High solids content emulsions. III. Synthesis of concentrated latices by classic emulsion polymerization

Two different methods of producing bi‐ and trimodal latices of a mixture of methyl methacrylate, butyl acrylate, and small amounts of acrylic acid were tested. It is shown that a combination of concentrating blends of seed particles by semibatch reaction, followed by a nucleation of small particles plus a second semibatch phase allowed us to obtain stable latices with solids contents over 65% and viscosities of below 2500 mPa s^?1 with little coagulum formation. The key parameter in determining latex stability, coagulum formation, and viscosity appears to be the the particle size distribution, and especially its modification attributed to secondary nucleation. Because it is not possible to eliminate water‐soluble monomers from the polymerization recipe, secondary (homogeneous) nucleation must be minimized by careful addition of the free‐radical initiator and choice of monomer feed flow rates. The nucleation of the third population in the trimodal latices is best accomplished with a mixed surfactant system because renucleation by anionic surfactant alone leads to detrimental changes in the particle size distribution (PSD) resulting from excessive flocculation of particles. In addition, it was found that the viscosity of the final products was not sensitive to small changes in the ionic strength of the latex, although neutralization to a pH of 6 effectively doubles the final latex viscosity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1916–1934, 2002; DOI 10.1002/app.10513     

超声提取-高效液相色谱法测定烟草中烟碱含量

确定了制备烟碱分析样品的超声波提取条件:0.4% NaOH溶液为溶剂,液固比40:1(mL·g-1),提取时间4 h.确定了高效液相色谱法检测烟碱含量的条件为Kromasil C18色谱柱(250 mm×4.6 mm,5 μm),检测波长259 nm,检测温度35 ℃,流动相CH3OH/0.02 mol·L-1磷酸盐缓冲溶液(V/V)为60/40,流速1.0 mL·min-1,进样量10 μL.平均加样回收率98.8%,相对标准偏差1.2%.结果表明超声提取-高效液相色谱法是一种准确度高,速度快的测定烟草中烟碱含量的检测方法.     

分光光度法测定锌铁合金镀层及镀液中的铁

采用分光光度法，以磺基水杨酸为显色剂、双氧水为氧化剂，锌铁合金镀层用稀盐酸溶解，控制pH值为1.5～3，在等吸收点处测定吸光度，并根据比耳定律计算镀层及镀液中的铁含量。     

硫酸法钛白粉生产中钛液的分析和铁分离

以硫酸法钛白粉生产工艺中间体浓钛液(硫酸氧钛)和偏钛酸为原料,分析了浓钛液中二氧化钛和铁的含量。总Ti的测试采用Al片还原法和高铁盐氧化还原滴定法,浓钛液中Ti3 直接用高铁盐氧化还原滴定法测定,铁含量用KMnO4氧化还原滴定法进行分析。采用无机陶瓷膜洗涤分离方法考查了水解后偏钛酸中的除铁效率,利用分光光度法和火焰原子吸收法分别测定洗涤液和二氧化钛粉体中的铁含量。试验表明,无机陶瓷膜洗涤分离方法可以将二氧化钛粉体中铁含量降到30×10-3‰以下,煅烧后产品白度大于94。陶瓷膜洗涤工艺可以实现连续操作,是一种值得推广的新工艺。     

Phase transitions and dimensional and morphological changes in an “Aluminum Hydroxide-Alumina” system under a shock-wave action

A method is proposed to study the sequence of phase transitions in powdered materials under a shock-wave action. It is shown that the aluminum hydroxide-alumina system has the following sequence of phase transformations under a shock-wave action: bayerite boehmite -Al₂O₃ -Al₂O₃. It is found that there are no transitional high-temperature modifications of alumina. A method is developed for obtaining a submicron alumina powder, which allows obtaining materials with a controlled phase composition, including a thermodynamically stable -modification of Al₂O₃. The specific features of the morphological structure and the phase and structural characteristics of powders after a shock-wave action are considered.Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 1, pp. 110–119, January–February, 2005.     

含水量对渠道保温板保温耐久性的影响及保温板厚度设计

北方渠道大多使用保温板防止混凝土衬砌受冻胀破坏。在计算保温板厚度时为了降低成本,容易忽略保温板使用过程中受各种因素的影响导致保温效果变差的情况,使混凝土衬砌达不到设计使用年限便提前被破坏。内蒙古河套灌区试验结果表明,由于受酸雨、冻融作用、含水量等因素的影响,保温板保温效果平均每年降低0.9℃,其中受含水量变化的影响最大。经试验测得:聚苯乙烯保温板(EPS)含水量每增加1%,会导致导热系数增大5%。基于多层材料串联热阻叠加原理和热阻等效原理,对保温板厚度计算公式进行完善,并提出相应的铺设方法和施工技术要求。该设计对保温板在季节性冻土区的推广应用具有一定参考价值。     

硫氰酸钠法明胶改性腈纶的研究

采用丙烯腈对明胶接枝改性 ,然后与聚丙烯腈共混纺丝的方法 ,制备了明胶改性腈纶 ,研究了改性比 (明胶 /丙烯腈 ,质量比 )和明胶含量对明胶改性腈纶机械性能、吸湿保水性能的影响。研究结果表明 ,当改性比为 0 .7～ 2 .0 ,明胶含量不超过 5 .0 %时 ,改性腈纶具有良好的机械性能 (断裂强度大于 3 .1c N/dtex) ,可以满足后纺加工的需要 ;改性腈纶纤维亲水性能良好 ,随着改性比的减小、明胶含量的增加 ,其回潮率和保水率都逐渐增大。     

Alcohol consumption detection through behavioural analysis using intelligent systems

We describe in this paper a new methodology for blood alcohol content (BAC) estimation of a subject. Rather than using external devices to determine the BAC value of a subject, we perform a behaviour analysis of this subject using intelligent systems. We monitor the user’s actions in an ordinary task and label those data to various measured BAC values. The obtained data-set is then used to train learning systems to detect alcoholic consumption and perform BAC estimation. We obtain good results on a mono-user base, and lower results with multiple users. We improve the results by combining multiple classifiers and regression algorithms.     

固相法低度氯化聚乙烯耐老化性能的研究

用室温对折断裂试验,研究固相法低度氯化聚乙烯老化性能,当氯含量约为7.4％时,其老化时间发生突跃,老化时间发生突跃时,氯含量与试样的氯化温度和老化温度有关.