Materials Science Forum Vols. 675-677

Abstract: In this paper, perovskite LaFeO3 nanoparticles were synthesised by a sol-gel method. Then, polypyrrole (PPy)/LaFeO3 nanocomposites were prepared by a simple in situ chemical polymerization method. By means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM), the microstructure of PPy/LaFeO3 nanocomposites was characterized. The XRD patterns indicated that LaFeO3 nanoparticles have a perovskite phase with orthorhombic structure, and incorporation of PPy did not change the crystalline structure of LaFeO3. The PPy was evenly dispersed on the surface of LaFeO3 particles, which was endorsed by FTIR spectral analyses. And SEM images indicate that the PPy was evenly dispersed on the surface of LaFeO3 particles without apparent agglomeration. And we found that the nanocomposites exhibited a higher response to CO gas.

Abstract: Keep the mixing amount of styrene-acrylic ester (SAE) constant, the mixtures of SAE and cellulose ethers (CE) were confected with tap water and filtered cement water respectively. The relationship between the mechanical properties of polymer modified cementitious composites (PMCCs) and the properties of polymer films was studied. It is discovered that when the cellulose ether-latex ratio (CE/L) increases, the polymer films become fragile. The properties of polymer films mutate when CE/L increases from 0.5‰ to 1.0‰. The tensile strength of the polymer films with filtered cement water is higher than that with tap water. However, the elongation at break is lower than that with tap water. The compressive strength of PMCCs decreases with the increase of the tensile strength of polymer films. Yet, the flexural strength of PMCCs does not relate to the properties of polymer films. The adhesive strength increases when CE/L increases from 0 to 1.0‰, but no longer after that.

Abstract: In this study, pervaporation membranes were prepared from poly( vinyl alcohol) (PVA) with different amounts of cellulose nanocrystals as filler, and characterized by scanning electron microscopy (SEM). The characterization results demonstrated that cellulose nanocrystal particles dispersed homogeneously within the PVA matrix. Moreover, the pervaporation performance of these membranes was investigated using the separation of ethanol-water mixture as model system. Among all the prepared membranes, PVA/cellulose nanocomposite membrane containing 1 wt% cellulose nanocrystals exhibited the best pervaporation performance, whose averaged permeation flux reduced slightly but separation factor was increased from 83 to 163 for 80% aqueous solution of ethanol at 80 °C respectively.

Abstract: In this article, the perforation mechanism(s) of polyethylene was investigated through experiments. Several polyethylene (PE) film samples were fabricated by compression molding technique. In order to examine the perforation mechanism of PE, perforation tests were conducted according to ASTM F 1306 Standard procedure. The damage and plastic zone areas around the perforated area in PE test samples under cross polarized light condition were studied using the optical microscope. The plastic zone area was measured using an image analysis technique. For further clarification of the perforation mechanism of medium density PE (MDPE) films, the micrographs obtained form scanning electron microscope were examined. SEM observation of the test specimens showed shear bands formed in the plastic zone around the perforated area. The shear bands were observed to be on 45° angle with respect to the direction of applied force.

Abstract: Nanocrystalline cellulose (NCC) was used to improve hydrophilic property and permeability of polysulfone (PS) membrane. It was prepared from cellulose pulp by acid-catalyzed hydrolysis and high-pressure homogenization. The casting solution of a PS/NCC blend was obtained by adding NCC to a PS membrane solution and the composite membrane was prepared by phase-inversion method. In addition, the concentration of NCC was increased gradually from 0 wt% to 1.1 wt% during the preparation in order to examine the pure water flux and the retention of a bovine serum albumin (BSA). Simultaneously, the porosity and mean pore size of the membrane was detected and calculated. The result showed that the capacity for ultrafiltration was enhanced with appropriate NCC content. The membranes were also observed with atomic force microscopy (AFM) and scanning electron microscopy (SEM) to explore their porous structures.

Abstract: One best way to harness the petroleum-based solid wastes is to develop biodegradable materials. Among which, PLA is the most important one, because it is made from renewable plant. But Poly(lactic acid) (PLA) is brittle and low impact resistance. The cellulose nanowhiskers are about 5-40 nm in diameter and the length can be from 100 nm to several micrometers depending on the source of cellulose and the processing technology. The cellulose nanowhiskers can act as efficient reinforcement because of the high aspect ratios, important surface areas and high modulus. The celluloses nanowhiskers are hydrophilic because of the abundant exposed hydroxyl (-OH) groups and PLA is hydrophobic. So we added the low molecular weight polymeric-poly (ethylene glycol) (PEG) to improve compatibility between PLA matrix and the cellulose nanowhiskers. The PLA/cellulose nanowhiskers composites were prepared by casting solution. The tensile strength and the elongation rate of the composites improved 56.7% and 48% comparing with the PLA/cellulose whiskers composites. The thermo gravimetric analysis indicated that the thermal decomposition of PLA/cellulose nanowhiskers/PEG composites include only one stage. The pictures of SEM showed the fracture morphology of the different kind of the composites. The structure of the PLA/cellulose nanowhiskers/PEG composites were characterized by AFM, which showed that the cellulose nanowhiskers dispersed evenly in the PLA matrix.

Abstract: A preparation method of modifier with low molecular weight and high reactivity is presented. This modifier （called KFK in lab）can impregnate into polar wood along trachea from the ends with pressurized impregnation method. In the following heating and pressing processes of the polar wood, the KFK polymerizes, and it enhances stability and strength of the wood. It showed that the favorable conditions for synthetic reaction of the KFK are: molar ratio of U and F, 1:1; reaction temperature, 20°C; reaction time, 3 hours; dosage of ignition primer A: 5%. Results from test showed the degree of crystallinity tested by XRD were 30%, 32% in different dosage of the modifier. Utilizing a combination of low molecular weight resin impregnation and pressing resulted in a density increase of KFK resin-treated wood from 0.214 to 0.268g/cm3. At the same time, the Young’s modulus and bending strength increased from 1.407GPa to 1.759GPa and 64MPa to 74.5MPa, respectively. It can be concluded that the effective utilization of KFK resin impregnated in polar wood is a promising technique for the production of high-strength in the drying and pressing processing.

Abstract: The starch-acrylamide-diallyl dimethyl ammonium chloride graft copolymer (St-AMDADMAC copolymer) was prepared firstly. Then the synthesized St-AM-DADMAC copolymer was analyzed by FTIR and SEM. Finally the synthesized St-AM-DADMAC copolymers were applied in making packaging paper, the first pass retention and the mechanical properties of the made packaging paper were determined. The FTIR of St-AM-DADMAC copolymer indicated that AM and DADMAC can be grafted in the chain of starch. The SEM of starch and St-AM-DADMAC copolymer indicated that the surface of starch had been changed obviously by grafting copolymerization. The first pass retention increased with the increase of degree of cationic of St- AM-DADMAC copolymer. When the dosage of St-AM-DADMAC copolymer was about 1% and the degree of cationic of St-AM-DADMAC copolymer was about 25.96%, the mechanical properties of the packaging paper were improved best.

Abstract: Influence of arc discharge to the contact strip of carbon-carbon composites was orthogonally studied on the HST-100 tribo-tester under electric current, which simulated working conditions of the pantograph-wire system used in electric railway. The regression equation between specific wear rate and arc discharge were obtained and analyzed through the non-linear regression and orthogonal design. The results of the experiments show that a power function between specific wear rate and arc discharge was obtained. Microstructure and phase composition were observed and analyzed by scanning electron microscope(SEM), energy dispersive X-ray spectrum(EDS) and temperature sensor. The results revealed that the arc discharge dissipation seriously affects tribological characteristics of the carboncarbon composites. The temperature of some local contact points beyond their melting point with the electric arc heat effect, and give rise to the desposite carbon and friber carbon were vaporazated, which form the lubrication film on the wear surface, and with the augmant of the arc discharge, the area of lubrication film of carbon was decrease. Therefore, the main wear form of the arc erosion of the carbon-carbon composites is evaporate erosion and material transfer.

Abstract: In this research, the urea-formaldehyde prepolymer and multilayer hot-press drying was used to obtain modified wood. The timbers were compressed and dried by the multilayer hot-press drying kiln. The combination of chemical modification and hot-press drying can improve the drying rate, which can also enhanced the physical and mechanical properties. Based on the findings, the basic density of modified wood improved 25.2 %, the bending strength and the bend elastic modulus improved 15.6 % and 25.0 % respectively. The dimensional stability of the treatment appeared to be slightly higher than that of untreated samples under the same conditions for processing temperatures and times. The improving dimensional stability of wood mainly was attributed to the prepolymer that changes wood cell wall components such as the degradation of the hemicelluloses and cellulose during hot-press drying treatment. The XRD results indicated that the degree of crystallinity increased to 35.45 %from 31.25 %. The TGA results show that the degradation of the samples can be divided into two step, both of the maximum weight loss velocity temperature of the two step increased to 266 °C, 355 °C from 244 °C and 341 °C.