Nanostructured Polymer Composites Research Articles

Advanced Electron Microscopy of Nanophased Synthetic Polymers and Soft Complexes for Energy and Medicine Applications.

After decades of developments, electron microscopy has become a powerful and irreplaceable tool in understanding the ionic, electrical, mechanical, chemical, and other functional performances of next-generation polymers and soft complexes. The recent progress in electron microscopy of nanostructured polymers and soft assemblies is important for applications in many different fields, including, but not limited to, mesoporous and nanoporous materials, absorbents, membranes, solid electrolytes, battery electrodes, ion- and electron-transporting materials, organic semiconductors, soft robotics, optoelectronic devices, biomass, soft magnetic materials, and pharmaceutical drug design. For synthetic polymers and soft complexes, there are four main characteristics that differentiate them from their inorganic or biomacromolecular counterparts in electron microscopy studies: (1) lower contrast, (2) abundance of light elements, (3) polydispersity or nanomorphological variations, and (4) large changes induced by electron beams. Since 2011, the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory has been working with numerous facility users on nanostructured polymer composites, block copolymers, polymer brushes, conjugated molecules, organic–inorganic hybrid nanomaterials, organic–inorganic interfaces, organic crystals, and other soft complexes. This review crystalizes some of the essential challenges, successes, failures, and techniques during the process in the past ten years. It also presents some outlooks and future expectations on the basis of these works at the intersection of electron microscopy, soft matter, and artificial intelligence. Machine learning is expected to automate and facilitate image processing and information extraction of polymer and soft hybrid nanostructures in aspects such as dose-controlled imaging and structure analysis.

A Review of Proton Conductivity in Cellulosic Materials

Cellulose is derived from biomass and is useful in a wide range of applications across society, most notably in paper and cardboard. Nanocellulose is a relatively newly discovered variant of cellulose with much smaller fibril size, leading to unique properties such as high mechanical strength. Meanwhile, electrochemical energy conversion in fuel cells will be a key technology in the development of the hydrogen economy, but new lower cost proton exchange membrane (PEM) materials are needed. Nanocellulose has emerged as a potential candidate for this important application. In this review we summarize scientific developments in the area of cellulosic materials with special emphasis on the proton conductivity, which is the most important parameter for application in PEMs. We cover conventional cellulose and nanostructured cellulose materials, polymer composites or blends, and chemically modified cellulose. These developments are critically reviewed, and we identify interesting trends in the literature data. Finally, we speculate on future directions for this field.

Влияние методов формирования полимерных композитных материалов с углеродными нанотрубками на механизмы электропроводности

The influence of the method of formation of nanostructured polymer composites filled with carbon nanotubes to their electrophysical properties was carried out. The influence of the «size effect» of multi-walled carbon nanotubes, functionalization method, and ultrasonic treatment method on the electrical conductivity of composite materials in the frequency range 50 Hz - 5 MHz and the temperature range 15 - 375 K has been established. The presence of various mechanisms of electric transport in composite materials that affect the final value of electrical conductivity is established. The best results of electrophysical parameters are observed with a combination of non-covalent functionalization of nanotubes and high-power ultrasonic exposure. This method allows us to achieve a conductivity value of composite materials of 0.01 S/cm in the studied frequency range at a filler concentration of 0.5 wt.%.

Ways to improve properties of high-strength building polymer composites

Ways to improve quality of composite materials, in particular, physical and physico-mechanical properties of nanostructured building polymer composites are described. Applications of polymer additives and superplasticizers for improving technological properties of composites are described. The main tasks of improving polymer composites are determined. The effect of surfactants on the properties of high-strength composites is identified. The dependence of the strength of cement stone on porosity is identified.

Carbon-based nanostructured composites for tissue engineering and drug delivery

Nanomaterials comprise extraordinary physicochemical and biological properties for therapeutic applications including three-dimensional porous structures as scaffolds for tissue engineering and as controlled release drug/gen delivery vehicles due to their small size, large surface area, and ability to interact with cells/tissues. Carbon-based nanostructures such as graphene, carbon nanotube, and nanodiamond have attracted both academic and industrial interest because they improve the chemical, mechanical, and biological properties to cellular adhesion tendency of different natural and synthetic polymers in bioapplication. This review covers the fabrication technique of carbon nanostructures and the development of carbon-based nanostructured polymer composites for application in drug/gen delivery and tissue engineering.

Ultra-broadband frequency responsive sensor based on lightweight and flexible carbon nanostructured polymeric nanocomposites

Strain sensing in an ultra-broadband frequency regime up to 400 kHz is obtained with developed lightweight and flexible carbon nanostructured polymer composites, in a frequency range far broader than any piezoresistive sensor previously reported. Various loadings, from static and low-frequency cyclic stretches, through high-frequency vibration, to ultrahigh-frequency ultrasonic guided waves, are applied for evaluation of the sensors' performance. Diverse content and type of carbon nanofiller, microstructure of the conductive network in the matrix, and electromechanical responses of the nanocomposites under broadband-frequency strain are discussed, in conjunction with dynamic mechanical analysis and a theoretical nanoscale model, to advance insight into the sensing mechanism of the sensors. Implementation of ultrasonic guided wave-based in-situ structural health monitoring using networked sensors made of carbon black/polyvinylidene fluoride nanocomposites indicates the significant application potential of the developed sensor to serve as an ultra-broadband and high-frequency responsive flexible strain sensor.

Nanostructured polymer composites with potential applications into the storage of blood and hemoderivates.

Nanostructured polymer composites with potential applications into the storage of blood and hemoderivates.

Controllable Nanostructure Formation through Enthalpy-Driven Assembly of Polyoxometalate Clusters and Block Copolymers

The coassembly of block copolymers (BCPs) with nanoscale inorganic objects is an important route to fabricate nanostructured polymer composites. However, the immiscibility of inorganic/polymeric interface is a recurring challenge to overcome, particularly for inorganic clusters, such as the polyoxometalates (POMs)/BCPs system. In this paper, we present a general method to incorporate POMs into BCP matrices, in which a POM cluster is embedded as a core in a supramolecular star polymer (SSP) whose arms possess the same chemical composition as a BCP segment. Because of the enthalpic interaction between SSP arms and BCP segments, the SSP can carry POM into BCP matrices to realize their coassembly. By this way, we successfully localize a Keggin-type POM cluster [CoW12O40]6– modified with polystyrene (PS) arms into the PS domain of poly(styrene-b-ethylene oxide) micelles, which induces the formation of a series of hybrid micelles with spherical, toroidal, and bicontinuous structures. The morphological transitio...

Processing and characterization of high content multilayer graphene/epoxy composites with high electrical conductivity

A new processing method was developed to fabricate nanocomposites with a high concentration of multilayer graphene (MLG) in a highly oriented morphology. MLG was first dispersed in a water-based solution with the aid of polyethylenimine. A thin MLG film (paper) having highly in-plane aligned platelets was produced by using a vacuum-assisted self-assembly (VASA) technique. After heat treatment, the MLG paper was immersed in an epoxy/acetone bath at room temperature under vacuum to produce an epoxy impregnated composite. After removal of the acetone, nanocomposites consisting of multiple layers of the MLG paper with up to 27 wt% MLG were fabricated and thermally cured. Scanning electron microscopy (SEM) examination showed that the MLG was well dispersed and aligned, and the MLG paper was fully impregnated with epoxy resin. At 30°C, dynamic mechanical analysis (DMA) results showed that the storage modulus of the resulting nanocomposites with 27.2 wt% MLG reached 10.2 GPa, a 300% increase compared to the neat epoxy. The resulting composites also exhibited electrical conductivity as high as 35 Siemens per centimeter (S/cm). This research demonstrates that the VASA processing technique is capable of fabricating well aligned, high content MLG nanostructured polymer composites with high electrical conductivity. POLYM. COMPOS., 37:2897–2906, 2016. © 2015 Society of Plastics Engineers

Description of mechanical properties of particulate-filled nanostructured polymer composites using fractal analysis

A number of the main mechanical characteristics (yield strength, impact toughness, microhardness) of particulate-filled polymer nanocomposites are quantitatively described using fractal analysis. The approach is used to study the main mechanical behavior features of these materials. The influence of the initial particle size of nanofiller and the degree of particle aggregation on the mechanical properties of nanocomposites is shown.

Dispersing hydrophilic nanoparticles in hydrophobic polymers: HDPE/ZnO nanocomposites by a novel template-based approach

The efficiency of a novel template-based approach for the dispersion of hydrophilic nanoparticles within hydrophobic polymer matrices is investigated. The procedure envisages the permeation of a well dispersed nanoparticle suspension inside a micro-porous matrix, obtained through selective extraction of a sacrificial phase from a finely interpen- etrated co-continuous polymer blend. Specifically, a blend of high density polyethylene (HDPE) and polyethylene oxide (PEO) at 50/50 wt% is prepared by melt mixing. The addition of small amounts of organo-clay promotes the necessary refinement of the blend morphology. Once removed the PEO, the micro-porous HDPE matrix is dipped in a colloidal sus- pension of zinc oxide nanoparticles which exhibits low interfacial tension with HDPE. A system prepared by traditional melt mixing is used as reference. Melt- and solid-state viscoelastic measurements reveal a good quality of the filler disper- sion despite the uneven distribution on micro-scale. The latter can be capitalized to minimize the filler content to attain a certain improvement of the material properties or to design nano-structured polymer composites.

Nanostructured composites based on carbon nanotubes and epoxy resin for use as radar absorbing materials

Nanostructured polymer composites have opened up new perspectives for multifunctional materials. In particular, carbon nanotubes (CNTs) present potential applications in order to improve mechanical and electrical performance in composites with aerospace application. The combination of epoxy resin with multiwalled carbon nanotubes results in a new functional material with enhanced electromagnetic properties. The objective of this work was the processing of radar absorbing materials based on formulations containing different quantities of carbon nanotubes in an epoxy resin matrix. To reach this objective the adequate concentration of CNTs in the resin matrix was determined. The processed structures were characterized by scanning electron microscopy, rheology, thermal and reflectivity in the frequency range of 8.2 to 12.4 GHz analyses. The microwave attenuation was up to 99.7%, using only 0.5% (w/w) of CNT, showing that these materials present advantages in performance associated with low additive concentrations.

Viscoelastic behavior of multiwalled carbon nanotubes into phenolic resin

Nanostructured polymer composites have opened up new perspectives for multi-functional materials. In particular, carbon nanotubes (CNTs) have the potential applications in order to improve mechanical and electrical performance in composites with aerospace application. This study focuses on the viscoelastic evaluation of phenolic resin reinforced carbon nanotubes, processed by using two techniques: aqueous-surfactant solution and three roll calender (TRC) process. According to our results a relative small amount of CNTs in a phenolic resin matrix is capable of enhancing the viscoelastic properties significantly and to modify the thermal stability. Also has been observed that when is used TRC process, the incorporation and distribution of CNT into phenolic resin is more effective when compared with aqueous solution dispersion process

The Microstructure and Local Piezoelectric Response in Polymer Nanocomposites with Different Ferroelectric Crystalline Additions

ABSTRACTIn this work, we report on local ferroelectric and piezoelectric properties of nanostructured polymer composites P(VDF-TrFE)+x(Ba,Pb)(Zr,Ti)O3 (x = 0 - 50 %). High-resolution imaging of ferroelectric domains, local polarization switching, and polarization relaxation dynamics were studied by piezoresponse force microscopy. In particular, we found that (Ba,Pb)(Zr,Ti)O3 inclusions usually show a strong unipolar piezoresponse signal, as compared to the polymer matrix. By scanning under high dc voltage the films can be polarized uniformly under both positive and negative electric fields. Stability of the polarized state is discussed.

Fabrication and Characterization of Nanostructured Polymer Composites Prepared by Melt Compounding

In this research we have investigated the effect of different percentages of nanoclay and matrix compositions on the characteristics of NR/BR blend prepared by open two-roll mill. The dispersion of the layered silicate in rubber matrix was characterized by X-ray diffraction (XRD) The results showed that the nanocomposites structure consisting of intercalated structure as well as partially exfoliated structure are obtained. Properties such as permeability and complex viscosity as well as storage modulus are tested to assess the effect of addition of the nanoclay and matrix composition. Permeability and compression set of the nanocomposite samples received markedly improvement. These results were confirmed by Gel content measurements since a noticeable decrease in the gel values was observed when the organoclay was added to the rubber compounds. The properties improvement caused by nanoclay are attributed to intercalation of the organophilic clay by NR/BR macromolecules and established interaction between nanoclay and polymer matrix which was evidenced by SEM photomicrographs. These results were accompanied by enhanced rheological properties.

Towards nanofibrillar single polymer composites

posites?’ (Macromolecules, 40 (2007) 8501–8517) Schaefer and Justice concluded that: ‘Composite materials loaded with nanometer-sized reinforcing fillers are widely believed to have the potential to push polymer mechanical properties to extreme values. Realization of anticipated properties, however, has proven elusive... With the exception of reinforced elastomers, nanocomposites have not lived up to expectations. Although claims of modulus enhancement by factors of 10 exist, these claims are offset by measurements that show little or no improvement...’. Obviously, today we can hardly be happy with the mechanical performance of polymer composites reinforced with nano-sized fillers of various origins. For this reason, in addition to the attempts to overcome the encountered problems, new routes to create polymeric materials with improved properties have to be searched. Attractive alternative in this respect seems to be the preparation of polymers themselves as nano-sized materials, as for example electrospinning does. This elegant technique has the disadvantage that not that much can be done practically with the fine nanofibers. The concept of microfibrillar composites (MFC), developed during the last decade, leads to the nanofibrillar composites (NFC), which are reinforced with polymer nanofibrils with diameters in the range of 50–150 nm. The latter can be isolated in a neat form after selective dissolution of the second blend component, even after preparation of fabrics or knitted articles from the blend yarn. The neat nanofibrils can be used as a starting material for preparation of nanostructured single polymer composites (SPC) applying the oneor two constituent approach. Very recently we demonstrated the superior mechanical properties of the new poly(ethylene terephthalate) (PET) nanofibrillar SPC prepared via hot compaction using one constituent – the modulus is competitive with that of the glass fiber/PET (40/60 by wt) composites. In conclusion, the MFC and NFC concept makes possible the conversion of any polymer in a neat nanoor microfibrillar form and to apply these materials for the preparation of oneor two constituent SPC via hot compaction. The final oneconstituent nanocomposite is manufactured starting from nano-sized material only, a case which seems to be very rare if not unique.

Preparation and Properties of Novel <i>In Situ</i> Composite Materials Based on Polyethylene-Polyamide Oriented Blends

The objective of this study is to manufacture and investigate novel nanostructured polymer composites (NPC) based on oriented blends of high-density polyethylene (HDPE) and polyamide 6 (PA6). Conventional polymer processing techniques are used for this purpose including extrusion blending, cold drawing and compression molding. Thus, various polymer blends are prepared comprising 10 and 20 wt% of PA6 and 0-10 wt% of a copolymeric compatibilizer. These blends are cold-drawn to high draw ratios and the oriented strands so produced are further compression molded at various temperatures between the melting points of HDPE and PA6. All NPC obtained are characterized by microscopy techniques, solid state NMR, mechanical tests and wide- and small-angle X-ray scattering from synchrotron. The mechanical and structural data of NPCs are discussed with relation with the polyamide fibrils’ orientation, as well as with the effect of compatibilizer at the matrix-fibrils interface.

Materials Processes of Graphite Nanostructured Composites Using Ball Milling

ABSTRACT Polymer nanocomposites are an emerging class of multifunctional materials that have not been optimized for their functional potential. As a part of a series of studies conducted by Wong and collaborators [1-6], a novel processing design for polymer nanocomposites using ball milling and nanoscale graphite platelets (NGPs) was recently investigated. Processes for carbon nanotube (CNT), despite its promise in maneuvering varied functionality, are prohibitively expensive at present for widespread composite applications. Instead of trying to discover lower-cost processes for CNT, we investigated the possibility of using ball milling to produce nanoscale reinforcements. The studied nanocomposites are distinct from existing sp3 carbon black, CNT, and nanoclay reinforcements. Materials processes to produce nanostructured polymer composites using the ball milling method are reported. It was found that ball milling primarily reduced particle sizes to smaller platelets. No other critical advantages were noted. A bimodal distribution of 100 and 400 nm particles was observed using a particle analyzer. The ultimate objective is to develop an alternative cost-effective nanoscale carbon material with comparable properties like carbon nanotubes for future composite applications.

EFFECT OF BLEND COMPOSITION ON THE STRUCTURE-PROPERTIES RELATIONSHIPS OF NANOSTRUCTURED POLYMER COMPOSITES FROM POLYCONDENSATE/POLYOLEFIN BLENDS

Nanostructured polymer composites (NPC) are obtained by melt-blending of poly(ethylene terephtalate) (PET) and polypropylene (PP) as well as polyamide 66 (PA66) and PP in wt. ratio 70/30, 50/50 and 30/70, followed by cold drawing of the extruded bristle and compression molding of the drawn bristles in form of film. The blends are studied by X-ray diffraction, scanning electron microscopy (SEM), and static mechanical testing. SEM and X-ray reveal different blend morphologies created during the stages of NPC manufacturing: isotropic blend after extrusion, fibrillization of both components after drawing, izotropization of the PP matrix with preservation of the PET- or PA66 fibrils after hot pressing. Also observed was a strong epitaxial effect of the nanostructured microfibrils of PET or PA66 on the non-isothermal crystallization of PP during cooling after compression molding at 215°C. Thus, the cold drawn and thermally treated PET/PP and PA66/PP blends represent anisotropic transcrystalline structures. The PP crystallites in the transcrystalline layers are reoriented at aprox. 40° with respect to the drawn direction (fiber axis). This is valid for the whole amount of PP in the case of PET/PP blend and only partially for the blend PA66/PP. These morphological peculiarities affect the mechanical properties of the NPC: the Youngs modulus and the tensile strength of the compression molded films are respectively about 4–6 and about 10–15 times higher (depending of the chemical composition and proportions of the components in the blends) than those of the compression molded neat PP.

Extruder processing for nanoblends and nanocomposites

AbstractStructuring multiphase polymer materials to a micrometer scale (micro‐structuration) is a facile engineering practice. However, structuring them to a nanometer scale (nano‐structuration) is a formidable engineering challenge. In this paper, it is shown first why traditional extruder compounding processes only lead to micro‐structuration and then how one may use the extruder type of mixer to structure multiphase polymer materials at a nano‐meter scale to obtain nanostructured polymer blends (nanoblends) and nanostructured polymer composites (nanocomposites).