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

Azobenzene-dyed, nanofibrous microstructure for improving photothermal effect of polymer gel electrolyte

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This chapter deals with the sliding wear performance of epoxy-based nanocomposites. It outlines the state of the art technology for preparing these nanocomposites. A general understanding of the role of nanoparticles and selection criterion for nanocomposite components in terms of wear and friction performance has not yet been established. This situation in turn leaves room for continuous researches in related areas.

Chapter 6 – Sliding wear performance of epoxy-based nanocomposites

We greatly appreciate Tomba's valuable comments on our paper appearing in Soft Matter (2012, 8, 4780). Our responses are listed below to provide additional information for academic discussion.

Reply to the 'Comment on "Observation of mutual diffusion of macromolecules in PS/PMMA binary films by confocal Raman microscopy"' by J. Pablo Tomba, Soft Matter, 2016, 12, DOI: 10.1039/C5SM02735G.

Nano-sized silica was pre-grafted with poly(glycidyl methacrylate) (PGMA) by solution free-radical polymerization. When these grafted silica particles were melt compounded with polypropylene (PP), reactive compatibilization effect was perceived due to the chemical bonding between the PGMA and amine functionalized PP, which led to a significant increase of tensile strength and notch impact strength of PP at rather low filler content. Accordingly, compatibility of each kind of the functionalized PP with grafted SiO2 was evaluated through investigating the mechanical properties, crystallization behavior and rheological performance of the composites. The results show that the reactive compatibilization is capable of providing stronger interfacial adhesion.

Reactive Compatibilization in Nano-Silica Filled Polypropylene Composites

For purposes of developing a novel epoxy with low viscosity and high activity, N,N-diglycidyl-furfurlamine (DGFA) was successfully synthesized through a two-step reaction between 2-furfurylamine and epichlorohydrin involving ring-opening and ring-closure mechanisms. The product structure was verified by FTIR, 1H-NMR, 13C-NMR and elemental analysis, respectively. Its viscosity was found to be 0.02 Pa·s at 25oC. To understand its curing behavior, exothermic habit of the model mixture of DGFA and the curing agent methylhexahydrophthalic anhydride (MHHPA) at stoichiometric ratio of epoxy ring/anhydride of 1:0.8 was inspected with DSC. By changing the heating rates from 2.5 to 15oC/min, activation energy for consolidation of the resin was estimated to be 46.2 kJ/mol, which is much lower than the value involved in curing of diglycidyl ether of bisphenol A catalyzed by anhydride. Besides, thermal decomposition performance of cured version of the newly synthesized epoxy was also examined. The predominant pyrolysis took place at around 330-390oC as a result of chain scission of epoxy. The cured resin possesses comparable mechanical properties as conventional diglycidyl ether of bisphenol A. Its flexural strength and modulus are 111MPa and 3.6GPa, respectively. Evidently, the resultant epoxy is provided with balanced properties for practical applications.

Ming Qiu Zhang

Papers

Azobenzene-dyed, nanofibrous microstructure for improving photothermal effect of polymer gel electrolyte

Chapter 6 – Sliding wear performance of epoxy-based nanocomposites

Reply to the 'Comment on "Observation of mutual diffusion of macromolecules in PS/PMMA binary films by confocal Raman microscopy"' by J. Pablo Tomba, Soft Matter, 2016, 12, DOI: 10.1039/C5SM02735G.

Reactive Compatibilization in Nano-Silica Filled Polypropylene Composites

Synthesis and Characterization of a Novel Epoxy with Improved Processability