Processing, Properties, and Applications of Polymer Nanocomposites Based on Layer Silicates: A Review

In vitro inflammation and toxicity assessment of pre- and post-incinerated organomodified nanoclays to macrophages using high-throughput screening approaches

BACKGROUND

Organomodified nanoclays (ONC), two-dimensional montmorillonite with organic coatings, are increasingly used to improve nanocomposite properties. However, little is known about pulmonary health risks along the nanoclay life cycle even with increased evidence of airborne particulate exposures in occupational environments. Recently, oropharyngeal aspiration exposure to pre- and post-incinerated ONC in mice caused low grade, persistent lung inflammation with a pro-fibrotic signaling response with unknown mode(s) of action. We hypothesized that the organic coating presence and incineration status of nanoclays determine the inflammatory cytokine secretary profile and cytotoxic response of macrophages. To test this hypothesis differentiated human macrophages (THP-1) were acutely exposed (0-20 µg/cm2) to pristine, uncoated nanoclay (CloisNa), an ONC (Clois30B), their incinerated byproducts (I-CloisNa and I-Clois30B), and crystalline silica (CS) followed by cytotoxicity and inflammatory endpoints. Macrophages were co-exposed to lipopolysaccharide (LPS) or LPS-free medium to assess the role of priming the NF-κB pathway in macrophage response to nanoclay treatment. Data were compared to inflammatory responses in male C57Bl/6J mice following 30 and 300 µg/mouse aspiration exposure to the same particles.

RESULTS

In LPS-free media, CloisNa exposure caused mitochondrial depolarization while Clois30B exposure caused reduced macrophage viability, greater cytotoxicity, and significant damage-associated molecular patterns (IL-1α and ATP) release compared to CloisNa and unexposed controls. LPS priming with low CloisNa doses caused elevated cathepsin B/Caspage-1/IL-1β release while higher doses resulted in apoptosis. Clois30B exposure caused dose-dependent THP-1 cell pyroptosis evidenced by Cathepsin B and IL-1β release and Gasdermin D cleavage. Incineration ablated the cytotoxic and inflammatory effects of Clois30B while I-CloisNa still retained some mild inflammatory potential. Comparative analyses suggested that in vitro macrophage cell viability, inflammasome endpoints, and pro-inflammatory cytokine profiles significantly correlated to mouse bronchioalveolar lavage inflammation metrics including inflammatory cell recruitment.

CONCLUSIONS

Presence of organic coating and incineration status influenced inflammatory and cytotoxic responses following exposure to human macrophages. Clois30B, with a quaternary ammonium tallow coating, induced a robust cell membrane damage and pyroptosis effect which was eliminated after incineration. Conversely, incinerated nanoclay exposure primarily caused elevated inflammatory cytokine release from THP-1 cells. Collectively, pre-incinerated nanoclay displayed interaction with macrophage membrane components (molecular initiating event), increased pro-inflammatory mediators, and increased inflammatory cell recruitment (two key events) in the lung fibrosis adverse outcome pathway.

Effect of CuO Nanoparticles on the Optical, Structural, and Electrical Properties in the PMMA/PVDF Nanocomposite

A polymeric nanocomposite film, composed of PMMA/PVDF and different amounts of CuO NPs, was successfully prepared using the casting method to enhance its electrical conductivity. Various techniques were employed to investigate their physicochemical properties. The addition of CuO NPs causes a noticeable difference in the intensities and locations of vibrational peaks in all bands, confirming the incorporation of CuO NPs inside the PVDF/PMMA. In addition, the broadening of the peak at 2θ = 20.6° becomes more intense with increasing amounts of CuO NPs, confirming the increase in the amorphous characteristic of PMMA/PVDF incorporated with CuO NPs in comparison with PMMA/PVDF. Furthermore, the image of the polymeric structure exhibits a smoother shape and interconnection of pore structure associated with spherical particles that agglomerate and give rise to a web-like organization that becomes a matrix. Increasing surface roughness is responsible for an increasing surface area. Moreover, the addition of CuO NPs in the PMMA/PVDF leads to a decrease in the energy band gap, and further increasing the additional amounts of CuO NPs causes the generation of localized states between the valence and conduction bands. Furthermore, the dielectric investigation shows an increase in the dielectric constant, dielectric loss, and electric conductivity, which may be an indication of an increase in the degree of disorder that confines the movement of charge carriers and demonstrates the creation of an interconnected percolating chain, enhancing its conductivity values compared with that without the incorporation of a matrix.

Durable PP/EPDM/GF/SiO2 nanocomposites with improved strength and toughness for orthotic applications

Ankle-foot orthotics need ideal specification of being light-weight, high strength, tough, stiff, and durable. Reinforced polypropylene (PP) composites with enhanced mechanical properties are the most favorable materials being used in this field, but still, it is challenging to achieve balanced blend of strength and toughness in the composites. The present study thus aims to achieve the challenging task of simultaneous improvement in stiffness and toughness in reinforced PP composites exploring the synergistic reinforcement effect of glass fibers (GFs) and nano silica (SiO2) as multiscale fillers and ethylene propylene diene monomer (EPDM) as impact modifier. EPDM is used as toughness modifier, addressing the brittle behavior, but at the cost of the strength of the polymer. Combined use of micro and nanofillers as reinforcement in toughened polypropylene provides a potential approach to balance the strength while maintaining the toughness. GFs could offer high strength and nanofillers offer ductile fracture to the material. PP, PP/GF, PP/EPDM/GF composites and PP/EPDM/GF/SiO2 nanocomposites are fabricated through melt blending technique and are characterized through SEM, mechanical evaluation, nanoindentation and dynamic mechanical analysis. Mechanical properties are evaluated in accordance with ASTM standards. PP/EPDM/GF/SiO2 nanocomposites exhibits remarkable enhancement in Tensile strength, tensile modulus, impact strength and percent elongation at break by 49 MPa (55% increase over PP), 2450 MPa (145% increase), 145 J/m (13% increase) and 156% (160% increase) respectively. The exceptional improvement in reduced modulus and hardness reveals good interfacial properties. Loss factor decrement reveals elastic behavior of nanocomposites suitable for thermoforming of nanocomposites for orthotic device fabrication.

Characterization of steel lined with multilayer micro/nano-polymeric composites

This work studied comparison of the mechanical and barrier resistance properties between different structures of three multilayers polymeric coating on each side of the steel coupons. Epoxy filled with 1 wt%, 2 wt%, and 3 wt% micron or nano-sized alumina (Al2O3) particles represented the coating layers to steel on both sides. Barrier resistance was performed by immersing the coated steel specimens in salt solution and in a citric acid medium. Adding alumina (Al2O3) particles in micron and nano size to epoxy coatings improved the barrier resistance, tensile, and hardness under dry and wet conditions as compared to pure epoxy coating. Further increases in Al2O3 micro/nanoparticles cause deterioration in tensile strength and barrier resistance. The steel lined with epoxy filled with 1 wt% Al2O3 nanoparticles has a maximum tensile strength of 299.5 MPa and 280.9 MPa under dry and wet conditions, respectively. However, the steel lined with epoxy filled with 1 wt% Al2O3 microparticles has a tensile strength of 296.5 MPa and 275.4 MPa under dry and wet conditions, respectively. Good properties were observed with stepwise graded micro/nanocomposite coatings. The steel lined with epoxy filled with 3 wt% Al2O3 nanoparticles has maximum hardness of 46 HV and 40 HV under dry and wet conditions, respectively.

Prospects of Polymeric Nanocomposite Membranes for Water Purification and Scalability and their Health and Environmental Impacts: A Review

Water shortage is a major worldwide issue. Filtration using genuine polymeric membranes demonstrates excellent pollutant separation capabilities; however, polymeric membranes have restricted uses. Nanocomposite membranes, which are produced by integrating nanofillers into polymeric membrane matrices, may increase filtration. Carbon-based nanoparticles and metal/metal oxide nanoparticles have received the greatest attention. We evaluate the antifouling and permeability performance of nanocomposite membranes and their physical and chemical characteristics and compare nanocomposite membranes to bare membranes. Because of the antibacterial characteristics of nanoparticles and the decreased roughness of the membrane, nanocomposite membranes often have greater antifouling properties. They also have better permeability because of the increased porosity and narrower pore size distribution caused by nanofillers. The concentration of nanofillers affects membrane performance, and the appropriate concentration is determined by both the nanoparticles' characteristics and the membrane's composition. Higher nanofiller concentrations than the recommended value result in deficient performance owing to nanoparticle aggregation. Despite substantial studies into nanocomposite membrane manufacturing, most past efforts have been restricted to the laboratory scale, and the long-term membrane durability after nanofiller leakage has not been thoroughly examined.

Modified Polymer Surfaces: Thin Films of Silicate Composites via Polycaprolactone Melt Fusion

Polymer/layered silicate composites have gained huge attention in terms of research and industrial applications. Traditional nanocomposites contain particles regularly dispersed in a polymer matrix. In this work, a strategy for the formation of a composite thin film on the surface of a polycaprolactone (PCL) matrix was developed. In addition to the polymer, the composite layer was composed of the particles of saponite (Sap) modified with alkylammonium cations and functionalized with methylene blue. The connection between the phases of modified Sap and polymer was achieved by fusing the chains of molten polymer into the Sap film. The thickness of the film of several μm was confirmed using electron microscopy and X-ray tomography. Surfaces of precursors and composite materials were analyzed in terms of structure, composition, and surface properties. The penetration of polymer chains into the silicate, thus joining the phases, was confirmed by chemometric analysis of spectral data and changes in some properties upon PCL melting. Ultimately, this study was devoted to the spectral properties and photoactivity of methylene blue present in the ternary composite films. The results provide directions for future research aimed at the development of composite materials with photosensitizing, photodisinfection, and antimicrobial surfaces.

Wastewater Treatment and Biomedical Applications of Montmorillonite Based Nanocomposites: A Review

Background::

Rapid industrialisation, population growth and technological race worldwide have brought adverse consequences on water resources and as a result affect human health. Toxic metal ions, non-biodegradable dyes, organic pollutants, pesticides, pharmaceuticals are among the chief hazardous materials released into the water bodies from various sources. These hazardous contaminants drastically affect the flora and fauna globally leading to health deterioration there by giving rise to new biomedical challenges.

Hypothesis::

Montmorillonite based nanocomposites (MMTCs) have drawn an attention of the researchers to design environmental friendly, advanced and hygienic nanocomposites for wastewater treatment and biomedical purposes. Montmorillonite clay possesses peculiar physical and chemical properties that include enhanced surface reactivity, improved rheological performance, exorbitant miscibility in water due to which it shows highly favourable interactions with polymers, drugs, metals, mixed metals and metal oxides leading to the fabrication of different types of advanced montmorillonite based nanocomposites that have remarkable applications

Methodology::

Here we review the structural characteristics of montmorillonite clay, advances in the synthetic techniques involved in the fabrication of montmorillonite nanocomposites, their applications in waste water treatment and in bio medical field. The recently developed montmorillonite nanocomposites for (1) waste water treatment as nano-adsorbents for the elimination of toxic inorganic species such as metal ions and heterogeneous photo-catalysts for photo degradation of dyes, pesticides and pharmaceuticals (2) biomedical utilization viz drug delivery, wound amelioration, bone cement, tissue engineering etc. are presented

Conclusion::

The review exclusively focuses on recent research on montmorillonite based nanocomposites and their application in wastewater treatment and in biomedical field

Polymeric Nanocomposites for Environmental and Industrial Applications

Polymeric nanocomposites (PNC) have an outstanding potential for various applications as the integrated structure of the PNCs exhibits properties that none of its component materials individually possess. Moreover, it is possible to fabricate PNCs into desired shapes and sizes, which would enable controlling their properties, such as their surface area, magnetic behavior, optical properties, and catalytic activity. The low cost and light weight of PNCs have further contributed to their potential in various environmental and industrial applications. Stimuli-responsive nanocomposites are a subgroup of PNCs having a minimum of one promising chemical and physical property that may be controlled by or follow a stimulus response. Such outstanding properties and behaviors have extended the scope of application of these nanocomposites. The present review discusses the various methods of preparation available for PNCs, including in situ synthesis, solution mixing, melt blending, and electrospinning. In addition, various environmental and industrial applications of PNCs, including those in the fields of water treatment, electromagnetic shielding in aerospace applications, sensor devices, and food packaging, are outlined.

Effect of Nanoparticles Surface Bonding and Aspect Ratio on Mechanical Properties of Highly Cross-Linked Epoxy Nanocomposites: Mesoscopic Simulations

The paper aims to study the mechanical properties of epoxy resin filled with clay nanoparticles (NPs), depending on their shapes and content on the surface of a modifying agent capable of forming covalent bonds with a polymer. The cylindrical clay nanoparticles with equal volume and different aspects ratios (disks, barrel, and stick) are addressed. The NPs' bonding ratio with the polymer (RGC) is determined by the fraction of reactive groups and conversion time and varies from RGC = 0 (non-bonded nanoparticles) to RGC = 0.65 (more than half of the surface groups are linked with the polymer matrix). The performed simulations show the so-called load-bearing chains (LBCs) of chemically cross-linked monomers and modified nanoparticles to determine the mechanical properties of the simulated composites. The introduction of nanoparticles leads to the breaking of such chains, and the chemical cross-linking of NPs with the polymer matrix restores the LBCs and strengthens the composite. At small values of RGC, the largest value of the elastic modulus is found for systems filled with nanoparticles having the smallest surface area, and at high values of RGC, on the contrary, the systems containing disk-shaped particles with the largest surface area have a larger elastic modulus than the others. All calculations are performed within the framework of a mesoscopic model based on accurate mapping of the atomistic structures of the polymer matrix and nanoparticles into coarse-grained representations, which, if necessary, allow reverse data mapping and quantitative assessment of the state of the filled epoxy resin. On the other hand, the obtained data can be used to design the functional materials with specified mechanical properties based on other practically significant polymer matrices and nanofillers.

The Effect of Surfactant-Modified Montmorillonite on the Cross-Linking Efficiency of Polysiloxanes

Polymer–clay mineral composites are an important class of materials with various applications in the industry. Despite interesting properties of polysiloxanes, such matrices were rarely used in combination with clay minerals. Thus, for the first time, a systematic study was designed to investigate the cross-linking efficiency of polysiloxane networks in the presence of 2 wt % of organo-montmorillonite. Montmorillonite (Mt) was intercalated with six quaternary ammonium salts of the cation structure [(CH₃)₂R’NR]⁺, where R = C₁₂, C₁₄, C₁₆, and R’ = methyl or benzyl substituent. The intercalation efficiency was examined by X-ray diffraction, CHN elemental analysis, and Fourier transform infrared (FTIR) spectroscopy. Textural studies have shown that the application of freezing in liquid nitrogen and freeze-drying after the intercalation increases the specific surface area and the total pore volume of organo-Mt. The polymer matrix was a poly(methylhydrosiloxane) cross-linked with two linear vinylsiloxanes of different siloxane chain lengths between end functional groups. X-ray diffraction and transmission electron microscopy studies have shown that the increase in d-spacing of organo-Mt and the benzyl substituent influence the degree of nanofillers’ exfoliation in the nanocomposites. The increase in the degree of organo-Mt exfoliation reduces the efficiency of hydrosilylation reaction monitored by FTIR. This was due to physical hindrance induced by exfoliated Mt particles.

Influence of the addition of organo-montmorillonite nanofiller on cross-linking of polysiloxanes - FTIR studies

The main aim of the present work was to investigate the effect of organo-montmorillonite nanofiller on the cross-linking process of polysiloxane. Two series of model polysiloxane nanocomposites were prepared by incorporating organoclay at different amounts such as 0, 1, 2, 4, and 8 wt% in relation to the weight of the polymer matrix. Poly(methylhydrosiloxane) (PMHS) was cross-linked with two linear vinylsiloxanes of different chain lengths between functional end-groups through hydrosilylation. This reaction was carried out in the presence of Karstedt's catalyst at equimolar ratios of reactive groups. Fourier-transform infrared (FTIR) spectroscopic measurements obtained during the cross-linking processes as well as for the reaction products revealed that the rate of hydrosilylation and its efficiency are influenced by the type of the cross-linking agent used and the amount of organo-montmorillonite introduced into the polysiloxane network. Quantitative analysis of the recorded FTIR spectra showed that as the amount of nanofiller in the polysiloxane matrix increased, the rate and efficiency of the cross-linking process decreased. Swelling measurements confirmed that the increase in the amount of unreacted Si-H groups in the system resulted in a lower cross-link density of the studied materials. Furthermore, X-ray diffraction and transmission electron microscopy were performed to determine the nature of dispersion of organoclay within the studied systems.

Carboxylated cellulose nanofiber/montmorillonite nanocomposite for the removal of levofloxacin hydrochloride antibiotic from aqueous solutions

Herein, we report the facile two-step synthesis of an effective carboxylated cellulose nanofiber/montmorillonite nanocomposite (CMNFs-MMT) adsorbent for levofloxacin hydrochloride (Levo-HCl). CMNFs-MMT was characterized using scanning electron microscopy, energy dispersive X-ray spectrometry, Brunauer-Emmett-Teller measurements, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Based on the central composite design, the effects of various factors on the removal of Levo-HCl by the CMNFs-MMT were explored, wherein the effect of pH was the most significant. To gain a clearer perspective on the adsorption process of Levo-HCl onto CMNFs-MMT, the adsorption kinetics and isotherms were also measured, revealing that the reaction is pseudo-second-order and the Sips models provide the best fit with experimental data. Comparing the adsorption in pure water with the removal in river water, the rate of river water removal (90.37%) was slightly lower than that of pure water (93.97%) when adsorption equilibrium was reached, confirming that CMNFs-MMT is not easily influenced by environmental conditions. Reusability experiments indicate that CMNFs-MMT can maintain a certain adsorption capacity for Levo-HCl after six uses. Overall, this work indicates that CMNFs-MMT is an effective adsorbent for eliminating Levo-HCl from aqueous media in future engineering applications.

The Stability of Intercalated Sericite by Cetyl Trimethylammonium Ion under Different Conditions and the Preparation of Sericite/Polymer Nanocomposites

Layered silicates are suitable for use as fillers in nanocomposites based on their particular features, such as large aspect ratio, easy availability, and chemical resistance. Among them, sericite is distinguished for its higher aspect ratio, higher resilience, and ultraviolet shielding and absorption. Previously, sericite was structure-modified and intercalated by CTAB to expand its interlayer space. The intercalated sericite seems promising for use in the fabrication of polymer/sericite composites or pillared sericite. However, special attention should be paid to the stability of the intercalated sericite because the CTAB inside the layer may be de-intercalated, which would affect the interlayer spacing and its surface properties. In this article, the stability of the sericite intercalated by CTAB was tested by changing different variables, such as different washing solvents, different temperatures, ultrasonic cleaning, and different solution conditions. Finally, sericite/polymer nanocomposites were produced with the stable intercalated sericite, and showed excellent properties compared with pure epoxy resin.

A versatile strategy for mechanically durable nanocomposite cryogels based on cationic (alkyl)methacrylates and hydrophilic bentonite via freezing (cryo)polymerization

A simple strategy for the preparation of organic-inorganic (alkyl)methacrylate-based nanocomposite gels was established. The preparation procedure was based on free-radical copolymerization of cationic monomer N,N-dimethylaminoethyl methacrylate (DMAEMA) in the presence of a low amount of ionic comonomer 2-acrylamido-2-methyl-propanosulfonic acid (AMPS), nanoclay bentonite (BENT) and diethyleneglycol dimethacrylate (DEGDMA) as a chemical crosslinker. The parameters of equilibrium volume swelling, initial swelling rate, diffusional exponent, and early- and late-time diffusion coefficients were evaluated from the swelling measurements in salt solutions. PDMAEMA retained its own characteristics regardless of the amounts of ionic comonomer AMPS and nanoclay bentonite. The prepared nanocomposite cryogels/hydrogels were found to be pH and temperature-responsive. The elastic moduli and compressibility of the nanocomposite NC/BENTm-Cgels were much higher than those of NC/BENTm-Hgels. The effective crosslink density distribution of the nanocomposite NC/BENTm-Hgels was evaluated from the elastic moduli data of the as-prepared state and the degree of crosslinking was described by a quadratic polynomial as a function of the clay concentration. At high clay content, the nanocomposite NC/BENTm gels exhibited a lower swelling degree, and thus a higher crosslinking density than the clay-free gels. Both NC/BENTm Hgels and Cgels exhibited obvious pH and temperature double sensitiveness; the equilibrium degree of swelling decreased as the solution's pH or the swelling temperature increased. The power law exponent values obtained from dynamic swelling in aqueous Na2SO4 solution indicated that the sorption mechanism of both the nanocomposite NC/BENTm-Hgel and NC/BENTm-Cgel samples was Fickian controlled. Overall, this study successfully establishes the thermodynamic relations between the physico-mechanical behavior and characteristic network parameters of (alkyl)methacrylate-based nanocomposite gels prepared at various BENT concentrations.

Short-Term Pulmonary Toxicity Assessment of Pre- and Post-incinerated Organomodified Nanoclay in Mice

Organomodified nanoclays (ONCs) are increasingly used as filler materials to improve nanocomposite strength, wettability, flammability, and durability. However, pulmonary risks associated with exposure along their chemical lifecycle are unknown. This study's objective was to compare pre- and post-incinerated forms of uncoated and organomodified nanoclays for potential pulmonary inflammation, toxicity, and systemic blood response. Mice were exposed via aspiration to low (30 μg) and high (300 μg) doses of preincinerated uncoated montmorillonite nanoclay (CloisNa), ONC (Clois30B), their respective incinerated forms (I-CloisNa and I-Clois30B), and crystalline silica (CS). Lung and blood tissues were collected at days 1, 7, and 28 to compare toxicity and inflammation indices. Well-dispersed CloisNa caused a robust inflammatory response characterized by neutrophils, macrophages, and particle-laden granulomas. Alternatively, Clois30B, I-Clois30B, and CS high-dose exposures elicited a low grade, persistent inflammatory response. High-dose Clois30B exposure exhibited moderate increases in lung damage markers and a delayed macrophage recruitment cytokine signature peaking at day 7 followed by a fibrotic tissue signature at day 28, similar to CloisNa. I-CloisNa exhibited acute, transient inflammation with quick recovery. Conversely, high-dose I-Clois30B caused a weak initial inflammatory signal but showed comparable pro-inflammatory signaling to CS at day 28. The data demonstrate that ONC pulmonary toxicity and inflammatory potential relies on coating presence and incineration status in that coated and incinerated nanoclay exhibited less inflammation and granuloma formation than pristine montmorillonite. High doses of both pre- and post-incinerated ONC, with different surface morphologies, may harbor potential pulmonary health hazards over long-term occupational exposures.

Ternary composites by an in situ hydrolytic polymerization process

Polyamide 6/modified silica composite materials have been prepared by a coupled polymerization procedure. For this purpose, the three-component-system we presented in a previous publication, consisting of ε-aminocaproic acid (ε-ACA), ε-caprolactam (ε-CL), and 1,1′,1′′,1′′′-silanetetrayltetrakis-(azepan-2-one) (Si(ε-CL)₄), has been combined with other silicon monomers with one or two methyl groups (MeSi(ε-CL)₃ and Me₂Si(ε-CL)₂). The simultaneous polymerization of ε-CL and silicon monomers leads to the in situ formation of silica/polysiloxane particles and the surrounding polyamide 6 matrix in one step. Moreover, 3-aminopropyltriethoxysilane has been added to the three-component-system to achieve covalent bonding between organic and inorganic phases and to inhibit agglomeration of the silica particles. Chemical structures and morphologies of the composites have been investigated by solid-state NMR and FTIR spectroscopy as well as electron microscopy and SEC measurements. Structural effects on thermal properties have been studied by DSC and TGA measurements.

Polyamide 6/silica/polysiloxane composites have been prepared in a one-step process using lactam-substituted silicon monomers.

Mechanical properties, thermal and crystallization behavior of different surface-modified silica nanoparticle-filled PA66 composites

In this study, two different surface-modified silica nanoparticles, amino-functionalized nanosilica (ATS) and methyl-functionalized nanosilica (HDS), were separately used as nanofillers to fabricate PA66-based nanocomposites by melt blending. The morphology and interface characteristics of the two nanofillers in the composite system and their influence on the mechanical properties, thermal decomposition behavior, and crystallization behavior of PA66 were investigated. The Avrami and Mo methods were applied to study the non-isothermal crystallization kinetics of the nanocomposites. The results revealed that different surface modifications of silica nanoparticles can produce different influences on the mechanical properties and thermal decomposition behavior of the final nanocomposites. The addition of ATS helps increase the strength and stiffness of PA66/ATS nanocomposites, and in the meantime enhances the thermal stability of PA66. The case of HDS is opposite to that of ATS; however, its incorporation can improve the toughness of the material. In addition, the results also indicate that ATS possesses strong heterogeneous nucleation capability, the introduction of which can accelerate the crystallization rate and increase the crystallization temperature, as well as the degree of crystallinity of PA66, while HDS displays an obvious blocking effect on the crystallization process of PA66.

Morphology Development and Mechanical Properties Variation during Cold-Drawing of Polyethylene-Clay Nanocomposite Fibers

In this work, the influence of composition and cold-drawing on nano- and micro-scale morphology and tensile mechanical properties of PE/organoclay nanocomposite fibers was investigated. Nanocomposites were prepared by melt compounding in a twin-screw extruder, using a maleic anhydride grafted linear low density polyethylene (LLDPE–g–MA) and an organomodified montmorillonite (Dellite 67G) at three different loadings (3, 5 and 10 wt %). Fibers were produced by a single-screw extruder and drawn at five draw ratios (DRs): 7.25, 10, 13.5, 16 and 19. All nanocomposites, characterized by XRD, SEM, TEM, and FT-IR techniques, showed an intercalated/exfoliated morphology. The study evidenced that the nanoclay presence significantly increases both elastic modulus (up to +115% for fibers containing 10 wt % of D67G) and drawability of as-spun nanocomposite fibers. Moreover, at fixed nanocomposite composition, the cold-drawing process increases fibers elastic modulus and tensile strength at increasing DRs. However, at high DRs, “face-to-edge” rearrangement phenomena of clay layers (i.e., clay layers tend to rotate and touch each other) arise in fibers at high nanoclay loadings. Finally, nanocomposite fibers show a lower diameter reduction during drawing, with respect to the plain system, and surface feature of adjustable roughness by controlling the composition and the drawing conditions.

Effects of surface modification of halloysite nanotubes on the morphology and the thermal and rheological properties of polypropylene/halloysite composites

Effects of unmodified halloysite nanotubes (HNTs) and hexadecyl trimethyl ammonnium bromide treated halloysite nanotubes (CTAB-HNTs) on the morphology as well as the thermal and rheological properties of the HNT-filled polypropylene (PP) composites were investigated. The composites were melt-blended with a novel vane mixer dominated by extensional deformation. Fourier transform infrared spectroscopy well demonstrated that ammonium molecules were successfully interacted with halloysite groups. Compared with unmodified HNTs, the modified HNTs had a better dispersion in the PP matrix. The degree of crystallinity increased with the introduction of HNTs into the PP matrix. Thermal analyses revealed that CTAB-HNTs can improve the composites’ thermal stability compared with unmodified HNTs. As for dynamic shear rheology, the PP/CTAB-HNT composites showed higher viscoelaticity than neat PP in most frequency regimes, and that the raw HNT/PP composites presented the opposite phenomenon. The relaxation time of PP melt and the availability of heterogeneous PP domains increased with the presence of CTAB-HNTs.

Three-Dimensional Printing of Multifunctional Nanocomposites: Manufacturing Techniques and Applications

The integration of nanotechnology into three-dimensional printing (3DP) offers huge potential and opportunities for the manufacturing of 3D engineered materials exhibiting optimized properties and multifunctionality. The literature relating to different 3DP techniques used to fabricate 3D structures at the macro- and microscale made of nanocomposite materials is reviewed here. The current state-of-the-art fabrication methods, their main characteristics (e.g., resolutions, advantages, limitations), the process parameters, and materials requirements are discussed. A comprehensive review is carried out on the use of metal- and carbon-based nanomaterials incorporated into polymers or hydrogels for the manufacturing of 3D structures, mostly at the microscale, using different 3D-printing techniques. Several methods, including but not limited to micro-stereolithography, extrusion-based direct-write technologies, inkjet-printing techniques, and popular powder-bed technology, are discussed. Various examples of 3D nanocomposite macro- and microstructures manufactured using different 3D-printing technologies for a wide range of domains such as microelectromechanical systems (MEMS), lab-on-a-chip, microfluidics, engineered materials and composites, microelectronics, tissue engineering, and biosystems are reviewed. Parallel advances on materials and techniques are still required in order to employ the full potential of 3D printing of multifunctional nanocomposites.

Swift Heavy Ion Irradiation as a Tool for Homogeneous Dispersion of Nanographite Platelets within the Polymer Matrices: Toward Tailoring the Properties of PEDOT:PSS/Nanographite Nanocomposites

Performance of the polymer nanocomposites is dependent to a great extent on efficient and homogeneous dispersion of nanoparticles in polymeric matrices. The dispersion of nanographite platelets (NGPs) in polymer matrix is a great challenge because of the inherent inert nature of the NGPs, poor wettability toward polymer matrices, and easy agglomeration due to van der Waals interactions. In the present study, attempts have been made to use a new approach involving the irradiation of polymer nanocomposites through swift heavy ion (SHI) to homogeneously disperse the NGPs within the polymer matrices. Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (

PEDOT

PSS)/nanographite nanocomposite (NC) films prepared by the solution blending method were irradiated with SHI (Ni ion beam, 80 MeV) at a fluence range of 1 × 10(10) to 1 × 10(12) ions/cm(2). XRD studies revealed that ion irradiation results in delamination and better dispersion of NGPs in the irradiated nanocomposite films compared to unirradiated films, which is also depicted through SEM, AFM, TEM, and Raman studies. In the irradiated polymer nanocomposite films, the conformation of PEDOT chains changes from coiled to extended coiled structure, which, along with homogeneously dispersed NGPs in irradiated NCs, shows an excellent synergistic effect facilitating charge transport. The remarkable improvement in conductivity from 1.9 × 10(-2) in unirradiated NCs to 0.45 S/cm in irradiated NCs is observed with marked improvement in sensing the response toward nitroaromatic vapors at room temperature. The temperature induced conductivity studies have been carried out for

PEDOT

PSS/nanographite NCs to comprehend the charge transport mechanism in NC films using the 3D Mott variable range hopping model also. The study reveals SHI as a novel method, addressing the challenge associated with the dispersion of NGPs within the polymer matrix for their enhanced performance toward various applications.

Water-Assisted Production of Thermoplastic Nanocomposites: A Review

Water-assisted, or more generally liquid-mediated, melt compounding of nanocomposites is basically a combination of solution-assisted and traditional melt mixing methods. It is an emerging technique to overcome several disadvantages of the above two. Water or aqueous liquids with additives, do not work merely as temporary carrier materials of suitable nanofillers. During batchwise and continuous compounding, these liquids are fully or partly evaporated. In the latter case, the residual liquid is working as a plasticizer. This processing technique contributes to a better dispersion of the nanofillers and affects markedly the morphology and properties of the resulting nanocomposites. A survey is given below on the present praxis and possible future developments of water-assisted melt mixing techniques for the production of thermoplastic nanocomposites.

Green aqueous surface modification of polypropylene for novel polymer nanocomposites

Polypropylene is one of the most widely used commercial commodity polymers; among many other applications, it is used for electronic and structural applications. Despite its commercial importance, the hydrophobic nature of polypropylene limits its successful application in some fields, in particular for the preparation of polymer nanocomposites. Here, a facile, plasma-assisted, biomimetic, environmentally friendly method was developed to enhance the interfacial interactions in polymer nanocomposites by modifying the surface of polypropylene. Plasma treated polypropylene was surface-modified with polydopamine (PDA) in an aqueous medium without employing other chemicals. The surface modification strategy used here was based on the easy self-polymerization and strong adhesion characteristics of dopamine (DA) under ambient laboratory conditions. The changes in surface characteristics of polypropylene were investigated using FTIR, TGA, and Raman spectroscopy. Subsequently, the surface modified polypropylene was used as the matrix to prepare SiO2-reinforced polymer nanocomposites. These nanocomposites demonstrated superior properties compared to nanocomposites prepared using pristine polypropylene. This simple, environmentally friendly, green method of modifying polypropylene indicated that polydopamine-functionalized polypropylene is a promising material for various high-performance applications.

Low Velocity Impact and Creep-Strain Behaviour of Vinyl Ester Matrix Nanocomposites Based on Layered Silicate

The impact properties of neat vinyl ester and the nanocomposites were performed using a low velocity impact testing. The addition of layered silicate into the polymer matrix shows that an optimum range of nanoclay reinforcement in the vinyl ester matrix can produce enhanced load bearing and energy absorption capability compared to the neat matrix. In addition, the amount of microvoids in the nanocomposites structure influences the overall properties. Likewise, the influence of the clay addition into the neat polymer on the creep relaxation behaviour at 25°C and 60°C was studied. In both cases, the presence of the layered silicate remarkably improved the creep behaviour. The improvement of these properties can be assigned to the stiff fillers and the configurational linkage between the polymer and the layered silicate which are supported by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterisations by showing a distinct change in surface morphology associated with improved impact toughness and creep response.