Polyamide Matrix Research Articles

Toward Reactive Processing of Polyamide 6 Based Blends with Polyethylene Grafted with Maleic Anhydride and Acrylic Acid: Effect of Functionalization Degree

AbstractThe reactivity of different polyethylene modifiers based on acrylic acid (AA) and maleic anhydride (MA) with polyamide 6 (PA6) is investigated, using several degrees of functionalization. The polymer blends are processed in an internal mixer and injection molded. Mechanical, rheological, infrared spectroscopy, thermal, thermomechanical properties, and morphology are evaluated. The torque rheometry results show that higher functionalization degrees favored a high reactivity with PA6. As a consequence, there is an increase in the viscosity of the polymer blends, which is reflected in the reduction of the melt flow index (MFI), compared to PA6. High impact strength and elongation at break properties confirm the blends' compatibility. The elastic modulus and the tensile strength maintain high values, suggesting a balance of mechanical properties. In addition, the polymer blends' heat deflection temperature (HDT) and thermal stability properties are comparable to neat PA6. The morphology obtained by scanning electron microscopy show dispersed and refined particles in the PA6 matrix, indicating stabilization at the interface. Incorporating only 10% of high‐density polyethylene grafted with acrylic‐acid (HDPE‐g‐AA) is very efficient in optimizing the properties of PA6, contributing to broadening the range of applications for the processing industry.

Dynamic sustainable polyamide elastomer toward ultratough and fully recyclable self-healing ionic conductors

The development of flexible ionic conductors with extreme elasticity, high ionic conductivity, desirable self-healing capacity and recyclability is a pressing need while challenging because the regulating of these performances is generally mutually exclusive. Herein, we report a dynamic double-crosslinking bio-based ionic conductive elastomer (DBICE), designed via the introduction of reversible covalent Diels-Alder motifs into a furan-functionalized biobased polyamide matrix, which realizes an ultratough, outstanding mechanical versatility (170.1 MJ m−3 toughness and 1342% elongation), unique self-healability (∼100% within 6 h), and capability to completely recycle and facilely reprocess. The specifically tailored ether-rich segments in the polyamide backbones with long-range ordering and selectively entrapped lithium-ion (Li+) provided high-efficient ion transport pathways, gaining remarkable room-temperature ionic conductivity of 1.66 × 10–3 S m−1. The resultant DBICE is assembled into a proof-of-concept flexible ionotronic sensor, exhibiting reliable resistivity sensing quality with high sensitivity and robust mechanosensation capability, and excellent recovery for the polymeric matrices and electronic components. This work provides a new molecular design principle for the sustainable development of advanced ionic conductors holding a great promise in wearable electronics or all-solid-state batteries.

Anisotropy and ageing effect on the mechanical behaviour of 3D-printed short carbon-fibre composite parts

The effect of ageing and anisotropy in 3D-printed composites including short carbon fibres embedded in a polyamide (PA/nylon®) matrix is analysed experimentally. A testing campaign including tensile and fracture toughness coupons with 100% infill is studied. The effect of anisotropy induced by the Fused Deposition Modelling (FDM) procedure, caused by the alignment of the fibres with the deposition direction (raster angle), is presented. Specifically, results showed that the Young modulus and the elastic limit values are lower for the ＋45/−45 infill configuration with respect to the 0/90 infill configuration. Conversely, the ultimate tensile strength, the ultimate tensile strain, and the fracture toughness values are higher for the ＋45/−45 infill configuration. Moreover, the crack path obtained in fracture toughness coupons always followed the raster angle. Additionally, experimental results show that the 3D-printed composite parts keep the hygrothermal properties associated to the matrix, thus an ageing effect is observed even for standard environmental conditions (room temperature, 50% relative humidity). Specifically, Young modulus, elastic limit and ultimate tensile strength values are lower for the older coupons. The ultimate tensile strain is higher for the older coupons while the fracture toughness is similar. Coupons stored in a desiccator also varied the properties but in a slightly manner.

Ultrathin thin-film composite membrane integrated with MoS2 conjugated with thiol ligands for isopropanol dehydration by pervaporation

In recent years, transition metal dichalcogenides (TMDs) have garnered much significant attention for their potential in fabricating high-performance membranes and applications in water treatment. In the present study, molybdenum disulfide (MoS2) nanosheets were modified using organic thiols to synthesize amino, hydroxyl, and carboxyl-functionalized MoS2. These modified nanosheets were subsequently integrated into polyamide matrix to develop thin-film nanocomposite (TFN) membranes for dehydration of isopropanol-water mixtures through pervaporation. A comprehensive examination of the impact of incorporating functionalized MoS2 on the physical and chemical properties and separation performance of the resulting TFN membranes was carried out. Embedding MoS2 created a bumpy structure with protuberances on the membrane surface. Amine groups from the modified MoS2 played a crucial role in crosslinking with trimesoyl chloride during interfacial polymerization, contributing to an enhanced crosslinking degree in the membrane. Compared with the pristine membrane, hydroxyl and carboxyl-modified MoS2, the TFN membrane incorporated with amine-modified MoS2 exhibited the highest separation performance with total flux of 1438 g m−2 h−1 and water content in permeate of 99.37 wt% for separating 70 wt% isopropanol aqueous solution. Remarkably, the TFN membrane exhibited a robust performance under high operating temperatures and high feed water concentrations, demonstrating its resilience in challenging conditions. Furthermore, the membrane exhibited stable long-term operational performance, highlighting its potential for pervaporation dehydration applications in the industry. The insights gained from this study contribute to the ongoing development of advanced membrane technologies based on TMDs.

In situ assembly of graphitic carbon nitride/polypyrrole in a thin-film nanocomposite membrane with highly enhanced permeability and durability

Although thin-film nanocomposite (TFN) membranes have been proposed as a competitive approach for improved reverse osmosis performance within the last decade, their intrinsically poor organic-inorganic interfacial compatibility and low durability still hinder further upscaling. In this study, a new in situ assembly strategy is proposed to solve this dilemma by using polypyrrole (PPy) to build a bridge between polyamide matrix and nanomaterial (graphitic carbon nitride, g-C3N4) and further fabricate g-C3N4/PPy-incorporated TFN membrane. The synthesized g-C3N4/PPy nanocomposites are hybridized into the interfacial polymerization process, which endows the TFN membrane with a smaller “ridge-valley”, higher hydrophilic and thinner polyamide layer. With 0.005 wt% of g-C3N4/PPy, the water permeability of TFN membrane is increased to 377 % (4.0 L·m−2·h−1·bar−1), while keeping a similar NaCl rejection (99.1 %) to pure polyamide membrane. Importantly, the resulting TFN membrane exhibits high chlorine resistance in acidic, neutral and alkaline environments. Moreover, the TFN membrane has superior antifouling performance for organic, inorganic and mixed organic-inorganic foulants, which is of vital importance for the long service life of TFN membranes. This study offers a facile avenue to solve the application needs of advanced TFN membranes for efficient desalination with stable high-quality water.

Mechanical and thermal properties of polyamide‐6 nanocomposites reinforced by graphene oxide with low loading by double extrusion method

AbstractThe high toughness, high abrasion resistance, and high water absorption capacity of polyamide‐6 (PA6), and the restacking of graphene oxide (GO) sheets make it quite challenging to get uniformly dispersed GO/PA6 nanocomposites. Herein, GO of different parts per hundred ratios (phr) was melt‐mixed with PA6 matrix by double extrusion using a twin‐screw compounder, followed by the micro twin‐screw extruder, and composites were prepared by injection molding method. The stress–strain curves from tensile measurements showed strain hardening in nanocomposites. The yield strength and Young's modulus increased by 11.3% and 16.7% respectively, for 0.1 phr GO loading. The crystallization and melting temperatures in differential scanning calorimetry (DSC) were increased by 4.7 and 9.6°C, respectively with 0.1 phr GO reinforcement. The Raman and XRD analysis showed continuous shifting in the intensity peaks with increasing reinforcements. Moreover, a double extrusion process imparts good mechanical and thermal stability to our composites. The significant improvement in mechanical and thermal performance of injection molded nanocomposites at very low reinforcements leads to their potential applications in automobiles, civil constructions, smart textiles, packaging, and sensors.

High-Flux Nanofibrous Composite Reverse Osmosis Membrane Containing Interfacial Water Channels for Desalination.

A nanofibrous composite reverse osmosis (RO) membrane with a polyamide barrier layer containing interfacial water channels was fabricated on an electrospun nanofibrous substrate via an interfacial polymerization process. The RO membrane was employed for desalination of brackish water and exhibited enhanced permeation flux as well as rejection ratio. Nanocellulose was prepared by sequential oxidations of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and sodium periodate systems and surface grafting with different alkyl groups including octyl, decanyl, dodecanyl, tetradecanyl, cetyl, and octadecanyl groups. The chemical structure of the modified nanocellulose was verified subsequently by Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), and solid NMR measurements. Two monomers, trimesoyl chloride (TMC) and m-phenylenediamine (MPD), were employed to prepare a cross-linked polyamide matrix, i.e., the barrier layer of the RO membrane, which integrated with the alkyl groups-grafted nanocellulose to build up interfacial water channels via interfacial polymerization. The top and cross-sectional morphologies of the composite barrier layer were observed by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM) to verify the integration structure of the nanofibrous composite containing water channels. The aggregation and distribution of water molecules in the nanofibrous composite RO membrane verified the existence of water channels, demonstrated by molecular dynamics (MD) simulations. The desalination performance of the nanofibrous composite RO membrane was conducted and compared with that of commercially available RO membranes in the processing of brackish water, where 3 times higher permeation flux and 99.1% rejection ratio against NaCl were accomplished. This indicated that the engineering of interfacial water channels in the barrier layer could substantially increase the permeation flux of the nanofibrous composite membrane while retaining the high rejection ratio as well, i.e., to break through the trade-off between permeation flux and rejection ratio. Antifouling properties, chlorine resistance, and long-term desalination performance were also demonstrated to evaluate the potential applications of the nanofibrous composite RO membrane; remarkable durability and robustness were achieved in addition to 3 times higher permeation flux and a higher rejection ratio against commercial RO membranes in brackish water desalination.

Fatigue Behaviour of Additively Manufactured Short Fibre Reinforced Polyamide

Additive manufacturing of Short Fibre Reinforced Polymers (SFRPs) combines good mechanical properties with high design flexibility. In this work, fatigue tests were performed on SFRP specimens with 0°/90° and ±45° raster orientations. Thermal and mechanical fatigue regimes were both observed. In thermal fatigue, self-heating, softening and changes in viscoelastic properties occurred. In mechanical fatigue, the material progressively stiffened, and dissipative effects due to viscoelasticity were reduced. Such a behaviour is unusual for composites, but mainly seen in neat polymers. These results suggest the fatigue behaviour of this material to be dominated by the polyamide matrix.

Additive manufacturing of nylon composites with embedded multi-material piezoresistive strain sensors for structural health monitoring

A hybrid additive manufacturing process is proposed to incorporate piezoresistive sensors into a polyamide matrix for real-time structural health monitoring. 3D-printed samples were tested under tensile, flexural, and indentation testing using various sizes, numbers, and locations of the sensors, while the electrical resistance was recorded in real-time. Under uniaxial tensile loading, strength reached 36 MPa, and the resistance values linearly increased by up to 105% at ∼150% of strain. During flexural testing, the sensor had higher resistance when it was located above the supports rather than under the loading roller. The conductive paths were placed near the plate's top, middle and bottom sections to localise the damage during indentation testing. The energy absorbed during indentation testing reached 34–36 J. Resistance readings of sensors with 1 cm width showed better linearity and sensitivity than their wide (10 cm) counterparts. Three 2D sensors were interconnected to make a 3D sensor. The resistance values gradually increased after each strike during repeated indentation, but the overall strength remained similar. In summary, this work demonstrates a novel approach toward customisable 3D-printed piezoresistive sensors for detecting global or local damage.

Smart integration of MOFs and CQDs to fabricate defect-free and self-cleaning TFN membranes for dye removal

The surface chemistry and functionality of metal-organic frameworks (MOFs) can be manipulated through a judicious choice of integration with other nanomaterials. In this work, heterojunctions of UiO-66-NH2 and carbon quantum dots (CQDs) were prepared to explore their synergetic advantages as nanofillers in thin-film nanocomposite (TFN) membranes for dye removal. The successful integration of UiO-66-NH2/CQD were verified by TEM, FT-IR and XPS. The uniform loading of ultra-small CQDs on the surfaces of UiO-66-NH2 can not only enhance their compatibility with the polyamide matrix, but also promote their photocatalytic oxidation under visible light. Therefore, comparing to the pristine thin-film composite membranes, the optimal TFN membranes embedded with 0.2 wt% of UiO-66-NH2/CQD have demonstrated remarkable improvements in pure water permeance by 89.7% and higher selectivity to dyes of different charges and molecular weights. In addition, the decrease of water flux caused by dye adsorption during the long-term filtration process can be recovered by 92–99% via photocatalytic degradation of the attached dyes within 10 min. This work may offer a new strategy for fabricating defect-free and self-cleaning nanofiltration membranes for dye removal and wastewater reclamation.

Effects of the Simultaneous Strengthening of the Glass Fiber Surface and Polyamide-6 Matrix by Plasma Treatment and Nanoclay Addition on the Mechanical Properties of Multiscale Hybrid Composites

To strengthen the mechanical properties of a fiber-reinforced plastic without deteriorating its toughness caused by adding nanomaterial, multiscale hybrid composites (MHC) composed of polyamide 6 (PA6), woven glass fibers (WGFs), nanoclay, and various additives were fabricated and characterized. A surfactant was used to improve the dispersion of the nanoclay in the composite, and a compatibilizer and toughening agent were added to enhance the interfacial interactions between the nanoclay and PA6 and the toughness of the MHC, respectively. In addition, the WGFs were pretreated with atmospheric-pressure air plasma to enhance the interfacial bonding between the WGF and the mixture composed of PA6/nanoclay/compatibilizer/toughening agent, which constitutes the matrix. The optimal composition of the PA6 mixture, optimal content of the nanoclay, and optimal conditions of the plasma pretreatment of the WGF surface were experimentally determined. A suitable manufacturing process was employed using a material composition that maximizes the mechanical properties of the MHC by mitigating the toughness deterioration owing to nanoclay addition. An appropriate quantity of the nanoclay increased the tensile properties as well as the elongation at the break of the MHC because the toughening agent prevented the reduction in the degree of elongation caused by increasing the clay content to a certain extent. Moreover, the plasma treatment of the WGF enhanced the flexural properties and impact resistance of the MHC. Therefore, not only the tensile strength, modulus, and elongation at the break of the PA6 nanocomposite, which constitutes the matrix of the MHC, increased up to 39.83, 40.91, and 194.26%, respectively, but also the flexural strength and modulus, absorbed impact energy, and penetration limit of the MHC increased by 20.2, 26.8, 83.7, and 100.0%, respectively.

Significant Improvement of Thermal Conductivity of Polyamide 6/Boron Nitride Composites by Adding a Small Amount of Stearic Acid.

This study investigates the effect of adding stearic acid (SA) on the thermal conductivity of polyamide 6 (PA6)/boron nitride (BN) composites. The composites were prepared by melt blending, and the mass ratio of PA6 to BN was fixed at 50:50. The results show that when the SA content is less than 5 phr, some SA is distributed at the interface between BN sheets and PA6, which improves the interface adhesion of the two phases. This improves the force transfer from the matrix to BN sheets, promoting the exfoliation and dispersion of BN sheets. However, when the SA content was greater than 5 phr, SA tends to aggregate and form separate domains rather than being dispersed at the interface between PA6 and BN. Additionally, the well-dispersed BN sheets act as a heterogeneous nucleation agent, significantly improving the crystallinity of the PA6 matrix. The combination of good interface adhesion, excellent orientation, and high crystallinity of the matrix leads to efficient phonon propagation, resulting in a significant improvement in the thermal conductivity of the composite. The highest thermal conductivity of the composite is achieved when the SA content is 5 phr, which is 3.59 W m-1 K-1. The utilization of a composite material consisting of 5phr SA as the thermal interface material displays the highest thermal conductivity, and the composite also demonstrates satisfactory mechanical properties. This study proposes a promising strategy for the preparation of composites with high thermal conductivity.

Lignin modification for in-situ cured lignin-maleyl network in semi-crystalline polyamide/lignin shape memory composites

Lignin-based shape memory polymers (SMPs) have received increasing attention in the context of lignin valorization. This work designed a novel SMP with high content of lignin and high transition temperature (>150 °C) for shape memory. Soda lignin (SL) was first modified with maleic anhydride resulting in a lignin derivative (MAL) as confirmed by FTIR, 31P NMR, 2D-HSQC and TGA. The modification results in an elevated molecular weight and reduced Tg. SMPs were designed based on a penetrating lignin-maleyl network in a crystalline polyamide (PA) matrix, the former serving as the lock for the permanent shape and the latter as the reversible switch. The SMPs were prepared via procedures of solution mixing, film casting and in-situ thermal curing. Rheological study revealed that the precursors can be fully cured at 200 °C within 20 min with the aid of a bismaleimide spacer, which ensures a proper temperature window for curing. Compared to the PA/SL series, the PA/MAL series demonstrated improved mechanical properties and well-integrated interfacial morphologies, which enables efficient shape memory performance. This work provides a proof-of-concept study demonstrating that the design of crosslinked semi-crystalline polyamide/lignin dual-phase composites with modified lignin enables high-transition-temperature shape memory behavior for potential demanding applications such as in aerospace or mining engineering.

Fabrication and properties of the 6-aminocaproic acid-modified MXene-based PA6 nanocomposites

ABSTRACT MXene is a new type of transition metal carbon/nitride two-dimensional nanolayered material, which has attracted extensive attention in many fields due to its unique physicochemical properties. Combining MXene with high-performance polymers is expected to obtain nanocomposites with excellent comprehensive properties. In this study, MXene was first modified with acidified 6-aminocaproic acid and then mixed with Polyamide 6 (PA6) matrix. The structure, thermal stability, mechanical properties, and electromagnetic interference shielding efficiency of MXene-based PA6 nanocomposites were studied. The modified MXene was well dispersed in the PA6 matrix with beneficial interfacial adhesion, and the mechanical properties and electromagnetic interference shielding efficiency were significantly enhanced. The method used in this study provides a novel route for fabricating MXene-based polymer nanocomposites with excellent performance.

Thermoplastic self‐healing polymer blends for structural composites: Development of polyamide 6 and cyclic olefinic copolymer blends

AbstractOne of the main limitations of high‐performance composite materials is failure due to fatigue crack propagation during service. Traditional repair methods can be expensive and time‐consuming. For this reason, the research in the field of self‐healing composites has considerably increased in the past decade. At this aim, this work is focused on the production of a polyamide 6 (PA6) matrix with self‐healing properties. Cyclic olefinic copolymer (COC) was selected as a healing agent and it was melt compounded with PA6. From scanning electron microscope micrographs, it was possible to highlight the immiscibility and the lack of interfacial adhesion between the constituents. The healing efficiency of the system was evaluated by comparing the blends' fracture toughness (KIC), both in quasi‐static and impact mode, before and after the healing process performed at 140°C by applying a pressure of 0.5 MPa. Through the addition of 30 wt% of COC, the fracture toughness of the virgin samples slightly decreased, passing from 2.3 MPa·m1/2 of neat PA6 to 2.1 MPa·m1/2. However, the presence of the 30 wt% of COC homogeneously distributed within the PA6 matrix led to a healing efficiency of 11% in quasi‐static mode and 35% in impact mode.

Dry sliding wear behavior of energy density dependent PA 12/Cu composites produced by selective laser sintering

Abstract The selective laser sintering process is widely used to fabricate polyamide matrix composites. Although various reinforcements are used to produce polyamide matrix composites, metallic-based reinforcements are used to improve the mechanical properties of the structure. Also, selective laser sintering process parameters significantly affect the microstructural and mechanical properties of the composite products. In this study, polyamide 12 (PA 12) matrix composites were produced with Cu particulates by selective laser sintering methods using various energy density values. Moreover, dry sliding wear of the energy density dependent PA 12/Cu composites was investigated. Worn samples were characterized by scanning electron microscopy and 2D profile analysis. The examinations revealed that the lower energy density values improve the microstructural properties and wear behavior of the PA 12/Cu composites. It was obtained that the lowest energy value provides the highest wear resistance for the PA 12/Cu composites.

Tailoring the selectivity of quasi-PIMs nanofiltration membrane via molecular flexibility of acyl chloride monomers for desalination from dye effluents

Nanofiltration is a promising technology to recover dye from textile wastewater with highly saline for sustainable resource recovery. However, it is difficult for the conventional piperazine-based nanofiltration membranes, which usually have a tight polyamide matrix structure, to precisely separate dye and salt in wastewater. In this study, 5,5,6’,6’-tetrahydroxy-3,3,3’,3’-tetramethyl spirobisindane (TTSBI) with rigidly contorted structure has been used instead of piperazine as aqueous-phase monomer to fabricate polyarylate (PAT) nanofiltration membranes with quasi-PIMs structure via interfacial polymerization (IP) with three types of acyl chloride, i.e., rigid trimesoyl chloride (TMC), short-chain glutaryl chloride (GC) and long-chain sebacoyl dichloride (SDC). The contorted structure of TTSBI introduces extra microporosity in nanofiltration membranes, and the differentia of three acyl chlorides in molecular flexibility further endows with tailoring the stacking density of as-formed PAT networks. The PAT NF membranes thereby exhibited high permeability and tunable size-selectivity in desalination from dye effluent. Among these PAT membranes, TTSBI-TMC membranes had the highest water flux of 480.5 LMH, nearly 7-fold increase compared traditional PA NF membranes, whereas TTSBI-SDC membranes had the highest dye rejection of 97.4%, and TTSBI-GC membrane had the relatively balanced dye desalination performance with high rejection 95.4% for Congo Red and 8.3% for NaCl accompanied by high flux of 402.4 LMH. Therefore, this study provides a new prospective for the fabrication of highly permeable nanofiltration membranes for precise separation.

Multiblock poly(ether-b-amide) copolymers comprised of PA1212 and PPO-PEO-PPO with specific moisture-responsive and antistatic properties

Functional multiblock poly(ether-b-amide) (PEBA) copolymers, comprised of PA1212 (polyamide 1212) as hard segments and Jeffamine ED-2003 as soft segments, were successfully prepared via two-step melt polycondensation without any amidation catalyst. Here, using diamino-terminated poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO), Jeffamine ED-2003, enhances the compatibility between polyamide oligomer and polyether, which is better than the traditional route using hydroxyl-terminated polyether. The chemical structure of multiblock PEBAs, as well as the microphase separated structure with crystalline phase of polyamide and polyether, were confirmed by heteronuclear multiple-bond correlation spectrum, heteronuclear multiple quantum correlation spectrum, Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry and dynamic mechanical analysis. The hydrophilic PEBA copolymers showed water adsorption ranging from 87.3% to 17.1% depending on the polyether content, and specially showed moisture responsive behavior within seconds when exposed to moisture. The corresponding mechanism was studied using time-resolved attenuated total reflectance FT-IR spectroscopy in the molecular level and the water diffusion coefficient was estimated to be 1.07 × 10–8 cm2∙s–1. Two-dimensional correlation FT-IR spectra analysis was performed to confirm that the interaction between water and polyether phase was in preference to that between water and polyamide matrix, and water molecule only forms hydrogen bond with the polyether segment. Due to the incorporation of PEO segments, the PEBAs have the surface resistivity varying from 5.6 × 109 to 6.5× 1010 Ω, which makes PEBA potential candidate as permanent antistatic agent.

Thin film composite nanofiltration membrane with nanocluster structure mediated by graphene oxide/metal-polyphenol nanonetwork scaffold interlayer

In this study, novel thin film composite (TFC) nanofiltration membrane with nanocluster structure was successfully synthesized by confining interfacial polymerization (IP) on graphene oxide/metal-polyphenol (GO/TA-Mn+) nanonetwork scaffold interlayer for the first time. By metal-polyphenol network coordination cross-linking, very stable GO/TA-Mn + nanonetwork scaffold was constructed via brush coating, which well-regulated the pore structure and distribution of the substrate, greatly restricting the invasion of polyamide (PA) matrix to the pore of substrate. Moreover, the GO/TA-Mn + modified substrate effectively mediated the amine monomers diffusion during interfacial polymerization, contributing to form an ultrathin PA layer (∼19.2 nm) with nanocluster structure. The separation performance therefore can feasibly be tuned by the metal ions of different valence states. The strategy also gives appropriate level of generality for synthesis of versatile defect-free TFC membranes on various substrates. The prepared TFC-GO/TA-Al3+ membrane held outstanding separation performance with water permeability of 16.87 L m−2 h−1 bar−1 and competitive rejection of 97.2% for Na2SO4, displaying the permeability increment of about 4.5 times without sacrificing salt rejection.

Polyamide thin film nanocomposite membranes with in-situ integration of multiple functional nanoparticles for high performance reverse osmosis

Polyamide (PA) thin film nanocomposite (TFN) reverse osmosis (RO) membranes have been vigorously developed, which could be used in saline water desalination, wastewater treatment and chemicals separation and purification. Aiming at further improving the TFN RO membrane comprehensive performances, such as the perm-selectivity, stability and anti-fouling/-microbial properties remains a great challenge. Herein, we proposed a biomimetic nanoparticle redox strategy to in-situ integration of multiple functional nanoparticles, i.e., biomimetic nanoparticles (BNPs) and silver (Ag) nanoparticles into the PA matrix for simultaneously regulating the membrane microstructure and optimizing the surface property. A much hydrophilic selective layer with interior transporting channel structure renders the resultant RO membrane PA-BNP-Ag with an enhanced water permeance of ∼4.2 L m−2·h−1bar−1 without sacrificing NaCl rejection (∼98.1%). The BNPs induce Ag nanoparticles uniformly distributed within the PA matrix, which significantly improves the membrane anti-fouling/-bacterial property. The water flux recovery ratio of PAM-BNP-Ag was improved to be higher than 96% during several cycles filtration of saline solution containing bovine serum albumin foulants. More importantly, the membrane sterilization rate against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) achieves nearly 100%. This work provides a new strategy for the construction of advanced PA TFN membranes with both high perm-selectivity and anti-fouling/-microbial property in RO desalination.