Structure Of Polymer Nanocomposites Research Articles

The structure of carbon nanotubes in a polymer matrix

We carried out an analytical structural analysis of interfacial effects and differences in the reinforcing ability of carbon nanotubes for polydicyclopentadiene/carbon nanotube nanocomposites with elastomeric and glassy matrices. In general, it showed that the reinforcing (strengthening) element of the structure of polymer nanocomposites is a combination of the nanofiller and interfacial regions. In the polymer matrix of the nanocomposite, carbon nanotubes form ring-like structures. Their radius depends heavily on the volume content of the nanofiller. Therefore, the structural reinforcing element of polymer/carbon nanotube nanocomposites can be considered as ring-like formations of carbon nanotubes coated with an interfacial layer. Their structure and properties differ from the characteristics of the bulk polymer matrix.According to this definition, the effective radius of the ring-like formations increases by the thickness of the interfacial layer. In turn, the level of interfacial adhesion between the polymer matrix and the nanofiller is uniquely determined by the radius of the specified carbon nanotube formations. For the considered nanocomposites, the elastomeric matrix has a higher degree of reinforcement compared to the glassy matrix, due to the thicker interfacial layer. It was shown that the ring-like nanotube formations could be successfully modelled as a structural analogue of macromolecular coils of branched polymers. This makes it possible to assess the effective (true) level of anisotropy of this nanofiller in the polymer matrixof the nanocomposite. When the nanofiller content is constant, this level, characterised by the aspect ratio of the nanotubes, uniquely determines the degree of reinforcement of the nanocomposites

Surface Functionalization-Induced Effects on Nanoparticle Dispersion and Associated Changes in the Thermophysical Properties of Polymer Nanocomposites

The degree of nanoparticle dispersion in a polymer matrix is challenging to predict a priori from the structure and composition of polymer nanocomposites. The consequences of changing the nanoparti...

Enhanced Mechanical, Thermal and Antimicrobial Properties of Additively Manufactured Polylactic Acid with Optimized Nano Silica Content.

The scope of this work was to create, with melt mixing compounding process, novel nanocomposite filaments with enhanced properties that industry can benefit from, using commercially available materials, to enhance the performance of three-dimensional (3D) printed structures fabricated via fused filament fabrication (FFF) process. Silicon Dioxide (SiO2) nanoparticles (NPs) were selected as fillers for a polylactic acid (PLA) thermoplastic matrix at various weight % (wt.%) concentrations, namely, 0.5, 1.0, 2.0 and 4.0 wt.%. Tensile, flexural and impact test specimens were 3D printed and tested according to international standards and their Vickers microhardness was also examined. It was proven that SiO2 filler enhanced the overall strength at concentrations up to 1 wt.%, compared to pure PLA. Atomic force microscopy (AFM) was employed to investigate the produced nanocomposite extruded filaments roughness. Raman spectroscopy was performed for the 3D printed nanocomposites to verify the polymer nanocomposite structure, while thermogravimetric analysis (TGA) revealed the 3D printed samples’ thermal stability. Scanning electron microscopy (SEM) was carried out for the interlayer fusion and fractography morphological characterization of the specimens. Finally, the antibacterial properties of the produced nanocomposites were investigated with a screening process, to evaluate their performance against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus).

Phase behavior of polymer-nanorod composites: A comparative study using PRISM theory and molecular dynamics simulations.

Well-dispersed composites of polymer and nanorods have many emerging applications and, therefore, are an important area of research. Polymer reference interaction site model (PRISM) theory and molecular dynamics simulations have become powerful tools in the study of the structure and phase behavior of polymer nanocomposites. In this work, we employ both PRISM theory and molecular dynamics simulations to determine the structure and spinodal phase diagram of 1% volume fraction of nanorods in a polymer melt. We make quantitative comparisons between the phase diagrams, which are reported as a function of nanorod aspect ratio and polymer-nanorod interactions. We find that both PRISM theory and molecular dynamics simulations predict the formation of contact aggregates at low polymer-nanorod attraction strength (γ) and bridged aggregates at high polymer-nanorod attraction strength. They predict an entropic depletion-driven phase separation at low γ and a bridging-driven spinodal phase separation at high γ. The polymer and nanorods are found to form stable composites at intermediate values of the polymer-nanorod attraction strength. The fall of the bridging boundary and the gradual rise of the depletion boundary with the nanorod aspect ratio are predicted by both PRISM theory and molecular dynamics simulations. Hence, the miscible region narrows with increasing aspect ratio. The depletion boundaries predicted by theory and simulation are quite close. However, the respective bridging boundaries present a significant quantitative difference. Therefore, we find that theory and simulations qualitatively complement each other and display quantitative differences.

PRISM Theory of Local Structure and Phase Behavior of Dense Polymer Nanocomposites: Improved Closure Approximation and Comparison with Simulation

We formulate a new closure approximation (triple-modified Verlet (MV)) for the polymer integral equation theory (PRISM) of microstructure and miscibility of dense polymer nanocomposites (PNC). Comp...

New Hybrid Polymer Nanocomposites Based on Polyvinylidene Fluoride and CdS/ZnS Nanoparticles: Structure and Dielecric Properties

The structure and dielectric properties of new hybrid polymer nanocomposites based on polyvinylidene fluoride (PVDF) and CdS and ZnS nanoparticles (NPs) have been studied. It was established that ZnS and CdS NPs, when added at low concentrations, define the structure of the host polymer matrix, and new polar groups and stable charge traps arise, which, in turn, leads to an increase in the dielectric permittivity and polarizing ability of the nanocomposites based on PVDF + CdS/ZnS NPs. As the NP concentration is increased, the NPs start to behave like a separate dispersion phase, and the conductivity of nanocomposites grows as the content of this phase increases, which results in the nanocomposite’s polarizing ability gradually diminishing.

Theory of microstructure-dependent glassy shear elasticity and dynamic localization in melt polymer nanocomposites.

We present an integrated theoretical study of the structure, thermodynamic properties, dynamic localization, and glassy shear modulus of melt polymer nanocomposites (PNCs) that spans the three microstructural regimes of entropic depletion induced nanoparticle (NP) clustering, discrete adsorbed layer driven NP dispersion, and polymer-mediated bridging network. The evolution of equilibrium and dynamic properties with NP loading, total packing fraction, and strength of interfacial attraction is systematically studied based on a minimalist model. Structural predictions of polymer reference interaction site model integral equation theory are employed to establish the rich behavior of the interfacial cohesive force density, surface excess, and a measure of free volume as a function of PNC variables. The glassy dynamic shear modulus is predicted to be softened, reinforced, or hardly changed relative to the pure polymer melt depending on system parameters, as a result of the competing and qualitatively different influences of interfacial cohesion (physical bonding), free volume, and entropic depletion on dynamic localization and shear elasticity. The localization of polymer segments is the dominant factor in determining bulk PNC softening and reinforcement effects for moderate to strong interfacial attractions, respectively. While in the athermal entropy-dominated regime, the primary origin of mechanical reinforcement is the stress stored in the aggregated NP subsystem. The PNC shear modulus is often qualitatively correlated with the segment localization length but with notable exceptions. The present work provides the foundation for developing a theory of segmental relaxation, Tg changes, and collective NP dynamics in PNCs based on a self-consistent treatment of the cooperative activated motions of segments and NPs.

Mechanical and Self-Healing Behavior of Matrix-Free Polymer Nanocomposites Constructed via Grafted Graphene Nanosheets.

Through molecular dynamics (MD) simulation, the structure and mechanical properties of matrix-free polymer nanocomposites (PNCs) constructed via polymer-grafted graphene nanosheets are studied. The dispersion of graphene sheets is characterized by the radial distribution function (RDF) between graphene sheets. We observe that a longer polymer chain length Lg leads to a relatively better dispersion state attributed to the formation of a better brick-mud structure, effectively screening the van der Waals interactions between sheets. By tuning the interaction strength εend-end between end functional groups of grafted chains, we construct physical networks with various robustness characterized by the formation of the fractal clusters at high εend-end values. The effects of εend-end and Lg on the mechanical properties are examined, and the enhancement of the stress-strain behavior is observed with the increase of εend-end and Lg. Structural evolution during deformation is quantified by calculating the orientation of the graphene sheets and their distribution, the stress decomposition, and the size of the clusters formed between end groups and their distribution. Then, we briefly study the effects of time and temperature on the self-healing behavior of these unique PNCs in the rubbery state. Lastly, the self-healing kinetics is quantitatively analyzed. In general, this work can provide some rational guidelines to design and fabricate matrix-free PNCs with both excellent mechanical and self-healing properties.

Highly Precise Determination of Structural and Optical Parameters of an Innovative (PVA-VOCl) for Flexible Polymer-Semiconductor Devices

A novel polymer-semiconductor nanocomposites of polyvinyl alcoholoxovanadium chloride (PVA-VOCl) films have been successfully synthesized by the simple solution casting technique. XRD analysis of the prepared films confirms the formation of VOCl nanocrystals with different particle sizes distributed in the PVA polymer resulting in the increment in the crystalline phase of the whole structure of PVA-VOCl polymer nanocomposite. The Fourier transform infrared (FT-IR) spectroscopy measurements indicate the distribution of VOCl in the polymer matrix. The optical absorption spectra measurements exhibit a complete blocking of the UV range (200–400 nm) due to VOCl dispersion in the polymer matrix. The optical gap Eg of the films were determined with a high degree of precision using Tauc relation, Absorption spectra fitting and the new accurate geometric method show a strong decrease from 5.2 eV for pure PVA to 2.85 eV with increasing the VOCl level in the polymer film. In addition, the high-frequency refractive index estimated from the optical gap values exhibits a significant increase from 1.70 to 2.07. Our samples can be considered as an innovative flexible optical material for UV filters, optoelectronics, and photonics applications.

Harnessing polymer grafting to control the shape of plasmonic nanoparticles

Matrix-free polymer grafted nanoparticles (NPs) are single component polymer nanocomposites (PNCs) for which the often reported severe aggregation of the conventional PNCs can be suppressed. For a given particle core, the size and shape of the polymer grafted nanoparticles can be controlled by the molecular weight of the polymer and its grafting density. However, the degree of homogeneity of one-component PNCs depends on the grafted chain molecular weight and grafting density, as well as on the shape of grafted NPs. Surface plasmon resonance enhanced dynamic light scattering from very dilute solutions, yielding both translational and rotational transport coefficients, complemented by UV–Vis extinction spectra, can detect deviations from spheres. Here, we report that poly(isobutylene)-grafted Ag NPs strongly deviate from the spherical shape and are modeled as prolate spheroids. This NP asphericity, due to inhomogeneous grafting, can impact the structure and properties of plasmonic PNCs in the solid state. Thus, characterizing this behavior is a crucial step prior to the formation of one-component PNCs.

Copper and copper oxide nanoparticles in polypropylene matrix: synthesis, characterization, and dielectric properties

ABSTRACT Copper nanoparticles via chemical reduction of copper sulfate by sodium borohydride in the presence of sodium oleate stabilizing agent have been synthesized and stabilized. X-ray phase analysis has shown that the synthesized nanoparticles in the core consist of metal nanoparticles and the surface is covered with a shell of copper oxide. SEM analysis of nanoparticles stabilized in the presence of sodium oleate showed that copper nanoparticles, coated with the shell of copper oxide, have a narrow particle size range of 14–25 nm. Polymer nanocomposites based on PP/Cu-CuO were obtained by the combining of ex-situ casting solution and hot pressing methods. The structure and electrophysical properties of polymer nanocomposites were investigated. Have been established that at lower concentrations, nanoparticles play the role of structurant, as a result the new polar groups and stable charge-trappings are created in the obtained nanocomposites, which in turn increases the value of dielectric permittivity of nanocomposites and enhances the polarizability of these materials.

Physical and mechanical properties of polymer nanocomposites of penton - carbon nanotubes system

The work is dedicated to the solution of an important task - the creation and study of new polymer compositions, which, unlike traditional polymeric materials, are characterized by polyfunctionality and high performance characteristics.Over the past few decades, among nanofillers, considerable attention has been paid to carbon nanotubes (CNTs) due to their special mechanical and thermal properties, geometric parameters, low mass density and their inherent electrical properties. As a polymer matrix for studying systems with an active interaction of components, it is proposed to use polymers that are capable of crystallization and include polar groups. A typical representative of such polymers is the high molecular weight polyester - penton. Such composite systems are favorably distinguished by the presence of two phase instabilities in the temperature range under study, namely, the melting of the crystalline phase and the glass transition of the amorphous component of the polymer matrix, which will provide more complete and deeper information about the mutual influence of the components of such systems. The ultrasonic method has been used for experimental study of the acoustic properties and structure of polymer nanocomposites of the penton - carbon nanotubes system. An analysis of the studied concentration dependences of the characteristics at frequencies of 5, 7.5, and 10 MHz indicates a strong character of the interaction between the penton - CNT system components. The research results indicate that the ultrasound velocity in filled systems in the entire studied concentration region is significantly higher than for an unfilled penton, and for thecarbon nanotubesfilled penton, a significant increase in the elasticity of the composite compared with an unfilled polymer matrix takes place. Obviously, this can occur due to a significant change in the structure of the polymer component of the system and the formation of an interfacial layer around the CNT with a more ordered structure respectively to pure penton. Additional information is provided by the dependences of the “jump” of the absorption coefficient on the frequency and the dependences of the tangent of the angle of mechanical losses (tgδ), which indicate that the size of carbon nanotube aggregates in the penton matrix as an obstacle to a mechanical wave is much smaller than the size of the penton particles, and the constancy of all studied characteristics when the concentration of CNTs φ ≈ 0.3 vol. % indicates the transition of the penton at this concentration to the state of the wall layer.

Comparative study of polymer-based nanocomposites microwave absorption performance in X–band

The present work focused on electromagnetic (EM) absorption performance comparison of different polymer nanocomposite structures. Synthesis and fabrication of polymer nanocomposite composed of graphene, polyurethane (PU), epoxy was done using in situ polymerization and resin transfer moulding respectively. The effect of polymer on EM properties of composite was carried out using waveguide measurement technique in X-band. Reflection Loss (RL) and shielding effectiveness (SE) were measured for various nanocomposites using EM wave theory. From the results it is observed that 2.5 wt% of PU/epoxy graphene nanocomposite has shown RL value −35 dB at 12.1 GHz and SE value of −45 dB.

Structure and properties of epoxy polymer nanocomposites reinforced with carbon nanotubes

A detailed analysis of nanocomposites based on epoxy polymers and various nanofillers, including one-, two- and three-dimensional carbon nanotubes, was carried out. Special attention is paid to the structure of epoxy nanocomposites and the interfacial layer in these systems. The data on the mechanical, electrophysical, magnetic, thermal, and tribological properties of epoxy nanocomposites are summarized. The influence of the nature of nanofillers (carbon nanotubes, metals, and minerals) on the properties of nanocomposites is analyzed. The problems and prospects of development of nanocomposites based on epoxy polymers reinforced with carbon nanotubes are considered.

2D nanosheet-constructed hybrid nanofillers for polymer nanocomposites with synergistic dispersion and function

Polymer nanocomposites (PNCs) are new-emerging multicomponent polymer composites consisting of a polymer matrix and well dispersed nanofillers. Nanofillers can be divided into one-dimensional, two-dimensional (2D), or three-dimensional nanoparticles according to their dimensions. Due to their outstanding physical properties, the achievement of homogeneous dispersion of 2D nanofillers in the polymer matrix plays a decisive role in the fabrication of high-performance and multifunctional PNCs. The construction of 2D nanosheets into hybrid nanofillers provides a new idea for achieving homogeneous dispersion of 2D nanofillers in the polymer matrix. In this review, recent developments on the design strategies and controllable preparation methods of hybrid nanofillers containing 2D nanosheets are summarized. The preparation, structure, and physical properties of PNCs with 2D nanosheet-constructed hybrid nanofillers are discussed in detail. Finally, challenges and future prospects of PNCs with 2D nanosheet-constructed hybrid nanofillers are highlighted.

Nonlinear optical and dielectric properties of TiO2 nanoparticles incorporated PEO/PVP blend matrix based multifunctional polymer nanocomposites

Poly(ethylene oxide) (PEO)/poly(vinyl pyrrolidone) (PVP) blend (50/50 wt%) and mixed-phase (anatase and rutile) titanium dioxide (TiO2) nanoparticles are used as organic host matrix and inorganic nanofiller, respectively, for the preparation of hybrid polymer nanocomposite (PNC) films (i.e. (PEO/PVP)–x wt% TiO2; x = 0, 1, 3, 5, 10, and 15) by solution casting method with deionized water as solvent. These PNC films are characterized by employing SEM, FTIR, XRD, UV–Vis, DSC, and DRS techniques. The effect of TiO2 nanofiller loading on the structural, morphological, thermal, optical, dielectric, and electrical properties of the PEO/PVP blend matrix, and also on the chain segmental dynamics of PEO in the PNC structures is investigated. It is revealed that the crystalline phase and spherulite morphology of PEO, and the polymer–polymer interactions in these PNC films have been primarily modified by the polymer–nanoparticle interactions. The optical energy band gap decreases, whereas UV absorbance enhances non-linearly with the increase of TiO2 concentration in the PNC films. The enthalpy of melting of the PEO irregularly reduces when the incorporated amount of TiO2 enhances in these films. The real part of complex permittivity and the dielectric loss tangent of these materials are found frequency independent in the range from 20 kHz to 1 MHz but these parameters increase non-linearly from ~ 1.6 to 2 and 0.006–0.008, respectively with the increase of TiO2 concentration up to 10 wt%, at 30 °C. The dominant contribution of interfacial polarization process increases the real part of complex permittivity of these PNC materials by about 1.3 times with the decrease of frequency from 20 kHz to 20 Hz which further enhances with the increment in the temperature of the film. The electrical behaviour of these materials has been examined by analyzing their ac electrical conductivity, complex impedance, and electric modulus spectra over the frequency range 20 Hz–1 MHz. The dc electrical conductivity of these PNC materials enhances nonlinearly with the increase of TiO2 loading in the PEO/PVP blend matrix. The optical and dielectric parameters of these flexible-type PNC materials confirm their multifunctional properties as UV absorber, optical energy band gap tuner, low permittivity tunable nanodielectric, electrical conductivity regulator, and novel host matrix for ion conducting materials. The results infer that these innovative technologically advanced engineered materials can be potential candidates for the next generation microelectronic devices.

Эффективность графена в качестве армирующего элемента структуры полимерных нанокомпозитов

Эффективность графена в качестве армирующего элемента структуры полимерных нанокомпозитов

Design and antimicrobial activity of piperazine polymer nanocomposite

Abstract Eco-friendly technique was adopted for the preparation of piperazine polymer nanocomposites is developed via green synthetic route in one-pot approach. The structure and properties of polymer nanocomposite were confirmed by using UV-Visible spectroscopy, XRD and SEM. The synthesized piperazine nanocomposite showed very good antimicrobial activity against gram-negative bacteria Escherichia coli (5.0-11.6 mm diameter) and gram-positive bacteria Staphylococcus aureus (4.6-8.6 mm diameter) in comparison with standard ciprofloxacin.

Improving Electrical Breakdown Strength of Polymer Nanocomposites by Tailoring Hybrid-Filler Structure for High-Voltage Dielectric Applications

In general, dielectric multifiller polymer composites have the potential to achieve enhanced performances by integrating the desirable properties of each filler. However, the improvement in thermophysical and dielectric properties is often accompanied by a deterioration of electrical breakdown strength (EBD). Here, we explore a two-filler polymer nanocomposite structure, based on polyolefins with montmorillonite and calcium carbonate fillers, and present an effective approach to obtain enhanced EBD by tailoring the composite morphology (by designing the pseudo-two-dimensional nanoclays to preferentially physisorb on the surfaces of calcium carbonates, so as to change the nature of the filler/polymer interfaces). It is shown that, in these structured polymer nanocomposites, the breakdown performance is substantially improved, exceeding the performance of the unfilled polymers and of the respective single-filler composites. The enhanced dielectric behavior originates from the specific composite morphology, ...

TRIBOLOGICAL TESTS OF NANOCOMPOSITES FOR DIRECT RESTORATION OF TEETH

The development of the interphase structure of polymer nanocomposites provides them with tribological properties difficult to obtain in traditional microfiller composites and microhybrid composites. In material solutions, it is preferable to modify the parameters of the material in order to obtain properties that are as close to the hard tissues of the teeth as possible. The aim of the study is to compare the wear resistance of new light-cured nanocomposites and to analyse the surface layer and structure before and after the wear process. Recently developed modern materials were selected for the study. In nanocomposites, G-aenial, G-aenial X FLO, and Essentia, an optimal structure was found in SEM images before and after wear, as well as low resistance to sliding friction and resistance to tribological wear. All tested composites were characterized by suitable properties for clinical applications.