Polyamide Matrix Research Articles

Sustainable Polyamide Composites Reinforced with Nanocellulose via Melt Mixing Process

Introduction of biomass-based nanofillers into the polyamide matrix may represent a sustainable approach for the development of high-performance engineering plastics. From this standpoint, nanocellulose, derived from various cellulosic sources, has attracted a great deal of attention because of is exceptional mechanical properties, lightweight nature, and biodegradability, which presents significant advantages over conventional inorganic fillers. However, a technical challenge arises in the industrially favorable melt processing of polyamides and nanocellulose. This challenge is associated with the thermal degradation of nanocellulose at high processing temperatures, as well as the strong tendency of nanocellulose to aggregate within the polymer matrix. This review examines recent developments to address these issues. Key approaches based on the surface treatment of nanocellulose as well as optimization of processing conditions are discussed in detail, which can provide insights on the development of nanocellulose-reinforced polyamide composites.

Ultraviolet Irradiation Surface Treatment to Enhance the Bonding Strength of Polyamide-Based Carbon Fiber-Reinforced Thermoplastic Polymers.

Adhesive bonding is a suitable joining method to satisfy the increasing industrial demand for carbon fiber-reinforced polymers without the need for a machining process. However, thermoplastic-based carbon fiber-reinforced polymers have small adhesive strength with structural thermoset adhesives. In this study, an ultraviolet irradiation surface treatment was developed to improve the adhesive bonding strength for polyamide-based carbon fiber-reinforced polymer. The type of ultraviolet wavelength, irradiation distance and irradiation time were optimized. Surface treatment with simultaneous UV irradiation of 185 nm and 254 nm wavelength generated unbound N-H stretching that was capable of chemical bonding with epoxy adhesives through a photo-scission reaction of the amide bond of polyamide matrix. Therefore, ultraviolet irradiation treatment improved the wettability and functional groups of the polyamide-based carbon fiber-reinforced polymers for adhesive bonding. As a result, the adhesive strength of the polyamide-based carbon fiber-reinforced polymers was increased by more than 230%.

Upcycling end-of-life carbon fiber in high-performance CFRP composites by the material extrusion additive manufacturing process

Each year, a significant amount of waste is produced from carbon fiber polymer composites at the end of its lifecycle due to extensive use across various applications. Utilizing regenerative carbon fiber as a feedstock material offers a promising and sustainable approach to additive manufacturing based on materials. This study proposes the additive manufacturing of recycled carbon fiber with a polyamide-12 polymer composite. Filaments of recycled carbon fiber-reinforced polyamide-12 (rCF-PA12) with different recycled carbon fiber contents (0%, 10%, and 15% by weight) in the polyamide-12 matrix are developed. These filaments are utilized for 3D printing of specimens by using various infill density parameters (80% and 100%) on a fused deposition modeling 3D printer. The study examined how the fiber content and infill densities influenced the flexural performance of the printed specimens. Notably, the part containing 15 wt% recycled carbon fiber (rCF) composites showed a significant improvement in flexural performance due to enhanced interface bonding and effective fiber alignment. The results indicated that reinforcing the printed part with 10% and 15 wt% recycled carbon fiber (rCF) improved the flexural properties by 49.86% and 91.75%, respectively, compared to the unreinforced printed part under the same infill density and printing parameters. The investigation demonstrates that the additive manufacturing-based technique presents a potential approach to use carbon fiber-reinforced polymers waste and manufacture high-performance engineering, economic, and environmentally friendly industrial applications with the complicated design using different polymer matrices.

High-flux polyamide nanofiltration membranes tuning by polydopamine-modified boron nitride nanosheets: Accelerating Mg2+/Li+ separation

As a promising technology for lithium extraction from salt lakes, nanofiltration membranes still face challenges in balancing between permeability and selectivity. In this paper, highly dispersed functionalized boron nitride nanosheets (BNNSs-NH2) were prepared by modifying exfoliated boron nitride nanosheets (BNNSs) with polydopamine, which were incorporated into a polyamide (PA) layer by aqueous phase conditioning to prepare positively charged polyamide nanofiltration membranes. Scanning electron microscopy (SEM) showed that the PDA nanoclusters on the surface of the BNNSs can disrupt the regular stacking parallel to the membrane surface. Energy spectrum (EDS) of SEM and X-ray photoelectron spectroscopy (XPS) etching further revealed that BNNSs-NH2 were dispersed within PA layer, creating transmembrane channels for molecular diffusion. The results showed a pure water permeance of 8.55 ± 0.24 L/m2 h bar, indicating that the stabilized intercalation of BNNSs-NH2 in the PA layer synergistically improved the water permeability. Meanwhile, the retention rate of MgCl2 remained at 94 %, which was attributed to the enhanced compatibility between BNNSs-NH2 and polyamide matrix by the polydopamine coating (PDA) on the surface, as well as the Dornan effect repulsion by the enhanced positive charge on the membrane surface. After the three-stage nanofiltration of membrane, the Mg2+/Li+ ratio decreased from 50 to 0.12. Overall, this method balances permeability and selectivity by adjusting pore size and positive charge, potentially offering new ideas and insights for the preparation and development of nanofiltration membranes for Mg2+/Li+ separation.

Sustainable preparation of nano monodispered ATP based color master batch and its application in PA6

AbstractAs a representative of dope‐dye, the color masterbatch method has been widely applied in modern dyeing processes, while it has difficulties in solving the dispersibility of inorganic pigments color master batch in the polymer matrix. In this work, attapulgite (ATP) was used as the adsorption carrier of inorganic pigments to prepare color‐dyed attapulgite (CD‐ATP). The selected environmentally friendly inorganic pigments were well adsorbed by ATP in KOH aqueous solution, and could stably be monodispersed in KOH aqueous solution for more than 168 h. Moreover, the KOH aqueous solution could be reused repeatedly, thereby, a sustainable method to prepare novel CD‐ATP was realized. By blending the as‐prepared CD‐ATP with polyamide‐6 (PA6), a series of dope‐dyed colorful PA6 composites was prepared. Scanning electron microscope (SEM) results indicated that the CD‐ATP was still monodispersed in the PA6 matrix, and endowed PA6 with a vivid color. Further studies show that the adding of CD‐ATP had little influence on the properties of PA6, but significantly reduced the water adsorption. This novel color‐dyed ATP has potential implications in making paper‐making blankets and is highly expected to have more extensive applications in many fields of life.

In Situ Growth of Highly Compatible Cu2O-GO Hybrids Via Amino-Modification for Melt-Spun Efficient Antibacterial Polyamide 6 Fibers.

Polyamide 6 (PA6) fiber has the advantages of high strength and good wear resistance. However, it is still challenging to effectively load inorganic antibacterial agents into polymer substrates without antimicrobial activity. In this work, graphene oxide is used as a carrier, which is modified with an aminosilane coupling agent (AEAPTMS) to enhance the compatibility and antimicrobial properties of the inorganic material, as well as to improve its thermal stability in a high-temperature melting environment. Cuprous oxide-loaded aminated grapheme (Cu2O-GO-NH2) is constructed by in situ growth method, and further PA6/Cu2O-GO-NH2 fibers are prepared by in situ polymerization. The composite fiber has excellent washing resistance. After 50 times of washing, its bactericidal rates against Bacillus subtilis and Escherichia coli are 98.85% and 99.99%, respectively. In addition, the enhanced compatibility of Cu2O-GO-NH2 with the PA6 matrix improves the orientation and crystallinity of the composite fibers. Compared with PA6/Cu2O-GO fibers, the fracture strength of PA6/Cu2O-GO-NH2 fibers increases from 3.0 to 4.2 cN/dtex when the addition of Cu2O-GO-NH2 is 0.2wt%. Chemical modification and in situ concepts help to improve the compatibility of inorganic antimicrobial agents with organic polymers, which can be applied to the development of medical textiles.

Insight into profiled CNT/polymer interphase: A molecular dynamic simulation study of load transfer and shock response

In this paper, by utilising molecular dynamic simulations, profiled carbon nanotubes (CNT), represented by CNT containing bead and spiral structure, were built from warping graphene layers with carefully introduced defects. The tensile behaviour of profiled CNTs, pulling and shock response of profiled CNTs within the polyamide matrix were investigated and compared to the corresponding conventional CNT. The result indicates that as mechanically interlocked with the matrix, profiled CNT could effectively relieve the stress concentration during load transfer by distributing the stress into a larger part of the matrix. In this case, a more efficient load transfer could be achieved, thus contributing to the mechanical performance of the composite without modification of the chemical structure. However, the profiling geometry, which is shaped by defects, will introduce stress concentration within the profile CNTs when subject to a tensile load. The stress concentration may not only deteriorate the tensile performance of CNTs, such as ultimate load at break and modulus but also result in an earlier deformation. In this case, care should be taken during the design phase of the profiled CNT. For shocking responses, profiled CNTs were capable of constraining the local chain move thus contributing to the integrity of the composite system during shockwave propagation.

Enhancing flame retardancy and heat insulation performances of polyamide 66 composite film by adding CNC/Al2O3 nanohybrids

Polyamide 66 (PA66) has garnered significant attention due to its exceptional properties; unfortunately, its flammability is challenging. Adding flame retardants (FRs) is a primary approach to enhance PA66 flame retardancy. This study developed a highly flame-retardant PA66 composite film by adding corn-like functional nanohybrids (CNC/Al2O3). Interestingly, CNC/Al2O3 nanohybrids not only formed hydrogen bond interactions with PA66 but also improved crystallization properties as heterogeneous nucleating agents, resulting in the excellent mechanical properties of PA66 composite film. Remarkably, the incorporation of 3 wt% CNC/Al2O3 nanohybrids into PA66 matrix contributed to increasing the LOI to 28.5 %. The pHRR, THR, and TSR were reduced obviously by 55.7 %, 15.3 %, and 65.2 %, respectively. The excellent flame retardancy of PA66 composite film was attributed to the forming of a compact carbon layer catalyzed by the CNC/Al2O3 nanohybrids. Besides, the homogeneous distribution of CNC/Al2O3 nanohybrids endowed the composite film with excellent heat insulation, and the heat insulation rate was up to 31.9 %. Thus, such PA66 composite films with excellent flame retardancy, heat insulation, and mechanical properties could meet the broader application requirements.

Macromolecular PEI-modified carbon nanotubes as multifunctional additives in controlling crystallization and enhancing comprehensive performance of polyamide 6 nanocomposites

Despite the promising potential of carbon nanotubes (CNTs) in polymer nanocomposites, their propensity for aggregation and random dispersion within the polymer matrix poses significant challenges. This study introduces a novel approach to enhance the interfacial properties between the CNTs and the polyamide 6 (PA6) matrix by anchoring the polyethyleneimine (PEI) onto the CNT surfaces. The integration of PEI, with abundant amino groups, provides the high density of nucleation sites, facilitating transcrystallization along the surfaces of the macromolecular polyethyleneimine (PEI) modified CNTs (m-CNTs). This transcrystallization process enhances the physical interactions between the m-CNTs and the PA6 matrix, resulting in the substantial improvements in the mechanical properties of the PA6 nanocomposites. Specifically, as compared to the neat PA6, the PA6/m-CNT nanocomposites exhibited the increase of 131.2 % and 54.3 % in tensile strength and Young's modulus, respectively. Additionally, the intimate contact between the embedded CNTs forms the efficient thermally conductive networks. The robust molecular interactions between the m-CNTs and the PA6 polymer chains promote the highly homogeneous dispersion within the PA6/m-CNT nanocomposites, thereby reducing the thermal resistance. This straightforward and effective method presents a viable strategy for improving the interfacial properties of the CNTs reinforced polymer nanocomposites, offering the extensive potential for the future advancements in the interfacial modifications of the polymer matrix nanocomposites.

Structure-property correlations study in biochar-enhanced polyamide composites for sustainable materials development

This study explores the synthesis and characterization of polyamide/biochar composites via in situ polymerization of 12-aminolauric acid with varying biochar concentrations. The motivation behind this research is to enhance the properties of polyamide 12 (PA12) by integrating biochar, a sustainable material derived from biomass, to improve both performance and environmental impact. A detailed structure-property correlation analysis was conducted to assess the effects of biochar on PA12's morphology, mechanical behavior, crystallinity, thermal stability, viscoelastic performance, and environmental sustainability. Key findings include successful PA12 synthesis, confirmed by FTIR and 1H NMR spectroscopy. Increased biochar content led to a decrease in molecular weight and an increase in crystallinity from 27 % to 38 %, suggesting enhanced nucleation effects. SEM analysis showed excellent dispersion and compatibility of biochar within the PA12 matrix, leading to significant improvements in tensile strength (from 38 ± 1 MPa to 54 ± 2 MPa) and modulus (from 745 ± 30 MPa to 2055 ± 65 MPa). Rheological tests demonstrated shear-thinning behavior, facilitating effective extrusion-based 3D printing of a complex object with 50 wt% biochar. A life cycle assessment revealed substantial environmental benefits, including a net reduction of 1.83 kg·CO₂ equiv.·kg⁻1 due to the use of biochar derived from wood pyrolysis. These findings highlight the potential of PA12/biochar composites as environmentally sustainable structural materials, combining enhanced functional properties with significant ecological advantages.

Polyfunctional Arylamine Based Nanofiltration Membranes with Enhanced Aggressive Organic Solvents Resistance.

Organic solvent nanofiltration (OSN) membranes with high separation performance and excellent stability in aggressive organic solvents are urgently desired for chemical separation. Herein, we utilized a polyfunctional arylamine tetra-(4-aminophenyl) ethylene (TAPE) to prepare a highly cross-linked polyamide membrane with a low molecular weight cut-off (MWCO) of 312 Da. Owing to its propeller-like conformation, TAPE formed micropores within the polyamide membrane and provided fast solvent transport channels. Importantly, the rigid conjugated skeleton and high connectivity between micropores effectively prevented the expansion of the polyamide matrix in aggressive organic solvents. The membrane maintained high separation performance even immersed in N,N-dimethylformamide for 90 days. Based on the aggregation-induced emission (AIE) effect of TAPE, the formation of polyamide membrane can be visually monitored by fluorescence imaging technology, which achieved visual guidance for membrane fabrication. This work provides a vital foundation for utilizing polyfunctional monomers in the interfacial polymerization reaction to prepare high-performance OSN membranes.

Molecular Dynamics Simulations of Gas Transport Properties in Cross-Linked Polyamide Membranes: Tracing the Morphology and Addition of Silicate Nanotubes.

This study employs molecular dynamics (MD) simulations to fundamentally provide insight into the role of cross-link density in the CO2 separation properties of interfacially polymerized polyamide (PA) membranes. For this purpose, two atomistic models of pure polyamide membranes with different cross-link densities are constructed by MD simulations to conceptually determine how the fractional free volume of polyamide affects the gas separation performance of the membrane. The PA membrane with a lower cross-link density (LCPA) shows a higher gas diffusion coefficient, a lower gas solubility coefficient, and a higher gas permeability than the PA membrane with a higher cross-link density (HCPA). Moreover, the pristine and modified silicate nanotubes (SNTs) as the fast gas transport channels are incorporated into the polyamide membranes to assess the effect of the SNT/PA interface chemistry on the CO2 separation properties of the membranes. SNTs are systematically modified by three modifying agents with different CO2-philic groups and different interfacial interaction energies with the polyamide matrix. The results of MD simulations demonstrate that the incorporation of silicate nanotubes into the PA matrix increases the gas diffusivity and permeability and decreases the CO2/gas selectivity. Moreover, the membranes containing modified SNTs possessing high CO2-philicity and high SNTs/PA interfacial interactions show a high CO2 separation performance.

Boosting polyamide 6: a comparative study on graphene and graphene oxide for improved mechanical and thermal properties

ABSTRACT This study investigates the impact of incorporating graphene (G) and graphene oxide (GO) on the mechanical and thermal properties of polyamide 6 (PA6) composites. We employ a melt-extrusion process to achieve homogeneous dispersion of varying G and GO loadings (1.0–5.0 wt%) within the PA6 matrix. Notably, 2.0 wt% of both G and GO achieve excellent dispersion, leading to significant enhancements in the degradation temperature and a reduction in the thermal decomposition rate of the PA6 blends. Compared to the neat PA6, these composites exhibit improved (mention specific mechanical properties observed, e.g. tensile strength, modulus). This research establishes a novel and cost-effective approach to improve the processability, mechanical properties, and thermal stability of PA6, making it a valuable contribution for applications demanding high performance.

Development of Eco-Efficient Composite from Textile Waste with Polyamide Matrix.

The main aim of the present work is to evaluate and characterize the mechanical, morphological and thermal properties of wastes coming from the textile industry, mainly composed of cotton and polyester. These wastes will be thereafter implemented in commodity plastic such as polyamide, in order to develop new formulations of environmentally friendly materials. The composites were produced by extrusion and injection-molded processes in amounts between 15 wt.% and 60 wt.% of textile waste. With the objective of improving the properties of the materials, silanes were used as a compatibilizer between the textile fibers and the polymeric matrix. The effect of the compatibilizer in the composites was studied together with the effect of the amount of textile fiber added to the composites. Mechanical, thermal, morphological and wettability properties were analyzed for each composite. The results show that the use of silanes improves the interaction especially in those composites with a higher amount of textile waste, offering a balanced mechanical behavior with significantly high quantities. On the other hand, the melting temperature does not vary significantly with the introduction of silanes and textile waste content, although the incorporation of textile waste slightly reduces up to 23% the degradation temperature of the resulting composites. The wettability of the composites is also increased up to 16% with the incorporation of textile waste. Finally, the appearance of the composites with textile waste is strongly influenced by the incorporation of the reinforcement, offering shades close to dark brown in the whole range of compositions.

Carbon nanotubes/α-ZrP sheets for high mechanical performance and flame-retarding polyamides using selective laser sintering

ABSTRACT The current study presents a facile approach to synthesis carbon nanotube-anchor α-ZrP (CNT@α-ZrP) nanohybrid for multifunctional polyamide 12 (PA12) composites via ball-milling followed by selective laser sintering (SLS) process. Herein, CNTs serve dual roles; firstly, they act as a pigment, imparting black colouration to both PA12 powder and α-ZrP sheets, facilitating rapid light absorption and heating. Secondly, CNTs complement α-ZrP sheets to reinforce the PA12 matrix for strong and functional structures. The dominant filler content is α-ZrP nanosheets in PA12 powder to study the functionality of α-ZrP sheets in SLS-PA12 composites. CNT@α-ZrP hybrid enhances mechanical, tribological, corrosion resistance and flame-retarding properties of PA12 composite parts. PA12/CNT@α-ZrP composite exhibited 98.9%, 33.1%, and 34.6% increments in Young's modulus, tensile strength and impact strength, respectively. To predict the response of the composites across a range of applications, the constants for different hyperelastic models describing their mechanical behaviour were determined. The coefficient of friction and wear rate of the sintered composite parts were reduced significantly. Additionally, 1 wt% CNT@α-ZrP reduced smoke production rate and total smoke production by 36.5% and 13.8%, respectively along with a 2.2- fold increment in time-to-ignition. The work presents an industrial method to develop strong and functional intricate structures via SLS.

Nanofiller‐and basalt fiber‐reinforced recycled polyamide 6 hybrid composites

AbstractThe influence of nanofillers (cellulose nanofibers (CNF) and halloysite nanotubes (HNTs)), and basalt fibers (BF) on the morphology, mechanical and thermal of recycled polyamide 6 (PA6) composites were investigated through scanning electron microscopy (SEM), mechanical testing, rotational rheometry, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). CNF, HNTs and BF were relatively well‐dispersed in the PA6 matrix and the incorporation of these nanofillers and BF increased the strength of the matrix, which indicates a good dispersion of the nanofillers and BF. CNF and HNTs‐filled PA6 nanocomposites increased the tnsile strength by 14% and 6% compared to the neat PA6, respectively. The composites elongation at break decreased with nanofiller, BF and combined nanofillers and BF. The shear storage modulus values of PA6/20B5C, PA6/20B5H, and PA6/25B are significantly elevated compared to neat PA6, with increases of 3.7, 2.8, and 2.5 times, respectively, at an angular frequency of 100 rad/s. PA6/20B5H composites with 20 wt.% BF and 5 wt.% HNTs exhibited the highest storage modulus (9.5 GPa) from the DMA study. Thermal stability and ash content at 800°C increased with the incorporation of HNTs and BF. The DSC findings showed that the glass transition (Tg) and melting temperature (Tm) of the composites did not exhibit any notable changes when nanofillers and BF were added to the resin. The nucleation ability of PA6 was enhanced attributable to BF and hybridization of BF and nanofillers since the crystallization temperatures of PA6 in BF filled and hybrid composites were around 5°C greater than neat PA6. The results suggest hybrid composites with potential environmental characteristics and higher mechanical properties can be utilized in semi‐structural applications in automotive and construction as a sustainable and lightweight alternative to steel and other materials.Highlights The addition of HNTs, CNF, BF and hybridization of nanofillers with BF reduced the brittleness of PA6. Nanoreinforced and hybrid PA6 composites achieved higher storage modulus than neat PA6. Thermal stability and ash content increased with the incorporation of HNTs and BF. The hybrid composites have a higher complex viscosity compared to PA6. The sustainable hybrid composites can be utilized in automotive and construction industries.

The effect of printing parameters on the mechanical properties of fiber-reinforced PA6 matrix composites in material extrusion-based additive manufacturing

PurposeThis study aims to understand the effect of the use of different proportions and types of fibers in the polyamide 6 (PA6) matrix during material extrusion-based additive manufacturing (MEX) and the effect of the manufacturing parameters on the mechanical properties. The mechanical, thermal and morphological properties of PA composites that are reinforced with carbon fiber (CF), glass fiber (GF) and as well as hybrid fiber (HF) were investigated.Design/methodology/approachIn this study, the effect of nozzle temperature and layer thickness on the mechanical properties of composite samples was investigated in terms of their behavior under tensile, impact and compression loads, manufacturing parameters as well as fiber ratio and type. The results were also consolidated by scanning electron microscopy.FindingsAt 20 Wt.% CF reinforcement PA6 samples, a tensile strength value of 125 MPa was obtained with a 60% increase in tensile strength value compared to neatPA6. The HF-reinforced ones also measured a tensile strength value of 106.69 MPa. This corresponds to an increase of 38% compared to neatPA6. The results also show that HF reinforcement can be an important component for many composites and a suitable material for use under compression loading.Originality/valuePA6, an engineering polymer, can be produced by MEX, which offers several advantages for complex geometries and customized designs. There are studies on different carbon and GF ratios in the PA6 matrix. Using these fibers together in a HF, the examination of their mechanical properties in the MEX method and the examination of the effect of GF reinforcement in the hybrid structure, which has a cost-reducing effect, has been an innovative approach. In this study, the results of the optimization of the parameters affecting the mechanical properties in the production of samples reinforced with different ratios and types of fibers in the PA6 matrix by the MEX method are presented.

A macromolecular flame retardant for polyamide 6 and its filaments with enhanced fire safety, tensile and UV-blocking performance

In the pursuit of enhancing the fire safety of polyamide 6 (PA6), the addition of flame retardants generally leads to hydrogen bond dissociation, which results in detrimental effects on the mechanical properties of PA6 composites and impedes processing and application in the textile field. In this study, a macromolecular flame retardant, PPB, designed with hydrogen bond donor-acceptor spacing aligned with PA6, was synthesized to increase the number of hydrogen bonds. The addition of 10 wt% PPB to the PA6 matrix (PA6/PPB10) endowed the composite with the limiting oxygen index (LOI) increased to 31.6 % and V-0 rating in the vertical burning (UL-94) test. PA6/PPB10 also exhibited significant enhancement in tensile strength by 12.6 % compared to pure PA6 and demonstrated a superior ultraviolet protection factor (UPF) value of 573, greatly exceeding the value of 3 for PA6. The quenching effect, diluting effect in the gas phase, and hydrogen bond interactions between PPB and PA6 backbones imparted PA6/PPB composites with satisfactory flame retardancy and mechanical properties. As a representative example, PA6/PPB10 was melt-spun into filaments with a pleasing tenacity of 3.6 cN/dtex and self-extinguishing capability within 5 s after ignition, confirming the sustained comprehensive properties after spinning and drawing into filaments.

In‐situ preparation and performance of cellulose nanocrystals grafted with polyamide 6 composites

AbstractNylon nanocomposites were prepared by in‐situ ring‐opening polymerization to overcome the problem of poor properties due to the uneven dispersion of the nanoparticles by the traditional melt blending. This high‐performance polyamide 6 (PA6) nanocomposites with high dispersion and strong interface was prepared by grafting PA6 onto the surface of cellulose nanocrystals (CNC). The micromorphology, mechanical, crystalline and thermal properties of the composites were also investigated. Firstly, the hydroxyl group on the surface of CNC reacted with the para isocyanate of toluene diisocyanate (TDI), and the remaining ortho isocyanate was blocked by caprolactam to prepare CNC grafted with caprolactam (CNC‐g‐CL). Then CNC‐g‐CL was used as an activator to prepare cellulose nanocrystal grafted with polyamide 6 (CNC‐g‐PA6) composites by the ring‐opening polymerization of caprolactam on the CNC. The effects of different reaction temperatures, solvent amounts and molar ratios on the grafting rate of CNC‐g‐CL were investigated. The results showed that the highest grafting rate of CNC‐g‐CL with 66.7% was achieved at a reaction temperature of 45°C, 0.1 g/mL CNC in toluene, and a molar ratio of 6 for TDI/CNC. Further, different CNC‐g‐PA6 composites prepared from different CNC content and activator content were explored. For CNC‐g‐PA6 composites, CNC was uniformly dispersed in the PA6 matrix and had a good compatibility with the matrix. CNC exhibited significant reinforcement in the composites with a tensile strength of up to 108 MPa. In addition, the glass transition temperature of CNC‐g‐PA6 was increased to 92°C, which significantly improved the heat resistance of the new composites.Highlights Effects of reaction condition of CNC and TDI on DSTDI and DSCL were studied. Effects of CNC and activator content on CNC‐g‐PA6 properties were studied. CNC is uniformly dispersed in PA6 with average particle size less than 1 micron. The nylon matrix was significantly strengthened by the addition of CNC. The addition of CNC significantly improved the heat resistance of the composites.

Enhancing ion separation efficiency: Janus charged nanofiltration membrane fabricated via polyethyleneimine-manipulated interfacial polymerization

This research introduces highly efficient nanofiltration (NF) membranes designed for the effective rejection of both divalent cations and anions, a critical feature for advanced water treatment technologies. We have devised a simple yet adaptable approach for fabricating Janus polyamide (PA) thin-films characterized by dual charges, which exhibit pronounced selectivity towards both mono-/divalent anions and cations. Leveraging a straightforward interfacial polymerization (IP) process, we integrated high molecular weight polyethyleneimine (PEI) within the PA matrix. This strategy ensured the preferential formation of a dense, negatively charged upper layer dominated by piperazine (PIP), while cationic macromolecular PEI facilitated the emergence of a loose and positively charged lower layer, thus giving rise to a distinctively charged and structurally heterogeneous PA thin-film. Furthermore, the strategic inclusion of PEI inhibits the diffusion of the PIP, thereby promoting the development of nano-wrinkled structures. This structural innovation not only enhances pure water permeance (16.0 L m−2 h−1 bar−1) but also optimizes ion selectivity through the coordination of steric hindrance and Donnan effects. Consequently, the Janus charged NF membranes we developed exhibit exceptional selectivity for mono-/divalent ions, particularly demonstrating remarkable ion selectivity for Cl−/SO42− and Li+/Mg2+ of 102 and 24, respectively. Our findings introduce a pioneering avenue for fabricating NF membranes that proficiently separate mono-/divalent ions, promising significant advancements in water treatment and purification endeavors.