Polyamide Nanocomposites Research Articles

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.

(Digital Presentation) Anelasticity, Mechanical Spectroscopy, Internal Friction in Radiation and Structural Functionalized Nanocomposites of Multiwalled Carbon Nanotubes and Polyamide, Polyvinylchloride, Polyethylene, SiO2

Experimental Methods Ultrasound (US) impulse-phase method using computerized “KERN-4” with frequencies f┴ ≈ 0,7 MHz and f║ ≈ 1 MHz was used [1,2]. The measured velocity error was equal to ΔV/V ≈ 1,5%. Results and Discussion The influencing of ultrasonic deformation εUS was researched on mechanical properties of nanocomposite. The important value is in position of formation in the polymeric matrix of molecular structures, as multiwalled carbon nanotubes serve as the centers of crystalline phase nanocomposite origin. Amplitude-dependent internal friction (ADIF) measurement can be used as the highly sensitive method of monitoring the nanoplastic deformation eND of nanocomposites. ADIF measurement makes it possible to record the moment of dislocation segments LC separation from stoppers. Internal friction (IF) is caused by various relaxation processes that are related to nanocomposites structure defectiveness. Even rather small strain can collect up in non-ideal nanocomposites, changing their anelastic and elastic characteristics. One of the ways to purposefully change the properties of multiwalled carbon nanotubes in order to use them in nanoelectronics is to introduce impurities of other elements. It was found that as the result of the structural defect annealing IF background Q0 -1 significantly decreases during measuring of IF temperature dependences Q-1(T), which indicates the improvement of nanocomposite structure. The samples were prepared by ultrasonic dispersion using digital ultrasonic (US) bath CE-6200A with power W = 70 W at frequency f ≈ 42 kHz [1,2]. Illustration of the window for processing data of quasilongitudinal elastic waves velocity measuring V║ = 3244 ± 10 m/sec m/sec in nanocomposite polyamide (PA-6) (NH(CH2)5CO)n + 0,1% multiwalled carbon nanotubes (MCNT) by by pulse-phase US method at frequency f║ ≈ 1 MHz after electron irradiation with dose De- ≈ 10 MRad with energy Ee- ≈ 2,0 MeV is represented in Fig. 1. Fig.1. Illustration of the window for processing data of quasilongitudinal elastic waves velocity measuring V║ = 3244 m/sec in nanocomposite polyamide (PA-6) (NH(CH2)5CO)n + 0,1% MCNT by pulse-phase US method at frequency f║ ≈ 1 MHz after electron irradiation with dose De- ≈ 10 MRad.Poisson coefficient μ and elastic modulus E completely characterize the elastic properties of polymer nanocomposite. Poisson coefficient μ - elastic value of ratio of relative transversal compression e^ to relative longitudinal lengthening e║ [1]. One oscillator produces 3 waves: 1 longitudinal and 2 transversal. Debye temperature θD was determined after the formula [2], where kB - Boltzmann constant, h - Plank constant, NA - Avogadro number, A - middle gram-molecular mass, V║ - quasilongitudinal US velocity, V┴ - quasitransversal US velocity.Complex elastic modulus of nanocomposite polyamide-6 (PA-6) (NH(CH2)5CO)n + % MCNT E* is equal to the sum of elastic dynamic modulus E’ = rV║ 2 and loss modulus E” = E’d [2], where δ - logarithmic decrement of US attenuation, ρ - nanocomposite density, V║ - longitudinal US elastic waves velocity, Q-1 - internal friction, where α - US attenuation coefficient, λ - US wavelength, f - US frequency. Internal friction is equal Q-1 = δ/π. The logarithmic decrement of attenuation δ of US oscillations with amplitude A = A0e- d x is equal: δ = ln(An+1/An). Conclusions The presence of the strong interaction for nanocomposite between polyamide-6 (NH(CH2)5CO)n and multiwalled carbon nanotubes was confirmed.The increase of the nanocomposite crystallinity degree at growth of multiwalled carbon nanotubes concentration filling with the nanotubes of matrix results in the decline of content of organized phase.The phenomenon of change of Poisson coefficient m, Debye temperature θD, dynamic elastic modulus E’ = rV║ 2, dynamic shear modulus G = rV^ 2 under the influence of radiative electronic e- radiation is caused by the appearance of primary radiation defects (RD). As the result of interdefect interactions primary RD form secondary RD. Acknowledgments This work has been supported by the Ministry of Education and Science of Ukraine: Grant of the Ministry of Education and Science of Ukraine for the prospective development of the scientific direction “Mathematical sciences and natural sciences” at Taras Shevchenko National University of Kyiv. References Onanko, A.P., Kuryliuk, V.V., Onanko, Y.A. et al. Features of inelastic and elastic characteristics of Si and SiO2/Si structures. Journal of Nano- and Electronic Physics13(5), 05017(5) (2021).Onanko, A.P., Kuryliuk, V.V., Onanko, Y.A. et al. Mechanical spectroscopy and internal friction in SiO2/Si. Journal of Nano- and Electronic Physics14(6), 06029(7) (2022). Figure 1

Nanocomposites of recycled and of virgin polyamide 6.6 with cellulose nanofibers

The inherent properties of cellulose nanofibers (CNFs) make them an interesting and sustainable choice for reinforcing polymeric matrices intended for the automotive, electronic, construction, and packaging sectors. Effective recycling and reuse of polyamide 6.6 significantly reduce the environmental impact of automotive components throughout its entire life cycle. Nanocomposites of recycled polyamide 6.6 and CNF and of virgin polyamide 6.6 and CNF were processed through dissolution in a formic acid/water mixture followed by melt extrusion and injection molding. The results show that pure recycled polyamide exhibited a thermal degradation onset temperature 10 °C lower and a 9 % lower crystallinity compared to pure virgin polyamide. The method used for processing the nanocomposites resulted in homogeneous dispersion and good anchoring of CNF in both polymer matrices. The processing method and the presence of CNF reduce the thermal stability by up to 15 °C for recycled polyamide nanocomposites and up to 26 °C for virgin polyamide nanocomposites. The processing method did not significantly impair the elastic modulus and tensile strength of both recycled and virgin polyamides, showing a 3 % and 1 % reduction in tensile strength for recycled and virgin polyamides, respectively. The incorporation of 1 wt% and 2 wt% of CNF in virgin polyamide showed an increase in the elastic modulus of 16 % and 5 %, respectively, and a reduction in ductility. In summary, this work offers an alternative processing pathway for nanocomposites of recycled or virgin polyamide 6.6 with CNF; however, some improvements are still necessary to achieve the reinforcing effect of CNF on the mechanical strength of the matrices.

Performance investigation of hydrothermally stressed polyamide nanocomposites for insulation applications

This paper investigates the performance of novel nano ZnO filled polyamide nanocomposites under hydrothermal conditions for cable insulation applications. Neat polyamide (PA0) and its nanocomposite with 0 wt% (PA0), 1 wt% (PA1), 3 wt% (PA3), 5 wt% (PA5), and 7 wt% (PA7) of nano ZnO were prepared and subjected to accelerated hydrothermal aging conditions in a programmable chamber at 85 °C and 85% relative humidity for 300 h. The samples were analyzed with visual inspection, hydrophobicity evaluation, optical microscopy, Fourier Transform Infrared (FTIR) spectroscopy, leakage current and UV–vis spectroscopy after every 100 h of aging. Scanning Electron Microscopy (SEM) and x-ray Diffraction (XRD) were employed for analyzing filler dispersion. Maximum filler dispersion was achieved in the case of 3 wt% of nanofiller. All the samples expressed surface degradation and increase in leakage current after aging. Maximum surface roughness and highest leakage current of 7 μA were noticed for PA0, however PA3 expressed lowest leakage current and surface degradation. PA0 expressed the lowest hydrophobicity class of HC-3 and lowest contact angle of 75° after aging. Among the nanocomposites, PA3 expressed the highest hydrophobicity class (HC-1) and contact angle (112°) after aging. FTIR results expressed that all the samples suffered from oxidation and the C=O peaks at ∼1728 cm−1 increased by 120%, 100% and 120% for PA1, PA3 and PA7 respectively. The peaks of –OH group at ∼3500 cm−1 increased for all the sample indicating moister absorption. However, it is observed that the addition of nanofiller enhanced the overall performance of composites and among the composites PA3 performed better.

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.

Tailoring Polyamide Nanocomposites: The Synergistic Effects of SWCNT Chirality and Maleic Anhydride Grafting

Tailoring Polyamide Nanocomposites: The Synergistic Effects of SWCNT Chirality and Maleic Anhydride Grafting

In Situ Polymerization of Antibacterial Modification Polyamide 66 with Au@Cu2O-ZnO Ternary Heterojunction.

In situ polymerization has proven to be an effective route through which to introduce function materials into polyamide materials. In this work, a nano-heterojunction material was evenly dispersed in PA66 via in situ polymerization methods to yield the antimicrobial PA66. The composites showed excellent antibacterial activity against Staphylococcus aureus and Escherichia coli, with strong mechanical properties. Fourier transform infrared spectroscopy (FTIR) showed that metal ions reacted with oxygen-containing functional groups. In addition, the shift of oxygen peaks in XPS spectra confirmed the occurrence of a complexation reaction. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) confirmed the effect of nano-heterojunction, which induced crystallization. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed uniform dispersion of heterojunctions in PA66. Tensile testing revealed decreased toughness with higher loadings. The nanocomposite polyamide material has good processing properties which can be processed into thin films, molds, and wires without changing the morphology, and can be widely used in a variety of fields.

CELLULOSE REINFORCED POLYAMIDE COMPOSITES: EFFECT OF PREPARATION METHOD ON COMPOSITE PROPERTIES

Over the years, the preparation method chosen for the preparation of cellulose reinforced nylon or polyamide (PA) composites has proven to be critical in determining the overall properties of the composites. For example, melt processing of cellulose reinforced nylon or PA composites presents challenges, such as (i) irreversible hornification of cellulose material upon drying, before melt processing; (ii) non-uniform dispersion or distribution of cellulose in the polymer matrix; (iii) thermal degradation of cellulose at elevated temperatures and (iv) structural integrity (fibrillation) and shortening of cellulose upon mechanical shearing during melt processing. All these challenges have the potential to compromise the overall properties of the prepared composites. In order to circumvent these challenges, several techniques have been used. For example, hornification, can be overcome by using a technique called wet feeding. Thermal degradation can be overcome by coating cellulose materials via either chemical or physical wrapping with a macromolecule or surfactant. The thermal degradation of cellulose can also be prevented by using in situ polymerization of PA via the ring opening polymerization technique during the manufacture of cellulose reinforced nylon composites, as well as solvent casting in formic acid/water mixtures. The incorporation of up to 50 wt% cellulose nanofibers (CNFs) in PA nanocomposites via solvent casting improved elastic modulus by 64% and tensile strength by 62%. The aim of this manuscript is to review preparation techniques of low cost, high strength composites using cellulose fibers and engineering plastics like polyamides (PAs, nylons).

Understanding the structural changes, interfacial mechanisms, and mechanical properties of polymer/MWCNT nanocomposites after microwave treatment

AbstractThe use of microwave radiation for the post‐processing treatment of engineering polymers is a recent trend not seen by many. In the case of polymers, their crystalline nature is a significant factor in optimizing the treatment time for maximum improvement in mechanical properties. With the advent of nanomaterials, the aim of the present work is to explore the possibility of post‐processing microwave treatment on the structure and property relationships in MWCNT‐reinforced polymer matrices. The microwave‐activated nucleating tendency of MWCNTs was found to be promoting molecular chain rearrangement in poly‐amide (PA) and poly‐butylene‐terephthalate (PBT) nanocomposites. This considerably improved the mechanical characteristics of the composites by facilitating the rearrangement of the crystalline segments of the polymer matrix. The wear performance of PA nanocomposite increased by 30%, while the elongation of PBT nanocomposite increased by 93%, after a treatment of only 15–20 s. However, comparing with previous studies, it was found that, similar to virgin polymers, the treatment time needed for maximum improvement in polymer/MWCNT nanocomposites is hugely dependent on polymer matrix crystallinity as well. A detailed analysis of the microwave‐treated nanocomposites' structure and mechanical properties illustrates the post‐processing microwave treatment as a time‐efficient, cost‐effective, and environmentally friendly technique.Highlights Direct use of microwave radiation to heat the finished polymeric component. Microwave treatment brings about structural changes resulting in enhanced properties. Instantaneous heating is a key reason for the systematic arrangement of polymeric chains. Microwave‐activated nucleating tendency of MWCNTs also promotes chain arrangement. Properties increase as high as 30% wear rate and 93% elongation.

Development of polyamide 6‐graphene oxide nanocomposite and direct‐joining with aluminum alloy for lightweight engineering applications

AbstractLightweight polyamide composites and structures have been widely studied and employed in several industrial sectors. In this study, the development of a nanocomposite of polyamide 6 and graphene oxide (PA6‐GO) by melt‐compounding and the joining with aluminum alloy AA6061 through direct‐adhesion injection overmolding are addressed. PA6‐GO nanocomposite exhibited well‐dispersed thin (300 nm) GO platelets distributed within the PA6 matrix, which resulted in an increase of 21% in the tensile modulus and 16% in the yield stress for a filler loading of 0.5 wt%. PA6‐GO/AA6061 hybrid joints showed good mechanical anchorage through the complete filling of the polymer into micro‐scale grooves designed onto the metal surface, which ensured outstanding shear strength of 7.1 ± 1.0 MPa, comparable to other polyamide‐metal hybrid joints reported in the literature. This indicates that the processing routes and materials developed are promising for lightweight engineering applications.Highlights A PA6‐GO nanocomposite with enhanced tensile properties was developed. A joint of PA6‐GO and AA6061 with outstanding shear strength was obtained. Fast and efficient melt‐processing routes were employed. These materials are promising for lightweight engineering applications.

Modification and Characterization of Polyamide Nanocomposites with Organobentonite Cetyltrimethylammonium Bromide

Modification of bentonite with Cetyl Trimethyl Ammonium Bromide (CTAB) has been successfully carried out, resulting in the application of organobentonite as a filler. The purpose of this study was to determine the characteristics of the polyamide nanocomposite material before and after the addition of organobentonite filler. Commercial bentonite after being modified with CTAB is organophilic with a particle size of 9.55 nm. The results of the Fourier Transform Infra Red spectrum analysis show that there is a wide and sharp absorption band at wave number 3749.6 cm-1 which indicates the presence of Al-OH groups. The results of Scanning Electron Microscopy analysis of the surface morphology of the polyamide/organobentonite nanocomposite obtained a homogeneous and compatible mixture. The conclusion from the CTAB research results can unite polyamide and bentonite which have different polarities

Thin film nanocomposite polyamide membrane doped with amino-functionalized graphene quantum dots for organic solvent nanofiltration

Thin film nanocomposite (TFN) organic solvent nanofiltration (OSN) membrane with improved separation performance was fabricated via interfacial polymerization reaction between amine-functionalized graphene quantum dots (af-GQDs) doped aqueous monomer solution of m-phenylenediamine (MPD) and n-hexane solution containing trimesoyl chloride (TMC) monomer. We emphasize the employment of extra-low content for both af-GQDs and MPD, so that we could maximize the function of these nanomaterials and eliminate their aggregation at the same time. The af-GQDs nanomaterials could regulate the interfacial polymerization process and could be strongly anchored in the polyamide film via covalent bonding, hence could prevent their loss while providing more channels for faster solvent penetration. As a result, the optimized OSN membrane, TFN-50, shows a super-smooth surface, with a surface roughness as low as 4.3 ± 0.2 nm, and excellent pure solvent permeances which reach 135.8, 112.7, and 69.8 L m−2 h−1 MPa−1 for methanol, DMF and ethanol, respectively, as well as a very high Rhodamine B (RDB, 479 Da) rejection of up to 99.2%, and an ethanol permeance of 61.4 L m−2 h−1 MPa−1. Furthermore, the TFN-50 OSN membrane still shows excellent filtration performance after being submerged in DMF for 336 h or continuous crossflow filtration with Rose bengal (RB, 1017 Da)/DMF solution for 136 h, demonstrating its excellent solvent resistance.

Green and edible cyclodextrin metal-organic frameworks modified polyamide thin film nanocomposite nanofiltration membranes for efficient desalination

Nanofiltration membranes are widely used in water treatment applications. However, their performance is often limited due to the trade-off between permeability and selectivity. To overcome this limitation, the incorporation of metal-organic frameworks (MOFs) into polyamide layers to prepare thin film nanocomposite polyamide membranes has been extensively investigated. However, these reported MOFs usually contain toxic heavy metal ions and ligands, posing the risk of leaching during the filtration process and being harmful to environment and even human health. In this work, γ-cyclodextrin and K+ were used to prepare green and edible cyclodextrin MOF (CD-MOF) nanoparticles. Furthermore, these CD-MOF nanoparticles were further loaded at the porous substrate surface to prepare polyamide nanofiltration membranes. The CD-MOF nanoparticles delay the diffusion of PIP molecules and leads to a thin PA layer. In addition, the rough substrate surface loaded with CD-MOF provide an uneven interfacial polymerization reaction interface. After the dissolvement of the CD-MOF nanoparticles, a wrinkled PA structure eventually formed. The PWP of the optimal membrane was 24.4 L m-2 h-1 bar-1, which was 502% higher than that of the controlled TFC membrane, and the Na2SO4 rejection was improved to 97.1%. More ordered surface and negative electrical properties increase the selectivity of divalent to monovalent ions. Compared to conventional TFC nanofiltration membranes, the novel TFN membrane successfully overcame the longstanding permeability and selectivity trade-off. The current work expands the potential of CD-MOF to be utilized in the fabrication of high-performance NF membranes.

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.

Enhancing boron rejection in low-pressure reverse osmosis systems using a cellulose fiber–carbon nanotube nanocomposite polyamide membrane: A study on chemical structure and surface morphology

Nanocomposite membranes based on carbon nanotubes (CNTs) or cellulose nanofibers (CNFs) are promising solutions for water filtration technologies such as seawater desalination, brackish water purification, and wastewater treatment. In this study, we investigated the effect of integrating CNTs and CNFs into a polyamide membrane (CNT–CNF–PA) on boron rejection in low−pressure reverse osmosis (RO) systems (0.75 MPa). A NaCl (500 ppm) and boron (5 ppm) based solution at pH = 7 was tested in an RO filtration system. The CNT–CNF–PA membrane exhibited a high boron rejection rate (up to 74%) and high permeation (greater than 1.0 m3/m2∙day). The chemical structure played a significant role in boron rejection performance. We conducted principal component analysis (PCA) to statistically study the changes in bond vibrations obtained by Fourier transform infrared (FTIR) spectroscopy, comparing the oxygenated and hydrogenated changes to sodium chloride rejection, boron rejection, and water permeation of the membranes. Additionally, the surface morphology, i.e., roughness, exhibits a direct positive effect on boron rejection, whereas the pore structure is linked to both sodium chloride and boron rejections. Molecular dynamic simulations revealed that the CNF and CNT structures suppress the hydrogen bonds between the PA matrix and boric acid, negatively affecting its diffusion and rejection. These findings help clarify the boron rejection mechanism, enabling further development of PA membranes.

Bio-based polyamide nanocomposites of nanoclay, carbon nanotubes and graphene: a review

Bio-based polyamide nanocomposites of nanoclay, carbon nanotubes and graphene: a review

Fabrication of novel thin-film nanocomposite polyamide membrane by the interlayer approach: A review

Thin-film nanocomposite (TFN) membrane based on polyamide (PA) chemistry was widely applied for water purification and desalination process due to the improved water permeance. It remains a great challenge to significantly enhance rejection because of the non-selective defects caused by the aggregation of nanomaterials in the PA layer. Novel interlayer-based TFN (iTFN) membrane containing nanomaterial interlayer between the porous substrate and PA layer is the promising candidate to improve PA integrity and thus overcome the ubiquitous trade-off between permeability and selectivity. The nanomaterial interlayer not only promotes the subsequent interfacial polymerization (IP) but also provides improved pathways for water transport, which leads to simultaneous improvement in membrane permeability and selectivity. This review systematically categorizes nanomaterial interlayers into three types according to construction methods, namely, direct deposition, in situ growth and functional group-anchored in situ assembly (FAISA). The mechanism of interlayer modulating IP process and PA structure, as well as the effects on water transport, are comprehensively analyzed. Encouraging results reveal that using MOFs interlayer prepared by FAISA is the most promising way to break the trade-off in manufacturing reverse osmosis membranes. Finally, challenges and future efforts are presented for advancing iTFN membranes.

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.

Enhanced thermal conductivity of polyamide nanocomposites involving expanded graphite–carbon nanotube network structure using supercritical CO2

In this study, supercritical carbon dioxide (scCO2) was used to form a network structure of expanded graphite (EG) and multi-walled carbon nanotube (MWCNT) to achieve high thermal conductivity. Continuous processes, such as supercritical drying and rapid expansion of supercritical solutions were applied to pristine graphite and MWCNT. Polyamide 6 (PA6) nanocomposites with scCO2-treated EG and MWCNT were prepared by twin-screw extruder-based melt compounding. In the PA6 nanocomposites, the EG sheets were homogenously dispersed, while the MWCNTs were located between the EG sheets, thereby acting as a bridge for the EG. Subsequently, the 35 wt.% imbedding in PA6 nanocomposite had an effective heat transfer pathway and high thermal conductivity (2.12 W m−1 K−1). It was observed that supercritical fluid processing is a facile and effective strategy to improve the thermal conductivity of polymer nanocomposites.

Scanning Electron Microscopy and Raman Spectroscopy Characterization of Structural Changes Induced by Thermal Treatment in Innovative Bio-Based Polyamide Nanocomposites

A comprehensive Raman scattering-based characterization of a full bio-based polyamide loaded with graphene nanoplatelets or layered double hydroxides (LDH) was assessed. The potential of the Raman spectroscopy was used to reveal several particularities of the nanocomposite structures induced by thermal treatment. Thus, a complete morpho-structural picture was obtained in combination with scanning electron microscopy (SEM) analysis of the neat polyamide and polyamide nanocomposites exposed at different thermal conditions (room temperature, 80 °C, and 145 °C). The analysis of G, D and 2D Raman peaks and their relative intensity ratio ID/IG, revealed the fact that the presence of graphene in polyamide is suitable for improving the essential physical properties and is also responsible for the decrease in the defects’ occurrence in the graphene layers. The surface of nanocomposites based on full bio-based polyamide, with different 2D fillers (graphenic and non-graphenic structures), was carefully evaluated before and after the thermal treatment by employing SEM and Raman analyses. The two thermal treatments allowed different chain mobility of the polymer (first temperature being over the polymer Tg and second one close to the melting phase in the viscoelastic stage). The spectroscopic and microscopic investigation was used to determine the conformational changes in filler aggregates and polymer surface, respectively.