Polyamide Nanocomposites Research Articles

Strong Polyamide-6 Nanocomposites with Cellulose Nanofibers Mediated by Green Solvent Mixtures.

Cellulose nanofiber (CNF) as a bio-based reinforcement has attracted tremendous interests in engineering polymer composites. This study developed a sustainable approach to reinforce polyamide-6 or nylon-6 (PA6) with CNFs through solvent casting in formic acid/water mixtures. The methodology provides an energy-efficient pathway towards well-dispersed high-CNF content PA6 biocomposites. Nanocomposite formulations up to 50 wt.% of CNFs were prepared, and excellent improvements in the tensile properties were observed, with an increase in the elastic modulus from 1.5 to 4.2 GPa, and in the tensile strength from 46.3 to 124 MPa. The experimental tensile values were compared with the analytical values obtained by micromechanical models. Fractured surfaces were observed using scanning electron microscopy to examine the interface morphology. FTIR revealed strong hydrogen bonding at the interface, and the thermal parameters were determined using TGA and DSC, where the nanocomposites’ crystallinity tended to reduce with the increase in the CNF content. In addition, nanocomposites showed good thermomechanical stability for all formulations. Overall, this work provides a facile fabrication pathway for high-CNF content nanocomposites of PA6 for high-performance and advanced material applications.

Shelf Life of Fresh Sliced Sea Bream Pack in PET Nanocomposite Trays.

Spoilage of fish due to microbiological activity is one of the biggest problems found by producers to take fresh fish products to customers. It is necessary packaging improvements to be able to increase fish shelf life and, thus, be able to travel further and to keep product freshness longer at customer’s houses. In the present work, a new material is developed for fish packaging in modified atmosphere (MAP). This material is poly(ethylene terephathalate) (PET) extruded with a polyamide (PA) nanocomposite containing nanosepiolite. Here, it is shown the production procedure from laboratory to industrial scale. Permeability to oxygen and impact mechanical properties results are shown for different samples, both at laboratory and industrial processes. At the end, a material composition is chosen to produce the finale tray which will contain the sliced sea bream. Microbiological analysis is done over the packed fish, resulting is a lower microbiological count compared to a PET control sample. This means that shelf life of pack sea bream could increase from 2–4 to 7–9 days, which is very important for both producers and customers. On the other hand, trays obtained comply with European regulations in food contact materials (FCM) and, overall, they are suitable for food packaging materials.

Additive manufacturing of polyamide nanocomposites for electrostatic charge dissipation applications

Polyamide 6 (PA 6) nanocomposites are viable engineered nanocomposite materials with potential application in electrostatic discharge dissipation applications. Creating an electrically conductive path to dissipate electrostatic charges in such materials can be a viable solution to electrostatic discharge (ESD) concerns. The addition of nanofillers can also enhance mechanical properties of the parent polyamide 6, a structural thermoplastic ideal for 3D printing via fused deposition modelling (FDM). While improving the ESD capability, it is imperative to sustain the structural integrity of the nanocomposites. Hence, this study evaluated the mechanical, thermal, and electrical properties of 3D printed PA6 nanocomposites for electrostatic discharge applications. 3 and 5 wt% of carbon nanofibers (CNF) was compounded with PA6 using co-rotating twin screw extruder to produce 1.75 mm diameter monofilaments for fused deposition modelling (FDM). The test samples were printed using commercial-off-the-shelf (COTS) 3D printer, Lulzbot TAZ 6 FDM printer. Mechanical, electrical, and thermal characterization was carried out according to their respective ASTM standard. The tensile and flexural properties were enhanced by 3 wt% addition of CNF, but no significant improvement was observed at 5 wt%. The CNF nanocomposites exhibited good thermal stability and crystallization phenomenon at both loading levels. The volume resistivity of the of the PA6 matrix was reduced to order of 1011 and 1012 by 3 wt% and 5 wt% CNF addition respectively, which seems promising for manufacturing static discharge products.

Carbon nanotube functional group-dependent compatibilization of polyamide 6 and poly(methyl methacrylate) nanocomposites

Nanocomposites of polyamide 6 (PA6)–poly(methyl methacrylate) (PMMA)–functionalized single-wall carbon nanotubes (f-SWCNTs) with hydroxyl (SWCNTOH) and carboxylic acid (SWCNTCOOH) in weight ratios of 79.5–19.5–1, 49.5–49.5–1, and 19.5–79.5–1 were fabricated and investigated in terms of morphology, mechanical and XRD studies. Blends of 80–20, 50–50, and 20–80 weight ratios of PA6–PMMA have functioned as references. The scanning electron microscopy images of nanocomposites showed a relatively uniform dispersion of PMMA domains as co-continuous phase morphology in the continuous phase of PA6 compared to their respective blends. The f-SWCNTs acted as functional group-dependent compatibilizers for the PA6–PMMA blend system. Compatibilization of PA6-PMMA blends was higher in the presence of functionalized SWCNTs. XRD analysis indicated that the αI and αII phases of the PA6 were dependent on the weight ratio of the PA6 and PMMA and the nature of the f-SWCNTs. The PMMA-rich blends and nanocomposites exhibited the rich αI phase. The melt strength of the nanocomposites was higher compared to that of the PA6–PMMA blends. All the nanocomposites exhibited higher tensile strength than their corresponding blends. Tensile modulus increased with increasing weight percent of PMMA in blends (from 810 to 1135 MPa) and in nanocomposites (from 854 to 1298 MPa). PA6–PMMA–SWCNTOH19.5–79.5–1 nanocomposites exhibited higher tensile modulus (1298 MPa) compared to all the blends and PA6–PMMA–SWCNTCOOH nanocomposites.

Graphene/graphene nanoplatelets reinforced polyamide nanocomposites: A review

Graphene and its derivatives have received considerable attention in industrial and academic research due to their unique, useful properties and applications. The use of graphene is still difficult due to its high cost of production. Hence, graphene nanoplatelets (GNPs) have been identified as a substitute for graphene, which are produced in large scale at a very low cost. Moreover, GNPs have played a significant role in various engineering thermoplastic materials [i.e., polyamides (PAs)] to enhance their properties and applications. The GNPs help in the production of low-cost multifunctional nanocomposites with notable useful properties such as high electrical conductivity, mechanical strength, and high aspect ratio. The GNPs based nanocomposites have a broad spectrum of application areas including 3D-printing, automotive materials, electrical appliances, low-cost composites films, and many more. This review summarizes different preparation techniques, properties, and applications of GNPs based PAs nanocomposites as reported in current literature.

Single-step preparation of nanocomposite polyamide 6 hollow fiber membrane with integrally skinned asymmetric structure for organic solvent nanofiltration

An integrally skinned organic solvent-resistant membrane with asymmetric structure for organic solvent nanofiltration (OSN) application was developed via thermally induced phase separation (TIPS) of nanocomposite polyamide 6. The nanocomposite polyamide 6 contains intercalated silicate sheets, which could improve the mechanical properties of the resultant membrane, as well as mitigate swelling after exposure in solvent. The influence of nanocomposite polyamide 6 composition of the hollow fiber membrane and the subsequent thermal annealing was investigated in this study. Crystallinity data revealed that polyamide 6 crystal formed during the TIPS process was primarily α-phase type, but the use of nanocomposite polymer initiated the formation of γ-type crystalline structure. Thermal annealing at 120 °C was also found to even promote a higher overall crystallinity of the membranes. The membranes were subjected for OSN operation with methanol (MeOH) as solvent and cyanocobalamin (vitamin B12) as the solute. The intercalated silicate sheets in the nanocomposite polyamide 6 brought about the dense outer surface and sublayer formation, resulting in higher mechanical properties and stability in MeOH; however, the membranes formed with purely nanocomposite polyamide 6 suffered from very low permeance, primarily due to the dense outer surface and sublayer. The membrane whose composition is 50% nanocomposite polyamide 6 exhibited MeOH permeance of 0.1 L m−2 h−1 bar−1 and vitamin B12 rejection of over 99.0%. This work was able to provide how polymeric material, thermal annealing, and the resultant crystallinity could affect the membrane’s mechanical properties and filtration performance with solvent resistance.

Mechanical Characterization and Selection of Polyamide Nano-Composites Subjected to Sea water Environment in Marine Applications

Though many studies have been conducted on thermoplastic matrix polymer composites in the past, marine applications have been found only during the recent times. In this paper, an attempt has been made to prepare polyamide 6 (PA-6) nano-composites reinforced with varying amounts (1 wt%, 3 wt% and 5 wt%) of montmorillonite (MMT) using twin-screw extruder mixed technique and then studied its mechanical characterization under sea water environment. The characteristics of the proposed composites are compared with some of the other polymer composites for the same purpose and are reported in the literature. Further, a decision-making methodology developed by using analytic hierarchy process (AHP), entropy weighting method and TOPSIS (Technique for order preference by similarity to ideal solution) have been adopted to find the rank order of the composites suitable for marine applications. The outcome of the study disclosed that the proposed polymer-nanocomposite reinforced with 3% MMT is more competent to other composites in view of attaining the objective of the study.

The mechanisms behind the tribological behaviour of polymer matrix composites reinforced with TiO2 nanoparticles

In this present work, the sliding wear behaviour of hybrid polymer nanocomposites was investigated under different loading conditions and against different counterface roughness. Two different polymers matrices, epoxy and polyamide 66, with classic micro-sized short carbon fiber and graphite flakes as tribo-fillers were investigated with and without TiO2 reinforcing nanoparticles. It was found that the synergistic effect between nanoparticles and micro-sized fillers on friction and wear performance depended on the tribological system involved. In particular, for epoxy-based composites, the incorporation of TiO2 nanoparticles was only beneficial against a sufficiently rough disc but detrimental otherwise. Whilst for polyamide nanocomposites, the combination of nanoparticles and other fillers resulted in low friction and wear against both rough and smooth disks, particularly at higher applied contact pressures. When the cross-sections of the transfer films were analysed using a high-resolution SEM, it was found that TiO2 nanoparticles are only beneficial if they can blend with other wear debris to form a TiO2-enriched transfer film. The strengthened film provides the support required for other dislodged TiO2 nanoparticles to achieve the rolling effect, thus reducing friction and wear. In contrast, if TiO2 cannot effectively blend into the transfer film, TiO2 nanoparticles act as an abrasive that readily abrades away the comparatively softer film, thus exposing the polymer to fresh asperities on the steel counterface, a detrimental outcome to both friction and wear. Hence, to design high wear resistant composite materials, it is important to understanding the interactions between different tribo-fillers for particular circumstances or contact conditions.

Enhanced Thermal Conductivity of Polyamide-Based Nanocomposites Containing Graphene Oxide Sheets Decorated with Compatible Polymer Brushes.

Polyamide-based nanocomposites containing graphene platelets decorated with poly(acrylamide) brushes were prepared and characterized. The brushes were grafted from the surface of graphene oxide (GO), a thermally conductive additive, using atom transfer radical polymerization, which led to the formation of the platelets coated with covalently tethered polymer layers (GO_PAAM), accounting for ca. 31% of the total mass. Polyamide-6 (PA6) nanocomposites containing 1% of GO_PAAM were formed by extrusion followed by injection molding. The thermal conductivity of the nanocomposite was 54% higher than that of PA6 even for such a low content of GO. The result was assigned to strong interfacial interactions between the brushes and PA6 matrix related to hydrogen bonding. Control nanocomposites containing similarly prepared GO decorated with other polymer brushes that are not able to form hydrogen bonds with PA6 revealed no enhancement of the conductivity. Importantly, the nanocomposite containing GO_PAAM also demonstrated larger tensile strength without deteriorating the elongation at break value, which was significantly decreased for the other coated platelets. The proposed approach enhances the interfacial interactions thanks to the covalent tethering of dense polymer brushes on 2D fillers and may be used to improve thermal properties of other polymer-based nanocomposites with simultaneous enhancement of their mechanical properties.

Preparation of new enforcement polyamide nanocomposite filled by ternary layer double hydroxide and investigation of electrochemical activity, optical and thermal properties

Herein, we report synthesis and manipulation of new reinforced polyamide nanocomposites filled by modified ternary (Mg, Zn, Al) layered double hydroxide by a solution intercalation technique. First, a new optically and electrochemically active polyamide 5 containing a new combination of azobenzene unit, imine function, triphenylamine segment and pyridine moiety in the main chain was prepared by reaction of a newly dicarboxylic acid 3 and 2,6-diaminopyridine 4. Then, two resulting nanocomposites containing 3 and 6% of DLDH were prepared and structures, morphology, electrochemical activity, thermal and optically properties of them were investigated. Also, dye-modified ternary layered double hydroxide was obtained by a co-precipitation method. The π–π* transition related to trans azobenzene chromosphere showed a single absorption between 290 and 350 nm. The electrochemically active behavior of resulting films onto glassy carbon exhibited cyclic voltammetry peak at 0.5–0.9 V, which was enhanced by filling polymer matrix with modified DLDH. On the other hand, significant improvements at T5, T10 and char yields of resulting nanocomposites were observed as compared to the polymer.

Exfoliated clay nanocomposites of renewable long-chain aliphatic polyamide through in-situ polymerization

The current study was performed to synthesize a series of renewable polyamide 614/organoclay nanocomposites (PAC) with the improved structural, mechanical, and thermal properties via in-situ polymerization. The uniform dispersion and exfoliation of clay into the PA614 matrix, particularly at a lower loading of organoclay (less than 3%), confirmed via structural analyses (XRD, SEM, and TEM). Furthermore, the mechanical tests revealed remarkable improvement; namely, the tensile strength and storage modulus increased by 27% and 30%, respectively, in the sample contained 2% organoclay. Similarly, the TGA results showed a slight improvement in the thermal stability of the nanocomposite samples. Altogether, these improvements confirmed excellent compatibility between nanofiller and matrix and the organoclay homogenous dispersion into the PA matrix achieved by employing in-situ polymerization. Furthermore, all the samples illustrated a shear-thinning behavior over frequency attributed to the lack of time for the polymer chain to respond to the applied oscillation. Finally, the crystallinity of the samples diminished upon increasing the filler's content, which could be due to the decrease of free volume resulting from the presence of organoclay. To sum up, the current investigation supported the benefit of employing in-situ polymerization to synthesize renewable PA614/clay nanocomposites with enhanced physio-mechanical properties, which could be appropriate candidates for engineering applications.

Temperature-Dependent Dielectric Properties of Polyimide (PI) and Polyamide (PA) Nanocomposites

Cryogenic dielectrics are a crucial component for applied superconducting systems such as high-temperature superconductor (HTS) cables. Here two types of polymer nanocomposites were investigated as dielectrics for cryogenic applications. Both polyimide (PI) and polyamide (PA) nanocomposites showed exceptional performance as dielectrics, with PI as the stronger material. Significant dielectric strength improvement was observed for samples tested in the cryogenic environment when compared to those tested at the room temperature. The PI exhibited a high dielectric strength of 347 ± 67 kV/mm at 92 K, while its nanocomposites were in the range of 261-280 kV/mm. The performance change of these dielectrics was influenced by a number of factors including the density of free charge carriers, localized heat generation and material degradation, thermal contraction of polymers, and polymer-nanoparticle interfacial changes at cryogenic temperatures. The findings from this research can help advance the understanding of breakdown failures in cryogenic dielectrics.

Facile Fabrication of Upconversion Photoluminescent Transparent Semiaromatic Polyamide Nanocomposites Through Interfacial Chemistry Modification.

Transparent upconversion photoluminescent polyamide nanocomposites were fabricated via a facile in situ polycondensation method with interfacial chemistry modification employing polyacrylic acid-functionalized upconversion nanoparticles (UCNP-PAA) as fillers and transparent semiaromatic polyamides (SAPA) as host materials. The as-prepared UCNP-PAA could be dispersed uniformly in the polyamide salt solution and the SAPA chains can be grafted to the UCNP-PAA through condensation reactions. The grafted SAPA ligand on the surface of UCNP increases the compatibility between SAPA and UCNP, thus causing uniform dispersion of the UCNP in the polyamide nanocomposites and improving the transmittance of the polyamide nanocomposites. The obtained polyamide nanocomposites are transparent and show strong green upconversion photoluminescence. This work solved the problem of the dispersity of incorporated nanoparticles and improving the transparency of nanocomposites and, more importantly, endowed the traditional engineering plastic with upconversion photoluminescent properties which can be applied in three-dimensional displays and the related solar cell field in the future.

Preparation of COOH-KCC-1/polyamide 6 composite by in situ ring-opening polymerization: synthesis, characterization, and Cd(II) adsorption study

A nanocomposite of carboxylic acid-functionalized fibrous silica KCC-1 and polyamide 6 (COOH-KCC-1/PA6 NC) was fabricated through an ultrasonic-assisted in situ ring-opening polymerization approach under an organic solvent-free condition. The presence of abundant functional groups like carboxylic, secondary amine, and ketone in the COOH-KCC-1/PA6 NC structure can make it a good candidate for the adsorption of heavy metals. Accordingly, COOH-KCC-1/PA6 NC was characterized and utilized as an adsorbent for Cd(II) uptake from aqueous media. Crucial adsorption factors, namely pH, adsorbent dosage, Cd(II) initial concentration, and contact time, affecting the removal of Cd(II) were monitored and the optimum adsorption conditions were determined. Isotherm and kinetic investigations were conducted and a non-linear fitting method of experimental data was used to obtain isotherm and kinetic parameters. The experimental maximum adsorption capacity of Cd(II) was found to be 109.2 mg g–1 (pH: 7.0, adsorbent dosage: 0.05 g, initial concentration: 80 mg L–1, time: 240 min, temperature: 25 ℃). The observed adsorption property is due to (1) the uniform distribution of COOH-KCC-1 filler within the PA6 matrix, (2) the presence of abundant adsorption sites like carboxylic acid (−COOH), ketone (–C=O), silanol (Si−OH), and secondary amine (–NH–) in the adsorbent structure, and (3) the structural stability of the adsorbent owing to strong interfacial interactions (physical and chemical bonding) between COOH-KCC-1 and PA6 polymer. Based on the results it can be suggested that the COOH-KCC-1/PA6 NC adsorbent can be handled for the adsorption of Cd(II) from aqueous media.

Nanofibrillar green composites of polylactide/polyamide produced in situ due to shear induced crystallization

Nowadays, extensive efforts are devoted to develop efficient ways to prepare in-situ fibrillated polymer-polymer nanocomposites which are both strong and ductile. Using entirely bio-sourced polymers is essential to keep a green nature of the obtained nanocomposites. In current work, sustainable in-situ green nanocomposites of polylactide (PLA) and biosourced polyamide (PA) were obtained in one stage of extrusion through applying high shear rate. The critical role of a high shear rate in the possibility of implementing two simultaneous processes, namely, the transition from droplet to fibrillar morphology and the subsequent instantaneous stabilization of the formed fibrillar morphology via the shear induced crystallization of minor phase, is highlighted. It is shown that in the case of PLA/PA blend, both of these processes are activated at a shear rate of 300 s−1 and lead to the formation of nanofibers with nanosized scale (150–550 nm) and aspect ratios of 45. At a low concentration of PA, 5 wt%, this results in the formation of an effective nanofibrillar network, which leads to strong interfacial adhesion between the phases. The Young's modulus, strain at break and impact strength of in situ generated PLA/PA composite undergoes an enhancement nearly 7, 4500, and 90%, respectively, while its tensile strength retains high.

The Effect of Various Nanoclay Surface Modifications on the Thermal and Mechanical Properties of Amorphous Polyamide Nanocomposites

The addition of nanoclay within polymer matrix is anticipate to enhance the properties of the polymer system. Nonetheless, one of the key elements in property enhancements of a polymer nanocomposites is the surface modifications of the nanoclay. This is due to the affinity between polymer matrix and nanoclay is of important factors should be considered. In this study, amorphous polyamide were melt blended with different nanoclay grades with different surface modifications in order to evaluate the best clay grade for the polymer system. The thermal analysis carried out on the amorphous polyamide nanocomposites were carried out by means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) whereas the mechanical properties were investigated using tensile testing. It was observed that there were changes in the glass transition temperature (Tg) of the nanocomposites due to clay additions. Further, the storage modulus was found to increase as a result of nanoclay incorporation. The type of clay grades significantly affects the mechanical properties of the amorphous polyamide nanocomposites.

Measurement possibilities of water content in polyamide

Water content of polyamide is an important parameter, because it has great effect on the elongation, toughness and impact strength. The aim of our research was to determine moisture in polyamide-6 and polyamide-6.6 granules with different pretreatment of the base material. The specimens were prepared and conditioned in distilled water or non-conditioned. Thermogravimetric analysis, moisture analysis and coulometric Karl-Fisher indirect titration were used for the determination of humidity content. We used polyamide granules and flakes, and polyamide nanocomposites filled with montmorillonite for the water content measurements. First, we compared the technics and chose the most applicable to measure the water content in the samples, and made further measurement of polyamide nanocomposites.

Simultaneous adsorption of dye and toxic metal ions using an interfacially polymerized silica/polyamide nanocomposite: Kinetic and thermodynamic studies

A silica/aromatic polyamide (SiPA) nanocomposite was synthesized by the interfacial copolymerization of a trimesoyl chloride (TMC) monomer and m-phenylene diamine (MPD) in silica. The obtained SiPA nanocomposite was investigated with a Fourier transform infrared spectrometer, a scanning electron microscope, and Brunauer-Emmett-Teller (BET) nitrogen adsorption/desorption. Adsorption of methylene blue (MB) on SiPA was evaluated for various factors influencing the process. The MB adsorption experimental data were fitted to Kinetic and thermodynamic models. The analysis indicates that adsorption of MB on SiPA fitted well with the Langmuir isotherm model, as well as to the pseudo-second-order model. The removal rate was rapid and equilibrium was attained in a short time. From a thermodynamic viewpoint, the adsorption was spontaneous and endothermic ∆H° = 12.6 KJ/mol, in addition to being favorable with qm = 44.6 mg/g. The prepared adsorbent showed good applicability to remove MB from real wastewater samples. The influence of the interference on adsorption was investigated in the presence of metal ions including Pb, Ni, Hg, Cd, As, Cu, Cr, and Mn. Interestingly, with ≈100% removal of the dye, the SiPA nanocomposite also exhibited a rapid simultaneous uptake of the toxic metals.

One-pot double in-situ fabrication of transparent semi-aromatic polyamide nanocomposites with upconversion nanoparticles

A simple one-pot double in-situ synthetic method was proposed to fabricate transparent semi-aromatic polyamides (SAPA) nanocomposites with upconversion nanoparticles (UCNP) as nanophase contents by combining hydrothermal method with melt polycondensation method. The key to this method is that the nanoparticles and polyamides were prepared in one-pot by simply mixing polyamides monomers and UCNP precursors as the raw materials without preparing polyamides or nanoparticles in advance. This approach enables the simple fabrication of transparent upconversion luminescent semi-aromatic polyamides nanocomposites with UCNP uniformly dispersed and can be extend to other kinds of polyamides and functional nanoparticles to prepare various polyamide nanocomposites.

Assessing the Performance of Thin-Film Nanofiltration Membranes with Embedded Montmorillonites.

In this study, the basal spacing of montmorillonite (MMT) was modified through ion exchange. Two kinds of MMT were used: sodium-modified MMT (Na-MMT) and organo-modified MMT (O-MMT). These two particles were incorporated separately into the thin-film nanocomposite polyamide membrane through the interfacial polymerization of piperazine and trimesoyl chloride in n-hexane. The membrane with O-MMT (TFNO-MMT) has a more hydrophilic surface compared to that of membrane with Na-MMT (TFNNa-MMT). When various types of MMT were dispersed in the n-hexane solution with trimesoyl chloride (TMC), O-MMT was well-dispersed than Na-MMT. The poor dispersion of Na-MMT in n-hexane led to the aggregation of Na-MMT on the surface of TFNNa-MMT. TFNO-MMT displayed a uniform distribution of O-MMT on the surface, because O-MMT was well-dispersed in n-hexane. In comparison with the pristine and TFNNa-MMT membranes, TFNO-MMT delivered the highest pure water flux of 53.15 ± 3.30 L∙m−2∙h−1 at 6 bar, while its salt rejection for divalent ions remained at 95%–99%. Furthermore, it had stable performance in wide operating condition, and it exhibited a magnificent antifouling property. Therefore, a suitable type of MMT could lead to high separation efficiency.