Search Results (383)

This work focused on the investigation of sulfonated lignin as a novel and sustainable reinforcing filler for polyamide 6 (PA6) composites. Different formulations were thus prepared by melt compounding, varying the lignin content (5, 10, and 20 wt%). The interaction between lignin and PA6 was systematically studied through rheological, structural, morphological, thermo-mechanical, and flammability tests. Rheological measurements showed an increase in the complex viscosity and viscoelastic moduli with increasing lignin content, suggesting restricted polymer chain mobility and the formation of strong physical interactions between the molten PA6 and the lignin particles. Microstructural observations through FESEM highlighted a good dispersion of lignin particles and efficient filler–matrix interfacial adhesion. Moreover, the addition of lignin significantly increased the tensile stiffness of the composites (up to 3.4 GPa), and a lignin content of 10 wt% enhanced the tensile strength up to 58.4 MPa (i.e., +45% compared to neat PA6) without compromising the ductility. Finally, UL-94 tests revealed an improvement in flame retardancy at higher lignin contents due to the intrinsic char-forming ability of this filler. These results demonstrated that lignin could be an effective multifunctional bio-based filler that can improve the thermo-mechanical performance of PA6 without the need for compatibilizing agents. Full article

The recycling of polyamide 6 (PA) and elastane (EL) from post-consumer textiles is increasingly relevant for sustainable materials development. This study investigates blends obtained from a commercial PA fabric containing 16% EL, processed via extrusion under various conditions to evaluate the influence of temperature, screw type, and speed on phase morphology and thermo-mechanical performance. The results demonstrate that processing parameters, particularly temperature, significantly affect melt viscosity and the final mechanical properties of the blends. Enhanced ductility was observed in all recycled samples compared to pure PA, indicating that mechanical recycling is a promising strategy for PA/EL textile waste. These findings support the feasibility of this approach, while highlighting the need for further research into compatibilization techniques and industrial scalability. Full article

To ensure the viability of polymer materials, given the properties and limitations of polymers, hybrid materials have been developed that blend the features of all included components. Researchers have not explored the impacts of the length aspect ratio of nanofillers on the mechanical properties of hybrids in great detail previously. Multi-walled carbon nanotubes are a valuable option because they exhibit improved mechanical properties. Using numerical simulation, the impacts of nanofiller content and the size aspect ratio on two base materials—polyamide 6, polyoxymethylene—and their blends, were determined as a function of the volume ratio, the MWCNTs aspect ratio and the base material blend composition. Numerical analysis employed the ANSYS Material Designer. Random samples of chopped-fibre representative volume elements were generated, meshed and analysed by finite element analysis to obtain the Young’s modulus and Poisson’s ratio for each sample. The results showed a generally linear dependence. Rises in both aspect ratio and volume fraction of MWCNTs increased the Young’s modulus up to 46% and decreased the Poisson’s ratio up to 1.6%. The findings suggest that although the impact of the aspect ratio is not as large as that of the volume ratio, longer MWCNTs are preferable. Full article

Melamine polyphosphate (MPP) is a widely employed additive-type flame retardant for polyamide 6. Generally, a higher loading of MPP leads to improved flame retardancy of polyamide 6 composites. Nevertheless, excessive addition tends to cause problems such as flame-retardant migration, leakage, and exudation. Against this background, this work focuses on covalently grafting melamine polyphosphate onto the surface of carbon nanotubes via a facile chemical reaction, with the aim of alleviating the migration and leakage of the flame retardant in the polyamide 6 matrix. Carbon nanotubes (CNTs) were surface modified with a silane coupling agent (KH560) to obtain CNTs bearing epoxy groups (CNT-KH560). Subsequently, a ring-opening addition reaction was conducted between the CNT-KH560 and melamine polyphosphate (MPP) yielding carbon nanotubes with surface-bonded flame-retardant MPP (CNTM). Polyamide 6 composite slices (PA6/CNTM) were prepared via twin-screw extrusion blending and compounding and then by hot-press molding into test specimens. The modified carbon nanotubes were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The results confirmed the successful grafting of MPP onto the carbon nanotube surface, with a grafting degree of 9.1 g/100 g measured. The flame retardancy of the PA6/CNTM composites were evaluated through UL 94 vertical burning and limiting oxygen index (LOI) tests and cone calorimeter. These flame retardancy results indicated that when the content of flame-retardant-modified carbon nanotubes was 10 wt%, the PA6/CNTM10 composites achieved UL 94 V-2 and the limiting oxygen index increased from 24.5% of pure PA6 to 29.1%. The PHRR value of pure PA6 decreased from 750 kW/m² to 614 kW/m². This design of surface-grafted flame retardant provides a new strategy for the preparation and application of high-performance polyamide 6 flame-retardant composites. Full article

The impact modification of polyamide 6 (PA6) using maleic anhydride-grafted ethylene/1-octene copolymers (EOR-g-MAH) involves a trade-off between improved compatibilization, grafting-induced changes in modifier molecular weight $MW$, and melt processability. In this study, EOR modifiers with comparable initial $MW$ but different octene contents ($c_{\mathrm{o}\mathrm{c}\mathrm{t}}$ = 13, 15, and 16 mol%) were grafted to two MAH levels ($c_{\mathrm{M}\mathrm{A}\mathrm{H}}$ = 0.5 and 1.0 wt%) and incorporated into PA6 at a fixed composition. The system was designed to maintain a comparable microstructure, enabling the isolation of grafting-induced changes in modifier properties from microstructural effects. $MW$ distributions were analyzed by gel permeation chromatography, and the impact behavior was evaluated over a wide temperature range, using an instrumented Charpy impact test. The results reveal a strong, interrelated, $c_{\mathrm{o}\mathrm{c}\mathrm{t}}$- and $c_{\mathrm{M}\mathrm{A}\mathrm{H}}$-dependent competition between β-scission and cross-linking during grafting, which governs the modifier’s $MW$ distribution and particle strength. Higher $c_{\mathrm{o}\mathrm{c}\mathrm{t}}$ (15 and 16 mol%) enhances the impact performance up to ≈0 °C, well above the brittle–ductile transition temperature (BDTT), through increased elastic and plastic deformation capability of the modifiers. At elevated temperatures, however, successive melting of the modifiers leads to a loss of particle strength. At high $c_{\mathrm{o}\mathrm{c}\mathrm{t}}$ and $c_{\mathrm{M}\mathrm{A}\mathrm{H}}$ = 1.0 wt%, susceptibility to β-scission increases, leading to $MW$ reduction that, for $c_{\mathrm{o}\mathrm{c}\mathrm{t}}$ = 16 mol%, is detrimental to impact performance, particularly above the BDTT. This effect is further amplified by reduced ductility due to stronger polar intermolecular interactions at high grafting levels. A moderate $c_{\mathrm{M}\mathrm{A}\mathrm{H}}$ = 0.5 wt% and $c_{\mathrm{o}\mathrm{c}\mathrm{t}}$ = 15 mol% provides an optimal compromise between strength and ductility, delivering high impact strength across a broad temperature range. At this $c_{\mathrm{M}\mathrm{A}\mathrm{H}}$ level, the number of PA6 chains covalently anchored to the modifier particles is moderate, resulting in lower compound viscosity and supporting favorable melt processability. Full article

The impact modification of polyamide 6 (PA6) using maleic anhydride grafted ethylene/1-octene copolymers (EOR-g-MAH) is well-established, yet the isolated influence of intrinsic modifier parameters—specifically octene content $c_{\mathrm{o}\mathrm{c}\mathrm{t}}$ and molecular weight $MW$—remains insufficiently understood due to confounding microstructural effects. This study presents a systematic approach to decouple these variables by maintaining constant grafting degree, modifier content, and compound morphology. A series of PA6/EOR-g-MAH compounds was prepared with controlled variations in $c_{\mathrm{o}\mathrm{c}\mathrm{t}}$ (8–15 mol%) and $MW$ (34–42 kg/mol). Instrumented Charpy impact testing across a temperature range from −40 °C to +23 °C enabled quantification of crack initiation and propagation energies ($E_{\mathrm{i}\mathrm{n}\mathrm{i}\mathrm{t}}$ and $E_{\mathrm{p}\mathrm{r}\mathrm{o}\mathrm{p}}$), providing mechanistic insight into the brittle–ductile transition. Complementary thermal, rheological, and tensile analyses of the modifiers revealed how $c_{\mathrm{o}\mathrm{c}\mathrm{t}}$ governs cavitation behavior and low-temperature toughness, while $MW$ in particular influences particle integrity and energy dissipation at elevated temperatures. The results demonstrate that targeted adjustment of $c_{\mathrm{o}\mathrm{c}\mathrm{t}}$ and $MW$ allows for the precise tuning of brittle–ductile transition temperature (BDTT) and impact resistance. The compound containing a high-$MW$ modifier with intermediate $c_{\mathrm{o}\mathrm{c}\mathrm{t}}$ (13 mol%) exhibited the most favorable balance of toughness and strength retention at elevated temperatures. These findings offer design principles for engineering thermoplastics with enhanced performance across broad service conditions. Full article

This research investigated the feasibility of 3D-printed external fixator (EF) rings made from carbon fiber reinforced polyamide 6 (PA6-CF) as an alternative to the conventional metallic counterpart. The study integrated tensile testing with digital image correlation (DIC) in as-printed and cold plasma-sterilized conditions, finite-element analysis (FEA) under wire loading, topology optimization for material and energy reduction, and evaluation of printability limits for large PA6-CF rings. The average Young’s modulus was 4.76 GPa and the maximum tensile strength was 60.5 MPa for as-printed samples, decreasing by 6.4% and 10.4% after sterilization, respectively. Using these properties as model inputs, FEA predicted safety factors larger than 1.42 for all configurations under 1000 N wire pretension, while topology optimization targeted up to 50% mass reduction without compromising ring stiffness. The study also revealed challenges in the printability of PA6-CF for large and thin components, including dimensional contraction, significant warping and moisture-induced defects, requiring an experienced 3D printer operator. Full article

Polyamide 6 (PA6) is limited in its application in precision and high-temperature fields due to its high moisture absorption, low heat resistance, and poor barrier properties. To overcome these intrinsic deficiencies, a rigid 9-(carboxyphenyl)carbazole-based diacid monomer (CzIPA) was incorporated into the PA6 backbone via one-step melt polycondensation. Structural analyses confirmed successful copolymer formation and effective modulation of hydrogen-bonding interactions and chain rigidity. The introduction of the bulky carbazole units markedly enhanced the thermal and physical properties of PA6. The glass transition temperature increased by up to 35.5 °C, while the maximum decomposition temperature rose by 23.8 °C, reflecting the reduced chain mobility and strengthened thermal resistance. The decreased amide-group density led to a 15% reduction in water absorption, improving dimensional stability. The Young’s modulus, flexural strength, and flexural modulus of the prepared copolymers were significantly improved compared to PA6, while the toughness was slightly reduced. Furthermore, oxygen and water-vapor permeabilities were simultaneously reduced by 30–35%, attributed to restricted diffusion pathways in the modified microstructure. Despite the increased rigidity, the copolymers maintained good melt processability with clear shear-thinning behavior. This study demonstrates CzIPA copolymerization as an efficient structural design strategy for producing high-performance PA6 materials with enhanced thermal stability, lower hygroscopicity, and superior barrier properties. Full article

The present study explores the possibility of combining membrane concentration, spray drying, and low-temperature precipitation into a single process for the valorization of spent lavender biomass as a source of ingredients rich in antioxidants. Lavender spent plant material was subjected to solid–liquid extraction, and the obtained hydroalcoholic extracts were further concentrated using a dead-end membrane filtration cell (METcell) with a polyamide–urea thin-film composite X201 membrane. The feed and the obtained retentate were subsequently spray dried using a Nano Spray Dryer B-90 (BÜCHI) under different temperature conditions (120 °C and 85 °C). Low-temperature precipitation was further applied for the retentate. An eight-fold concentration of the extracts was achieved, with membrane rejection coefficients of 100% for antioxidant activity and 98.5% for dry solids content. The permeate flux ranged from 2.25 to 0.201 L·m⁻²·h⁻¹. Spray drying at a lower inlet temperature resulted in minimal losses for antioxidant activity (below 6%). The low-temperature storage of the membrane concentrate led to clear phase separation, allowing for the recovery of a precipitated fraction. The obtained results demonstrate that the integrated approach may support the sustainable and scalable valorization of lavender by-products. Full article

This study explored, for the first time, the simultaneous dyeing and functionalization of textiles using enzymatically synthesized mixtures of phloridzin and esculin oligomers. Initial screening using multifiber fabric containing diacetate, cotton, polyamide, polyester, polyacrylonitrile, silk, viscose, and wool revealed that the oligomers successfully imparted color and high antioxidant activity to cotton, polyamide, and viscose. These three materials were therefore selected for determination of key process parameters’ influence, including temperature (35 °C and 75 °C), reaction time (6 h and 19 h), and oligomers’ concentration (1.5 and 3.0 mg/mL). Treated fabrics were evaluated for color strength (K/S), antioxidant activity, and prebiotic capacity (in vitro stratum corneum model), with all properties assessed before and after washing. The results showed that several functionalized fabrics retained coloration and functionality after washing, while fabrics functionalized with esculin oligomers’ mixture showed strong prebiotic capacity. Overall, the polyamide that functionalized with 3.0 mg/mL esculin oligomers for 19 h at 35 °C was identified as a promising candidate for reusable colored textiles, including dermatology-oriented garments for sensitive or atopic skin, sportswear, protective workwear, and daily use functional items such as hygienic pads or cloth liners. These findings demonstrate the feasibility of developing textiles with targeted prebiotic functionality. Full article

Thermoplastic carbon fiber-reinforced polymer (CFRP) composites possess the intrinsic capability to heal delamination and matrix cracks via thermal re-melting. However, under impact loading, they are prone to severe fiber fracture, which significantly compromises their repairability. To address this, this study introduced polytetrafluoroethylene (PTFE) films as pre-set interlaminar defects within continuous carbon fiber-reinforced polyamide 6 (CF/PA6) thermoplastic cross-ply laminates. Low-velocity impact tests were conducted at varying energy levels to comparatively investigate the impact response and damage mechanisms of the CFRPs with and without embedded defects. Experimental results indicate that the embedded interlaminar defects triggered a transition in the failure mode of the CFRP from brittle fracture to progressive damage behavior. Compared to the baseline laminates, the specimens with embedded defects maintained higher flexural stiffness under low-energy impact. Furthermore, they effectively reduced the extent of fiber breakage by dissipating impact kinetic energy through extensive delamination, interlaminar frictional sliding, and plastic micro-deformation. These findings verify the feasibility of achieving macroscopic pseudo-ductility through interlaminar microstructural tailoring. This research provides an experimental basis and methodological support for the pseudo-ductile design of thermoplastic composites. Full article

This study investigates the acid dyeing of Polyamide 6 (PA6) fabric by comparing conventional heating and microwave-assisted techniques. The influence of critical process parameters—namely pH, temperature, dyeing time, and dye concentration—on color strength (K/S) was systematically evaluated using C.I. Acid Blue 324. Results indicated an inverse correlation between pH and K/S for both methods, with the maximum color yield achieved at pH 3.0. While dye uptake improved with increasing temperature, time, and concentration in both systems, the microwave-assisted approach (160 W) significantly accelerated the process. Optimal conditions for conventional dyeing were established at pH 3, 95 °C, and a 30 min reaction time with 1.5% dye concentration. In contrast, the microwave-assisted process reached equivalent exhaustion levels in only 10 min under otherwise identical conditions. The findings confirm that microwave-assisted dyeing is a rapid, energy-efficient, and sustainable alternative for PA6 processing, offering substantial reductions in production time. Full article

Global concerns regarding microplastics emerging in the environment have been raised recently. Using samples collected during the OceanXplorer mission in Aqaba, we explored the depth-based and regional variations of microplastics across pelagic and benthic zones. Microplastics (63.0–950.0 μm) from the surface seawater, middle seawater, bottom seawater, and deep-sea sediment were quantified and identified using a dissecting microscope and Fourier Transform Infrared microscope (μ-FTIR). The results revealed that the average abundance of microplastics was 6.7 ± 6.05 particles L⁻¹ in the pelagic zone and 2900 ± 1650 particles kg⁻¹ in the benthic zone. A size gradation of microplastics was observed across depths from 5 to 840 m, accompanied by a shift in particle types: fragments were the most common in the benthic zone, whereas fibers dominated the pelagic zone. μ-FTIR analysis identified the presence of the following polymers: polyethylene (PE), polyvinyl chloride (PVC), polyamide 6 (PA 6), and polypropylene (PP). These findings establish baseline data for future monitoring and management efforts addressing microplastic pollution in the Gulf of Aqaba. Full article

The global crisis concerning multidrug-resistant microorganisms necessitates the development of innovative antimicrobial strategies that avoid conventional antibiotics and overcome the toxicity and environmental persistence associated with traditional metal-based biocides. This work aims to develop safe and sustainable antibacterial filtration materials by integrating cationic hyperbranched polymer dendrimers (HBP) into electrospun nanofibers. Cationic HBPs were successfully embedded into recycled polyamide 6 nanofibers using industrial needleless electrospinning. Filtration efficiency, assessed against a 0.3 µm paraffin oil aerosol according to EN 149:2001, consistently exceeded 99.8%, meeting and surpassing the FFP3 classification threshold while maintaining low air resistance. The HBP-functionalized nanofibers exhibited pronounced contact-active antibacterial activity against Staphylococcus aureus and Escherichia coli. Quantitative plate count assays confirmed viability reductions of up to 74.1% after 2 h of co-incubation. Crucially, the absence of inhibition zones in agar diffusion tests confirmed that the active polymer was stably embedded within the nanofiber matrix and did not leach. Comprehensive toxicological tests, including cell line and 3D human skin and airway tissue models, confirmed the material’s safety for both dermal and respiratory contact. This study presents a scalable, metal-free, and environmentally responsible next-generation filtration system that combines high mechanical efficiency with active antimicrobial functionality. Full article

Polyamide 6 is an important engineering thermoplastic; however, its practical use is often constrained by its high flammability. Although aluminum diethylphosphinate is widely employed as a flame retardant for polyamide 6, its relatively slow char-forming kinetics hinders the attainment of the stringent 750 °C glow-wire ignition temperature required for electrical applications at moderate loadings. To address this limitation, a synergist was fabricated via the self-assembly of phytic acid, benzoguanamine, and ZnSO₄·7H₂O and subsequently incorporated to enhance the char-forming capability and flame retardancy of polyamide 6/aluminum diethylphosphinate composites. The results revealed that the synergist acted as an efficient charring promoter, improving flame retardancy. At a total loading of 15 wt%, the composite reached a UL-94 V-0 rating and high limiting oxygen index of 30.7%. Cone calorimetry data indicate that the peak heat release rate decreased by 34.0%, and the smoke production rate decreased by 33.3% compared with the polyamide 6/aluminum diethylphosphinate composites. Mechanistic analysis indicated that the synergist catalyzed the carbonization of the polyamide 6, enabling the formation of a dense thermally insulating char barrier in the condensed phase. Notably, the optimized formulation achieved a glow-wire ignition temperature of 750 °C, demonstrating its strong potential for high-safety electrical applications. Full article