Young's modulus of effective clay clusters in polymer nanocomposites

In polymer nanocomposites, the interfacial region plays a key role in the reinforcement of materials properties. Traditional two-phase micromechanical models usually ignore the contribution of such interfacial region to the overall materials properties. In this study, we use molecular dynamics simulation to determine the effective size and the Young's modulus of effective clay clusters which are regarded as basic building blocks in clay-based polymer nanocomposites. Two types of clay clusters are considered: one is fully exfoliated clay and another is partially exfoliated clay. The calculated Young's modulus of effective clay clusters can be used to predict the overall mechanical properties of clay-based polymer nanocomposites.     

Low-dimensional carbonaceous nanofiller induced polymer crystallization

Low-dimensional carbonaceous nanofillers (LDCNs), i.e., fullerene, carbon nanofiber, carbon nanotube, and graphene, have emerged as a new class of functional nanomaterials world-wide due to their exceptional electrical, thermal, optical, and mechanical properties. One of the most promising applications of LDCNs is in polymer nanocomposites; these materials endow the polymer matrix with significant physical reinforcement and/or multi-functional capabilities. The relations between properties, structure and morphology of polymers in the nanocomposites offer an effective pathway to obtain novel and desired properties via structure manipulation, wherein the interfacial crystallization and the crystalline structure with the matrix are critical factors. By now, extensive studies have reported that LDCNs are highly effective nucleating agents that can significantly accelerate their crystallization kinetics and/or induce unique crystalline morphologies in nanocomposites. This review presents a thorough survey of the current literature on the issues relevant to LDCN-induced polymer crystallization. After a brief introduction to each type of LDCN and its derivatives, LDCN-induced crystallization kinetics with or without flow fields, crystalline modification, and interfacial crystalline morphologies are thoroughly reviewed. Then, the origins of LDCN-induced polymer crystallization are discussed in depth based on molecular simulation and experimental studies. Finally, an overview of the challenges in probing LDCN-induced polymer crystallization and the outlook for future developments in polymer/LDCN nanocomposites conclude this paper. Understanding LDCN-induced polymer crystallization offers a helpful guidance to purposefully regulate the structure and morphology, then achieving high-performance polymer/LDCN nanocomposites.     

Carbon nanotube-based nanocomposites and their applications

The purpose of the current review article is to present a compherensive understanding regarding pros and cons of carbon nanotube–related nanocomposites and to find ways in order to improve the performance of nanocomposites with new designs. Nanomaterials including carbon nanotubes (CNTs) are employed in industrial applications such as supercapacitors, and biosensors, and etc. The present article has been prepared in three main categories. In the first part, carbon nanotube types have been presented, as single-walled carbon nanotubes, multi-walled carbon nanotubes, and also equivalent circuit models, which have been used to more clarify the experimental measurements of impedance. In the second part, nanocomposites with many carbon, inorganic and polymeric materials such as polymer/CNT, activated carbon/CNT, metal oxide/CNT, and carbon fiber/CNT have been investigated in more detail. In the third part, the focus in on the industrial applications of CNTs. including supercapacitors, biosensors, radar absorbing materials, solar cells, and corrosion protection studies. This review article explains the latest advances in carbon nanotubes and their applications in electrochemical, electrical and optical properties of nanocomposites.     

Polymer nanocomposites: structure, interaction, and functionality

This feature article discusses the main factors determining the properties of polymer nanocomposites with special attention paid to structure and interactions. Usually more complicated structure develops in nanocomposites than in traditional particulate filled polymers, and that is especially valid for composites prepared from plate-like nanofillers. Besides the usually assumed exfoliated/intercalated morphology, i.e. individual platelets and tactoids, such nanocomposites often contain large particles, and a network structure developing at large extent of exfoliation. Aggregation and orientation are the most important structural phenomena in nanotube or nanofiber reinforced composites, and ag-gregation is a major problem also in composites prepared with spherical particles. The surface characteristics of nanofillers and interactions are rarely determined or known; the related problems are discussed in the paper in detail. The surface of these reinforcements is modified practically always. The goal of the modification is to improve dispersion and/or adhesion in nanotube and spherical particle reinforced composites, and to help exfoliation in nanocomposites containing platelets. However, modification decreases surface energy often leading to decreased interaction with the matrix. Very limited information exists about interphase formation and the properties of the interphase in nanocomposites, although they must influence properties considerably. The properties of nanocomposites are usually far from the expectations, the main reason being insufficient homogeneity, undefined structure and improper adhesion. In spite of considerable difficulties nanocomposites have great potentials especially in functional applications. Several nanocomposite products are already used in industrial practice demonstrated by a few examples in the article.     

One-dimensional conducting polymer nanocomposites: Synthesis, properties and applications

Intrinsically conducting polymers have been studied extensively due to their intriguing electronic and redox properties and numerous potential applications in many fields since their discovery in 1970s. To improve and extend their functions, the fabrication of multi-functionalized conducting polymer nanocomposites has attracted a great deal of attention because of the emergence of nanotechnology. This article presents an overview of the synthesis of one-dimensional (1D) conducting polymer nanocomposites and their properties and applications. Nanocomposites consist of conducting polymers and one or more components, which can be carbon nanotubes, metals, oxide nanomaterials, chalcogenides, insulating or conducting polymers, biological materials, metal phthalocyanines and porphyrins, etc. The properties of 1D conducting polymer nanocomposites will be widely discussed. Special attention is paid to the difference in the properties between 1D conducting polymer nanocomposites and bulk conducting polymers. Applications of 1D conducting polymer nanocomposites described include electronic nanodevices, chemical and biological sensors, catalysis and electrocatalysis, energy, microwave absorption and electromagnetic interference (EMI) shielding, electrorheological (ER) fluids, and biomedicine. The advantages of 1D conducting polymer nanocomposites over the parent conducting polymers are highlighted. Combined with the intrinsic properties and synergistic effect of each component, it is anticipated that 1D conducting polymer nanocomposites will play an important role in various fields of nanotechnology.     

骨组织工程中的碳纤维材料

归纳了聚合物支架材料在提高其力学性能方面的一些研究工作,并综述了碳纤维材料在骨组织工程上应用的进展.分析表明,骨组织工程是修复骨缺损的有效方法之一,而碳纤维材料的结构性能优势使其成为提高组织工程支架性能的首选材料之一.在提高聚合物支架力学性能的同时,进一步提高材料的生物活性和促进骨的修复是目前研究的重点和难点.指出可通过对碳纤维材料的改性、有序排列等手段来进一步提高碳纤维材料的作用.     

Role of free volume characteristics of polymer matrix in bulk physical properties of polymer nanocomposites: A review of positron annihilation lifetime studies

Polymer nanocomposites which have one or more nano-dimensional phases dispersed in polymer matrix show enhancement in bulk physical properties. In order to achieve the desired properties, a large number of polymer nanocomposites have been prepared by choosing different polymers and nanofillers. These studies showed that interfacial interaction between polymer molecules and nanofillers is the most important factor to achieve the synergistic effect towards enhancement in the bulk physical properties. The strong interfacial interaction also promotes the fine dispersion of nanofillers in a polymer matrix which consequently enables the preparation of polymer nanocomposites with higher loading of nanofillers. The polymer matrix constitutes a large volume fraction of polymer nanocomposites and hence the molecular packing of the polymer matrix itself plays a deterministic role in governing the physical properties of the nanocomposites. The strong interfacial interaction brings severe changes in the original molecular packing. In order to establish the structure-property relationships for polymer nanocomposites, characterization of molecular packing of polymer matrix in its nanocomposites is essential. In this aspect positron annihilation lifetime spectroscopy (PALS) is a highly suitable technique for characterization of free volume holes in polymers or polymer nanocomposites. The present review briefly describes the positron annihilation lifetime spectroscopy technique and relevant models for calculations of free volume hole’s size, density and their size distribution in polymer nanocomposites. We present a summary of the recent studies focussed on investigation of free volume structure (molecular packing) of polymer nanocomposites using PALS and its impact on transport, thermal and mechanical properties of the nanocomposites.     

多功能性聚苯胺/聚合物纳米复合材料的制备及应用

基于国内外最新研究文献及本课题组的研究,综述了多功能性聚苯胺/聚合物纳米复合材料的制备方法、性能及应用前景。聚苯胺/聚合物纳米复合材料可以由机械共混法、涂布法和原位聚合法,如分散聚合法、模板诱导聚合法及电化学聚合法制备得到。聚苯胺/聚合物纳米复合材料在透明导电塑料薄膜、防静电涂料、导电纤维、电致发光器件、电磁屏蔽材料等领域有着广阔的应用前景。     

Transport performance in novel elastomer nanocomposites: Mechanism,design and control

Functional elastomer nanocomposites have found numerous applications in diverse hi-tech areas. Transport phenomena, such as electrical conductivity, thermal conductivity and gas/liquid barrier properties, have been the major focus of functional elastomer nanocomposite research. Despite essential progress in these areas, a summary and discussion of state-of-the-art strategies for regulating the transport performances of nanocomposites based on the transportation mechanisms of electrons, phonons and mass are lacking. In the present review, a brief introduction of transport mechanisms in elastomer nanocomposites precedes a systematic summary of the important progress in elastomer nanocomposites with electrical/thermal conductivities and lowered mass permeabilities, with emphasis on the latest structural control strategies for tuning transport properties. Key applications of functional elastomer nanocomposites related to transport phenomena are also introduced. Overall, this review summarizes the state of the art in the design and performance enhancement of elastomer nanocomposites based on the relationships between their structures and transport properties, governed by the components/composition, interface/dispersion and fabrication.     

Graphene and graphene oxide and their uses in barrier polymers

Currently, there is great interest in graphene‐based devices and applications because graphene has unique electronic and material properties, which can lead to enhanced material performance. Graphene may be used in a wide variety of potential applications from next‐generation transistors to lightweight and high‐strength polymeric composite materials. Graphene, which has atomic thickness and two‐dimensional sizes in the tens of micrometer range or larger, has also been considered a promising nanomaterial in gas‐ or liquid‐barrier applications because perfect graphene sheets do not allow diffusion of small gases or liquids through its plane. Recent molecular simulations and experiments have demonstrated that graphene and its derivatives can be used for barrier applications. In general, graphene and its derivatives can be applied via two major routes for barrier polymer applications. One is the transfer or coating of few‐layered, ultrathin graphene and its derivatives, such as graphene oxide (GO) and reduced graphene oxide (rGO), on polymeric substrates. The other is the incorporation of fully exfoliated GO or rGO nanosheets into the polymeric matrix. In this article, we review the state‐of‐the‐art research on the use of graphene, GO, and rGO for barrier applications, including few‐layered graphene or its derivatives in coated polymeric films and polymer nanocomposites consisting of chemically exfoliated GO and rGO nanosheets, and their gas‐barrier properties. As compared to other nanomaterials being used for barrier applications, the advantages and current limitations are discussed to highlight challenging issues for future research and the potential applications of graphene/polymer, GO/polymer, and rGO/polymer composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39628.     

Recent development in thermoplastic/wood composites and nanocomposites: A review

Thermoplastic composites filled with wood-base fillers have gained increasing attention, because compared to virgin polymers they have many advantages of light weight, high strength and stiffness, low cost, biodegradability and renewability. These advantages let them find a large dispersal in many areas of technical applications. However, poor interfacial interaction between hydrophilic wood-base fillers and hydrophobic polymer matrices should be improved to get reasonable physical properties for their wide applications. The interfacial interaction could be improved by addition of coupling agents and chemical modifications of wood-base fillers. To improve physical properties of the thermoplastic/wood composites, further nanofillers can be incorporated. This review summarizes recent developments in thermoplastic/wood composites and deals with wood-base fillers for thermoplastics, various interface modification methods and various thermoplastic/wood composites as well as nanocomposites. This review can provide reasonable future perspectives in this research area and stimulate development of new innovative thermoplastic/wood composites as well as nanocomposites.     

Sulfonated Styrene-(ethylene-co-butylene)-styrene/Montmorillonite Clay Nanocomposites: Synthesis, Morphology, and Properties

Sulfonated styrene-(ethylene-butylene)-styrene triblock copolymer (SSEBS) was synthesized by reaction of acetyl sulfate with SEBS. SSESB-clay nanocomposites were then prepared from hydrophilic Na-montmorillonite (MT) and organically (quaternary amine) modified hydrophobic nanoclay (OMT) at very low loading. SEBS did not show improvement in properties with MT-based nanocomposites. On sulfonation (3 and 6 weight%) of SEBS, hydrophilic MT clay-based nanocomposites exhibited better mechanical, dynamic mechanical, and thermal properties, and also controlled water–methanol mixture uptake and permeation and AC resistance. Microstructure determined by X-ray diffraction, atomic force microscopy, and transmission electron microscopy due to better dispersion of MT nanoclay particles and interaction of MT with SSEBS matrix was responsible for this effect. The resulting nanocomposites have potential as proton transfer membranes for Fuel Cell applications.     

Preparation and Properties of Halloysite Nanotubes/Poly(ethylene methyl acrylate)-Based Nanocomposites by Variation of Mixing Methods

Halloysite nanotube-based inorganic–organic polymer nanocomposite has been developed with improved mechanical strength in one direction by solution mixing followed by melt mixing. Melt mixing, solution mixing, and melt-cum-solution mixing were performed to optimize the mechanical strength of the nanocomposites. The field emission scanning electron microscopic images and small-angle X-ray scattering spectrum can support the unidirectional array of halloysite nanotubes in the matrix. The tensile properties revealed that solution–melt mixing is the most desired way to develop clay-based nanocomposites. Thermal characterizations implied that thermal stability was improved after nanoclay incorporation. Dynamic mechanical analysis showed the flow properties and the “Payne effect” of the nanocomposites.     

Review on Polymer/Carbon Nanotube Composite Focusing Polystyrene Microsphere and Polystyrene Microsphere/Modified CNT Composite: Preparation,Properties, and Significance

In recent times, carbon nanotubes play a promising role in a wide variety of technical applications due to improved structural properties, multifunctional features, mechanical strength, and electrical properties. Initially, problems interrelated to dispersion and alignment of nanotubes inside polymer/carbon nanotubes nanocomposites have been discussed. Fabrication methods and properties of polymer/carbon nanotubes nanocomposites were also highlighted. Main spotlight of the review article was the preparation, properties, and applications of polystyrene microspheres. The carbon nanotubes functionalization and physical/covalent grafting of polystyrene microspheres onto the sidewall of nanotubes is a rousing research spot. The article also evaluates the characteristics and potential applications of polystyrene microsphere-grafted-modified carbon nanotubes.     

Recent Advances in Polyurethane-Based Nanocomposites: A Review

This review addresses recent advances in polyurethane-based nanocomposites. It focuses on the enhancement of mechanical, electrical, thermal, acoustic, chemical, shape memory, and viscoelastic properties of the existing polyurethane using nanoparticles or fiber materials and it is also directed to analyze the potential of incorporating these hybrid polymer composites’ applications. Research on hybrid polymer composites has increased in recent years due to the inherence properties of mixing two or more constituents to reinforce the base material properties. From the discussion in this paper, we can see that polyurethane-based nanocomposite can be modified to suit various applications.     

Novel Microwave-Assisted Synthesis of Nickel/Carbon (Ni/C) Nanocomposite with Tannin as the Carbon Source

Abstract

Metal/carbon nanocomposites find use in many potential applications, in areas such as batteries, catalysts, inks, polymer additives, and solar cells. Nickel/carbon nanocomposites are widely used as heterogeneous catalysts in oil processing and other catalytic reactions. Here we describe a novel microwave-assisted synthesis of nickel/carbon nanocomposites, achieved within a few minutes, starting from nickel salts and a renewable high-content carbon source, tannin. The carbon precursor is Quebracho tannin, which is a renewable-resource material obtained from the hot-water extraction of Schinopsis lorentzii and Schinopsis balansae, which are indigenous to Argentina and Paraguay. The process involves a simultaneous carbonization of the carbon precursor as well as the reduction of nickel ions to elemental nickel nanoparticles in an ambient atmosphere. Thus, this technique provides a fast, easy, and economical way to produce nickel/carbon nanocomposites without requiring the need for hydrogen or inert gas during the transformation. This technique could be used to synthesize a wide range of other metal/carbon nanocomposites and therefore holds tremendous economic promise. The nanocomposites have a high surface area and may be suitable as high efficiency catalysts.     

细菌纤维素纳米复合材料的研究进展

细菌纤维素是一种新型微生物合成材料,与植物纤维素相比,无木质素和半纤维素等伴生产物,同时具有高结晶度和高聚合度、超精细的网络结构、极高的抗张强度和优异的生物相容性,在食品、医药、纺织、化工等方面有着巨大的应用潜力。利用细菌纤维素的纳米网络结构和超强弹性模量等特点可以用于增强聚合物基体,制备无机纳米粒子的模板、分散载体以及用于制备透明增强复合材料。重点介绍了细菌纤维素与高分子材料、无机纳米材料等的纳米复合材料的研究进展,阐述了现阶段存在的问题并对该种复合材料的发展趋势进行了展望。     

Recent advance in research on halloysite nanotubes-polymer nanocomposite

Halloysite nanotubes (HNTs) are novel 1D natural nanomaterials with predominantly hollow tubular nanostructures and high aspect ratios. Due to their high mechanical strength, thermal stability, biocompatibility, and abundance, HNTs have a number of exciting potential applications in polymer nanocomposites. In this article, we review the recent progress toward the development of HNTs-polymer nanocomposites, while paying particular attention to interfacial interactions of the nanocomposites. The characteristics of the HNTs relative to the formation of the polymer nanocomposites are summarized first. The covalent or non-covalent functionalization methods for HNTs and various fabrication approaches for HNTs-polymer nanocomposites are introduced afterward. Polymer nanocomposites reinforced with HNTs possess highly increased tensile and flexural strength, elastic moduli, and improved toughness. HNTs-polymer nanocomposites also exhibit elevated thermal resistance, flame retardance and unique crystallization behavior. Due to the tubular microstructure and the biocompatibility of HNTs, HNTs-polymer nanocomposites have demonstrated good drug encapsulation and sustained release abilities, gaining them extensive use as tissue engineering scaffolds and drug carriers. Finally, we summarize the characteristics of HNTs-polymer nanocomposites and predict for the development of the potential applications in high-performance composites for aircraft/automobile industries, environmental protection, and biomaterials.     

Reinforcement in melt-processed polymer–graphene composites at extremely low graphene loading level

We have prepared polymer nanocomposites reinforced with exfoliated graphene layers solely via melt blending. For this study polyethylene terephthalate (PET) was chosen as the polymer matrix due to its myriad of current and potential applications. PET and PET/graphene nanocomposites were melt compounded on an internal mixer and the resulting materials were compression molded into films. Transmission electron microscopy and scanning electron microscopy revealed that the graphene flakes were randomly orientated and well dispersed inside the polymer matrix. The PET/graphene nanocomposites were found to be characterized by superior mechanical properties as opposed to the neat PET. Thus, at a nanofiller load as low as 0.07 wt%, the novel materials presented an increase in the elastic modulus higher than 10% and an enhancement in the tensile strength of more than 40% compared to pristine PET. The improvements in the tensile strength were directly correlated to changes in elongation at break and indirectly correlated to the fracture initiation area. The enhancements observed in the mechanical properties of polymer/graphene nanocomposites achieved at low exfoliated graphene loadings and manufactured exclusively via melt mixing may open the door to industrial manufacturing of economical novel materials with superior stiffness, strength and ductility.     

Polymer nanocomposites from modified clays: Recent advances and challenges

Since the end of the last century, the discovery of polymer nanocomposites and their ever-expanding use in various applications has been the result of continuous developments in polymer science and nanotechnology. In that regard, progress in developments on the use of modified natural and synthetic clays for designing polymer nanocomposites is presented herein. The modified clays used in composite preparation include natural clays such as montmorrilonite, hectorite, sepiolite, laponite, saponite, rectorite, bentonite, vermiculite, biedellite, kaolinite, and chlorite, as well as synthetic clays including various layered double hydroxides, synthetic montmorrilonite, hectorite, etc. The preparation, structure and properties of polymer nanocomposites using the modified clays are discussed. Even at a low loading, these composites are endowed with remarkably enhanced mechanical, thermal, dynamic mechanical, adhesion and barrier properties, flame retardancy, etc. The properties of the nanocomposites depend significantly on the chemistry of polymer matrices, nature of clays, their modification and the preparation methods. The uniform dispersion of clays in polymer matrices is a general prerequisite for achieving improved mechanical and physical characteristics. Various theories and models used to design polymer/clay nanocomposites have also been highlighted. A synopsis of the applications of these advanced, high-performance polymer nanocomposites is presented, pointing out gaps to motivate potential research in this field.