活性催化剂氢化钠直接合成方法的研究

以石蜡油做分散剂，在常压下金属钠与氢气反应可以定量地转化成氢化钠，考察了反应温度和反应时间对钠氢化反应转化率的影响，确定了最佳的反应条件为：反应温度３００～３２０℃；反应时间１ｈ。在此条件下可得到钠的转化率８０％以上，比表面积测定值为５．８ｍ２／ｇ。活性测定表明产品有较好的催化活性。又进行了一定规模的放大实验，证明该方法可用于小型生产。     

Effect of nanoclay on shrinkage control of low profile unsaturated polyester (UP) resin cured at room temperature

The addition of a small amount of nanoclay (1-3 wt%) can provide excellent volume shrinkage control of unsaturated polyester (UP)/styrene (St)/poly(vinyl acetate) (PVAc) systems cured at room temperature. PVAc serves as the low profile additive (LPA). In this study, both temperature-induced phase separation of the uncured resin mixture and transmission electron microscopy (TEM) of the cured sample revealed that nanoclay resided in the LPA-rich phase, leading to a higher reaction rate and earlier onset of micro-cracking in the LPA-rich phase or at the interface of the LPA-rich and UP-rich phases. Consequently, an earlier volume expansion during curing was observed in reactive dilatometry, resulting in better shrinkage control. On-line measurement of the composite thickness change during vacuum-infusion liquid composite molding [e.g. the Seemann Composite Resin Infusion Molding Process (SCRIMP)] further proved excellent volume shrinkage control of nanoclay filled systems, leading to a smoother composite surface.     

A MODELING STUDY ON HYDROLYSIS OF LACTOSE RECOVERED FROM WHEY AND β-GALACTOSIDASE STABILITY UNDER SONIC TREATMENT

In the present study, the aim was to investigate the effect of ultrasonication on the kinetics of hydrolysis of lactose recovered from whey. The effects of the duty cycle, acoustic power of sonifier, reaction volume, and the hydrolysis products on hydrolysis degree as well as on enzyme stability were studied. The hydrolysis reactions were carried out in 25 mM phosphate buffer solution by using a commercial β-galactosidase produced from Kluyveromyces marxianus lactis under the conditions of 37°C, pH 6.5, and processing time of 30 min. Under ultrasonic treatment, 92% of lactose charged was hydrolyzed and the residual enzyme activity was 77% under the optimum operational conditions: acoustic power of 20 W, duty cycle rate of 10%, and reaction volume of 250 mL. The corresponding values of hydrolysis degree and residual enzyme activity without ultrasonic irradiation were 81% and 68%, respectively. These results show that sonication was beneficial for hydrolysis of lactose recovered from whey. The mathematical models were derived by using the experimental data of residual lactose concentration and residual enzyme activity depending on the operating conditions. In addition, an exponential equation was used for reflecting the ultrasonic energy regarding the hydrolysis and enzyme inactivation. After evaluation of the data, the activation energy required for hydrolysis of lactose recovered from whey (E _H ) and the inactivation energy for β-galactosidase enzyme (E _D ) were found as 0.0489 and 0.0804 J mL^?1, respectively.     

Preparation and Physico-Chemical Study of Sandwich Glass-Jute-Bisphenol-C-Formaldehyde Resin Composites

Glass-Jute-bisphenol-C-formaldehyde (Glass-Jute-BCF) sandwich composites were prepared by hand lay-up technique at 150°C under 30.4 MPa pressure for 2 h. The resin, glass and jute fiber content in the sandwich composite were 33.3, 10.4 and 56.3 wt%, respectively. 10 prepregs containing 8 inner prepregs of jute mats sandwiched between 2 outer prepregs of glass mats. Glass-Jute-BCF sandwich composite has 23 MPa tensile strength, 119 MPa flexural strength, 1.72 kV/mm electric strength and 1.25 × 10¹² ohm cm volume resistivity. Tensile strength and volume resistivity both decreased, while flexural strength and electrical strength both improved upon hybridization. Sandwich composite showed high diffusivity in water, 10% NaCl and 10% HCl solutions as compared to Glass-BCF composite. Equilibrium water absorption time is found to be 72 h in all 3 environments. Comparatively low diffusivity is observed due to silane treated glass fibers. No effect of boiling water is observed on stability of composite. Saturation time in boiling water reduced 18 times without any damage to the composite. Glass-Jute-BCF sandwich composite may be useful for low load bearing applications in construction, electrical and electronic industries as well as in harsh acidic and saline environments.     

Performance of Room Temperature Vulcanized (RTV) Silicone Rubber-Based Composites: DBDPO/RTV and DBDPE/Sb2O3/RTV

Composites with high flame-retardant behavior based on room temperature vulcanizing silicone rubber (RTV), decabromodiphenyloxide (DBDPO) and decabromodiphenylethane (DBDPE)/Sb₂O₃ as fire retardant were fabricated employing reactive solution mixing process and the method of three-roller milling. The influences of DBDPO and DBDPE/Sb₂O₃ on the morphologies, mechanical properties, flame-retardant properties, OI, insulating properties, hot properties of RTV were systematically investigated. It has been discovered that both kinds of doping agents can significantly improve the property characteristics of RTV matrix composites. Also, DBDPE/Sb₂O₃/RTV were of better comprehensive performances than DBDPO/RTV. We report final performances as follows: tear strength was 13.68 kN/m; elongation at break was 233.4%; tensile strength was 2.18 Mpa; the level of flame-retardant property was FV-0; OI was 46; Volume electric resistivity was 6.9 × 10¹⁴Ω · m; the range of decomposition temperature was 300°C to 690°C and the ending percentage of remain weight was 30.6%. The above properties were acquired on the condition of mass percent of DBDPE/Sb₂O₃ as 15 wt% for DBDPE/Sb₂O₃/RTV.     

Effects of saliva contamination on bonding performance of self-etching adhesives

Purpose: This study investigated the effects of saliva contamination on bonding performance of two self-etching adhesives. Materials and Methods: Forty caries-free extracted human third molars’ cusps were cut off to expose mid-coronal dentin surfaces. Two one-step self-etching adhesives and the respective resin composite from the same manufacturer (Adper Easy One?+?Filtek Z350 (3?M ESPE); Clearfil S3 Bond?+?Clearfil Majesty (Kuraray Co.)) were applied onto the dentin surfaces for micro-tensile bond strength (MTBS) test. The dentin surfaces were not contaminated (A), were contaminated with saliva before/after priming (B/C), or they were water-sprayed after saliva contamination occurred before/after priming (D/E). The resin–dentin interfaces were analyzed by scanning electron microscopy. After the two adhesives were polymerized on saliva-contaminated or uncontaminated conditions, they were determined by Fourier transform infrared spectroscopy for degree of conversion (DC), and analyzed by AFM spectroscopy for spatial homogeneity of the adhesives. The data were analyzed using factorial design ANOVA and one-way ANOVA. Results: Compared with control group (A), the saliva contamination after priming significantly reduced both dentin MTBS (p?<?0.05). Thorough water-spraying could significantly improve the MTBS of the saliva-contaminated dentin (p?<?0.05) or completely restore it. Saliva contamination deteriorated the resin–dentin adaptation, DC, and spatial homogeneity of adhesives. Conclusions: Saliva contamination had a negative effect on bonding performance of self-etching adhesives regarding their dentin MTBS, resin–dentin adaptation, DC, and spatial homogeneity. However, the effect of saliva contamination on the dentin MTBS was related to the individual adhesive used and the time point of contamination.     

变频调速型50 m2转鼓真空过滤机结构设计与应用

介绍了自行研制的变频调速型 50m2 转鼓真空过滤机工作原理、结构设计及应用情况。     

共注射成型充填过程的运动界面追踪

基于Hele-Shaw流动模型推导出共注射成型充填模拟的数值模型基础上,通过引入厚度分数,采用控制体积法实现了充填过程中多重运动界面的追踪。等温数值模拟结果与MOLDFLOW的模拟结果相吻合,并能正确反映粘度对层厚分布的影响。     

Polypropylene/polyamide 6/polyethylene-octene elastomer blends. Part 3. Mechanisms of volume dilatation during plastic deformation under uniaxial tension

It has been shown in a previous paper in this series that important dilatation is produced by plastic deformation under tension of neat PP and PP/PA6/POE blends, for which the POE to PA6 concentration ratio equals 1/2. In this work, the detailed mechanisms of this volume change are investigated from electron micrographs (SEM and TEM) obtained in the deformed state. At low alloy content, it is thus observed that dilatation results from decohesion of the PA6 particles from the PP matrix. As the amount of PA6 and POE increases, voids are nucleated preferentially in the thicker POE interphase making a shell around the PA6 particles, and secondarily in isolated POE particles. Unexpectedly, it has been found that the overall volume dilatation decreases with total alloying content. This is interpreted by: (i) the increasing contribution of PA6 that intrinsically deforms with less cavitation than PP, (ii) the post-cavitation rubber-like stretching of POE particles and, (iii) the early formation of a percolating network of shear bands from the diffuse array of voids formed after the yield point. These mechanisms explain the gradual increase of the resistance to impact of the PP/PA6/POE as their alloying content is increased.     

Conversion measurement in polyethylene/peroxide coupling system under steady shear flow

The coupling reaction of melt linear low density polyethylene (LLDPE) initiated by dicumyl peroxide (DCP) in steady shear flow field was investigated. The conversion of DCP was measured by electron spin resonance (ESR) and chemical titration. An absolute method was proposed to calculate the actual conversion of DCP from rheological data. The coupling efficiency of DCP was obtained from those analyses, which was shown to increase at first, reach a maximum and then decrease in the end stage. A linear relationship between the coupling efficiency of DCP and the concentration of macroradicals was also found in the experiments.