Water flux,DSC, and cytotoxicity characterization of membranes of cellulose acetate produced from sugar cane bagasse,using PEG 600

Summary In this article, cellulose acetate produced through the homogeneous acetylation of sugar cane bagasse cellulose was used to produce membranes, using poly(ethyleneglycol) 600 (PEG 600) as an admixture. The membranes were characterized using water flux measurements (Payne’s cup), differential scanning calorimetry (DSC) and neutral red uptake (cytotoxicity). The results showed that PEG 600 acts as a crystallinity inductor and/or pore former in the cellulose acetate matrix. The induction of crystallinity is important for this system since it had not been reported on the literature yet. The results also demonstrated that the studied membranes present a nontoxic behavior.     

Conformational analysis of poly(MDI-butandiol) hard segment in polyurethane elastomers

As part of our study of the structure of the hard segments of polyurethane elastomers, we have used conformational analysis to predict the conformation of the polyurethane chain formed from diphenylmethane 4,4′-diisocyanate (MDI), with butandiol as the chain extender. X-ray diffraction indicates the chain conformation is highly extended in the solid state, with a monomer repeat of 18.95 Å. The chain conformation can be predicted from the interaction between the large contiguous groups. Semiempirical and CNDO/2 molecular orbital calculations have been used to investigate the phenyl-phenyl, phenyl-urethane, and urethane-butandiol interactions. Minimum energy for the diphenyl-methane section occurs for a CCH₂C bridge angle of θ = 110°. However, the more likely conformation in the polymer is probably that at the subsidiary minimum at θ = 118°, in which the phenyl rings are mutually perpendicular, which is comparable to the conformation seen for model compounds. For the phenyl-urethane interactions the energy minimum is at $\text{ч = ±90°}$, with the combination $\text{(ч}{}_1\text{, ч}{}_2\text{) = (?90°, +90°)}$ leading to the necessary extended conformation. Calculations for the butandiol segment favour an all-trans conformation which is coplanar with the urethane groups. The predicted conformation of the polymer chain has a fibre repeat which matches the observed value, and this cannot be attained if the butandiol unit contains any gauche bonds. Model compounds show large variations for the phenyl-urethane conformation from the predicted minimum at $\text{ч = ±90°}$, indicating the importance of intermolecular stacking forces in determining the polymer conformation. However, provided the adjacent butandiol and urethane groups are coplanar, the fibre repeat is relatively insensitive to variations of ч.     

熔体直纺12改18头纺技术探讨

以TMT的615R 12饼卷绕头改18饼为例介绍了多丝饼改造技术,以及纺同一品种丝的工艺和生产情况,并对改造前后纺同一品种的丝的物理指标进行了比较,认为多丝饼改造是目前生产差别化纤维,提高产品附加值比较理想的方法。     

八碳烯分离工艺的研究

从能量综合集成的角度提出了八碳烯精馏分离工艺 ,对所提流程进行了优化模拟计算及分析 ,为八碳烯分离工艺的施工设计提供了充分的依据。投产情况表明 ,该研究改变了八碳烯的生产现状 ,使得八碳烯生产的经济效益显著提高     

Activities of MFI-Supported Rhenium Catalysts for the Aromatization of Methane: Effect of Cationic Form of the Inorganic Carrier

MFI type inorganic carrier was used in two different cationic forms, hydrogen and calcium respectively. MFI-supported molybdenum and rhenium catalysts were prepared. The activities of the catalysts were compared for the aromatization reaction of methane. Higher activity values were attained with the catalysts supported on HZSM-5. Aromatics were also observed with the catalysts supported on CaZSM-5, despite their deficiency in acid sites. Highly dispersed rhenium is expected to be formed with the use of the inorganic carrier in calcium form. On the other hand, lower reaction rates were observed with rhenium supported on CaZSM-5, in spite of the improved dispersion of the active rhenium species on this catalyst. This was interpreted in terms of the critical role of the acid sites in the conversion of methane to aromatics, compared to the improved dispersion of the active metal.     

合成丁酸异戊酯的新方法

采用超强酸代替浓硫酸作催化剂，对丁酸异戊酯合成反应进行了研究，讨论了影响收率的多种因素，在最佳条件下，酯化反应时间短，催化剂可以重复使用，丁酸异戊酯收率达到９８％。     

铜氨废水处理与废铜液回收

简述某电子厂生产电路板过程中产生的镀铜废液，废水回收处理方法，介绍应用高质量浓度含铜废液制取工业硫酸铜与海绵铜的工艺方法和流程，铜氨废水的处理要用破络添加混凝剂沉淀后可达标排放，对调试，运行中一般故障的排除进行了论述。     

4S集团选择美容项目战略合作伙伴的8要素

正随着中国市场化的逐步放开和信息化时代的全面到来,中国4S店的整车销售高利润的时代已经一去不复返了!几乎所有的厂商都全面重视售后市场,全面进军美容、装潢和精品等市场领域。装潢项目大部分4S单店采用售车促销赠送方式,虽然其他销售业绩可观,但是随着市场信息透明度的加强,类似隔热膜的利润随年下降。精品项目随着网购井喷