Improving interfacial interaction of l‐phenylalanine‐functionalized graphene nanofiller and poly(vinyl alcohol) nanocomposites for obtaining significant membrane properties: Morphology,thermal, and mechanical studies

In polymer nanocomposite synthesis, the challenges are achieving well dispersion of nanofiller and its maximum interfacial interaction with polymer matrix at low loading percent. In this study, the preparation of poly (vinyl alcohol) (PVA) nanocomposites with l ‐phenylalanine‐functionalized graphene (f‐graphene) using a simple water solution processing method is reported. Graphene layers were functionalized with l ‐phenylalanine amino acid as a biocompatible and environmentally friendly modifier. The obtained PVA/f‐graphene nanocomposite membranes were smooth, uniform, and flexible. Efficient interaction was found between f‐graphene and PVA matrix, which caused significant improvement in mechanical and thermal properties of the graphene‐based nanocomposite with homogeneous dispersion. POLYM. COMPOS., 37:1924–1935, 2016. © 2015 Society of Plastics Engineers     

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.     

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.     

Effect of polymer matrix and nanofiller on non-bonding interfacial properties of nanocomposites

To investigate the effect of polymer matrix and nanofiller on interfacial mechanical properties of their resulting nanoreinforced composites, pull-out tests of different nanofillers, such as graphene (GE), graphane (GA) and carbon nanotube (CNT), from various polymer matrix including polyethylene (PE), poly(methyl methacrylate) (PMMA), polytetrafluoroethylene (PTFE) and poly(vinylidene chloride) (PVDC), are simulated using molecular dynamics method (MD). The velocity-load model is applied in MD simulations, and the variation of non-bonding energy (van der Waals interaction), pull force and the average interfacial shear strength (ISS) in the pull-out process are obtained and presented graphically. Under the same mass density, when PE is used as polymer matrix for GE and CNT nanofillers, the resulting nanoreinforced composite possesses the highest non-bonding interfacial energy and the strongest ISS, and the pull force required for pulling out the nanofiller is the largest. For GA nanofiller, the GA-PMMA produces the highest non-bonding interfacial energy and the ISS. With the increase of diameter of CNT, the effect of its reinforcement becomes weak gradually. The chirality of GE does not influence the interfacial mechanical property of GE-reinforced nanocomposite. The (3, 3) CNT nanofiller produces the almost identical interfacial characteristic compared with GE nanofiller. However, when the GA nanofiller is used, the non-bonding energy, pull force and the average ISS of nanocomposite increases by nearly 100%.     

Mechanical properties of defective carbon nanotube/polyethylene nanocomposites: A molecular dynamics simulation study

Because of their remarkable performance properties and technological promise, polymer nanocomposites reinforced with single‐walled carbon nanotubes (SWCNTs) have attracted considerable attention in the engineering, applied physics, and materials science communities. Recent experimental and computational investigations have shown that the presence of nanoscale defects in CNTs can significantly impact their electrical, mechanical, and thermal properties. In this article, for the first time, we examine the effect of defective CNTs on the interfacial characteristics and mechanical properties of CNT/polyethylene (PE) nanocomposites. Our molecular dynamics simulations show that as few as five vacancy defects in each CNT in a high‐volume‐fraction CNT/PE nanocomposite can decrease the longitudinal Young's modulus of the nanocomposite by as much as 18%, and the shear stress at the CNT/polymer interface by as much as 38%. By accounting for nanoscale defects and their effect on the CNT/polymer interfacial mechanics, our findings provide a practical guide for designing nanocomposites that are capable of attaining a desired set of elastic performance properties. POLYM. COMPOS., 305–314, 2016. © 2014 Society of Plastics Engineers     

Effect of organoclay chemistry and morphology on properties of poly(lactic acid) nanocomposites

Poly(lactic acid) (PLA) nanocomposites with different layered organoclays (variation in the surface treatment of silicate) and one special nanofiller (mixed mineral thixotrope) were melt-compounded using a semi-industrial co-rotating twin-screw extruder. Effects of the silicate surface treatment and shape on the structure as well on processing and utility properties in PLA matrix were investigated. The structural changes in polymer matrix were evaluated from dynamic experiments in the shear flow using low-amplitude oscillatory measurements. Moreover, new approach for morphological investigation of nanocomposites using small-angle X-ray scattering was presented. Concerning utility properties, tests of mechanical and barrier properties were performed to compare enhancement of PLA matrix due to incorporation of different nanoparticles. Surprisingly, filling the PLA matrix with mixed mineral thixotrope resulted into very high material performance (in particular, significant improvement in barrier properties) compared to filling with commercial layered silicates. In this way, new type of nanofiller for PLA applications has been successfully tested.     

Mechanical and morphological characterization of polymer-carbon nanocomposites from functionalized carbon nanotubes

Carbon nanotubes were functionalized with poly(vinyl alcohol) (PVA). The water-soluble PVA-functionalized carbon nanotubes were then embedded into PVA matrix via a wet-casting method, resulting in polymer-carbon nanocomposite films with homogeneous nanotube dispersion. Composites with pristine and functionalized nanotubes were tested in tension. It was found that the mechanical properties of these nanocomposite films were significantly improved compared to the neat polymer film. Functionalization allowed good distribution of the nanotubes in the matrix, leading to higher film strength. Scanning electron microscopy shows an apparent good wetting of the nanotubes by the PVA matrix. These results are supportive of good interfacial bonding between the functionalized carbon nanotubes and the hosting polymer matrix.     

Nanocomposites of polypropylene/titanate nanotubes: morphology,nucleation effects of nanoparticles and properties

High-quality titanate nanotubes (TiNT) were mixed with modified polypropylene (PP*) by a batch melt-mixing procedure. To improve compatibility between the nanofiller and the matrix, polypropylene (PP) was modified by electron beam irradiation. Effects of TiNT nanoparticles on crystallization, mechanical, thermal and rheological properties of the modified polypropylene were studied and compared with the analogous systems filled with commercial micro- (mTiO₂) and nano- (nTiO₂) titanium dioxide particles. Nucleation effects of the TiO₂-based fillers on PP* crystallization were investigated in detail. The microstructure of the PP*/TiNT nanocomposites shows well-dispersed TiNT sparse aggregates (clouds), penetrated by the polymer. A large-scale structure in the nanocomposite melts confirmed also rheology. In comparison to the matrix characteristics, the stiffness and microhardness of the TiNT nanocomposites increase by 27 and 33 %, respectively. The enhancement in mechanical properties demonstrates that the quality titanate nanotubes can be used as an efficient filler in non-polar polymers using the polymers modified by irradiation. In the case of the nanocomposites containing nTiO₂-anatase particles, the increase in these mechanical characteristics is lower. The investigated changes in the rate of crystallization indicate a marked nucleation effect of the nanotubes. The crystallization kinetics data, processed by the Avrami equation, suggest 3-dimensional crystal growth in the polypropylene matrix. The observed improvement in mechanical properties of the TiNT nanocomposites is induced not only by the nanofiller reinforcement but also by the changes of supermolecular structure of the polymer matrix due to nucleated crystallization.     

Morphological and physical properties of a thermoplastic polyurethane reinforced with functionalized graphene sheet

BACKGROUND: Functionalized graphene sheet (FGS) was recently introduced as a new nano‐sized conductive filler, but little work has yet examined the possibility of using FGS as a nanofiller in the preparation of polymer nanocomposites. In particular, there are currently no published papers that evaluate polyurethane/FGS nanocomposites. The purpose of this study was to prepare a polyurethane/FGS nanocomposite and examine the morphological and physical properties of the material. RESULTS: A cast nanocomposite film was prepared from a mixture of thermoplastic polyurethane (TPU) solution and FGS suspended in methyl ethyl ketone. The FGS dispersed on the nanoscale throughout the TPU matrix and effectively enhanced the conductivity. A nanocomposite containing 2 parts of FGS per 100 parts of TPU had an electrical conductivity of 10^?4 S cm^?1, a 10⁷ times increase over that of pristine TPU. The dynamic mechanical properties showed that the FGS efficiently reinforced the TPU matrix, particularly in the temperature region above the soft segment melt. CONCLUSION: Our results show that FGS has a high affinity for TPU, and it could therefore be used effectively in the preparation of TPU/FGS nanocomposites without any further chemical surface treatment. This indicates that FGS is an effective and convenient new material that could be used for the modification of polyurethane. It could also be used in place of other nano‐sized conductive fillers, such as carbon nanotubes. Copyright © 2009 Society of Chemical Industry     

Preparation and crystallization behavior of multiwalled carbon nanotubes/poly(vinyl alcohol) nanocomposites

The poly(vinyl alcohol) (PVA)‐based nanocomposites embedded with modified multiwalled carbon nanotubes (MWCNTs) were prepared. To enhance the interfacial interaction between MWCNTs and PVA, acid‐treated MWCNTs were grafted with PVA chains, compatibilizing MWCNTs and the matrix. The better dispersion of MWCNTs in PVA matrix was obtained by the introduction of MDI reaction bridges and then PVA molecules onto the surface of MWCNTs. Moreover, strong interaction between MWCNTs and PVA matrix was evidenced through the measurement results of the melting behavior, polarized Raman measurement, and nonisothermal crystallization behavior of the nanocomposites. Owing to the reinforcement of MWCNTs, the tensile strength and modulus of PVA nanocomposite containing 0.9 wt% MWCNTs were increased by 160.7 and 109.2%, respectively, compared to neat PVA. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Carbon nanoparticles/polyvinyl alcohol composites with enhanced optical,thermal, mechanical,and flame-retardant properties

In this work, polyvinyl alcohol (PVA) is chemically bonded to carbon nanoparticles (CNPs) by a very simple and versatile solution casting method. Five different kinds of CNPs/PVA composite films were prepared; 0.5, 1.0, 1.5, 2.0, and 3.0 wt% CNPs dispersed in PVA. The as-prepared samples were characterized using various characterization techniques. The resulting nanocomposites proved to possess homogeneity and better mechanical, thermal, optical, and flame-retardant properties than pure PVA. Most of the CNPs with average particle size ≤100 nm were homogeneously dispersed in the PVA matrix showing fluorescence in the violet color zone. The crystallinity of the nanocomposites show a decline in the diffraction intensity as compared to pure PVA which results from the dwelling of CNPs inside the gaps of stacked-layer chains of PVA. The mechanical properties of nanocomposites indicated enhancement in toughness, elastic modulus and tensile strength with an increase in CNPs contents. The assessment for flame-retardant properties was carried out through cone calorimetry. The results show a decrease in both total heat release rate (THRR) and peak heat release rate (pHRR) of the resulting nanocomposites as compared to pure PVA. The superior properties of the CNPs/PVA composites stemmed from the good interfacial bonding between the CNPs and PVA matrix.     

Synthesis of bio‐based polymeric nanocomposites from acrylated epoxidized soybean oil and montmorillonite clay in the presence of a bio‐based intercalant

Polymeric nanocomposites were synthesized from functionalized soybean‐oil‐based polymer matrix and montmorillonite (MMT) clay using an in situ free radical polymerization reaction. Acrylated epoxidized soybean oil combined with styrene was used as the monomer. Organophilic MMT (OrgMMT) was obtained using a quaternized derivative of methyl oleate, which was synthesized from olive oil triglyceride, as a renewable intercalant. The resultant nanocomposites were characterized using X‐ray diffraction and atomic force microscopy. The effect of increased nanofiller loading on the thermal and mechanical properties of the nanocomposites was investigated using thermogravimetric analysis and dynamic mechanical analysis. It was found that the desired exfoliated nanocomposite structure was achieved when the OrgMMT loading was 1 and 2 wt%, whereas a partially exfoliated or intercalated nanocomposite was obtained for 3 wt% loading. All the nanocomposites were found to have improved thermal and mechanical properties as compared with virgin acrylated epoxidized soybean‐oil‐based polymer matrix. The nanocomposite containing 2 wt% OrgMMT clay was found to have the highest thermal stability and best dynamic mechanical performance. Copyright © 2010 Society of Chemical Industry     

Property enhancement in unsaturated polyester nanocomposites by using a reactive intercalant for clay modification

Polymeric nanocomposites were synthesized from unsaturated polyester (UPE) matrix and montmorillonite (MMT) clay using an in situ free radical polymerization reaction. Organophilic MMT was obtained using a quaternary salt of coco amine as intercalant having a styryl group making it a reactive intercalant. The resultant nanocomposites were characterized via X‐ray diffraction and transmission electron microscopy. The effect of increased nanofiller loading on the thermal and mechanical properties of the nanocomposites was investigated. All the nanocomposites were found to have improved thermal and mechanical properties as compared with neat UPE matrix, resulting from the contribution of nanolayer connected intercalant‐to‐crosslinker which allows a crosslinking reaction. It was found that the partially exfoliated nanocomposite structure with an exfoliation dominant morphology was achieved when the MMT loading was 1 wt %. This nanocomposite exhibited the highest thermal stability, the best dynamic mechanical performance and the highest crosslinking density, most probably due to more homogeneous dispersion and optimum amount of styrene monomer molecules inside and outside the MMT layers at 1 wt % loading. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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     

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.     

Enhanced interfacial interaction for effective reinforcement of poly(vinyl alcohol) nanocomposites at low loading of graphene

The graphene/poly(vinyl alcohol) (PVA) nancomposites with homogeneous dispersion of the nanosheet and enhanced nanofiller–matrix interfacial interaction were fabricated via water blending partially reduced graphene oxide and PVA. The nanocomposites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetry. The graphene nanosheets were fully exfoliated in the PVA matrix and a new covalent linkage was formed between graphene and PVA matrix. Uncommon to conventional method, the enhanced interfacial adhesion resulted from covalent interaction and hydrogen bondings between graphene and PVA backbone. The mechanical and thermal properties of the nanocomposites were significantly improved at low graphene loadings. An 116% increase in tensile strength and a 19 °C improvement of onset thermal degradation temperature were achieved by the addition of only 0.8 wt% graphene.     

Comparative study on the natural rubber nanocomposites reinforced with carbon black nanoparticles and graphite oxide nanosheets

To achieve dramatic improvements in the performance of natural rubber (NR), the graphite oxide nanosheets (GON)‐reinforced NR nanocomposites have been prepared through solution mixing on the basis of pretreatment of graphite. The mechanical and thermal properties of GON/NR nanocomposites were characterized in contrast to the carbon black (CB)/NR nanocomposite. The mechanical properties of the GON‐reinforced NR showed a considerable increase compared to the neat NR and traditional CB/NR nanocomposite. The initial modulus of pure NR was increased for up to 53.6% when 7 wt% GON is incorporated. The modulus and strength of NR with GON appear to be superior to those of CB with the same filler content. The dispersion state of the nanofillers into NR was investigated by scanning electron microscopy and X‐ray diffraction, and the results indicated that nanofillers have been dispersed homogeneously in the NR matrix. Fourier transform infrared spectra showed possible interfacial interactions between fillers and NR matrix. Differential scanning calorimetry and thermogravimetric analysis showed that the T _g and thermal decomposition temperature of NR slightly increased with the addition of the fillers, especially for that of GON/NR nanocomposites. According to this study, application of the physical and mechanical properties of GON to NR can result in rubber products which have improved mechanical, physical, and thermal properties, compared with existing NR products reinforced with CB. POLYM. COMPOS., 38:1427–1437, 2017. © 2015 Society of Plastics Engineers     

Eco-friendly poly(vinyl alcohol)/delaminated V2C MXene high-k nanocomposites with low dielectric loss enabled by moderate polarization and charge density at the interface

High-dielectric-constant (high-k) polymer/conductor composites with low dielectric loss are desirable for energy storage. However, high leakage currents from interfacial regions with high charge density are difficult to handle. In this work, high permittivity and low dielectric loss were achieved in poly(vinyl alcohol) (PVA)/V₂C MXene nanocomposite films fabricated by solution casting by taking advantage of the interfacial compatibility and moderate interfacial charge density of the nanocomposites. Water-soluble PVA was utilized as the polymer matrix. Delaminated V₂C MXene nanosheets with appropriate conductivity were prepared and used as the filler. The mild interface polarization of the nanocomposites was responsible for achieving favourable permittivity values. The small gap between the work functions of PVA and V₂C contributed to moderate interfacial charge density values and thus low dielectric loss values. A proportional correlation between the interfacial charge density and the conductivity of composites was also verified. The depth of charge injection from the MXene to PVA was found to be half of the interlamellar spacing of the delaminated MXene. The dependence of the electrical properties of the nanocomposites on the frequency and MXene content was also studied. The composite with 4 wt% MXene exhibited a permittivity of ~24 (16 times that of PVA) and a dielectric loss of ~0.14 (1.5 times that of PVA) at 1 kHz, as well as breakdown strength of ~31 MV m⁻¹ (63% of PVA). This work might enable environmentally friendly fabrication of promising composite dielectrics.     

Preparation and characterization of alkylated carbon nanotube/polyimide nanocomposites

BACKGROUND: The development of carbon nanotube‐reinforced composites has been impeded by the difficult dispersion of the nanotubes in polymers and the weak interaction between the nanofiller and matrices. Efficient dispersion of carbon nanotubes is essential for the formation of a functional nanotube network in a composite matrix. RESULTS: Multiwalled carbon nanotubes (MWNTs) were incorporated into a polyimide matrix to produce MWNT/polyimide nanocomposites. To disperse well the MWNTs in the matrix and thus improve the interfacial adhesion between the nanotubes and the polymer, ‘branches’ were grafted onto the surface of the nanotubes by reacting octadecyl isocyanate with carboxylated MWNTs. The functionalized MWNTs were suspended in a precursor solution, and the dispersion was cast, followed by drying and imidization to obtain MWNT/polyimide nanocomposites. CONCLUSION: The functionalized MWNTs appear as a homogeneous dispersion in the polymer matrix. The thermal stability and the mechanical properties are greatly improved, which is attributed to the strong interactions between the functionalized MWNTs and the polyimide matrix. Copyright © 2009 Society of Chemical Industry     

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.