Encapsulation of titanium dioxide in styrene/n‐butyl acrylate copolymer by miniemulsion polymerization

Miniemulsion copolymerization of styrene/n‐butyl acrylate was investigated as a means of encapsulating hydrophilic titanium dioxide (TiO₂) in a film‐forming polymer. Dispersion studies of the TiO₂ were first carried out to determine the choice of stabilizer, its concentration, and the dispersion process conditions for obtaining stable TiO₂ particles with minimum particle size. Through screening studies of various functional stabilizers and shelf‐life stability studies at both room and polymerization temperatures, Solsperse 32,000 was selected to give relatively small and stable TiO₂ particles at 1 wt % stabilizer and with 20–25 min sonification. The subsequent encapsulation of the dispersed TiO₂ particles in styrene/n‐butyl acrylate copolymer (St/BA) via miniemulsion polymerization was carried out and compared with a control study using styrene monomer alone. The lattices resulting from the miniemulsion encapsulation polymerizations were characterized in terms of the encapsulation efficiencies (via density gradient column separations; DGC) and particle size (via dynamic light scattering). Encapsulation efficiencies revealed that complete encapsulation of all of the TiO₂ by all of the polymer was not achieved. The maximum encapsulation efficiencies were 79.1% TiO₂ inside 61.7% polystyrene and 63.6% TiO₂ inside 38.5% St/BA copolymer. As the density of the particles collected from the DGC increased from one layer to another, both the average particle size and the number of the TiO₂ particles contained in each latex particle increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3479–3486, 2006     

Experimental and modelling study of gas dispersion in a double turbine stirred tank

Gas dispersion in a double turbine stirred tank is experimentally characterised by measuring local gas holdups and local bubble size distributions throughout the tank, for three liquid media: tap water, aqueous sulphate solution and aqueous sulphate solution with PEG. For all these media, bubble coalescence generally prevails over breakage. Where average bubble size decreases, this can be attributed to the difference in slip velocity between different sized bubbles. Most of the coalescence takes place in the turbine discharge stream.A compartment model that takes into account the combined effect of bubble coalescence and breakage is used to simulate gas dispersion. The model predicts spatial distribution of gas holdup and of average bubble size, with average bubble size at the turbines as an input. Reasonable agreement between experiment and simulation is achieved with optimisation of two parameters, one affecting mainly the slip velocity, the other related mainly to the bubble coalescence/breakage balance. Different sets of parameters are required for each of the three liquid systems under study, but are independent of stirring/aeration conditions. The model only fails to simulate the smaller average bubble diameters at the bottom of the tank.     

分散聚合法制备窄分散聚苯乙烯微球

以苯乙烯（St）为单体,偶氮二异丁腈（AIBN）为引发剂,聚乙烯毗咯烷酮（PVP）为分散稳定剂,在甲醇（MeOH）反应介质,使用分散聚合法制备了窄分散的聚苯乙烯微球．分别采用红外（IR）、扫描电镜（sEM）、粒度分析（SPAN）等手段,表征了聚苯乙烯（PS）微球的组成成分、表面形貌、粒径及其分布．并讨论了个各个因素对所制备微球的粒径及其分布的影响．当St质量分数为溶剂量的10％,AIBN质量分数为单体量的0．15％,PVP质量分数为单体量的1．5％时,该条件下制备的微球粒径为1．38μm,SPAN值为0．77,微球形貌及其分散性最佳．     

石英晶体最大双折射率色散特性的椭偏测量

为了测量石英晶体最大双折射率的色散特性,在椭偏光谱仪的水平透射测量模式下,通过对确定厚度的石英波片相位延迟量的精确测量,计算出了石英晶体的最大双折射率值,并进行了误差分析。结果表明:这种方法光路简单、操作方便,屏蔽了光源的不稳定性;双折射率测量精度达到了10-6,比连续偏光干涉法的测量精度提高了1个数量级;实现了对石英晶体的最大双折射率色散特性的连续光谱测量;此方法对其它双折射晶体材料的双折射率色散特性的研究也同样适用。     

量子Klein-Gordon模型色散关系的含时变分法研究

通过采用含时变分原理,在结合Hartree型多粒子试探波函数和Jackiw-Kerman型单粒子波函数的基础上,研究了带对称单阱非谐格点势的量子Klein-Gordon模型的声子色散关系.在满足最小测不准关系的条件下,导出了粒子的期望值所满足的运动方程,并以此得到了声子色散关系.结果表明:与经典模型相比,由于量子涨落的影响,量子模型中的有效格点势的二次方项系数增大,声子元激发的带隙变宽;二次方项系数和带隙随着量子涨落和格点势的四次方项系数的增大而增大.     

两性聚丙烯酰胺水分散体系的制备

以丙烯酰胺(AM)、甲基丙烯酰氧乙基三甲基氯化铵(DMC)以及丙烯酸(AA)为单体,聚甲基丙烯酰氧乙基三甲基氯化铵(PDMC)为分散稳定剂,2,2′-偶氮(2-脒基丙烷)二盐酸盐(V-50)为引发剂,在硫酸铵水溶液中成功制备了两性聚丙烯酰胺(am-PAM)。考察了分散稳定剂相对分子质量、反应介质pH值、反应温度以及搅拌速度对水分散体系的影响,并用红外光谱仪以及扫描电镜对产品结构进行表征。研究得到合成两性聚丙烯酰胺水分散体系的较佳工艺条件:PDMC的相对分子质量30×104～46×104,反应介质的pH5.0～6.5,反应温度55～65℃,搅拌速度75～125 r.min-1,所得体系相界面明显,颗粒呈球形。     

脱硫灰与石灰石粉复合制备沥青填料研究

通过XRD及马歇尔稳定度试验等方法,研究把脱硫灰用作沥青复合填料。试验结果表明,以不大于40%的脱硫灰与石灰石粉复合可制备沥青填料,所制备的沥青混合料各项指标均能满足规范要求,可应用于沥青道路工程,其中以约30%脱硫灰取代石灰石粉所制备的复合沥青填料效果较好。     

基于神经网络的面波迭代反演应用研究

根据滩浅海近地表结构特征,尝试利用地震记录中的面波进行近地表结构研究,以便了解滩浅海地区的近地表地层介质结构变化,为深层油气勘探提供准确的低降速带资料.针对面波频散反演已有方法存在的不足,引入一种基于BP神经网络的迭代反演方法对面波的频散曲线进行拟合迭代,用于反演预测滩浅海低降速带地层参数.由于神经网络具有很强的自学习、自适应、自组织和容错能力,它的反演预测能力非常强大,能够较精确地预测出所要求解的目标数据,同时结合传统迭代反演方法的优点,增强了该方法的反演预测能力.通过对滩浅海近地表结构模型试算,获得好的效果,同时进一步对实际记录进行了计算,也取得了比较满意的结果.     

基于悬臂梁啁啾调谐的光纤光栅滤波器

提出并发展了一种基于悬臂梁结构的啁啾光纤Bragg光栅(CFBG)啁啾调谐方案,获得了一系列性能优异的可调谐CFBG滤波器,包括调谐范围达到36 nm(1.8～37.8 nm)的带宽可变反射滤波器、色散在178～2 100ps/nm范围内可调的色散补偿器、基于取样CFBG或重叠写入CFBG的信道间隔可调谐滤波器等。这些FBG滤波器不但能维持较高的反射率,还能保持中心波长基本不变。     

光源谱宽通过光纤色散对AOCS输出的影响

基于光纤色散引起的脉冲展宽效应,在理论和实验上研究了有源光学电流传感器（AOCS）中宽带光源对系统输出的影响．理论结果表明：对于长度为500m的光纤,当光源谱宽在40—60nm之间变化时,多模光纤传输下的脉冲展宽范围在0．5～0．8ns,单模光纤传输下的脉冲展宽范围在2×10^-5～4×10^-5,信号衰减量对系统输出影响很小,且随光源谱宽的增加而有微弱的增加,实验与理论相符合．