Effects of filler contents and processing parameters on the weldline strength of compression molded natural rubber

The presence of weldlines in rubber products is regarded as a one of the most undesirable phenomena, since it results in poor mechanical properties. Compression molding of large or complicated products are prepared by multiple charges, which produces weldlines once the melt fronts are joined by the impingement flow. In this work, the effects of curing systems, processing parameters, filler types, and contents on weldline strength of compression molded natural rubber (NR) were investigated. Furthermore, the effects of curing systems on the aging properties of NR vulcanizates were studied in details. The results show that an increased amount of calcium carbonate does not affect the weldline strength. However, the difference in tensile strength between weldline and nonweldline specimens becomes larger with the high loading of silica and carbon black. In addition, for the factors selected in the experiments, clamping pressure, and curing system were found to be the principal factors affecting the weldline property of vulcanizates. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

RNA干扰抗乙肝病毒的研究进展

乙型肝炎病毒导致的慢性感染、肝炎、肝硬化和肝癌已经成为威胁全球健康的主要问题之一。至今,还没有找到能够彻底治愈慢性乙肝的特效药。RNA干扰(RNAi)研究快速发展,已被广泛用于基因功能研究和疾病治疗。阐述了小干扰RNA(siRNA)和微小RNA(miRNA)抗HBV的研究进展。     

Synthesis and characterization of polyurethane rigid foams from polyether polyols with isosorbide as the bio-based starting agent

In this study, with the isosorbide as bio-based starting agent, a series of bio-based polyether polyols with different hydroxyl values were synthesized and used to prepare polyurethane rigid foams (PURF). The structures of as-synthesized polyols were studied by FT-IR and ¹H NMR methods. The thermal properties, mechanical properties, microscopic morphology, thermal conductivity and dimensional stability of PURF have been characterized by several physico-chemical and ASTM methods. The initial decomposition temperature T_5% and the maximum decomposition temperature T_max for PURF from isosorbide-based polyols with 458 mg KOH/g hydroxyl value are about 312 °C and 354 °C, improved 61 °C and 75 °C comparing with the PURF from 1,2-propanediol-based polyols. The maximum compressive strength of PURF from isosorbide-based polyols is 141 kPa, comparing with 118 kPa of PURF from 1,2-propanediol-based polyols. Meanwhile, the dimensional stability of PURF from isosorbide-based polyols has been improved twofold, and the water absorption was obviously reduced by 50%. All these results suggest that polyols of isosorbide-based starting agent should be promising feedstock for PURF with high performance.     

高弹瓦楞纸板性能研究

在实验室制作高低瓦楞芯纸,对高低瓦楞芯纸、A瓦楞芯纸和B瓦楞芯纸进行平压强度测试和压缩回弹性能检测,比较它们的试验结果,为实际生产提供参考数据。     

11α hydroxylation of 16α, 17‐epoxyprogesterone in biphasic ionic liquid/water system by Aspergillus ochraceus

BACKGROUND: The improved efficiency of steroid biotransformation using the biphasic system is generally attributed to the positive effect on the solubility of substrate in aqueous media. A promising alternative for the application of organic solvents in biphasic systems is the use of ionic liquids (ILs). This study aims to investigate the applicability of the biphasic ILs/water system for 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by Aspergillus ochraceus. RESULTS: Of the seven ILs tested, [C₃mim][PF₆] exhibited the best biocompatibility, with markedly improved biotransformation efficiency. In the [C₃mim][PF₆]‐based biphasic system, substrate conversion reached 90% under the condition in which buffer pH, volume ratio of buffer to ILs, cell concentration, and substrate concentration were 4.8, 10/1, 165 g L^?1 and 20 g L^?1, respectively. This is more efficient than that of the monophasic aqueous system. The effects of the cations and anions of these ILs on the 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by A. ochraceus is also discussed. CONCLUSION: The above results showed that IL/water biphasic system improved the efficiency of 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by A. ochraceus, thus suggesting the potential industrial application of ILs‐based biphasic systems for steroid biotransformation. © 2012 Society of Chemical Industry     

公路工程项目成本控制

本文介绍了笔者所在企业进行成本管理和控制的经验,阐述了如何有效地进行公路成本控制,以实现成本管理的目的,使企业取得最大的经济效益。     

挖斗式清车机工作机构优化设计

本文对挖斗式矿车清理机所采用的两自由度五杆机构工作机构进行了分析,在满足挖掘力和运动轨迹的前提下。对工作机构进行了优化设计,最终获得最佳的结构尺寸。生产实践已经证明,该机构是挖斗式矿车清理机理想的工作机构。     

钾钠氟在烧结过程中的行为

通过烧结中断试验，研究了包钢烧结过程中钾、钠、氟的行为：原矿中的微斜长石，霓石和萤石分别形成了钾霞石、三斜霞石和枪晶石，并存于烧结矿中；同时还发现烧结过程中产生了少量钾、钠、氟的挥发物，并为湿料带所吸附，而在烧结饼上部产生了区域净化现象。因此，为减少钾、钠、氟对高炉冶炼的危害，需要把烧结矿烧好烧透。     

由磷石膏和氯化钾制取农用硫酸钾

由本工作详细研究了在氨水存在下,由磷石膏和氯化钾反应制取农用硫酸钾的过程,进行了各种条件的试验。在氨的存在下,用氨水作为反应液相,实验条件为低温常压,溶液中氨水浓度控制在35％左右,溶液中高浓度的氨改变了硫酸钾和石膏以及其他盐类的溶解度,硫酸钾的溶解度明显下降,使硫酸钾优先沉淀下来,分离后即得硫酸钾产品,该产品的物相组成,经X衍射分析证明为K_2SO_4。     

自然低温对温室不同品种黄瓜耐寒生理及产量的影响

研究和比较了7个黄瓜品种在自然低温下的生理效应及其产量,结果表明:绿宁3号、寒月和津绿3号的根系活力较高;津优30号、永昌9618、绿宁3号和津绿3号的耐低温性较强;津优30号和津绿3号的畸形瓜少,产量高。在根系活力、耐低温性和产量方面,津优30号和津绿3号最好,津优2号和北极星低。