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

Low carbon black filled polyurethane composite as candidate for wide spectrum gas-sensing element

Topological rearrangement-derived homogeneous polymer networks capable of reversibly interlocking: From phantom to reality and beyond

To obtain comprehensive knowledge of the interfacial effect on the impact performance of sisal fiber reinforced epoxy composites, the fiber surface was modified in different ways prior to compounding. By using a surface tensiometer and dynamic mechanical analyzer, interfacial interactions in the composites were characterized. The results indicated that the chemical treatments brought about strong bonding between sisal bundles and the epoxy matrix. The subsequent impact tests revealed that the microfailure mechanism involved is a function of interfacial adhesion and fiber length continuity (i.e., continuous or discontinuous fiber). In the case of unidirectional laminates, an optimum fiber treatment should be able to result in an increased affinity between fiber bundles and matrix and a decreased intercellular adhesion. In this way, extension and uncoiling of the spirally arranged microfibrils, a main energy consumption process of plant fibers, can impart significant toughness to the composites. For short fiber composites, the interfacial strength should be properly tailored so as to increase energy dissipation through debonding and pull-out of fiber bundles.

Interfacial interaction in sisal/epoxy composites and its influence on impact performance

The objective of this article is to review progress in the study and development of thermoplastic polyurethane (TPU)/polyolefin (PO) blends, a series of thermoplastic elastomers having the advantage of easy regulation of mechanical properties within a wide range. Important aspects including coalescence behaviour, compatibilizer species and compatilization mechanisms are discussed. The effects of interfacial interactions, surface free energy of the blend components, viscoelasticity and concentration of the dispersed phase, and mixing conditions are summarized and analyzed. Emphasis is placed on recent trends to produce stable TPU/PO blends with specific properties that are not available in either the single component of the blends or other polymers.

Polyurethane/Polyolefin Blends: Morphology, Compatibilization and Mechanical Properties:

A continuum-mechanics approach has been applied to model the mechanical properties of high density polyethylene (HDPE) filled with differently coated SiO2 nanoparticles. The tensile yield stress has been predicted with a finite-element model (FE-model) taking into account the microstructural features, e.g. matrix, filler content and the interphase formed around the filler. A good agreement between the experimental and modelled data has been found. Additionally, the FE-model has been compared with a semi-empirical model and an analytical model with similar input parameters to predict the composite property. It was found that all models are congruent with respect to solution space.

Ming Qiu Zhang

Papers

Low carbon black filled polyurethane composite as candidate for wide spectrum gas-sensing element

Topological rearrangement-derived homogeneous polymer networks capable of reversibly interlocking: From phantom to reality and beyond

Interfacial interaction in sisal/epoxy composites and its influence on impact performance

Polyurethane/Polyolefin Blends: Morphology, Compatibilization and Mechanical Properties:

Modelling of Mechanical Properties of Nanoparticle Filled Polyethylene