Preparation of Poly(Vinyl Alcohol) Nanocomposite Films Reinforced with Poly(Amide–Imide)/CuO Having N-trimellitylimido-L-valine Linkages for the Improvement of Mechanical and Thermal Properties

In this investigation, nanocomposite films were fabricated by dispersion of poly(amide–imide)/CuO nanocomposites as nanofiller in the poly(vinyl alcohol) matrix via an ultrasonic process. The nanofiller was prepared and mixed with PVA matrix. After dispersion of nanofiller into the poly(vinyl alcohol), the mechanical properties of the nanocomposites were improved. For example, the addition of 6 wt% nanofiller into the poly(vinyl alcohol) matrix enhanced the tensile modulus by 39%. The residual weight at 800°C was 7% for pure poly(vinyl alcohol) while the nanocomposites illustrated 12–19% residue at this temperature.     

In situ polymerization of polyurethane‐silver nanocomposite foams with intact thermal stability,improved mechanical performance,and induced antimicrobial properties

Silver nanoparticle‐reinforced thermoplastic polyurethane (PU/AgNP) nanocomposite foams were prepared using in situ polymerization techniques in accordance with DOW chemicals’ industrial standards. The foams exhibited improved mechanical performance, induced antimicrobial properties, and intact stability when subjected to a thermal degradation treatment. Scanning electron microscopy (SEM) indicated a homogeneous dispersion of the silver nanoparticle (AgNP) within the polymeric matrix at low filler loadings and a cluster formation at higher loadings. SEM also indicated the agglomeration of the silver nanofiller particles as a result of the thermal degradation treatment, which caused them to lose their nanoscopic characteristics and act as ordinary silver metal. Molecular modeling techniques were used to explain these observations and confirmed the higher repulsive interactions between the polymer chains and the silver nanoparticles with the increase in the nanofiller content. Stress relaxation of the nanocomposites showed optimum mechanical performance and lowest hysteresis for the 0.1% AgNP nanocomposites due to the confinement of the PU chains between the large number of the nanoparticles. Incubation with 0.1% foam inhibited the growth of Klebseilla spp. and Escherichia coli and to some extent Staphylococcus spp. This is very interesting as the same nanocomposite loaded with 0.1% AgNp has also shown the best mechanical performance highlighting the strong action of this “unclustered” low concentration on both the material and biomedical sides. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43125.     

Functionalized graphene-reinforced polysiloxane nanocomposite with improved mechanical performance and efficient healing properties

It is a challenge to design nanofiller reinforced self-healing nanocomposites with both improved mechanical properties and highly efficient self-healing properties. In this work, we report a self-healing polysiloxane nanocomposite using furan-functionalized graphene (G-FA) as reinforcement based on Diels−Alder (DA) chemistry. The formed interactions between G-FA and polysiloxane chains were reversible DA bonds, which negligibly affected the nanocomposites healing efficiency. The self-healing polysiloxane nanocomposite with 6% G-FA has a tensile strength of 0.25 MPa that was improved by 140% when compared to an elastomer without G-FA. The healable polysiloxane nanocomposite recovered more than 90% of its tensile strength and 98% of its elongation-at-break, demonstrating that the nanocomposite exhibited highly efficient self-healing properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47725.     

Mechanical Properties of Single-Layer Diamond Reinforced Poly(vinyl alcohol) Nanocomposites through Atomistic Simulation

Low-dimensional carbon nanostructures are ideal nanofillers to reinforce the mechanical performance of polymer nanocomposites due to their excellent mechanical properties. Through molecular dynamics simulations, the mechanical performance of poly(vinyl alchohol) (PVA) nanocomposites reinforced with a single-layer diamond – diamane is investigated. It is found the PVA/diamane exhibits similar interfacial strengths and pull-out characteristics with the PVA/bilayer-graphene counterpart. Specifically, when the nanofiller is fully embedded in the nanocomposite, it is unable to deform simultaneously with the PVA matrix due to the weak interfacial load transfer efficiency, thus the enhancement effect is not significant. In comparison, diamane can effectively promote the tensile properties of the nanocomposite when it has a laminated structure as it deforms simultaneously with the matrix. With this configuration, the interlayer sp³ bonds endows diamane with a much higher resistance under compression and shear tests, thus the nanocomposite can reach very high compressive and shear stress. Overall, enhancement on the mechanical interlocking at the interface as triggered by surface functionalization is only effective for the fully embedded nanofiller. This work provides a fundamental understanding of the mechanical properties of PVA nanocomposites reinforced by diamane, which can shed lights on the design and preparation of next generation high-performance nanocomposites.     

Stretchable,mechanically resilient,and high electromagnetic shielding polymer/MXene nanocomposites

The increasingly disturbing electromagnetic wave pollution has intensified research for high-performance shielding materials to protect humans and the environment. It remains a great challenge to combine high electromagnetic interference (EMI) shielding performance with mechanical robustness and stretchability. These crucial features have been simultaneously achieved in this work by using a facile method to prepare elastomer/MXene nanocomposites. An EMI shielding effectiveness of 49 dB was obtained from a 1-mm thick nanocomposite film at 19.6 vol% of MXene; the film has a density of 1.25 g/cm³. The outstanding electrical conductivity of MXene – 4350 ± 125 S·cm⁻¹ – provided free charge carriers in the matrix to absorb electromagnetic signals, leading to the dominance of absorption mechanism over reflection mechanism. Owing to a nanofiller modification step, the nanocomposite films demonstrated not only outstanding EMI shielding but sufficient strength and stretchability. A nanocomposite at 14.0 vol% exhibited Young's modulus of 15.85 ± 0.75 MPa and tensile strength 25.94 ± 0.81 MPa with elongation at break of 170 ± 5.6%, which relates to high stretchability. These impressive properties make our nanocomposites suitable for use in harsh environments as well as applications in stretchable devices, protective clothing, aerospace, aircraft, and automotive industries.     

Nanocomposites of ethylene vinyl alcohol copolymer with thermally resistant cellulose nanowhiskers by melt compounding (I): Morphology and thermal properties

In this study, ethylene‐vinyl alcohol copolymer (EVOH) nanocomposites were prepared by melt compounding both plant cellulose nanowhiskers (CNW) and bacterial cellulose nanowhiskers (BCNW) as nanofillers. Electrospinning and a “dissolution precipitation” method were used as strategies for the incorporation of CNW in EVOH before melt compounding with the aim of enhancing the degree of dispersion of the nanocrystals when compared with direct melt‐mixing of the freeze‐dried product with the polymer. As revealed by morphological characterization, the proposed preincorporation methods led to a significant improvement in the dispersion of the nanofiller in the final nanocomposite films. Furthermore, it was possible to incorporate concentrations as high as 4 wt % BCNW without causing significant agglomeration of the nanofiller, whereas increasing the CNW concentration up to 3 wt % induced agglomeration. Finally, DSC studies indicated that the crystalline content was significantly reduced when the incorporation method led to a poor dispersion of the nanocrystals, whereas high‐nanofiller dispersion resulted in thermal properties similar to those of the neat EVOH. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Convenient approach to making nanocomposites based on a chitosan–poly(vinyl pyrrolidone) polymer matrix and a graphene nanofiller

Conducting, mechanically durable, elastic nanocomposite films were prepared with chitosan (CS) as the polymer matrix, graphene obtained from highly exfoliated graphite as the nanofiller, and poly(vinyl pyrrolidone) (PVP) as the stabilizer of the graphene sheets. The maximum graphene content in the composites without a loss of uniformity and other useful properties increased up to 4.0 wt %. The resulting composites were characterized by scanning electron microscopy, Raman spectroscopy, X‐ray diffraction analysis, mechanical testing, and electrical conductivity testing to determine the effects of the addition of graphene on the morphology and mechanical and electrical properties of the CS–PVP–graphene nanocomposite films. In this study, we took an approach to making nanocomposites from the perspectives of green chemistry, environmental protection, regenerative medicine, and low cost. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45038.     

Electrical conductivity and transparency of polymer hybrid nanocomposites based on poly(trimethylene terephthalate) containing single walled carbon nanotubes and expanded graphite

Single‐walled carbon nanotubes (SWCNT)/expanded graphite (EG)/poly(trimethylene terephthalate) (PTT) hybrid nanocomposites were prepared via in situ polymerization. Raman spectroscopy and scanning electron microscopy (SEM) were employed to determine both, purity and morphology of the nanofillers and the dispersion of nanotubes and nanosheets. The electrical and optical properties of thin polymer films based on both “single” nanocomposites and hybrid nanocomposites were studied. For PTT/SWCNT nanocomposites, results confirmed that films optical transmittance decreases as the concentration of SWCNT increases, attaining almost no optical transmittance for 0.3 wt % of nanofiller. Conversely, the electrical conductivity of nanocomposites was found to increase by increasing the nanofiller amount and the σ_dc values indicate that percolation occurs at a very low SWCNT content (around 0.05 wt %). In the case of PTT/SWCNT + EG nanocomposites, when the content of SWCNT is 0.05%, the hybrid system presents lower conductivity than that corresponding to the “single” nanocomposite. The incorporation of additional EG to the PTT/SWCNT nanocomposite has a small effect on the electrical conductivity but inhibits the transparency of the system. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44370.     

Polystyrene/Polyolefin Elastomer Blends Loaded with Halloysite Nanotubes: Morphological,Mechanical, and Gas Barrier Properties

Herein, a simple melt-blending method is utilized to disperse of halloysite nanotubes (HNTs) in polystyrene/polyolefin elastomer (PS/POE) blends. Based on morphological studies, the PS/POE/HNT nanocomposite containing up to 3 phr HNTs shows excellent nanofiller dispersion, while those filled with 5 phr HNTs exhibit nanofiller aggregation. To overcome the nanofiller aggregation issue, the polypropylene-grafted-maleic anhydride (PP-g-MA) compatibilizer is added to the PS/POE/HNT nanocomposite, which results in improved mechanical properties for the nanocomposite sheets. Furthermore, the addition of compatibilized HNTs to the PS/POE blends leads to decreased O₂ and N₂ gas permeabilities. Besides, incorporating POE, HNTs, and PP-g-MA leads to a decrease in water vapor transmission of PS. In the end, the experimentally-determined mechanical properties and gas permeabilities of the nanocomposite sheets are compared to those predicted by prevalent theoretical models, revealing a good agreement between the experimental and theoretical results. Molecular-dynamics simulations are also carried out to calculate the gas diffusion coefficients in the different sheets to further support the experimental findings in this study. Overall, the PS/POE/HNT/PP-g-MA nanocomposite sheets fabricated in this work demonstrate excellent mechanical and gas barrier properties; and hence, can be used as candidate packaging materials. However, the strength of the resulting PS/POE blend may be inferior to that of the virgin PS.     

Tin-based “super-POSS” building blocks in epoxy nanocomposites with highly improved oxidation resistance

A novel tin-based POSS analogue, butylstannoxane dodecamer, was incorporated as chemically active nanofiller in epoxy resins and achieved a considerable anti-oxidative activity already near 0.05 wt% and very high activity near 1 wt%. The amino-functional nanofiller, which bonds as a linear segment, displayed a high reactivity towards the resin components during cure and was very poorly extractable. Interestingly, at elevated temperatures, the stannoxane nanofiller, whose functional substituents are attached by ionic bonds, displays a considerable short-range mobility in the matrix, and in course of a nano-phase-separation process, rearranges and polymerizes to needle-like nano-domains. This effect leads to additional crosslinking in the nanocomposite. This “solid-phase nano-precipitation” does not occur under oxidative conditions, where the nanofiller preferentially undergoes crosslinking with matrix chains and is thereby immobilized. Nanocomposite synthesis, characterization and the concentration dependence of the nanofiller effect are presented.     

Structure‐property relationships in copolyester elastomer‐layered silicate nanocomposites

While the field of polymer–clay nanocomposites is reaching maturity, some parts of the studied systems still present researchers with possibilities for the improvement of material properties. This study entails the understanding of the relationships in copolyester elastomer/organically modified layered silicate nanocomposite and the structure–property relationships within the system of the nanocomposite. A series of these nanocomposites was prepared via twin‐screw extrusion melt compounding. The experiments included the following three types of synthetic organosilicates: high aspect ratio Somasif (ME100) fluoromica and two lower aspect ratio Laponite synthetic hectorites, (WXFN) and (WXFP). These organosilicates were modified with quaternary octadecyltrimethylammonium bromide (ODTMA) and were used to prepare the nanocomposites. The nanocomposite structure on a micro‐ and nanometre scales was evaluated by two techniques, such as X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The mechanical properties of the nanocomposites were examined to determine the impact aspect ratio of the nanofiller and wt % loading have on performance. The addition of the 2 wt % high aspect ratio of ME100‐ODTMA, in particular, showed statistically improved tensile strength, tear resistance, creep resistance, and water vapor permeation barrier enhancement. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41742.     

Progression from Graphene and Graphene Oxide to High Performance Polymer-Based Nanocomposite: A Review

In this article, various types of carbon nanofiller and modification of graphene oxide and graphene for the preparation of polymer-based nanocomposites are reviewed. Recently, polymer/graphene and graphene oxide-based materials have attracted tremendous interest due to high performance even at low filler content. The property enhancement is due to the high aspect ratio, high surface area and excellent electrical, thermal and mechanical properties of nanofiller. Different techniques have been employed to fabricate polymer/graphene and graphene oxide nanocomposite with uniform dispersion due to fine matrix/nanofiller interaction. Here we discuss the structure, properties and preparation of these nanocomposites.     

Multiscale modeling of interface debonding effect on mechanical properties of nanocomposites

Mechanical behavior of SiO₂ nanoparticle‐epoxy matrix composites was investigated via finite element analysis with an emphasis on the nanofiller‐interphase debonding effect using a three‐dimensional nanoscale representative volume element (RVE). The new model, in which a cohesive zone material (CZM) layer is considered as an inclusion‐interphase bonding, can be applied to polymer nanocomposites reinforced by inclusions of different forms, including spherical, cylindrical, and platelet shapes. Upon validation by experimental data, the model was used to study the effects of interphase properties, nanoparticle size, and inclusion volume fraction on the mechanical properties of nanocomposites. According to the results, taking into account the inclusion‐interphase debonding provides more precise results compared with perfect bonding, especially in nanocomposites with nanoparticles of smaller size. Moreover, the outcomes disclosed that the amount of changes in the elastic modulus by particle size variation is higher when the relative thickness (the interphase thickness to the particle diameter ratio) increases. For relative thicknesses lower than a critical value, the particle size and the interphase properties have negligible effect on the elastic modulus of the nanocomposite, and the elastic modulus of nanocomposite mostly depends on nanofiller content. POLYM. COMPOS., 38:789–796, 2017. © 2015 Society of Plastics Engineers     

Morphology and viscoelastic properties of melt‐spun HDPE/hydrotalcite nanocomposite fibers

Viscoelastic properties of nanocomposite fibers of high density polyethylene (HDPE) and organically modified hydrotalcite were studied. Neat and nanofilled HDPE fibers (with nanofiller content between 0.5 and 3 wt%) were produced by melt spinning and hot‐drawing at different draw ratios up to 20. Effect of temperature on storage modulus, loss modulus, and creep compliance were compared. Rising nanofiller content and/or drawing ratio accounted for an increase in storage modulus in the glassy (i.e., below the γ transition at −100°C) as well as in the rubbery state of non‐crystalline regions. The α relaxation temperature read‐off for the maximum of the loss modulus peak ranged from 20 to 60°C being dependent on frequency, filler content and draw ratio. Sumita model was successfully applied to evaluate the effective volume fraction of the dispersed phase; maximum fraction of immobilized matrix was observed for the composite with 1 wt% of nanofiller. Creep behavior was evaluated by fitting experimental data with the Burgers model. The addition of a small amount of well‐dispersed hydrotalcite (0.5–1 wt%) had a beneficial effect on the creep resistance of drawn fibers at room temperature as well as at 70°C. TEM analysis evidenced a good dispersion of 0.5% nanofiller in as‐spun fibers and improved interfacial adhesion after drawing. The best mechanical properties were observed for the composition with 1 wt% of hydrotalcite, due to combined effects of nanofiller reinforcement and stiffening produced by hot drawing. POLYM. COMPOS., 288–298, 2016. © 2014 Society of Plastics Engineers     

Elastic response of nanocomposite poly(vinylacetate)‐hydroxyapatite with varying particle shape

The mechanisms by which hydroxyapatite nanofiller promotes reinforcement in poly(vinylacetate) matrix is investigated. Hydroxyapatite nanofillers with spherical and platelet particle shape were synthesized. Particle size was in the range from 5 to 60 nm. Filler concentration in composites was limited to maximum of 5 vol% to minimize filler networking. Effect of the nanofiller particle shape on the elastic response of nanocomposite was examined using dynamic‐mechanical thermal spectroscopy. Attempt to interpret the observed phenomena was based on the molecular approach. POLYM. COMPOS., 28: 365–371, 2007. © 2007 Society of Plastics Engineers     

Influence of TiO2 nanofiller geometry on the rheological and optical properties of poly(acrylic acid)-based nanocomposite hydrogels

The properties of macroscopic polymer nanocomposites are highly dependent on the nanoparticle–polymer interfacial region, which varies with the morphology of the nanoparticles. Herein, we used TiO₂ nanofillers with very low aspect ratio, the same chemical composition, and surface functions, but different geometries (nanospheres and nanoplates) dispersed in a poly(acrylic acid) matrix to analyze the influence of the nanoparticle geometry on the properties of nanocomposite hydrogels. The geometry was found to affect the swelling and rheological properties of the nanocomposite polymers. Particularly, the yield strain (from 25% to 130%), modulus (from 17,500 to 25,000 Pa), and brittleness of nanoplates based nanocomposite increased more significantly. Finite-difference time-domain simulations demonstrated that nanoplates increased the wavelength of the absorption maxima (224 nm for NS to 240 nm for NP) and charge distribution. The results obtained in this research indicate that the nanofiller shape markedly influences the rheological properties of the nanocomposite polymers, opening the door to further research focused on polymer–nanofiller interactions, and their effect on the macroscopic properties of the nanocomposites.     

Investigation of the elastic properties of poly (methyl methacrylate) reinforced with graphene nanoplatelets

The technique for synthesis of poly (methyl methacrylate) (PMMA) by atom transfer radical polymerization has been strengthened by using graphene nanoplatelets (GNPs) to enhance the elastic properties of the polymer. In order to improve practical, economical and mechanical performance, the requirements for effective implementation of production control as a smart bulk polymer nanocomposite were determined for cost-effective bulk production. Three-dimensional inspection (using an ultrasound interrogation method for the whole volume under test) confirmed the synthesis of the nanocomposite to be free of agglomeration and bubbles. As a result of this elimination of defects, an enhancement in compressive strength of 42.7% was achieved and the Rockwell hardness was increased by 19.9% through the addition of GNPs at 2 wt% by mass. The deformation and mechanical failure properties have been characterized in the mechanical enhancement of the polymer nanocomposite. Elastic parameters determined using ultrasound testing identified that changes in the structural features following the addition of these GNPs were uniquely connected to the enhancements in these elastic parameters (such as Young's modulus, Poisson's ratio, shear modulus, and microhardness) of the PMMA/GNPs nanocomposite.     

Morphology and mechanical properties of rubber modified aromatic-ether bismaleimide matrix resins

An aromatic ether bismaleimide (BMI) was modified by copolymerization with various CTBN and ATBN liquid elastomers. Dynamic mechanical (DMA), flexural, and SEM fractography studies indicate that cured specimens containing various amounts of the different elastomers have widely varying morphologies and properties. The experimental parameters of interest in this study included the type of elastomer reactive end group, elastomer acrylonitrile content, elastomer concentration, and cure reaction conditions. The ATBNs are clearly more compatible than CTBNs. CTBN modified compositions show a distinct, low temperature rubber phase mechanical loss dispersion, reduced modulus and ultimate strength values, and only slight improvements in elongation. Cured compositions with small amounts of ATBN elastomers (5 phr), however, show no reduction in modulus but improved elongation and ultimate strength values. The “rubber” domains in these systems are small, typically < 5 μm, and consist of copolymerized BMI and elastomer. DMA data for these systems show no distinct low temperature elastomer peak but a broad “interphase” loss dispersion covering a wide range of temperatures. Failure in the ATBN modified BMIs involves initiation of numerous microcracks with obvious crack deflection at the rubber particles. No cavitation of rubber particles occurs, as is frequently the case with the CTBNs.     

Studies of reinforcement behavior of unique elastomer‐based nanocomposite gels

Unique nanocomposite (NC) gels were prepared by blending water swollen unmodified montmorillonite clay suspension with natural rubber (NR) and styrene‐butadiene rubber (SBR) latices followed by prevulcanization. These were extensively characterized by dynamic light scattering, solvent swelling, tensile, and dynamic mechanical measurements. Reinforcement behavior of NC gels was investigated by adding NC gels into virgin NR and SBR matrices at various loadings. The distribution and morphology of NC gels in the elastomer matrices was studied by X‐ray dot mapping and high‐resolution transmission electron microscopy. Experimental results indicated tremendous improvement of tensile strength (TS) and modulus of the NC gel‐filled matrices along with noticeable changes in dynamic mechanical and rheological properties. Compared with virgin NR, the TS of 16 phr NC gel‐filled NR system increased by 117%. Similar level of enhancement of TS was also registered for the NC gel‐filled SBR systems. NC gel‐filled systems showed higher shear viscosities and lower die‐swell values compared with their virgin counterparts. Contemporary particulate composite and nanofiller reinforcement models were used to understand the reinforcing behavior of these NC gels. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Hydrophobic nanocomposites of PBAT with Cl-fn-POSS nanofiller as compostable food packaging films

Antibacterial nanocomposite films of poly(butylene adipate-co-terephthalate) (PBAT) incorporated with different weight percentage of octakis(3-chloropropyl)octasilsesquioxane (chloropropyl functionalized POSS [Cl-fn-POSS]) nanofiller were prepared. The mechanical, thermal, morphological, barrier, and antimicrobial properties were examined. The mechanical properties of the nanocomposite films were enhanced by the addition of Cl-fn-POSS nanofiller. An optimum filler loading of 3 wt% is identified to be best suited for maximum enhancement in tensile strength (24 MPa for 3 wt% filled PBAT vs 11 MPa for neat PBAT) while a 1 wt% filler loading was adequate to double the tensile strength. The barrier properties (WVTR and oxygen transmission rate) of PBAT was improved by the presence of Cl-fn-POSS. A volume of 3 wt% filler loading results in 50% reduction of water permeation and 10% reduction in oxygen transmission. The thermogravimetric analyses of the nanocomposites indicated that the filler enabled the enhancement of thermal stability of PBAT. The nanocomposite films revealed antimicrobial activity with this activity increasing with increasing filler content. PBAT is compostable under suitable conditions and with a low weight percentage of filler that is largely made of silicon dioxide these nanocomposite films can find application as biodegradable food packaging material given their flexibility.