New intramolecular effect observed for polyesters: An anomeric effect

A series of polyesters was prepared to evaluate hydrolytic stability as a function of cyclohexyl dibasic acid content. The three cyclohexyl dibasic acids: 1,2; 1,3; and 1,4 were formulated into polyesters with two glycols. The proportion of cis and trans isomers was evaluated via ¹H NMR. The hydrolytic stability of short chain polyesters was evaluated in an acetone/water mixture which solubilized the polyesters to mimic oligoester behavior within a thermosetting polyester coating environment. The rate of hydrolysis was monitored by acid titration and corroborated by GPC. Surprisingly, 1,2-cylohexyl diacid-based polyesters were robust, and 1,3-cyclohexyl diacid-based polyesters were the most susceptible to hydrolysis. Evidently, a 1,2-anchimeric effect for cyclohexyl dibasic acid polyesters was not an important consideration, while the 1,3-cyclohexyl ester interaction was. Consequently, an anomeric effect was proposed. Presented at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 12–14, 2003, in Philadelphia, PA.     

建筑围护结构与节能

针对我国夏热冬冷地区的建筑气候特点,对建筑围护结构节能在设计中的要点和意义进行了讨论。     

半导体元件清洗技术浅谈

随着社会的进步和科学技术的迅猛发展,对洗净技术的要求也越来越高。清洗方式多种多样,但最主要的是突出在喷射清洗和超声波清洗两大方面,应用于全国各行各业,并且也得到了明显进步。     

高压电动机定子线圈匝间绝缘问题的探讨

在实践经验的基础上，分析了我国匝间绝缘短路的主要原因，提出在匝间绝缘的设计，制造工艺及耐压试验等工序采取合理措施，以提高匝间绝缘的可靠性。     

Analysis of lightning surge propagation in wind farm

Wind power generation is expected to become more important in future distribution systems. Although several prospective reports such as IEC 61400‐24 and NREL SR‐500‐31115 indicate an insulation scheme and grounding design for lighting protection, there still seems to be too few investigations on the problems. This paper therefore discusses lightning surge analysis using a wind farm model with 2 or 10 ideal wind turbines. Changing parameters such as grounding resistance and lightning strike points, several cases were studied. As a result of the analysis using digital simulator ARENE, it is clear that the surge tends to propagate toward the end of a distribution line in a wind farm and there is the possibility of insulation accidents at the other wind turbines when lightning attacks a wind turbine. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(2): 30– 38, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20364     

Thermal Radiative Properties of Xonotlite Insulation Material

Introduction Xonotlite-type calcium silicate (6CaO?6SiO2?H2O) is synthesized porous insulation material by hydrothermal processing with quartz powder and limestone as the raw material (with CaO/ SiO2≈1:1). Compared with fire- retardant fibre, xonotlite has more excellent insulating performance, such as low thermal conductivity, environment friendly, high intension, and wide applying temperature range, which has been emphasized in recent years by many scholars and widely used in many indu…     

一种简易的手工网印序号工艺法

通过一种简易的手工丝印序号工艺法,可以连续完成逐张PCB的序号印制且质量稳定。     

Improved shape evolution of copper interconnects prepared by jet-stream etching

In the preparation of copper interconnects in the conductor pattern of a printed circuit board (PCB), wet etching processes are commonly adopted for creating patterns of high-density interconnects. Currently available techniques of immersion and spray etching could lead to poorly shaped wires due to complex flow fields or the disturbing puddling effect. A modified technique of arrayed jet-stream etching was developed in this work, aiming at producing well-defined copper interconnects on a PCB in a significantly shorter time. The results were appealing in that copper interconnects of 35/140 μm (thickness/width) exhibiting etching factors of greater than 6 were obtained in 20 s, much better than the conventional ones with etching factors of 3 to 5 and etching times of at least 2 min. In addition, uniformly etched copper interconnects with less than 20 μm undercuts were observed on one etching line. One additional point to note is that no banking agents or inhibitors as commonly seen in conventional etching techniques were needed in this new processing method.     

Novel blood-compatible waterborne polyurethane using chitosan as an extender

A series of novel block polymers of polyurethane (PU) and chitosan have been prepared in two steps. The first step is the preparation of PU prepolymer, obtained from polytetramethylene oxide glycol (PTMO, M_n = 1000), isophrone diisocyanate (IPDI), and 2,2′-dimethylol propionic acid (DMPA), followed by ionizing PU prepolymer with triethylamine (TEA). The second step involves PU chain-extended by water-soluble chitosan of low molecular weight (M_n = 5000) by self-emulsion polymerization method. The sizes of the latex particles, morphology, and copolymer architecture have been characterized by dynamic light scattering (DLS), general tensile test, infrared spectroscopy (IR), surface contact angle measurement, and transmission electron microscopy (TEM). Furthermore, it shows that the addition of chitosan remarkably increases anticoagulative property of PU elastomers confirmed by the recalcification time. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

二甲基乙醇胺在高回弹聚氨酯泡沫中的应用

分别采用二甲基乙醇胺(DMEA)和二月桂酸二丁基锡(DBTL) 2种催化剂制备了高回弹聚氨酯(HRPU)泡沫塑料.探讨了DMEA和DBTL对HRPU泡沫组合料反应活性、流动性及制品物理性能、热稳定性的影响.结果表明,以DMEA作催化剂的HRPU泡沫物理性能、热老化性及工艺稳定性优于DBTL催化剂,DMEA可以替代DBTL应用于HRPU泡沫塑料.