In the mineral processing, mining, oil and gas industries, it is not uncommon to find mechanical components exposed to degradation and wear from slurries. Polymeric matrix composites (PMCs) are considered as potential alternatives to replace metallic materials in such severe environments because of their high strength to weight ratio, ease of production, high wear resistance and good corrosion/chemical resistance. Often, seemingly erratic wear behaviour is observed making preventive maintenance and time-to-failure difficult to manage. A major culprit is the complex physical and chemical interaction with the slurry, such as exposure to high temperatures, high alkalinity, high slurry density, insoluble inorganic contents, high hardness of suspended particles and humidity. It is well understood that the addition of reinforcing fibres greatly improves the stiffness and strength of polymeric matrix composites. However, the effect the reinforcement has on the wear performance is far less established and a framework to analyse the effect of fibre volume fraction is yet to be established. The difficulties in establishing such a framework lay in the multi-factorial contributions and the potential trade-offs with mechanical performance. This makes it much more difficult to isolate clear trends. The objective of the present work is to present a comprehensive review on the influence reinforcing fibres play on wear behaviour of PMCs. The influence of fibre volume fraction on wear performance of polymeric composites reinforced with man-made fibres is presented. The applied load, fibre length, coefficient of friction and chemical treatment of fibres are analysed with respect to wear performance of PMCs. Future trends in the use of fibre-reinforced polymeric composites in wear critical applications are identified. Research gaps in designing composites for wear applications are explained, aiming at motivating future research to address these gaps.
There is increasing demand for synthetic bone scaffolds for bone tissue engineering as they can counter issues such as potential harvesting morbidity and restrictions in donor sites which hamper autologous bone grafts and also address the potential for disease transmission in the case of allografts. Due to their excellent biocompatibility, titanium scaffolds have great potential as bone graft substitutes as they can mimic the structure and properties of human cancellous bone. Here we report on a new thermoset bio-polymer which can act as a binder for Direct Ink Writing (DIW) of titanium artificial bone scaffolds. We demonstrate the use of the binder to manufacture porous titanium scaffolds with evenly distributed and highly interconnected pores ideal for orthopaedic applications. Due to their porous titanium structure, the scaffolds exhibit an effective Young's modulus similar to human cortical bone, alleviating undesirable stress-shielding effects, and possess superior strength. The biocompatibility of the scaffolds was investigated in vitro by cell viability and proliferation assays using human bone-marrow-derived Mesenchymal stem cells (hMSCs). The hMSCs displayed well-spread morphologies, well-organised F-actin and large vinculin complexes confirming their excellent biocompatibility. The vinculin regions had significantly larger Focal Adhesion (FA) area and equivalent FA numbers compared to that of tissue culture plate (TCP) controls, showing that the scaffolds can support cell viability and promote attachment. In conclusion, we have demonstrated the excellent potential of thermoset bio-polymer as a Direct Ink Writing ready inkjet binder for manufacture of porous titanium scaffolds for hard tissue engineering.
A c c e p t e d M a n u s c r i p t BET specific surface areas were determined by Inverse Gas Chromatography for samples of flax, kenaf and cellulose fibres. The effect of experimental conditions on the BET surface area values were investigated. Bast fibres showed a large variability within a batch compared to synthesised cellulose fibres. An experimental procedure to determine the BET surface area values for natural fibres is proposed.
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