Biocomposites reinforced with natural fibers: 2000–2010

There have been a number of review papers on layered silicate and carbon nanotube reinforced polymer nanocomposites, in which the fillers have high aspect ratios. Particulate–polymer nanocomposites containing fillers with small aspect ratios are also an important class of polymer composites. However, they have been apparently overlooked. Thus, in this paper, detailed discussions on the effects of particle size, particle/matrix interface adhesion and particle loading on the stiffness, strength and toughness of such particulate–polymer composites are reviewed. To develop high performance particulate composites, it is necessary to have some basic understanding of the stiffening, strengthening and toughening mechanisms of these composites. A critical evaluation of published experimental results in comparison with theoretical models is given.

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Effects of particle size, particle/matrix interface adhesion and particle loading on mechanical properties of particulate–polymer composites

Electrolytes have been identified as some of the most influential components in the performance of electrochemical supercapacitors (ESs), which include: electrical double-layer capacitors, pseudocapacitors and hybrid supercapacitors. This paper reviews recent progress in the research and development of ES electrolytes. The electrolytes are classified into several categories, including: aqueous, organic, ionic liquids, solid-state or quasi-solid-state, as well as redox-active electrolytes. Effects of electrolyte properties on ES performance are discussed in detail. The principles and methods of designing and optimizing electrolytes for ES performance and application are highlighted through a comprehensive analysis of the literature. Interaction among the electrolytes, electro-active materials and inactive components (current collectors, binders, and separators) is discussed. The challenges in producing high-performing electrolytes are analyzed. Several possible research directions to overcome these challenges are proposed for future efforts, with the main aim of improving ESs' energy density without sacrificing existing advantages (e.g., a high power density and a long cycle-life) (507 references).

A review of electrolyte materials and compositions for electrochemical supercapacitors

Studies on the use of natural fibers as replacement to man-made fiber in fiber-reinforced composites have increased and opened up further industrial possibilities. Natural fibers have the advantages of low density, low cost, and biodegradability. However, the main disadvantages of natural fibers in composites are the poor compatibility between fiber and matrix and the relative high moisture sorption. Therefore, chemical treatments are considered in modifying the fiber surface properties. In this paper, the different chemical modifications on natural fibers for use in natural fiber-reinforced composites are reviewed. Chemical treatments including alkali, silane, acetylation, benzoylation, acrylation, maleated coupling agents, isocyanates, permanganate and others are discussed. The chemical treatment of fiber aimed at improving the adhesion between the fiber surface and the polymer matrix may not only modify the fiber surface but also increase fiber strength. Water absorption of composites is reduced and their mechanical properties are improved.

Chemical Treatments of Natural Fiber for Use in Natural Fiber-Reinforced Composites: A Review

This paper provides an overview of recent progress made in the area of cellulose nanofibre-based nanocomposites. An introduction into the methods used to isolate cellulose nanofibres (nanowhiskers, nanofibrils) is given, with details of their structure. Following this, the article is split into sections dealing with processing and characterisation of cellulose nanocomposites and new developments in the area, with particular emphasis on applications. The types of cellulose nanofibres covered are those extracted from plants by acid hydrolysis (nanowhiskers), mechanical treatment and those that occur naturally (tunicate nanowhiskers) or under culturing conditions (bacterial cellulose nanofibrils). Research highlighted in the article are the use of cellulose nanowhiskers for shape memory nanocomposites, analysis of the interfacial properties of cellulose nanowhisker and nanofibril-based composites using Raman spectroscopy, switchable interfaces that mimic sea cucumbers, polymerisation from the surface of cellulose nanowhiskers by atom transfer radical polymerisation and ring opening polymerisation, and methods to analyse the dispersion of nanowhiskers. The applications and new advances covered in this review are the use of cellulose nanofibres to reinforce adhesives, to make optically transparent paper for electronic displays, to create DNA-hybrid materials, to generate hierarchical composites and for use in foams, aerogels and starch nanocomposites and the use of all-cellulose nanocomposites for enhanced coupling between matrix and fibre. A comprehensive coverage of the literature is given and some suggestions on where the field is likely to advance in the future are discussed.

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Review: current international research into cellulose nanofibres and nanocomposites

Resonance light scattering (RLS) spectra were used to study the formation of complexes of carboxymethyl cellulose (CMC) and polylactic acid (PLA) in a mixed solvent of 10% DMSO/90% H2O(V/V). The RLS results showed that the CMC and PLA could form a steady homogeneous complex due to the interaction of hydrogen bonding. With the increasing of CMC mass fraction in the complex, the observed durative enhancement RLS signal with two inflexion points indicated the forming of complexes and aggregation of complexes. The aggregation equilibrium and thermo stability of the complexes were also investigated based on RLS values.

Association behaviors between carboxymethyl cellulose and polylactic acid revealed by resonance light scattering spectra

To improve the conductive properties of carbon-black-filled low-density polyethylene, in situ grafting of certain monomers was applied during the melt compounding process. The experimental data obtained demonstrated that chemical bonding could thus be established between the fillers and the matrix polymer. The degree of enhancement of the filler/matrix interfacial interactions in the composites prepared in this way depends on the species of the grafting monomers being employed. When compared with the untreated carbon black composites, the composites manufactured through in situ melt grafting exhibited reduced room temperature resistivities and greatly increased positive temperature coefficient intensities, as well as favorable performance reproducibility. This proposed technical route has several advantages, including simplicity, low cost and easy control. Copyright © 2004 Society of Chemical Industry

In situ melt grafting in carbon black/polyolefin composites and its influence on conductive performance

Glass transition in polymers monitored by synchronous scan spectra

Surface treatment proves to be an effective way to enhance the mechanical properties of stainless steel fiber (SSF)-filled polymer composites, a candidate for shielding electromagnetic interference applications. To reveal the details of interfacial interaction in polypropylene (PP)-based composites, micro- and macromechanical performance of the materials as well as surface chemical features of the fibers extracted from composites were characterized. The results suggest that a chemical bond was formed between the SSF surface and modified PP (i.e., PP grafted maleic anhydride copolymer, PP-g-MAH) in addition to van der Waals forces, which accounts for the improved interfacial adhesion in the SSF/PP-g-MAH/PP system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2174–2179, 2000

Interfacial interaction in stainless steel fiber-filled polypropylene composites

Copper selenide is widely considered to be a promising candidate for high-performance flexible thermoelectrics; however, most of the reported ZT values of copper selenides are unsatisfactory at a relatively low temperature range. Herein, we utilized some wet chemical methods to synthesize a series of copper selenides. XRD, SEM and TEM characterizations revealed that CuSe, Cu3Se2 and Cu2−xSe were prepared successfully and possessed different morphologies and sizes. Based on the analysis of their thermoelectric properties, Cu2−xSe exhibited the highest Seebeck coefficient and lowest thermal conductivity among the three samples owing to its unique crystal structure. After being sintered at 400 °C under N2 atmosphere, the electrical conductivity of Cu2−xSe enhanced considerable, resulting in a significant improvement of its ZT values from 0.096 to 0.458 at 30 to 150 °C. This result is remarkable for copper selenide-based thermoelectric materials at a relatively low temperature range, indicating its brilliant potential in the field of flexible thermoelectric devices.

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Ming Qiu Zhang

Papers

Association behaviors between carboxymethyl cellulose and polylactic acid revealed by resonance light scattering spectra

In situ melt grafting in carbon black/polyolefin composites and its influence on conductive performance

Glass transition in polymers monitored by synchronous scan spectra

Interfacial interaction in stainless steel fiber-filled polypropylene composites

Facile synthesis of copper selenides with different stoichiometric compositions and their thermoelectric performance at a low temperature range