Materials Science Forum Vol. 956

Abstract: For the better mechanical and thermal properties of polypropylene (PP), PP sea-island structured composites with elastomer ethylene-propylene-diene monomer (EPDM) and coal powder were prepared by melt-blending method. Coupling agent γ-methacryloxypropyltrimethoxysilane (KH-570) was used as modifier to improve the superficial capacity of coal powder. The structural changes and properties of modified coal powder and composites were characterized and analyzed by Fourier Transform Infrared Spectroscopy (FTIR), surface contact angle analysis, scanning electron microscope (SEM), thermogravimetric analysis (TGA) and mechanical testing. Results show that the modified coal powder has good hydrophobicity and sea-island structure is beneficial in improving the comprehensive performance of composites. The contact angle increases from 33.8° to 91.6° after modification. The initial decomposition temperature (T₀) and largest weight loss temperature (T_md) both have an increase with coal powder content and the maximum are 431.02 °C and 465.33 °C. The mechanical properties tend to go up first and then down with the addition of coal powder. PP/26EPDM/4coal composite has best mechanical properties as well as the impact strength and elongation at break are 60.9 MPa, 615.0%, respectively.

Abstract: In view of the phenomenon that the interfacial adhesion between bamboo fiber（BF）and polylactic acid (PLA) is poor and incompatible. Firstly the BF-g-PLA structure with hydrophobicity is synthesized through grafting lactic acid into bamboo fiber, then plasticizing the composite. Three-element compound plasticizer was prepared by mixing glycerol, tributyl citrate and formamide. The effect of the proportion and addition content of three-element plasticizer on the interfacial compatibility of the composite was investigated. The BF-g-PLA/PLA composites were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and rotational rheometer (RC) The composites were tested for their bending properties, tensile properties and water resistance properties using national standards. The experimental results show that the best interfacial adhesion between BF-g-PLA and PLA was obtained when the addition content of glycerol, tributyl citrate, formamide was 10%. At the same time, the flexural strength, elastic modulus, tensile strength and elongation at break of composites all reached the maximum, as well as the thermal stability and the storage modulus.

Abstract: An algorithm for generating the representative structures of covalent triazine-based frameworks (CTFs) is proposed, and examined by being applied to the framework synthesized by the trimerization of dicyanobenzene. The algorithm is validated by the comparison between the calculated and experimental results of the structural properties such as surface areas and pore size distributions, which shows acceptable consistency. Moreover, the presented modeling approach can be expected for more extensive use for other CTFs. Thus the simulated atomistic strucutures produced from the modeling method can improve the understanding for amorphous structures of the CTFs which have already been developed, as well as predict the theoretical model of new CTFs, and provide useful design strategies for the future experimental efforts.

Abstract: Poly(hydroxyethyl methacrylate) liquid crystal gel was synthesized by chemical crosslinking. The structures and performance of the product were characterized by IR, TG, POM and SEM. The effect of the amount of liquid crystal on the properties of structure and swelling were conducted. The swelling behavior was investigated by crosslinking dosage, initiator dosage, neutralization and water retention. The results showed that the optimal preparation conditions of poly(hydroxyethyl methacrylate) liquid crystal gel was mCLC:mHEMA=2:1, mAPS/(mCLC:mHEMA) =1.5%, mMBA/(mCLC:mHEMA)=0.05%, neutralization=70% by orthogonal experiment. With the increasing of mCLC:mHEMA, the swelling property of liquid crystal gel firstly increased and then decreased. When mCLC:mHEMA=3, the swelling property reached the maximum value and the APS dosage was 2% of the total mass, and the liquid crystal gels had the highest swelling property up to 1024 g/g. When the MBA dosage was 0.05% of the total mass, the swelling performance of liquid crystal gel reached the maximum. The internal structure was relatively compact with forming the most folds on the outer surface, which could improve the free space on the surface and inside, and the liquid crystal gel formed 2~8 μm channel structure by introducing different crosslinking dosage. With the increasing of neutralization, the swelling property of liquid crystal gel firstly increased and then decreased. The neutralization was 90%, and the swelling property reached the maximum value. Liquid crystal gels were dried for 10 h at 60 °C, 70 °C, 80 °C, 90 °C and 100 °C, and the residual moisture contents were 70%, 65.44%, 55.8%, 47.2% and 34.63%, respectively. The materials had good water retention.

Abstract: In this paper, Sb₂O₃/PP composite specimens were prepared by ball milling and melt blending. The effects of Sb₂O₃ particle size and filling amount on the toughening, reinforcing effect and crystallinity of PP composites were analyzed by notch impact test, tensile test, SEM, XRD and DSC characterization. The experimental results show that the filling of Sb₂O₃ particles can improve the mechanical properties and crystallization properties of Sb₂O₃/PP composites. With the increase of filling amount of Sb₂O₃ particles, the tensile strength and impact strength of Sb₂O₃/PP composite increased first and then decreased. When the content of Sb₂O₃ is 2 wt.%, the tensile strength and impact strength of Sb₂O₃/PP composites reach the maximum. When the filling amount is the same, the crystallization and mechanical properties of nanoSb₂O₃/PP composites are better than those of micron Sb₂O₃/PP composites.

Abstract: Spray deposited SiCP/Al-Fe-V-Si composite is characterized with pores and oxide films between deposited particles, therefore further densification is needed. Densification of the composite preforms in large size has becomes the research emphasis and challenge. Current research of the composite is focused on densification technologies used to eliminate metallurgical defects. Key parameters of wedge pressing, density and stress distribution, flow behaviour, densification mechanism and regularity are investigated by combining experiment and finite element modelling. Pass reduction of 10%~15% and space of about 10mm between one end of the plate blank and the steel mould is beneficial to wedge pressing because of the effective deformation. Density and stress of the external layer are higher than that of the inter layer, density and stress distribution become uniform with overall reduction. Materials in preformed area flows along thickness direction as thickness of the plate decreases, while materials in main deformation area flows along length direction with increasing length of the plate. Wedge pressing of the spray deposited Al matrix composite plate follows porous metal plastic deformation mechanism under the condition of plane strain. Practical relative density of the plate is higher than the calculated value in the initial stage of pressing, while the practical relative density becomes lower than the calculated value as true strain exceeds 0.55, which can be attributed to the pores resulted from aggregation and breaking of SiC particles.

Abstract: The quasi-static and dynamic compressive mechanical behaviors of two kinds of fiber reinforced SiC ceramic matrix composites including 2D-C/SiC and 2D-SiC/SiC were investigated. Their compressive behaviors of materials at room temperature and strain rate from 10^-4 to 10⁴ /s were studied. The fracture surfaces and damage morphology were observed by scanning electron microscopy (SEM). The results showed that the dynamic failure strengths of 2D-C/SiC and 2D-SiC/SiC obeyed the Weibull distribution. The Weibull modulus of the two materials were 13.70 (2D-C/SiC) and 5.66 (2D-SiC/SiC), respectively. It was found that the two kinds of fiber reinforced ceramic matrix composites presented a transition from brittle to tough with the decrease of strain rate. The 2D-SiC/SiC materials demonstrated a more significant strain rate sensitivity and smoother fracture surface compared to the 2D-C/SiC composites, implying that the former composites present brittle features. This was because the SiC/SiC composites possessed high density and the bonding strength in interface of fiber/matrix is very strong.

Abstract: In this study, the effect of wall thickness on the extrudate swell of plastic microtubules was investigated by using the finite element numerical method. For the traditional extrusion and gas-assisted extrusion, under the same process parameters, the extrudate swell ratios of plastic microtubules with the different wall thicknesses were all obtained. Moreover, to analyze the difference between the traditional extrusion and gas-assisted extrusion, the physical fields distributions, such as flow velocities, pressure and the stresses distributions of plastic microtubules with the different wall thicknesses under two kinds different extrusions were also obtained and compared. Numerical results show that, for the traditional extrusion, the extrudate swell ratio decreases with the increasing of the wall thickness, but for the gas-assisted extrusion, the swell ratios are equal to 0 and not changed. In addition, from the viewpoints of physical fields distributions, for the traditional extrusion, with the increasing of the wall thickness, the velocities, pressure and stresses of melt are all decreased, which result in the reducing of the extrudate swell phenomenon. However, for the gas-assisted extrusion, the X velocity, pressure, and stresses are all equal to 0, which results in the elimination the extrudate swell phenomenon of plastic microtubules.

Abstract: Amphiphilic functionalized montmorillonite (MMT) has been employed in hydrophobic compounds delivery systems. In the present study, MMT intercalated by 3-aminopropyl trimethoxysilane (APS) was employed for the delivery of the model compounds of resveratrol (RSV). The structure and surface morphology of APS-MMT were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetry, scanning electron microscopy, and contact angle analysis. The loading and release efficiencies of RSV were also investigated. Our study showed that the aminosilane-modified MMT is promising for use in poorly water-soluble compounds carrier systems owing to their natural and excellent performance.

Abstract: MnO_x/wasted rock dust catalyst (WZ01) and modified wasted rock dust catalyst (WZ02) were prepared by impregnation method and hydrothermal method as the wasted rock dust (WRD) generated in stone processing plants was used as carriers. The structure of the two catalysts were characterized by energy dispersive spectrometer (EDS), X-ray diffraction (XRD), N₂ adsorption-desorption, scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR). Their removal efficiencies and reaction mechanisms of oxalic acid were compared and analyzed, which could provide an innovative perspective for catalytic efficiency improvement and cost reduction. The results showed that the WRD contained O, Si, Al, K, Mg, Fe, Ca and Na elements. Mn was amorphous in WZ01 and loaded on the surface of WRD, and Mn was in the form of orthorhombic Mn₂O₃ in WZ02. WZ02's surface morphology showed obvious changes and was wrinkled with many microchannels. The specific surface area, total pore volume and average pore size of WZ02 had been improved. After 30 minutes of reaction at room temperature, the removal efficiencies of oxalic acid with an initial concentration of 500 mg·L^-1 were 40.6% and 54.6% by using WZ01 and WZ02 as catalysts with catalyst dosages of 2 g·L^-1 and O₃ concentration of 4.92 mg·L^-1, respectively. The removal efficiency of oxalic acid decreased greatly after WZ01 recycling and Mn, which acted as active components, was massively washed out. The removal efficiency of oxalic acid was stable after WZ02 was triply recycled as only a small amount of Mn was washed out. The removal efficiency of oxalic acid reduced after tert butanol was introduced into the two reaction systems, and a large amount of •OH was detected by using coumarin fluorescence technology. The removal of oxalic acid by WZ01 and WZ02 catalyzed ozonation were achieved by the combination of adsorption and hydroxyl radical reaction.