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Table of Content

    25 November 2008, Volume 36 Issue 11
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    Chemistry & Chemical Engineering
    Factors to Affect Preparation of Pt/C Catalyst via Organic Colloidal Method
    Liao Shi-jun Chen Min
    2008, 36(11):  1-6. 
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    This paper deals with the effects of some preparation factors, such as the pretreatment of carbon support, the preparation conditions, the reduction temperature and the initial pH value, on the properties of catalysts prepared via the organic colloidal method. Experimental results show that the heat pretreatment of carbon support at a suitable temperature, especially at the optimal value of 300 ℃ , greatly enhances the dispersion of active components and the performance of the catalyst, that the catalyst prepared in nitrogen atmosphere behaves better performances than that prepared in air atmosphere, that a low reduction temperature benefits the preparation of high-dispersion catalyst, that the catalyst prepared over the optimal reduction temperature （140 ℃ ） shows a slight activity decline, and that the optimal initial pH value is about 11. It is thus demonstrated that the Pt/C catalyst prepared at the optimal conditions possesses higher electrochemical activity for the oxidation of methanol, as compared with the commercial Pt/C catalyst.

    Thermal Conductivity of Al2O3-H2O Nano-Fluid
    Zhu Dong-sheng Li Xin-fang Wang Nan Wang Xian-ju Li Hua Yang Shuo
    2008, 36(11):  7-11. 
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    The thermal conductivity of Al2O3-H2O nano-fluid was measured using a Hotdisk thermophysical analyset, and the effects of pH value, dispersant concentration and nano-particle content （ mass fraction） on the thermal conductivity were investigated. The results show that, when the pH value and the dispersant dosage are both optimal, the absolute value of surface Zeta potential of Al2O3-H2O nano-fluid in aqueous solution significantly improves, thus increasing the electrostatic repulsive force among particles and resulting in better dispersion behavior and higher thermal conductivity of the nano-fluid. Moreover, it is found that pH 8.0 favors the dispersion behavior and the thermal conductivity, that the optimized content of sodium dodecylbenzenesulfonate is 0. 10% for 0. 10% Al2O3-H2O nano-fluid, and that the thermal conductivity of Al2O3-H2Onano-fluid, which is higher than that calculated based on the Hamilton-Crosser model, nonlinearly increases with the mass fraction of nano-particles.

    Investigation into Heat Soliton and Phase-Change Heat Transfer in Minichannel
    Luo Xiao-ping
    2008, 36(11):  12-16. 
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    This paper deals with the phase-change heat transfer in a minichannel. In the investigation, first, an ensemble formula is put forward to calculate the average evolution radius of bubbles based on the known bubble equilibrium diameter and initial value. Next, a random dynamic differential equation describing the growth of bubbles in the minichannel is deduced based on the correlations of random growth factors and the proposed ensemble formula. Then, the potential energy and probability density of the bubble growth system varying with the radius are obtained according to the steady-state solution to the proposed dynamic equation. Furthermore, a formula describing the phase-change heat transfer with nucleate flow boiling is put forward according to the heat soliton expression describing the heat flux of reaction bubbles in the minichannel. Finally, some phase-change heat transfer experiments are carried out for 23 parallel minichannels with the size of 0.3 mm × 2 mm. It is indicated that the proposed formula is feasible because the theoretical results accord well with the experimental ones with an error of less than 7 %.

    Heat Transfer and Flow Resistance Properties in Twisted Oblate Tube with Large Twist Ratio
    Gao Xue-nong Zou Hua-chun Wang Duan-yang Lu Ying-sheng
    2008, 36(11):  17-21,26. 
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    Water was used as a working medium to investigate the internal heat transfer and flow resistance properties of the twisted tube with large twist ratio in the conditions of variable short-long diameter ratio （ B/A = 0. 27- 0.47） and twist ratio （the lead-to-diameter ratio, S/de = 17.19 - 50.62）. Experimental results indicate that the B/A value greatly affects the internal Nusselt number and friction factor of the twisted tube because the parameters decrease with the increase of B/A and S/de values, more rapidly with the former, and that the Nusseh number and friction factor of the twisted oblate tube increase respectively by 30% - 150% and 20% - 50% , as compared with those of the smooth tube at the same Reynolds number and Prandtl number. Moreover, the formulae of Nusselt number and friction factor of the twisted oblate tube with large twist ratio are both deduced based on the multiple linear regression of experimental data, the maximum errors of which being respectively 12% and 6%. The proposed formulae lay a foundation for the design of heat exchanger with twisted oblate tubes.

    Elimination of Oxygen from Hydrogen with Catalysis of Palladium
    Zeng Li-ding Zhu Dong-sheng Wang Chun-hua Xie Zhen
    2008, 36(11):  22-26. 
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    Palladium catalysts with different contents of palladium supported by activated Al2O3 were prepeared by means of ultrasonic impregnation to eliminate trace oxygen from hydrogen. The effects of the palladium content and the H2 space velocity on the O2 content after the reaction were then discussed. Moreover, the reaction region on the catalyst bed was detected by means of infrared thermal imaging. The results show that the conversion of O2 decreases with the increase of H2 space velocity, and that two inflection points occur at the H2 space velocities of 10 - 12s- 1 and 15 - 17s-1, respectively, which become more acuate at a higher palladium content. It is thus concluded that the internal diffusion is the controlling step of the catalytic reaction, that the reaction is not sensititive to the palladium content more than 0. 20%, and that the catalytic reaction becomes more effective in the conditions of low palladium content, small catalyst particle size and large catalyst dosage.

    Removal of Toluene by Non-Thermal Plasma Combined with Photocatalyst TiO2
    Huang Bi-chun Yang Yue Zhang Xiao-ming Ye Dai-qi
    2008, 36(11):  27-33. 
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    Non-thermal plasma-photocatalysis （NTP-P） is employed to remove the toluene existing in volatile organic compounds （VOCs）. The mechanisms of toluene removal including the reaction mechanism and the macrodynamics are then analyzed in the case of adding 02 and Ar to the NTP-P system. The results show that photocatalyst TiO2 improves the removal rate of toluene in not only the nitrogen plasma field （NTP-P-O2/N2） eradiating ultraviolet light but also the argon plasma field （NTP-P-Ar） eradiating visible light. This supports the idea that both the UV light and the high-energy electron in the plasma field can activate TiO2. Furthermore, the toluene removal rate in NTP-P-Ar system is 5% higher than that in NTP-P-O2/N2 system, confirming that high-energy electron has greater effect on the degradation performance of toluene, as compared with UV light. Based on the classical kinetic analysis method, a dynamic model of toluene degradation in non-thermal plasma-photocatalysis system is established, whose validity is proved from the consistency between the calculated data and the experimental ones.

    Synthesis Technology of 2-Methylpyridine
    Zou Hua-sheng Pan Xue-min Lin Gang
    2008, 36(11):  34-37,44. 
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    This paper proposes a novel synthesis technology of 2-methylpyridine from acetylene and acetonitrile, and determines the optimal synthesis conditions by experiments. The results indicate that 2-methylpyridine with a yield of 50.88% can be prepared in the optimal conditions, that is, an acetylene pressure of 1.1 MPa, an acetylene dosage of 7.332g, a reaction temperature of 180℃, an organic cobalt catalyst dosage of 200mg and a reaction period of 12 h, that 2-methylpyridine with a purity of more than 98% can be obtained ＇after the filtration and batch distillation of the reacted solution mixture, and that the proposed technology is potentially applicable in industry due to its simple operation and high yield.

    Determination of Chemical Components of Extractives from Santalum album L. Leaves by Means of Py-GC/MS
    Peng Wan-xi Zhang Ning-nan Zhang Dang-quan Xu Da-ping Wu Shu-bin
    2008, 36(11):  38-44. 
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    In order to avoid the great resource waste due to the discard of Santalum album L. leaves, the Py-GC/ MS was employed to analyze the extractives from Santalum album L. leaves. The results indicate that there are 118 compounds in the benzene/ethanol extraetives from Santalum album L. leaves, including 16-hentriacontanone （8.69%）, 11, 14, 17-eicosatrienoic acid methyl ester （ 8.49% ）, hexadecanoie acid （ 5.38% ）, pyrazine （4.01%）, eyclooctacosane （3.89%）, phenol （3.19%）, etc. , and that there are 48 compounds in the acetone extractives, including lupan-3-ketone （ 39.35% ） , taraxasterol （7.60%） , β-sitosterol （5.38%） , taraxerol （3.42%）, acetaldehyde （2.37%） and androstan-6-ketone-（5α） （2.36%）, etc. It is thus concluded that the extraetives from Santalum album L. leaves contain rare medicinal materials and rare spices, and that the extraction by-products can be used as not only top-grade cosmetics but also biological energy.

    Synthesis and Characterization of Polyurethane-Epoxy Resin-Rosin Hybrid Emulsion
    Guo Wen-fie Fu He-qing Huang Hong Chen Huan-qin
    2008, 36(11):  45-50. 
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    Waterborne polyurethane （WPU） hybrid emulsions were prepared from polycaprolactone glycol （PCL）, tolylene diisocyanate （TDI） and dimethylolpropionic acid （DMPA）, with trimethylol-propane （TMP） as the crosslinking agent and with epoxy resin and rosin as the modification agents. The structures and properties of the products were then characterized by means of FTIR, particle size analysis, GPC and DSC. The results indicate that the preparation of WPU is due to the formation of urethane groups via the reaction between the hydroxyls in epoxy resin and the diisocyanate groups in TDI, to the ring-opening reaction, and to the participation of grafting of epoxy resin onto the polyurethane （PU） molecules via a ring-opening reaction, and to the participation of carboxyls in rosin in the reaction. Moreover, it is found that the average particle size of WPU hybrid emulsions increases with the contents of epoxy resin and rosin, that the relative molecular mass of the modified WPU is up to 7.43 × 105 , that the content of TMP should not be more than 2. 7% due to its great effect on the peeling strength of WPU film, that epoxy resin, PU and rosin all have good compatibil- ity after the modification, and that the decomposition temperature of the cast films is more than 260 ℃, revealing strong adhesion strength of the adhesive formulated by the modified WPU emulsion for various laminated package films.

    Dynamic Optimization and Integrated Control of Batch Reaction Process
    Zhou Hua Qian Yu Li Xiu-xi Xu Liang
    2008, 36(11):  51-56. 
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    In order to implement the safe operation of batch reaction and to guarantee the quality of a desired product, the dynamic programming method is adopted to solve the optimization problem, and the common model control algorithm is employed to dynamically optimize and integratedly control the batch reaction process. In the investigation, first, the reaction process is divided into a dynamic optimization model and a process control one. Then, by considering the effects of uncertain parameters, the dynamic optimization and the close-loop control strategy are integrated to imporve the product quality and guarantee the operation safety. The proposed method is finally applied to a batch reactor adopting the consecutive exothermic reaction scheme. The results verify the feasibility and correctness of the method.

    Characterization of Self-Similarity of Periodical Chaotic Mixing
    Xu Bai-ping Qu Jin-ping Song Jian Xie Fang Peng Xiang-fang
    2008, 36(11):  57-62. 
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    Based on the Galerkin method, the approximate analytical solution to the transient velocity field is obtained for the high-viscosity fluid in a square cavity driven by the vibration of upper and bottom lids. Then, a dynamic equation describing the mixing process is proposed and the configuration variation of the tracer with time is obtained via the front tracking of passive tracer that numerically integrated by the fourth-order Runge-Kutta scheme. It is found that there exists periodic chaos in the square cavity because the flow field is sensitive to the initial position of particles, that when the micro-elements of fluid with different initial orientations are advected from the same initial position, the interface tension approaches to an asymptotical distribution mode and displays an exponential growth with the time, while the length ratio keeps constant, and that not only the interface tension of the tracers advected from different initial positions but also the geometrical configurations of tracer interfaces display a self-similarity.

    Effect of Ultrasonic Treatment on Gel Properties of Potato Starch Paste
    LiLin Lin Jing-yun Li Jian-bin Chen Ling Li Bing Li Xiao-xi
    2008, 36(11):  63-67. 
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    In order to reveal the influence of ultrasonic treatment on the gel properties of starch pastes, the gel properties of potato starch paste with variable concentration were investigated using a texture analyzer in different ultrasonic treatment conditions. Then, the microstructure of the potato starch paste after the ultrasonic treatment was observed by means of SEM. The results show that the ultrasonic treatment greatly affects the gel properties of potato starch, and that the gel strength decreases with the prolonging of ultrasonic treatment time and with the increase of ultrasonic intensity, the decreasing degree being positively linear with the concentration of starch paste. Moreover, it is demonstrated that the degradation of gel properties mainly results from the variation of paste mierostructure caused by ultrasonic treatment, concretely, after the ultrasonic treatment, the microstructure of starch paste changes from a stronger composite network to a loosen and group-gathering one.

    Preparation of Amphoteric Tapioca Carboxylic Ester Starch and Corresponding Mechanism
    Luo Ming-hui Lu En-xi Zhang Ben-shan
    2008, 36(11):  68-73. 
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    Amphoteric tapioca starch with carboxyl groups was produced via crosslinking, oxidation and etherization reactions. The product was then characterized by means of SEM, XRD and colloid titration, with the preparation mechanism being also investigated. The results indicate that the degrees of substitution （DS） of carboxyl groups and quaternary ammonium groups respectively reach 0. 018 and 0. 033, that the viscosity of the product with a content of 6% is 258mPa· s at 50℃, and that there exists a competition between the carboxyl groups and the negative oxygen ions. It is also revealed from the viewpoint of micromechanism that the modification reactions has no effect on the crystalline structure of the starch.

    Properties of High-Amylose Maize Starch Paste Treated with Ultrasonic in Water System
    Luo Zhi-gang Fu Xiong Luo Fa-xing He Xiao-wei Tu Ya-jun
    2008, 36(11):  74-78. 
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    High-amylose maize starch paste with a moisture content of 70% was treated with ultrasonic, and the properties of the native and the treated starch pastes were investigated using a Brabender viscoamylograph and a rotary viscosimeter to reveal the effect of ultrasonic treatment. The results show that, with the increase of ultrasonic power, neither the pasting temperature of high-amylose maize starch nor the C-type Brabender viscosity curve changes, while the peak viscosity decreases, that the stability of cold starch paste improves and the retrogradation decreases after the ultrasonic treatment, that the high-amylose maize starch pastes treated by different ultrasonic powers are al2 pseudoplastie, that the apparent viscosity of the paste decreases with the increase in shear rate, that the shear thinning becomes more obvious with the increase of starch concentration, and that the thixotropy of the paste reduces with the increase in ultrasonic power.

    Nonisothermal Crystallization Kinetics of Polycaprolactone/Starch Blends
    Su Jian-yu Chen Ling Yang Lian-sheng Li Xiao-xi Yu Long
    2008, 36(11):  79-84. 
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    Starch/polycaprolactone （SPCL） blends with different contents were prepared via the blending extrusion, with methylenediphenyl diisocyanate （MDI） as the compatibilizer. The crystallization and nonisothermal crystallization kinetics of the products were then investigated by means of XRD and DSC. The obtained data were finally analyzed by using Ozawa＇s and Mo＇s methods. The results indicate that the crystallization degree of SPCL decreases with the increase of starch content, that the starch acts as a nucleating agent for the nonisothermal crystallization of PCL because it quickens the crystallization although it lowers the crystallization degree. Modeling results show ‘that Ozawa＇s method is well fit to describe the nonisothermal crystallization of PCL but not that of SPCL, while Mo＇s method is suitable for both PCL and SPCL.

    Food Science & Technology
    Effect of High-Intensity Pulsed Electric Field Treatment on Quality of Peanut Oil
    Zeng Xin-an Zi Zhi-hong Yang Lian-sheng
    2008, 36(11):  85-90. 
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    High-intensity pulsed electric field （PEF） with the intensity of 0 -50 kV/cm was adopted to treat peanut oil samples to reveal the variations of acid value （AV）, peroxide value （PV） and carbonyl group value （CGV） with storage periods. Then, GC-MS and GC were used to qualitatively and quantitatively analyze the fatty acid in the samples. The results indicate that both the AV and the PV increase with the electric intensity, while the CGV has no significant change, that there occurs an oxidative rancidity during the storage, followed by gradually increasing AV, PV and CGV, that PEF treatment effectively reduces the oxidation rate, and that when the electric intensity is more than 40 kV/cm, the unsaturated fatty acids and nutritional value of peanut oil can be effectively reserved due to the composition change of peanut oil caused by PEF treatment.

    Optimization of Culture Medium to Improve Monascus Yellow Pigment Hue via Response Surface Methodology
    Zhou Bo Yang Ling Cui Si-ying Wang Ju-fang Liang Shi-zhong
    2008, 36(11):  91-95,100. 
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    In order to improve the hue of Monascus yellow pigment, six factors including the glucose, cornstarch, calcium chloride, peptone, KH2PO4 and NH4NO2 were considered to optimize the culture medium of Monascus anka mutant MYM2 via the response surface methodology （RSM） after several single-factor tests. The results show that glucose, NH4NO3 and KH2PO4 all have great effect on the yellow pigment hue, the corresponding minimum concentrations respectively being 14.2, 6.7 and 5.7 g/L, that the theoretical hue of Monascus yellow pigment is 4.58 according to the fit-model equation, and that, through five replication experiments, the Monascus yellow pigment value and the average hue respectively reach 88. 14U/mL and 4. 21, thus concluding that the proposed model is reliable.

    Architecture & Civil Engineering
    Simplified Method to Calculate Evaluation Index of Urban Thermal Environment in Hot-Humid Regions
    Zhang Lei Meng Qing-lin Zhao Li-hua Zhang Yu-feng
    2008, 36(11):  96-100. 
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    Wet bulb globe temperature （WBGT）, an evaluation index of urban thermal environment, is difficult to measure and calculate via field observation and numerical simulation. In order to solve this problem, some data of the air dry bulb temperature, the wet bulb temperature, the globe temperature, the relative humidity, the air velocity, the solar radiation and the WBGT were collected in summer in Guangzhou. The data were then used to perform a correlation analysis and a regression analysis. The results of correlation analysis indicate that the dry bulb temperature, the relative humidity, the solar radiation and the WBGT are linearly interrelated to a certain degree, and that these four parameters can be used in the simplified model to predict WBGT. The results of regression analysis indicate that the regressive formula is highly related to the measured WBGT and well satisfies the checking indices of multiple linear regression. So the regressive formula is feasible in the field observation and simulation research of urban thermal environment, which can be used as a simplified model for calculating WBGT.

    Seismic Response of Long-Span Bridge Under Multi-Support Excitation
    Su Cheng Chen Hai-bin
    2008, 36(11):  101-107. 
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    For long-span bridges, there exists obvious time difference in seismic input among different piers due to different geological conditions of the pier base. Thus, the multi-support excitation effect should be taken into consideration in the analysis of seismic response. In this paper, based on the large-mass method, the seismic responses of long-span bridges under multi-support excitation are analyzed on the platform of commercial finite element program Strand7. Afterwards, the seismic responses of a three-span continuous middle-supported steel arch bridge with a main span of 428m are analyzed under different input conditions such as uniform excitation, traveling wave excitation and muhi-support excitation. The results indicate that the traveling wave excitation and the multi-support excitation should be considered in the seismic analysis because both of them have significant influence on the seismic responses of long-span arch bridges.

    Sensitive Factors to Influence Seismic Response of Long-Span Suspension Bridge
    Xu Xun Ren Wei-ping Qiang Shi-zhong
    2008, 36(11):  108-113,120. 
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    In this paper, by taking the Sidu River Bridge as the example, a spatial dynamic model of long-span suspension bridges with steel truss stiffening girder is established, and the nonlinear motion equations in the multisupport excitation condition are deduced based on Leger＇s large-mass method （LMM） and the pseudo static displacement conception. Then, a 3D nonlinear time-history analysis of the seismic response of the bridge is performed, and the effects of soil-pile-bridge interaction and central buckle configuration on the seismic response are investigated. The results show that the effect of soil-pile-bridge interaction on the seismic response of suspension bridge is closely related to the excitation ways of seismic ground motion and is greatly affected by the horizontal component of seismic wave but slightly affected by the vertical component, that a pair of flexible central buckles has adverse effect on the longitudinal displacement and the stress response of stiffening girder, while a pair of rigid central buckles and three pairs of flexible central buckles significantly restrict the longitudinal displacement of stiffening girder although the seismic stress response of the structure greatly increases in this case.

    Normalization of Load-Displacement Curves of Tension Piles
    Sun Xiao-li Mo Hai-hong Yang Min
    2008, 36(11):  114-120. 
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    Tension piles are widely employed to resist the uplift loads of underground structures and commonly used as the foundations of tall buildings subjected to high bending moments. However, as compared with compressive piles, tension piles are seldom studied in the aspect of deformation, and most of existing methods are too complex to be applied to practical projects. In order to solve this problem, some normalizing parameters are selected to normalize different load-displacement curves to a single, which is then fitted by using a regression formula that is expanded to the condition of layered soil. By comparing modeling results with the field ones, it is found that the proposed method simplifies the calculation of deformation of tension piles with reasonable results.

    Comparative Evaluation of Correctness Between MAP and Pushover Analyses
    Ma Qian-li Ye Lie-ping Lu Xin-zheng
    2008, 36(11):  121-128. 
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    As the conventional pushover procedure only considers the first-order vibration mode, this paper proposes a multi-mode pushover analysis （MPA） procedure based on the mode-superposition response spectrum method to consider the effect of high-order vibration modes. In order to impersonally evaluate the correctness of the proposed MPA procedure and the traditional pushover procedure, an incremental elasto-plastic time-history analysis is performed. Based on the analytical results and the fiber models of a six-storey and a ten-storey reinforced concrete frame, the two procedures in different lateral force modes are compared. The results indicate that, as compared with the conventional pushover procedure, the proposed MPA procedure gives more accurate predicted response of maximum elasto-plastic vertex displacement. However, the estimated accuracy of the maximum storey drift of the structure obtained by MPA procedure still needs to be improved.

    Materials Science & Technology
    Hydrolytic Copolycondensation of γ-Aminopropyltriethoxysilane and Phenyltriethoxysilane
    Liu Shu-mei Fu Yi Zhang Chen Chen Jun Ye Hua Zhao Jian-qing
    2008, 36(11):  129-133. 
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    The hydrolytic copolycondensation of phenyhriethoxysilane （PTES） and γ-aminopropyhriethoxysilane （APS） was carried out in such four reaction systems as the toluene/water/hydrochloric acid, the tetrahydrofuran/ water/hydrochloric acid, the ethanol/water/ammonia and the sodium dodecyl sulfate/water/tetramethylammonium hydroxide. Resinoid particles, copolymer particles with a diameter of 200 nm, spherical particles with an average size of 3 μm and emulsive copolymers polyaminopropyl/phenylsilsesquioxane （PAPQ） were then obtained via interfacial polymerization, solution polymerization, dispersion polymerization and emulsion polymerization, respectively. Moreover, the compositions and structures of the products were confirmed by means of element analysis, FTIR and NMR. The results indicate that, in opposition to the copolymers prepared with basic or acid-then-basic catalysts, the copolymer prepared with acid catalyst possesses low crosslinking degree and good solubility, and that the polarity of cosolvents greatly influences the formation of PAPQ and the suspension of copolymer particles.

    Effects of Preparation Conditions on NOx Storage Capacity of Perovskite-Type BaZrO3
    Gao Ai-mei Wang Zhou-feng
    2008, 36(11):  134-137. 
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    Perovskite-type BaZrO3 catalysts were prepared by means of a modified citric acid complex sol-gel method. Then, the effects of calcination temperature, adsorption temperature and SO2 concentration on the NOx storage capacity （NSC） of BaZrOz in the presence of excess oxygen were investigated. Moreover, a temperature-programmed desorption （TPD） of adsorbed NOx was performed and the BET surface area and XRD techniques were used to reveal the structure of perovskite-type BaZrO3  and to investigate its influence on performance. The results indicate that, as compared with the BaZrO3  calcinated at 900 ℃, the catalyst ealcinated at 750℃ possesses much higher BET surface area （ 84. 0m^2/g） and greater NSC, that BaZrO3  is the main absorption center of NOx, and that the optimum temperature for NO/storage by BaZrO3  is about 400 ℃.

    Effect of Pretreatment of Silica Fume on Mechanical Properties of High-Performance Cement-Based Materials and Corresponding Mechanism
    Lin Dong Xi Xiao-lin Fang Man-man Wen Zi-yun
    2008, 36(11):  138-142,146. 
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    In this paper, the effect of the pretreatment of silica fume on the mechanical properties of cement-based materials was discussed to prepare high-performance cement-based materials, and the corresponding mechanism was analyzed. The results show that the mechanical properties of cement-based materials improve after the pretreatment of silica fume, the compressive strength and the flexural strength respectively being more than 200 MPa and 30 MPa. Moreover, according to the calculated results obtained via the Aim-Goff model and the tested results of particle size distribution test, it is concluded that the pretreatment of silica fume disperses the agglomeration of silica fume and increases the filling index of the system, thus improving the density of the material. It is also indicated from SEM and XRD results that the pretreatment of silica fume improves the strength of the cement-based material because the structure of the interface transition zone through the dispersion of silica fume is improved. In addition, how to overcome the strong agglomeration effect and to improve the dispersion of silica fume nano-particles are the key to the full utilization of physical and chemical performances of silica fume.

    Storage Modulus and its Characterization of Inorganic Particulate-Filled Polymer Composites
    Liang Ji-zhao
    2008, 36(11):  143-146. 
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    This paper deals with the storage modulus, an important index to evaluate the rigidity and elasticity of polymer composite. In the investigation, first, the factors affecting the storage modulus of inorganic particulate-filled polymer composites were discussed and quantitatively characterized. Next, the dynamic mechanical properties of glass bead-filled low-densitypolyethylene composites （LDPE/GB） were measured using a DuPont dynamic mechanical analyzer at -150 -100 ℃. Then, the relative storage moduli of LDPE/GB and Al（OH） 3-filled ethylene-propylene-diene mischpolymere composites （EPDM/AI（OH） 3 ） reported in the literature were estimated based on the equation proposed in this paper. The results were finally compared with those obtained from some other existing equations. It is demonstrated that the predicted results accord with the measured ones, meaning that the proposed equation is feasible.

    Preparation of Natural Rubber/Modified Fumed Silica Nano-Composites
    Jia Zhi-xin Luo Yuan-fang Zhou Yang-bo Jia De-min
    2008, 36(11):  147-152. 
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    Fumed silica was surfacely modified with resorcinol and hexamethylenetetramine complex （RH）, and the product was then reacted with natural rubber （NR） to prepare NIL/modified fumed silica （NR/M-silica） nanocomposites via a mixing and curing process. Moreover, the structure and properties of NR/M-silica nano-composites were investigated by mechanical testing, crosslinking density determination, TEM, DSC, FTIR and XPS, and the reinforcement mechanism of M-silica for natural rubber was also discussed. The results show that M-silica has grea- ter reinforcement effect on NR vulcanizate than the common fumed silica, that the comprehensive mechanical properties of NIL/M-silica nano-composite vulcanizates are optimum at a M-silica content of 4% - 10%, that M-silica well disperses in rubber matrix, that both the crosslinking density and the glass transition temperature of the vulcanizate increase, and that, with the addition of modifier RH, there occurs hydrogen bonds between the silicon hydroxyl groups of fumed silica surfaces and the phenol hydroxyl groups of resoreinol formaldehyde resin formed by heating RH, because the characteristic absorption peaks of Si-O bond and silicon hydroxyl group of fumed silica obviously blue-shift and because the binding energy of O atom obviously changes.

    Effects of Three Zinc Salt Accelerators on Vulcanization of Natural Rubber
    Lin Xin-hua Chen Zhao-hui Wang Di-zhen
    2008, 36(11):  153-156,161. 
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    The effects of three organic zinc salt accelerators, such as zinc dibutyl dithiocarbamate （ BZ）, zinc O,O′-dibutyldithiophosphate （ZnDBDP） and zinc dibenzothiazole disulphide （MZ）, on the curing characteristics and vulcanization reversion of natural rubber （NR） were investigated, and the mechanical properties of three vulcanizates respectively accelerated by the three kinds of salts were comparatively analyzed. Moreover, the crosslinking densities of the vulcanizates were determined by means of the equilibrium swelling method, and the content of polysulphidic cross-links in vulcanizates was detected via a special chemical reagent method. Finally, the mechanism of sulfur vulcanization catalyzed by the three accelerators was analyzed. The results show that both the catalysis and the reversion of ZnDBDP are greater than those of MZ but less than those of BZ, and that the stronger the ionization of accelerator, the more rapid the vulcanization.

    Electrostatic Spinning of Aqueous Gelatin Solution
    Zhao Yao-ming Zhu Rui-tian Yan Yu-rong Zhang Zhen-bin Zeng Xian-min
    2008, 36(11):  157-161. 
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    Uhrafine fibers of gelatin were spun from aqueous gelatin solution via an electrostatic spinning process at 60 - 65 ℃, and the effects of the gelatin dosage, the electrostatic voltage and the spinning distance on the spinning process were investigated. The results indicate that, at 60 - 65 ℃, the viscosity of gelatin/water system greatly increases with the dosage of gelatin in a secondary exponential relationship, that the average diameter of fibers decreases from 266.5nm to 167.7nm corresponding to the gelatin dosage decreasing from 25% to 15% , that the fiber diameter decreases with the increase of spinning voltage to a constant at a voltage of more than 17 kV, and that the diameter slightly changes from 165 to 210 nm when the spinning distance varies form 11 to 21 cm.

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