不饱和腙类化合物的三氟甲基化反应

氟具有强的吸电子性、亲脂性,将含氟的取代基引入药物中能显著改变药物的药代动力学性质,包括极性、亲脂性、代谢稳定性等,因此向化合物中引入三氟甲基是近期有机合成及医药领域的热点,开发利用经济、高效、绿色的三氟甲基试剂具有重要的意义。以三氟甲烷亚磺酸钠为三氟甲基源,在温和的条件下实现不饱和腙类化合物的三氟甲基化。结果表明,三氟甲烷亚磺酸钠作为三氟甲基源具有良好的反应活性,反应条件温和,符合绿色化学要求,并提供了向不饱和腙类化合物引入三氟甲基的新方法。     

Magnesium fluoride (MgF2) – A novel sintering additive for the preparation of transparent YAG ceramics via SPS

The effect of MgF₂ as a sintering additive for the preparation of YAG ceramics via spark plasma sintering (SPS) is investigated with promising results, as nearly complete densification (0.58% porosity) is achieved at relatively low temperature and moderate pressure. Higher temperature and dwell time resulted in a translucent/transparent body. On the other side, significant grain growth was observed with MgF₂ addition.     

PVDF/PMMA共混物非等温结晶动力学和晶体结构

通过差示扫描量热仪（DSC）、X射线衍射仪（XRD）对纯聚偏氟乙烯（PVDF）和PVDF/聚甲基丙烯酸甲酯（PMMA）共混物在不同降温速率下的非等温结晶行为和晶体结构进行表征和分析,并采用Jeziorny法和莫志深法研究了各组样品的非等温结晶动力学。结果表明,PMMA含量过多（PVDF/PMMA质量比为6/4和5/5）会完全抑制PVDF结晶;对于纯PVDF和可结晶的共混物（PVDF/PMMA质量比为9/1、8/2、7/3）样品,随着PMMA含量的增加,共混物结晶温度先升高后降低,结晶速率先少许增大后减小,说明少量PMMA起异相成核作用,可促进共混物结晶,而大量PMMA可明显阻碍分子重排,抑制其结晶;PMMA的加入可促进共混物晶体结构向低维转变;共混物晶体结构主要是α晶型,PMMA含量的增加不改变共混物的晶型,且使共混物结晶度先增大后减小。     

硅藻土作为吸附材料去除水中氟的研究进展

水中氟化物的含量对人体的健康有重大影响,饮水中最佳的氟含量介于0.5~1.0mg/L之间。归纳了氟污染的来源、危害及含氟废水的处理方法,论述了硅藻土作为吸附材料去除水中氟的作用机理及硅藻土改性研究进展,指出今后应加强硅藻土处理含氟废水的基础研究、硅藻土改性研究及硅藻土水处理技术的工业化研究。     

Adsorption‐concentration polarization model for ultrafiltration in mixed matrix membrane

Adsorption has been found to be significant in ultrafiltration by mixed matrix membrane. Removal of very low molecular weight solutes compared to the molecular weight cut off of the membrane is facilitated by adsorption. The modeling of the adsorption coupled with concentration polarization is presented based on the mathematical approach developed by Gekas et al. (Gekas et al. Chem Eng Sci. 1993;48:2753–2765), from the first principles. However, extensive modifications were included in theoretical development including those suggested by Ruiz‐Bevia et al. (Ruiz‐Bevia et al. Chem Eng Sci. 1997;52:2343–2352). The developed model captured the rejection dynamics with the help of retention factor. The model equations were solved under the framework of boundary layer analysis, using the integral approach. Effects of the adsorption isotherm and the different parameters affecting the system performance were also investigated. Further, experimental validation of the model results with two different mixed matrix ultrafiltration studies was also elucidated. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2354–2364, 2014     

Achieving β-phase poly(vinylidene fluoride) from melt cooling: Effect of surface functionalized carbon nanotubes

Poly(vinylidene fluoride) (PVDF) based nanocomposites with different surface-functionalized multi-walled carbon nanotubes (MWCNTs) were prepared by melt mixing in a small scale compounder. With the incorporation of commercial functionalized MWCNTs, the β-phase in PVDF can be directly achieved from melt cooling, as verified by results of Fourier transform infrared spectrum and X-ray diffraction. Interestingly, nanocomposites with amino group functionalized MWCNTs showed the highest percentage of β-phase (17.4%) formation in PVDF, followed by those with hydroxyl groups (11.6%) and unmodified MWCNTs (9.4%). However, the nanocomposites containing MWCNTs with carboxyl groups which were thought to be able to well interact with the dipoles on PVDF chains have the lowest amount of β-phase, i.e. 4.7%. The analysis on the mechanism of the influence of surface functionalization of MWCNTs on the formation of β-phase in PVDF shows that the combined effects of the dispersion of MWCNTs and the nanotube–polymer interactions account for the formation of the β-phase in PVDF.     

Poly(vinylidene fluoride) ultrafiltration membranes containing hybrid silica nanoparticles: Preparation,characterization and performance

Poly(vinylidene fluoride) (PVDF) ultrafiltration membranes were prepared by immersion precipitation method using poly(hydroxyethyl methacrylate)-block-poly(methyl methacrylate) grafted silica (PHEMA-b-PMMA@SiO₂) nanoparticles as additives. The hybrid nanoparticles were synthesized by the surface initiated atom transfer radical polymerization (SI-ATRP), and they were characterized in detail by FT-IR, TEM, DLS and GPC. Results confirm that core–shell structure is formed after grafting PHEMA-b-PMMA brushes on the silica nanoparticles. Their average hydrodynamic diameter also increases with the prolongation of grafting time. After blending PVDF with the hybrid silica nanoparticles, the composite PVDF membranes exhibit high porosity and improved water permeation. Especially, when the molecular weight is 1.73 × 10⁵ g/mol for PHEMA-b-PMMA on the hybrid nanoparticles, the water flux of the PVDF composite membrane is 2.5 times than that of the control PVDF membrane, while the rejection to bovine serum albumin (BSA) remains at a high level (>90%). In addition, all the composite PVDF membranes show lower BSA adsorption and larger water flux recovery ratio than the control PVDF membrane. The improvement of membrane performance is attributed to the good hydrophilicity of PHEMA-b-PMMA@SiO₂ nanoparticles. Our results suggest that PHEMA-b-PMMA@SiO₂ nanoparticles with moderate molecular weight of PHEMA-b-PMMA are suitable for the property optimization of PVDF-based composite membranes.     

Electroactive phases of poly(vinylidene fluoride): Determination,processing and applications

Poly(vinylidene fluoride), PVDF, and its copolymers are the family of polymers with the highest dielectric constant and electroactive response, including piezoelectric, pyroelectric and ferroelectric effects. The electroactive properties are increasingly important in a wide range of applications such as in biomedicine, energy generation and storage, monitoring and control, and include the development of sensors and actuators, separator and filtration membranes and smart scaffolds, among others. For many of these applications the polymer should be in one of its electroactive phases. This review presents the developments and summarizes the main characteristics of the electroactive phases of PVDF and copolymers, indicates the different processing strategies as well as the way in which the phase content is identified and quantified. Additionally, recent advances in the development of electroactive composites allowing novel effects, such as magnetoelectric responses, and opening new applications areas are presented. Finally, some of the more interesting potential applications and processing challenges are discussed.     

The antiwear and extreme pressure action mechanism of CeF3 in grease

Cerium (III) fluoride as an antiwear or extreme pressure additive has been used in grease and bonded solid film lubricant, but its action mechanism has not been clarified. In this paper, the tribological characteristics of lithium grease containing CeF₃, CaF₂, SbF₃, CeO₂ and graphite fluoride ((CF)_n) were evaluated with an SRV tester. The results show that pastes containing CaF₂ and (CF)_n give good antiwear and anti-friction performance, but do not possess extreme pressure properties. Adding CeO₂ to grease offers no benefit to the antiwear and anti-friction performance of the paste. Paste containing SbF₃ has poor lubricating properties. XPS analysis shows that the good antiwear and extreme pressure properties of paste containing CeF₃ can be attributable to the formation of a physically adherent film and a chemical reaction film on the rubbing surface. Thermogravimetry shows that CeF₃ acts as an agent for the slow release of the fluorine element.     

聚偏氟乙烯膜生物反应器处理城市污水的膜污染分析

膜污染是制约膜生物反应器应用的关键因素,通过实验分析了聚偏氟乙烯膜生物反应器运行操作压力的变化.膜通量为10/L(h·m2)时,操作压力在3.73×104Pa以下,比较了降低膜污染的不同方法:水力清洗能恢复操作压力77%;倾斜50°放置,压力增长缓慢;膜组件离容器底部最佳位置为20 cm.计算了膜总阻力的组成.