic liquids (ILs), namely, 1-butyl-3-methylimidazolium acetate (BmimAc), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimTFSI) and 1-ethyl-3-methylimidazolium dicyanamide (EmimDCA), either individually or as binary mixtures. Moreover, γ-valerolactone (GVL) was tested as a co-solvent derived from renewable sources to replace dimethyl sulfoxide (DMSO), aimed at making the viscosity of the cellulose solutions suitable for electrospinning. A BmimAc and BmimAc/EmimTFSI (1:1 w/w) mixture could dissolve BC up to 3 w%. GVL was successfully applied in combination with BmimAc as an alternative to DMSO. By optimizing the electrospinning parameters, meshes of continuous BC fibers, with average diameters ~0.5 μm, were produced, showing well-defined pore structures and higher water absorption capacity than pristine BC. The results demonstrated that BC could be dissolved and electrospun via a BmimAc/GVL solvent system, obtaining ultrafine fibers with defined morphology, thus suggesting possible greener methods for cellulose processing.

Mesenchymal stromal cell-derived small extracellular vesicles (MSC-sEVs) have shown great promise in promoting tissue repair, including skin wound healing, but challenges like rapid degradation and short retention have limited their clinical application. Hydrogels have emerged as effective carriers for sustained EV release. Three-dimensional printing enables the development of personalized skin substitutes tailored to the wound size and shape. This study aimed to develop 3D bioprinted gelatin–genipin hydrogels incorporating human umbilical cord MSC-sEVs (hUCMSC-sEVs) for future skin wound healing applications. Gelatin hydrogels (8% and 10% w/v) were crosslinked with 0.3% genipin (GECL) to improve stability. The hydrogels were evaluated for their suitability for extrusion-based 3D bioprinting and physicochemical properties, such as the swelling ratio, hydrophilicity, enzymatic degradation, and water vapor transmission rate (WVTR). Chemical characterization was performed using EDX, XRD, and FTIR. The hUCMSC-sEVs were isolated via centrifugation and tangential flow filtration (TFF) and characterized. The crosslinked hydrogels were successfully 3D bioprinted and demonstrated superior properties, including high hydrophilicity, a swelling ratio of ~500%, slower degradation, and optimal WVTR. hUCMSC-sEVs, ranging from 50 to 200 nm, were positive for surface and cytosolic markers. Adding 75 μg/mL of hUCMSC-EVs into 10% GECL hydrogels significantly improved the biocompatibility. These hydrogels offer ideal properties for 3D bioprinting and wound healing, demonstrating their potential as biomaterial scaffolds for skin tissue regeneration applications.

Tannins, present in all plants, are the most abundant polyphenols in the world. Their potential as a raw material for modifying wood alongside furfuryl alcohol (FA) has already been demonstrated in previous studies. This study focused on using large quantities of hydrolysable tannins from chestnut (Castanea sativa) to replace as much FA as possible to chemically modify beech wood (Fagus sylvatica L.). Impregnation was carried out using different concentrations and ratios of both FA and tannins and tartaric acid as catalysts through a vacuum/atmospheric pressure cycle. Copolymerization was carried out for 24 h at 120 °C. Properties such as weight percent gain (WPG), leachability, anti-swelling efficiency (ASE), thermal stability, wettability and durability against brown rot (Coniophora puteana) and white rot (Coriolus versicolor) were analyzed and compared to a furfurylation treatment without the addition of tannins. These treatments were also chemically characterized using FTIR spectroscopy. The results showed that replacing 50% of FA mass by tannins largely increased WPG and demonstrated similar leachability and dimensional stability to standard furfurylation. Above all, the new treatment showed to have better resistance to wood-degrading fungi, in addition to improved wettability and thermal stability.

Hybrid composite materials reinforced with both fibers and particulate fillers are increasingly used in engineering due to their favorable balance of mechanical strength, reduced weight, and enhanced tribological performance. This study investigated the effect of CuSn10 bronze powder additions (5%, 10%, and 15% by weight) on the mechanical and tribological properties of novel basalt fiber-reinforced polymer (BFRP) composites. The composites were fabricated via vacuum-assisted processing and tested under dry sliding conditions with varying loads (10, 20, and 30 N) and sliding speeds (0.1, 0.25, and 0.36 m/s). The results show that the optimal tensile strength (440.6 MPa) was achieved at 10 wt% CuSn10, while the best tribological performance was observed at 15 wt% CuSn10, under a 10 N load and 0.25 m/s sliding speed, where the coefficient of friction decreased by up to 38% and the specific wear rate was reduced by more than 50% compared to the unreinforced BFRP composite. These enhancements are attributed to the formation of a stable oxide-based tribolayer (CuO, SnO2) and improved load transfer at the fiber–matrix interface. Statistical analysis (GLM) confirmed that CuSn10 content had the most significant influence on tribological parameters. The findings provide valuable insight into the design of high-performance hybrid composites for structural and tribological applications.

Optimisation of the tensile strength of thermoplastic polymer-matrix composites remains a scientific as well as technological challenge for 3D printing technology due to the mass application of composite materials. Inadequate mechanical properties are due to the mismatch in the surface energies of the polymer and fillers. In this study, an additively manufactured composite was 3D-printed and tested. The composite consisted of a linear low-density polyethylene matrix filled with glass fibres. Composite filaments were extruded from neat and plasma-treated polymer powders. Plasma was sustained in oxygen at 100 Pa by a pulsed microwave discharge, and 250 g of polymer powder of average diameter 150 µm was placed into a dish and stirred during the plasma treatment. The O-atom density at the position of the dish containing polymer powder was about 2 × 1021 m−3, and the treatment time was varied up to 30 min. A gradual improvement in the composites’ tensile and flexural strength was observed at the plasma treatment time up to about 10 min, and the mechanical properties remained unchanged with prolonged treatment time. The tensile strength of composites prepared from plasma-treated polymer increased by one-third compared to those based on untreated powder. However, reinforcing the modified polyethylene with plasma-treated glass fibres did not result in further significant mechanical improvement compared to untreated fibres. In contrast, strength values doubled using glass fibres with silane sizing in combination with plasma-modified matrix. The results were explained by the increased surface energy of the polymer powder due to functionalisation with polar functional groups during plasma treatment.

This study explores the fabrication, structural characteristics, and performance of an innovative porous geopolymer membrane made from waste natural zeolite powder for Pb(II) removal, with potential applications in wastewater treatment. A hybrid geopolymer membrane incorporating polyvinyl acetate (PVAc) (10, 20, and 30 wt.%) was synthesized and thermally treated at 300 °C to achieve a controlled porous architecture. Characterization techniques, including Fourier-transform infrared spectroscopy (FTIR), revealed the disappearance of characteristic C=O and C-H stretching bands (~1730 cm−1 and ~2900 cm−1, respectively), confirming the full degradation of PVAc. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) indicated a total mass loss of approximately 14.5% for the sample with PVAc 20 wt.%, corresponding to PVAc decomposition and water loss. Energy-dispersive spectroscopy (EDS) elemental mapping showed the absence of carbon residues post-annealing, further validating complete PVAc removal. X-ray diffraction (XRD) provided insight into the crystalline phases of the raw zeolite and geopolymer structure. Once PVAc removal was confirmed, the second phase of characterization assessed the membrane’s mechanical properties and filtration performance. The thermally treated membrane, with a thickness of 2.27 mm, exhibited enhanced mechanical properties, measured with a nano-indenter, showing a hardness of 1.8 GPa and an elastic modulus of 46.7 GPa, indicating improved structural integrity. Scanning electron microscopy (SEM) revealed a well-defined porous network. Filtration performance was evaluated using a laboratory-scale dead-end setup for Pb(II) removal. The optimal PVAc concentration was determined to be 20 wt.%, resulting in a permeation rate of 78.5 L/(m2·h) and an 87% rejection rate at an initial Pb(II) concentration of 50 ppm. With increasing Pb(II) concentrations, the flux rates declined across all membranes, while maximum rejection was achieved at 200 ppm. FTIR and EDS analyses confirmed Pb(II) adsorption onto the zeolite-based geopolymer matrix, with elemental mapping showing a uniform Pb(II) distribution across the membrane surface. The next step is to evaluate the membrane’s performance in a multi-cation water treatment environment, assessing the sorption kinetics and its selectivity and efficiency in removing various heavy metal contaminants from complex wastewater systems.

This study investigates the efficient and recyclable use of polymer-based membrane materials in wastewater treatment, focusing on calcium-based montmorillonite (Ca-MMT), pyrrole (Py), and polypropylene (PP). Through sodium activation, organic modification, pyrrole intercalation, and in situ polymerization, polypyrrole/montmorillonite (PPy/MMT) was synthesized. A polypyrrole/montmorillonite/polypropylene composite membrane (PPy/MMT/PP) was then fabricated using melt compression and coating techniques for pollutant adsorption. The modification of montmorillonite by PPy was examined, alongside the morphology, composition, and structure of PPy/MMT/PP. The membrane’s adsorption performance for methyl orange and Pb2⁺ was evaluated, with a focus on cyclic adsorption. The results showed that PPy increased the interlayer spacing of montmorillonite from 1.23 nm to 1.74 nm and enhanced its specific surface area by 99.424 m2/g. The composite membrane exhibited improved wettability and adsorption capacity, achieving removal rates of 95.98% for methyl orange and 88.48% for Pb2⁺, following pseudo-second-order kinetics. The membrane demonstrated recyclability, maintaining efficient adsorption/desorption over three cycles. This work provides valuable insights and technical support for sustainable wastewater treatment using polymer-based membranes.

The present study explores the effects of pre-coating on the wear performance of milled carbon fiber-filled basalt composites via laser texturing. Laser texturing was used to change surface topography, enhancing adhesion and wear resistance. Incorporated 0 wt.% and 5 wt.% milled carbon fibers in an epoxy matrix. A fiber laser system was employed for surface treatment, in which power, scanning speed, and pulse frequency were optimized. For pre-coating, an epoxy-based primer was used, and the adhesion and wear performance of the coating was studied using ball-on-disc wear tests. Experimental results demonstrate that laser texturing significantly increases coating adhesion by enhancing the surface roughness and mechanical interlocking. The laser-induced textures displayed mostly square-shaped dimples, reducing practically by around 22% the deformation of the primer coating when used in combination with 5 wt.% carbon fiber milling. The textured surfaces reduced friction noticeably, leading to a decrease of as much as 23% in the coefficient of friction from untreated surfaces. SEM and 3D profilometry analysis indicate that the lower delamination observed in the laser treatment led to optimal coating retention. The original contribution of this work consists of the unique integration of laser surface engineering with pre-coating treatments toward improved tribological performance.

3,3-Bis (azide methyl) oxy-butyl ring (BAMO)-tetrahydrofuran (THF) copolyethers (PBT) are some of the most promising energetic binders. In this paper, the methods of synthesis of PBT binders are reviewed, and the research progress in PBT binders and PBT-based solid propellants in terms of their thermal and combustion behavior, curing and rheology properties, energy and aging properties, and mechanical and safety performances are systematically summarized. The problems and shortcomings of PBT binders in the application of solid propellants and their thriving trends are pointed out, providing support for speeding up the practical application of PBT binders in high-energy solid propellants.

To extend food shelf life and reduce plastic pollution, halloysite nanotubes (HNTs) were employed as a carrier to load cinnamon essential oils (CEOs), and the nanotubes were blended with polybutylene adipate co-terephthalate (PBAT) resin to fabricate the film with non-contact antimicrobial activity. The results showed that the HNTs had a high loading efficiency (about 11%) for CEOs. The retention rate of CEOs in HNTs was still 33% after twenty days later, which indicated that the CEOs/HNTs nanoparticles had a long-acting controlled-released effect. The composite films represented excellent mechanical properties and antibacterial effects against Staphylococcus aureus and Escherichia coli due to the non-contact antimicrobial activity of CEOs. The strawberries remained fresh after five days when the composite film was applied in the packaging of strawberries, which proves that composite films can extend the shelf life of food. Therefore, it has potential application prospects in the food industry.

N-butylnitroxyethylnitramine (BuNENA) is a high-energy plasticizer with high plasticizing ability, low sensitivity, and high energy. It has broad application prospects in HTPE propellants. Nevertheless, as an energetic plasticizer, it requires treatment to reduce its sensitivity. To this end, the passivation process for BuNENA was simulated using a mixing model analogous to nucleate boiling. This method involves tracking the formation and movement of bubbles using a Lagrange frame, and the bubbles themselves are modeled as rigid spheres subject to buoyancy and viscous forces. A variational multiscale (VMS)-based Euler framework was employed to simulate the fluid surrounding the bubble. The movement process of the bubbles was analyzed, and it was found that the amount of bubbles and the movement speed were higher at high temperatures and in a high vacuum, and the passivation effect on BuNENA was better. At a pressure of 40 mbar and a temperature of 50 °C, BuNENA demonstrated an 89% water removal rate. A comparison of the experimental results with the simulation results revealed slight discrepancies between them. A meticulous analysis of the passivation process for BuNENA is rendered possible by integrating experimental and simulation methodologies, a feat that has immense implications for the realm of composite solid propellant passivation.

This study proposes a novel numerical approach to simulate damage accumulation and failure in polymer materials under thermal fatigue, using an entropy-based damage criterion. Unlike the many experimental studies in this area, few numerical simulations exist due to the complexity of modeling thermal fatigue. In our method, thermal and mechanical stresses arising from thermal expansion mismatches and temperature gradients are modeled through a coupled simulation approach. A viscoelastic constitutive equation is implemented in ABAQUS via a user-defined subroutine to capture damage progression. The method includes surface and internal thermal conduction, thermal deformation, and time–temperature superposition using reduced viscosity, enabling accurate simulation under varying thermal conditions. The results show that localized thermal stresses induced by temperature gradients lead to progressive damage and failure. This study demonstrates the first successful numerical simulation of thermal fatigue-induced damage in polymer materials. The proposed framework reduces the need for extensive experiments and offers insights into residual stress prediction and durability evaluation, contributing to polymer design and application in high-performance environments.

The partial nitrification–anammox process offers a cost-effective, energy-efficient, and environmentally sustainable approach for nitrogen removal in wastewater treatment. However, its application under low ammonia nitrogen conditions faces operational challenges including prolonged start-up periods and excessive nitrite oxidation. This study employed a strategy combining polyurethane surface positive charge enhancement and zeolite loading to develop a carrier capable of microbial enrichment and inhibition of nitrate generation, aiming to initiate the partial nitrification-anammox process in a sequencing batch reactor. Operational results demonstrate that the modified carrier enabled the reactor to achieve a total nitrogen removal efficiency of 78%, with the effluent nitrate nitrogen reduced to 6.03 mg-N/L, successfully initiating the partial nitrification-anammox process. The modified carrier also exhibited accelerated biofilm proliferation (both suspended and attached biomass increased). Additionally, 16S rRNA revealed a higher relative abundance of typical anammox bacteria Candidatus Brocadia in the biofilm of the modified carrier compared to the original carrier, alongside a decline in nitrifying genera, such as Nitrolancea. These microbial shifts effectively suppressed excessive nitrite oxidation, limited nitrate accumulation, and sustained efficient nitrogen removal throughout the reactor’s operation.

Three new amide-preformed triphenylamine-diamine monomers, namely 4,4′-bis(p-aminobenzamido)triphenylamine (4), 4,4′-bis(p-aminobenzamido)-4″-methoxytriphenylamine (MeO-4), and 4,4′-bis(p-aminobenzamido)-4″-tert-butyltriphenylamine (t-Bu-4), were synthesized and subsequently used to produce three series of electroactive aromatic poly(amide-imide)s (PAIs) via two-step polycondensation reactions with commercially available tetracarboxylic dianhydrides. Strong and flexible PAI films could be obtained by solution casting of the poly(amic acid) films followed by thermal imidization or direct solution casting from the organosoluble PAI samples. The PAIs had high glass-transition temperatures of 296–355 °C and showed no significant decomposition below 500 °C. The PAIs based on diamines MeO-4 and t-Bu-4 showed high electrochemical redox stability and strong color changes upon oxidation. For the PAIs derived from diamine 4, the TPA radical cation formed in situ during the electro-oxidative process could dimerize to a tetraphenylbenzidine structure, resulting in an additional oxidation state and color change. These PAIs exhibited increased solubility, lowered oxidation potentials, and enhanced redox stability compared to their polyimide analogs.

Microcrystalline cellulose (MCC) possesses important attributes, including high crystallinity, a large surface area, excellent mechanical strength, chemical stability, and biodegradability. This study aims to research MCC extraction from bamboo (Phyllostachys edulis (Carrière) J. Houz.) fiber by assessing the impact of key processing variables such as acid concentration, temperature, and hydrolysis duration. Experimental results indicate that hydrolysis time and hydrochloric acid (HCl) concentration significantly influence yield. After evaluating the effects of various hydrolysis conditions, the optimal parameters were determined to be a 2.0 M HCl concentration, 90 °C, and 10 min of reaction time. The MCC produced under optimal conditions displayed improved crystallinity (77.2%) while retaining functional groups similar to those found in raw bamboo. Morphological analysis revealed an irregular rod-like shape with rough surfaces. This optimized hydrolysis process offers a viable approach for MCC production from raw bamboo and holds potential as a precursor for developing environmentally friendly biodegradable fiber materials.

The production of fibre-reinforced composites for use in applications such as type-4 pressure vessels for hydrogen storage is achieved through the use of a thermoset matrix. However, the recycling of thermosets presents a significant challenge due to the lack of established recycling methods. Epoxy-based vitrimers show thermoset characteristics during the manufacturing and utilisation phases but exhibit thermoplastic behaviour at elevated temperatures of 190 °C. This study investigates the industrial-scale production of carbon fibre reinforced vitrimers via a wet filament winding, as exemplified by a type-4 pressure vessel demonstrator. Processing conditions of industrial processes have yet to be applied to vitrimers; therefore, two vitrimer formulations are compared to a conventional epoxy thermoset. The processability and resulting composite quality of wound composites using these materials as matrices are compared. The mechanical properties of the composites are compared using an interlaminar shear strength test, demonstrating that the vitrimeric matrices exhibit 19.8% (23 °C) and 49.2% (140 °C) improved interlaminar strength. Consequently, the epoxy-based vitrimers investigated in this study can be employed as a direct replacement for the thermoset matrix in industrial-scale applications, with the potential for recycling the composite. To increase composite qualities, the winding process must be adapted for vitrimers, since a pore free composite could not be achieved.

In this study, poly(methyl methacrylate) (PMMA) nanofiber scaffolds reinforced with synthesized nano-hydroxyapatite (n-HA) were fabricated through electrospinning to enhance their potential for applications in bone tissue engineering. Sodium tripolyphosphate (STTP) was utilized as a surfactant to achieve a uniform distribution of particles and improve the structural integrity of the scaffolds. PMMA solutions were prepared at concentrations of the addition of STTP effectively stabilized n-HA dispersion, leading to enhanced fiber morphology, as confirmed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The PMMA_10_HA_S nanofibers demonstrated a homogeneous fiber distribution with an average diameter of 345.40 ± 53.55 nm and a calcium content of 7.1%. Mechanical testing revealed that adding STTP enhanced the mechanical properties, with the n-HA-reinforced 10 wt.% PMMA nanofibers achieving a maximum tensile stress of 4.16 ± 2.13 MPa and an elongation of 7.1 ± 1.95%. Furthermore, cell cytotoxicity assays of different concentrations (25, 50, 75, and 100 mg/mL) using L929 fibroblast cells demonstrated no cytotoxic effect of PMMA_10_HA_S nanofibers. These findings, reinforced by STTP and n-HA, highlight the potential of PMMA_10_HA_S nanofiber scaffolds as promising candidates for bone tissue applications.

Among the proposed leather recycling options, the incorporation of leather waste in rubber has been the subject of multiple studies, where the effects of leather content on the mechanical and rheological properties of the composites are usually studied. However, the effects of leather size have never been addressed in a systematic way. The reasons to study this parameter are twofold: it affects the physicochemical properties and processing conditions of the composites, and leather grinding is a costly and time-consuming process. In this work, leather waste (LW) with particle sizes ranging from ≤0.5 mm to ≤3 mm was incorporated in styrene–butadiene rubber (SBR) in contents of up to 50 phr. It was concluded that the composites with finer leather sizes exhibited a more uniform particles dispersion, and tensile strength was not significantly affected by the presence of LW, especially for the finer granulometries. However, there is a remarkable increase in the stiffness with the increase in leather content, particularly with the finer particles. The abrasion increased with the incorporation of leather across all particle sizes, especially for the ≤0.5 mm leather particles. The thermal stability of the composites was not affected by either the particle size or the amount of LW, except for high contents.

Active food packaging is a significant trend in recent years in the food industry. This paper presents the results of studies on selected properties of a mixture of polylactide and polycaprolactone containing 1 or 5 wt.% of tannic acid. The function of tannic acid was to improve the miscibility of the polymers used and to give the obtained composition antibacterial properties. Studies were carried out on color and transparency, microscopic analysis, water vapor permeability, mass flow rate, static tensile properties, impact strength, dynamic mechanical analysis, thermogravimetry and differential scanning calorimetry. The obtained results did not confirm the compatibilizing effect of tannic acid, because the obtained mechanical properties were slightly worse than those of materials without the addition of this compound. However, the obtained mixture was characterized as having biocidal properties against two strains of Escherichia coli (ATCC 8739) and Staphylococcus aureus (ATCC 6538P). Antibacterial properties together with acceptable processing, mechanical and thermal properties indicate that the presented polymer material may be a potential material for the production of active food packaging.

The development of sustainable nanofiltration membranes requires alternatives to petroleum-derived polymer substrates. This study demonstrates the successful use of an eco-friendly cellulose acetate/cellulose nitrate (CA/CN) blend substrate for fabricating high-performance modified thin-film composite (mTFC) membranes. A dense, non-porous polyamide (PA) selective layer was formed via the interfacial polymerization method and modified with 0.05–0.1 wt.% HKUST-1 (Cu3BTC2, MOF-199). Characterization by FTIR, XPS, SEM, AFM, and contact angle measurements confirmed the CA/CN substrate’s suitability for TFC membrane fabrication. HKUST-1 incorporation created a distinctive ridge-and-valley morphology while significantly altering PA layer hydrophilicity and roughness. The mTFC membrane performance could be fine-tuned by the controlled incorporation of HKUST-1; incorporation through the aqueous phase slowed down the formation of the PA layer and significantly reduced its thickness, while the addition through the organic phase resulted in the formation of a denser layer due to HKUST-1 agglomeration. Thus, either enhanced permeability (123 LMH bar−1 with 0.05 wt.% aqueous-phase incorporation) or rejection (>89% dye removal with 0.05 wt.% organic-phase incorporation) were achieved. Both mTFC membranes also exhibited improved heavy metal ion rejection (>91.7%), confirming their industrial potential. Higher HKUST-1 loading (0.1 wt.%) caused MOF agglomeration, reducing performance. This approach establishes a sustainable fabrication route for tunable TFC membranes targeting specific separation tasks.

Carbon fabric reinforced polyetherketoneketone (CFF/PEKK) composites have garnered significant attention from researchers due to their superior properties and have been successfully applied in various engineering fields. Environmental conditions are known to directly influence the mechanical properties and service life of composites; however, limited literature exists on the mechanical behavior of CFF/PEKK composites under different environmental conditions. This study elucidates the correlation between the bending and shear behaviors of CFF/PEKK composites and environmental factors, thereby offering robust data support for engineering applications. In this work, CFF/PEKK composite laminates with a fiber volume fraction of 55 vol% were fabricated and subjected to saturated moisture absorption treatments at 70 °C. The moisture absorption characteristics of the material were investigated. The bending and shear properties of CFF/PEKK composites were characterized under three environmental conditions: −55 °C dry state (CTD), room temperature dry state (RTD), and 70 °C wet state (ETW). Failure modes and mechanisms of composite specimens were also analyzed. The equilibrium moisture absorption rate of CFF/PEKK composites is approximately 0.27%. Hygrothermal aging resulted in noticeable fiber pull-out in mechanical specimens, indicating damage to the interfacial performance of the composites. Furthermore, no cracks or delamination were observed. Results indicate that in the CTD condition, the bending strength and shear strength of CFF/PEKK composites are higher compared to those in the RTD condition, while the modulus remains relatively unaffected. In the ETW condition, both bending and shear properties exhibit a significant decline, with the most pronounced reduction observed in interlaminar shear strength. No significant differences in failure modes were noted across different environmental conditions.