Advanced Materials Research Vols. 488-489

Abstract: Bamboo fibrosis veneers were impregnated with diammonium hydrogen phosphate, and the content of diammonium hydrogen phosphate was 8%, 13% and 17%, respectively. Then bamboo-fiber based composites were prepared with PF resin adhesive. Combustion and mechanical properties of these fire retardant bamboo-fiber based composite were measured. The result showed that: 1) with the increase of diammonium hydrogen phosphate content, combustion properties increased while mechanical properties fell down, 2) when the diammonium hydrogen phosphate content reached 17%, the heat release rate, total heat release, effective heat of combustion, mass loss rate and ignition time went down by 70.1%, 68.8%, 68.5%, 32.0% and 27.1%, compared with the untreated bamboo-fiber based composites, meanwhile, 3) the MOR was 159.5MPa, MOE was 21241.5MPa and IB was 3.51MPa.

Abstract: Silica fibers have been fabricated via sol-gel reaction and electrospinning. The precursor solution was prepared from tetraethyl-orthosilicate (TEOS), ethanol and aqueous hydrochloric acid. The viscous solution was electrospun at 15kV applied voltage and 20 cm tip-to-collector distance. The process yielded nonwoven sheet of silica fibers with good mechanical integrity. The silica fiber specimens were calcined at different temperatures: 400°C, 600°C and 800°C. Scanning electron microscope (SEM) observation reveals smooth and long fibers with average diameter below 0.5μm for all samples, both as spun and calcined. Fourier transform infrared spectroscopy (FT-IR) spectra show effects of calcination temperature on chemical structure of the fibers. Calcination results in the removal of organic residuals and leaving mostly silica content

Abstract: Synthesis of alumina-mullite-silicon carbide composite (Al₂O₃-Al₆Si₂O₁₃-SiCw) was obtained in situ by carbothermal reduction of a mixture of kaolin and two different silica sources. The carbothermal reduction was carried out in a horizontal tube furnace under flow of argon gas. The synthesized products were mixtures of alumina, mullite and silicon carbide in the form of whiskers. The effects of adding two different silica sources of rice husk ash and silica powder to the mixture of kaolin and activated carbon were investigated. XRD and SEM analyses indicate complete reaction of precursors to yield Al₂O₃-Al₆Si₂O₁₃-SiC as product powders, with the SiC having whisker morphology.

Abstract: In this study, natural rubber/styrene butadiene rubber (NR/SBR) and NR/carboxylated styrene butadiene rubber (NR/XSBR) nanocomposites with carbon nanotube (CNT) were prepared by a latex compounding method. The dry weight ratio of either NR/SBR or NR/XSBR was fixed to 80/20 and the CNT loading in each blend was varied from 0.1 to 0.4 phr. The nanocomposite latices were cast into sheets on a glass mold and then cured at 80°C for 3 h. The tensile properties (tensile strength, modulus at 300% strain, elongation at break) and dynamic mechanical properties (storage modulus, loss tangent) of the vulcanizates were then evaluated. The results showed that the addition of CNT at a very loading could enhance the tensile strength, modulus at 300% strain and storage modulus of these two rubber bends in a dose dependent manner, except that the tensile strength peaked at an optimum filler level, declining at higher filler loadings, whilst the elongation at break deteriorated. Moreover, the tensile strength and modulus at 300% strain of the NR/XSBR nanocomposites appeared to be higher than those of the NR/SBR nanocomposites at the same CNT loadings.

Abstract: In order to provide higher energy absorption capacity in fiber reinforced composites, it is normally required to use more volumes of fibers. This leads to economical limitations as the fiber content usually controls the cost of the composite mix. This research has tried to enhance the energy absorption capacity of the composite while keeping the fiber content constant or at the minimum possible value. A series of laboratory tests were conducted in Iran and Turkey with the same material and fiber type and some recommendations for achieving the optimized results were proposed. Beam and panel tests were used to account for the energy absorption and the results were used for tunnel lining design.

Abstract: Long chain cellulose ester (LCCE) synthesized by acylation reaction via microwave process was used as a compatibilizer for banana stem microcrystalline cellulose/polylactic acid (BS MCC/PLA) composite. The proper reaction time and power output for LCCE synthesis were 150 second and 160 watt, respectively, which resulted in the highest weight increase (%) of LCCE synthesis. The FT-IR and NMR results confirmed that long chain acyl ester was grafted on cellulose structure. The degree of substitution (DS) of LCCE was 2.41. The BS MCC content was fixed at 40wt% while LCCE content was varied from 0-9 wt%. The Tensile properties properties of BS MCC/PLA composites with or without LCCE were studied by tensile test. The results revealed that the addition of LCCE enhanced the elongation at break of 40wt% BS MCC/PLA composite owing to the improvement of compatibility between PLA and MCC, particularly the addition of 5wt% of LCCE which led to the highest elongation at break. However, when the addition of LCCE was greater than 5wt%, the elongation at break was slightly decreased because of the small aggregation of BS MCC and LCCE in PLA matrix as supported by morphological analysis. Nevertheless, the addition of LCCE contributed to the decrease in tensile strength and Young’s modulus of 40wt% BS MCC/PLA composite slightly because of the decreasing of crystallinity in PLA composite.

Abstract: The optical and electronic structures of poly (N-carbazole) (PVK) blend with poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) and polyvinylpyrrolidone (PVP) in the same composition were investigated. Polymer coating was carried out using doctor blade technique on a glass substrate. Uv-vis and photoluminescence spectrum revealed that there are significant different results obtained between PVK, PVK:PVP and PVK:PVDF-HFP. The electronic parameters such as absorption edge (Ee), allowed direct bandgap (Ed), allowed indirect bandgap (Ei) and Urbach edge (Eu) were calculated by using Tauc/Davis-Mott Model. The value of Ee and Ed for PVK and PVK:PVDF-HFP almost same but there was significant different value between Eu and Ei.

Abstract: The mechanical properties (tensile properties, tear strength) and morphology of plasticized poly(vinyl chloride) (PVC) nanocomposites filled with varied loadings of nanosilica (nano-SiO2) (3-9 phr) were investigated. It is found that the addition of nano-SiO2 into the plasticized PVC by melt mixing process results in the increase in the Young’s modulus and tear strength, but the decrease in the tensile strength and elongation at break in a dose dependent manner. The SEM micrographs show ductile fractured surfaces for the neat plasticzed PVC and for the nanocomposites with low nano-SiO2 loadings (3 and 5 phr). As the nano-SiO2 loadings are 7 and 9 phr, SEM images illustrate smoother surfaces, caused by the reduction in the flexibility of the plasticized PVC nanocomposites.

Abstract: Biodegradable plastic reinforced natural fiber composites are finding applications in many fields ranging from construction industry to food industry. The use of natural bio based fillers as reinforcements in composites has several advantages over inorganic fillers including lower density, renewability, and biodegradability. In this research, polylactic acid (PLA)/ microcrystalline cellulose (MCC) composites were investigated as a means to reduce the material cost and enhance the material properties. The coir fibers were used to prepare microcrystalline. Subsequently, the prepared MCC was treated with 3-amiopropyl triethoxysilane (APS) to improve interfacial adhesion between fiber and polymer matrix. Treated and untreated MCC were then mixed at 0-10 wt.% with PLA by twin-screw extruder and fabricated into test specimens by compression molding. The effects of MCC loading and surface treatment on morphology, mechanical properties, and thermal properties of PLA/MCC composites were investigated. The results showed that the PLA with 5 wt.% of MCC exhibited the best mechanical properties compared with all prepared composites. Thermal stability of PLA composites were decreased with increasing MCC content but it can be improved by treated the MCC with APS.

Abstract: The impact strength, thermal stability and morphology of polypropylene (PP) composites filled with pottery stone (PTS) and magnesium oxysulfate (MOS) were investigated. PP/PTS composites were prepared by melt mixing of PP with four loadings of PTS (5, 10, 15 and 20 phr) and each PP/PTS composite with two loadings of MOS (3 and 5 phr) on a twin screw extruder, followed by injection molding into the impact test specimens. The SEM images show a particulate form of PTS particles and a needle-shaped particle with high aspect ratio of MOS. It is found that the impact strength of PP increased with increasing PTS and MOS loading levels. This is because PTS and MOS provide high ability to transfer energy from one phase to another. The thermal stability of PP was improved by shifting the T_onset, T_end set and %char residue towards higher values. Moreover, SEM images of the fractured surfaces show that PTS and MOS are well dispersed in the PP matrix.