The thermal, thermo-mechanical and flammability properties of kenaf core hybrid polymer nanocomposites reinforced with unbleached and bleached nanocrystalline cellulose (NCC) were studied. The studied chemical composition found that unbleached NCC (NCC-UB) had 90% more lignin content compared to bleached NCC (NCC-B). Nanocelluloses were incorporated within polypropylene (PP) as the matrix, together with kenaf core as a main reinforcement and maleic anhydride grafted polypropylene (MAPP) as a coupling agent via a melt mixing compounding process. The result showed that the thermal stability of the nanocomposites was generally affected by the presence of lignin in NCC-UB and sulfate group on the surface of NCC-B. The residual lignin in NCC-UB appeared to overcome the poor thermal stability of the composites that was caused by sulfation during the hydrolysis process. The lignin helped to promote the late degradation of the nanocomposites, with the melting temperature occurring at a relatively higher temperature of 219.1 °C for PP/NCC-UB, compared to 185.9 °C for PP/NCC-B. Between the two types of nanocomposites, PP/NCC-B had notably lower thermo-mechanical properties, which can be attributed to the poor bonding and dispersion properties of the NCC-B in the nanocomposites blend. The PP/NCC-UB showed better thermal properties due to the effect of residual lignin, which acted as a compatibilizer between NCC-UB and polymer matrix, thus improved the bonding properties. The residual lignin in PP/NCC-UB helped to promote char formation and slowed down the burning process, thus increasing the flame resistance of the nanocomposites. Overall, the residual lignin on the surface of NCC-UB appeared to aid better stability on the thermal and flammability properties of the nanocomposites.
In this work, the performance of polydimethylsiloxane (PDMS) nanocomposites with carbon black (CB) and multi-walled carbon nanotube (MWCNT) fillers was studied. The carbon nanofillers were first introduced in the solvent to promote an adequate dispersion. The silicone rubber was then reinforced with the carbon nanofillers by a mechanical mixing process followed by film casting. It was found that only small amount of MWCNTs is required to reach the percolation threshold that produces high electrical conductivity. Filler size and segregation, as observed by scanning electron microscopy, play important roles in determining the electrical properties of silicone elastomer filled composites. Transmission electron microscopy was also performed to examine the tube–tube interaction of MWCNT in silicone rubber. The MWCNT/PDMS nanocomposites have higher electrical conductivity value compared to the CB/PDMS nanocomposite. The percolation threshold for MWCNT/PDMS nanocomposites was approximately 1.0 vol% of MWCNT loading with a value of –4.06 log σ (S/cm). On the contrary, no obvious percolation threshold of CB/PDMS nanocomposites was observed, as the CB fillers added from 0.5 to 2.0 vol% in the PDMS. The MWCNT/PDMS nanocomposite also showed better thermal stability than the CB/PDMS nanocomposite. The onset temperature for 0.5 vol% of MWCNT/PDMS and CB/PDMS nanocomposites were 528°C and 492°C, respectively.
Abstract. The focus of this study was to obtain the optimum alkaline treatment for pineapple leaf fibre and its effect on the mechanical and chemical properties, surface topography, heat resistivity, as well as its interfacial bonding with epoxy matrix. There were 6 different treatment conditions set for the fibre. The morphology of a single fibre observed under the Digital Image Analyzer indicates slight reduction in fibre diameter with increasing NaOH concentration. The Scanning Electron Microscope (SEM) results show the deteriorating effect of alkali, which can be seen from the removal of impurities and increase in surface roughness. The mechanical analysis indicates that 6% NaOH treatment with 3-hour immersion period yielded the highest tensile strength. The adhesion between single fibre and epoxy resin was analysed through the micro-droplet test. Alkaline treatment results in better mechanical bonding between fibre and epoxy resin. It was found that 6% NaOH treatment with 1-hour immersion yielded highest interfacial shear stress. However, as NaOH concentration went above 6 %, the fibre started to show reduction in mechanical properties, as well as fibre-matrix interlocking. The TGA analysis implies that alkaline treatment improved the thermal stability and heat resistivity of the fibre.
Recent progress in research on the key thermal expansion properties of amorphous, silicaͲbased, alkaliͲactivated geopolymers and their potential applications are here reviewed and addressed. Besides having great potential as thermal insulators and fire resistant materials since they are not combustable, geopolymers can be applied as interior aircraft components to improve fire resistance, and as coatings for insulator applications and many other potential applications. The raw materials used to make geopolymers are alumino silicates such as fly ash, granulated blast furnace slag, and calcined kaolinite clays. The raw materials can be obtained from biomass waste such as rice husk ash, palm oil ash, and rice husk bark ash. Different raw materials will exhibit different thermal expansion/shrinkage due to their different chemical compositions. In addition, processing of geopolymer material will result in diverse thermal properties due to the different molarity of the alkaline activated solutions used and method of preparation. Interestingly, it was found that the dilatometer curve is influenced by many factors such as aluminosilicate source, silica to alumina ratio, geopolymer mixing ratio, chemical composition and type of geopolymer Ͳ such as composite, coating or hybrid. These characteristics are investigated further in this review paper. AbstractRecent progress in research on the key thermal expansion properties of amorphous, silicaͲbased, alkaliͲactivated geopolymers and their potential applications are here reviewed and addressed. Besides having great potential as thermal insulators and fire resistant materials since they are not combustable, geopolymers can be applied as interior aircraft components to improve fire resistance, and as coatings for insulator applications and many other potential applications. The raw materials used to make geopolymers are alumino silicates such as fly ash, granulated blast furnace slag, and calcined kaolinite clays. The raw materials can be obtained from biomass waste such as rice husk ash, palm oil ash, and rice husk bark ash. Different raw materials will exhibit different thermal expansion/shrinkage due to their different chemical compositions. In addition, processing of geopolymer material will result in diverse thermal properties due to the different molarity of the alkaline activated solutions used and method of preparation. Interestingly, it was found that the dilatometer curve is influenced by many factors such as aluminosilicate source, silica to alumina ratio, geopolymer mixing ratio, chemical composition and type of geopolymer Ͳ such as composite, coating or hybrid. These characteristics are investigated further in this review paper.
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