Grafting vinyl monomers onto silk (Bombyx mori) using different initiators: Properties of grafted silk

The graft–copolymerization of silk with methacrylamide (MAA), 2‐hydroxyethyl methacrylate (HEMA), and methyl methacrylate (MMA) was studied using three different free‐radical initiators: an inorganic peroxide [ammonium persulfate (APS)] and two azo compounds [2,2′‐azobisisobutyronitrile (AIBN) and 2,2′‐azobis(2‐methylpropionamidine) dihydrochloride (ADC)]. The rate and yield of grafting followed the order: APS > AIBN > ADC. The performance of AIBN was close to that of APS in terms of weight gain attained. The degree of yellowing of grafted silk varied as a function of the initiator–monomer system used. APS induced the highest degree of yellowing, regardless of which monomer was used, whereas silk grafted with the MAA/AIBN system displayed the lowest level of yellowing. Moisture regain of grafted silk changed as a function of the hydrophilic/hydrophobic character of the grafted polymer, regardless of the kind of initiator used. Accordingly, tensile properties showed a tendency to decrease with increasing weight gain of grafted silk, the extent of which was independent of the kind of monomer and initiator used. The different initiators did not induce any appreciable change in the fine structure of silk, as demonstrated by optical measurements. Uneven surface deposition of homopolymer was detected to variable extent with MMA and HEMA grafting, whereas the surface of MAA‐grafted silk was completely free of any foreign deposit, independently of the initiator used. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1401–1409, 2001     

DYNAMIC MODELING AND OPERATION OF A SEEDED BATCH COOLING CRYSTALLIZER

In this study, a dynamic model of a batch cooling crystallizer is developed. The seeded crystallization of potash alum from aqueous solutions. Four different cooling policies namely natural cooling, linear cooling, optimal cooling, and controlled cooling (nonlinear geometric control (NGC) cooling) are presented. The simulation results indicate that both optimal and controlled cooling improve the weight mean size of the final product significantly. The influence of seed loading policy on the end product quality is also studied for the NGC cooling. It is found that the appropriate seed loading is important to achieve a good final CSD, especially for a fixed batch time.     

壳聚糖季铵盐对味精废水絮凝作用

用氯化三甲基壳聚糖季铵盐作絮凝剂处理味精废水。壳聚糖季铵盐适宜的pH值为9－13,CODCr去除率80％以上,高浓度壳聚糖季铵盐絮凝效果优于低浓度,延长振荡时间能提高絮凝效果,助凝剂的加入不有明显提高壳聚糖季铵盐的絮凝效果。     

不饱和季铵盐的加压制备法

介绍一种在一定压力下,制取不饱和季铵盐的通用方法,并用二甲胺基乙基丙烯酸酯（DMAEA）和一氯甲烷为原料,制取丙烯酸乙酯基三甲基氯化铵（DMAEA－Q）为例作了具体研究。     

新型Gemini阳离子表面活性剂的合成和性能（1）：从长链烷基二甲基胺及其盐酸盐和环氧氯丙烷合成双烷基双季铵盐阳离子

概述了从长链烷基二甲基叔胺及其盐酸盐和环氧氯丙烷或其他连接剂在温和条件下合成新型双烷基双季铵盐型阳离子表面活性剂的方法,产品的表面活性以及烷基链长、连接基团结构对产物表面活性的影响。     

25℃NH_4Cl-KCl- H_2O三元体系相平衡的研究

研究了２５℃ＮＨ４Ｃｌ－ＫＣｌ－Ｈ２Ｏ三元体系的固液相平衡关系,测定出有关溶解度数据, 结果表明该体系存在纯 ＮＨ４Ｃｌ、纯 ＫＣｌ、 ＮＨ４Ｃｌ为主的固溶体及 ＫＣｌ为主的固溶体等 ４个 结晶区．     

氯化铵法处理氟碳铈矿原矿提取稀土

四川冕宁含稀土原矿经Na2 CO3脱氟后 ,采用氯化铵焙烧法提取稀土。通过正交试验确定了脱氟最佳条件 :温度650℃ ,脱氟剂用量m(Na2 CO3) /m(原矿 ) =0 .2 5,反应时间 30min ,原矿脱氟率达到 95%以上。同时考察了温度、时间及NH4Cl对脱氟原矿稀土氯化的影响 ,在优化条件下氯化 ,其稀土回收率达到 95%以上。浸出液的成分分析结果表明 ,氯化过程中Fe ,Si和Al的溶出量很少 ,有利于该浸出液中稀土的提取与分离。     

Methane Emission from Irrigated and Intensively Managed Rice Fields in Central Luzon (Philippines)

Methane (CH₄) emissions were measured with an automated system in Central Luzon, the major rice producing area of the Philippines. Emission records covered nine consecutive seasons from 1994 to 1998 and showed a distinct seasonal pattern: an early flush of CH₄ before transplanting, an increasing trend in emission rates reaching maximum toward grain ripening, and a second flush after water is withdrawn prior to harvesting. The local practice of crop management, which consists of continuous flooding and urea application, resulted in 79–184 mg CH₄ m^–2 d^–1 in the dry season (DS) and 269–503 mg CH₄ m^–2 d^–1 in the wet season (WS). The higher emission in the WS may be attributed to more labile carbon accumulation during the dry fallow period before the WS cropping as shown by higher % organic C. Incorporation of sulfate into the soil reduced CH₄ emission rates. The use of ammonium sulfate as N fertilizer in place of urea resulted in a 25–36% reduction in CH₄ emissions. Phosphogypsum reduced CH₄ emissions by 72% when applied in combination with urea fertilizer. Midseason drainage reduced CH₄ emission by 43%, which can be explained by the influx of oxygen into the soil. The practice of direct seeding instead of transplanting resulted in a 16–54% reduction in CH₄ emission, but the mechanisms for the reducing effect are not clear. Addition of rice straw compost increased CH₄ emission by only 23–30% as compared with the 162–250% increase in emissions with the use of fresh rice straw. Chicken manure combined with urea did not increase CH₄ emission. Fresh rice straw has wider C/N (25 to 45) while rice straw compost has C/N = 6 to 10 and chicken manure has C/N = 5 to 8. Modifications in inorganic and organic fertilizer management and water regime did not adversely affect grain yield and are therefore potential mitigation options. Direct seeding has a lower yield potential than transplanting but is getting increasingly popular among farmers due to labor savings. Combined with a package of technologies, CH₄ emission can best be reduced by (1) the practice of midseason drainage instead of continuous flooding, (2) the use of sulfate-containing fertilizers such as ammonium sulfate and phosphogypsum combined with urea; (3) direct seeding crop establishment; and (4) use of low C/N organic fertilizer such as chicken manure and rice straw compost.     

Combined monte carlo/thermodynamic model of formation of microporous aggregate structure like silica from quaternary ammonium silicate solutions

Quaternary ammonium silicate is a surfactant with very high content of silica that allows its use for preparation of protective coatings. The problem of silica aggregation from quaternary ammonium solution in limited volume is the focus of this paper. The system is described by a model based on a Monte Carbo approach with thermodynamic limitations. Thermodynamic characteristics are estimated by statistical polymer method. The model is employed for estimation of such properties as monomer concentration and tortuosity. The results of computer simulation are used for forecasting properties of coatings and for practical preparation of samples coated with quaternary ammonium silicate-based composition.     

Synthesis and characterization of new cationic surfactants derived from lactic acid

A series of new cationic surfactants was prepared by condensation of lactic acid with N,N-dimethyl propylamine, followed successively by acetylation with acid chloride or ester and by quaternization with dimethylsulfate. Each surfactant and its precursors' structural assignments were based on infrared spectra and ¹H and ¹³C nuclear magnetic resonance spectra. Critical micelle concentrations, contact angles, kinetics of drop spreading, and foam capacities were determined.