The synergistic effect of dicyandiamide and resorcinol in the curing of epoxy resins

The synergistic effect of dicyandiamide (Dicy) and phenolic substances was studied, with resorcinol as a model compound. It was found that when Dicy and resorcinol are used jointly, the curing temperature of epoxy resin can be significantly lowered. FTIR and DSC data were used to illustrate the mechanism of the synergism. The addition of the phenolic hydroxyl group to epoxide was facilitated by Dicy, which favors the formation of phenoxy anions. The reaction of Dicy with epoxide was facilitated by resorcinol, which can exert “electrophilic assistance” for the addition of the amino group to epoxide. The presence of resorcinol also favors the addition of the hydroxyl group to the cyano group. The thermal and mechanical properties of the epoxy resins cured with Dicy/resorcinol or Dicy/phloroglucinol were studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1869–1874, 2003     

纳米凹凸棒土改性聚氨酯纤维的结构与性能

以物理共混的方法制备了纳米凹凸棒土(AT)/聚氨酯(PU)共混纤维。通过红外测试表明:AT与PU的硬段发生相互作用,增强了PU链段之间的氢键作用。动态力学性能分析的结果表明:AT可视作为物理交联点,限制了PU分子链的运动。相对于纯PU纤维,纳米AT/PU共混纤维的拉伸力学性能有了明显的提高,热稳定性能也有一定改善。     

Coupling granule properties and granulation rates in high-shear granulation

It is possible to link granulation rates to granule properties. The linkage is by multiple dimension population balance equations that, by means of simplifying assumptions, can be reduced to multiple one-dimensional (1-D) population balance equations (PBEs). Using simple physically based models, this paper demonstrates how multiple one-dimensional population balance equations can describe the results of high-shear granulation experiments of two different materials, calcium carbonate and lactose. Good agreement between experimental and simulated results was achieved enabling the granulation rates to be defined by two model parameters: the critical binder volume fraction and the aggregation rate constant. The modelling framework presented in this paper also provides a basis for the kinetic analysis of granulation experiments so that with further work, it is possible to determine the effect of process conditions and material properties on the model parameters.     

应用WCA微扰理论推算非极性液体比热容的新方法

本文首次将统计热力学的Ｗｅｅｋｓ－Ｃｈａｎｄｌｅｒ－Ａｎｄｅｒｓｏｎ（简称ＷＣＡ）微扰理论应用于非极性液体定容比热容和定压比热容的推算，用一些液体的ｐ－ｖ－Ｔ实验数据拟合了理论中所用ＬＪ势能函数的势能参数，并提出一个通用关联式。本文方法具有通用性，在编制的计算程序中只需输入物质的临界温度、临界比容、偏心因子等就能算出相应的比热容，工程应用十分方便。     

Effect of Surface Forces on Subcritical Crack Growth in Glass

Data on the growth of cracks tested in aqueous solutions were interpreted in terms of surface force theory. For applied stress intensity factors greater than 0.25 MPa · m½, the position and the slope of the curves and their dependence on pH and ion concentration can be explained in terms of surface force theory, provided these forces are of a magnitude and range that are representative of those involved in the cohensive bonding of solids. Weaker forces, such as structural, double-layer, or dispersion forces, have little effect on crack growth in silica glass for K _I > 0.25 MPa · m½.     

微生物聚酯的合成和应用研究进展

微生物聚酯是由发酵技术生产、具有生物降解性的热塑性高分子材料。本文介绍了３－羟基丁酯均聚物（ＰＨＢ）和共聚物的基本结构、生物降解性能、生物合成及其应用研究的进展。     

Adsorption and electrothermal desorption of organic vapors using activated carbon adsorbents with novel morphologies

Novel morphologies of activated carbons such as monolith, beads and fiber cloth can effectively capture organic vapors from industrial sources. These adsorbent materials are also unique because they can undergo direct electrothermal regeneration to recover the adsorbed organic vapors for potential re-use. This investigation compares and contrasts the properties of these adsorbents when using electrothermal-swing adsorption. The adsorption systems consisted of an organic vapor generation system, an electrothermal-swing adsorption vessel, a gas detection unit, and a data acquisition and control system. The activated carbon monolith (ACM) had the lowest pressure drop, highest permeability, highest electrical resistivity and lowest cost as compared to the activated carbon beads (ACB) and the activated carbon fiber cloth (ACFC). ACB had the largest throughput ratio and lowest length of unused bed as compared to the other adsorbents. However, ACFC had the largest adsorption capacity for toluene when compared to ACM and ACB. ACFC was also faster to regenerate and had a larger concentration factor than ACM and ACB. These results describe relevant physical, electrical, adsorption and cost properties for specific morphologies of the adsorbents to more effectively capture and recover organic vapors from gas streams.     

PbNb2O6基压电陶瓷的高温介电性能研究

本文在PbNb2O6基础上采用Ba^2＋取代Pb^2＋离子,并通过添加Cr2O3、Y2O3、Sm2O3、Nd2O3和CeO2等氧化物进行掺杂改性,研究不同掺杂剂对PbNb2O6陶瓷材料结构的影响,寻找提高压电性能及居里温度的途径.试验结果表明,掺杂后的偏铌酸铅显微结构发生了变化,适量的掺杂可获得压电性能和工艺稳定性能很好,且居里温度较高（420℃～600℃）的改性PbNb2O6系压电陶瓷,可分别满足350℃和500℃以上高温应用环境的要求.     

Controlled coagulation of emulsion polymers

Coagulation of latex particles is most often carried out in the diffusion limited aggregation (DLA) regime where the time for coagulation to take place is on the millisecond timescale. This process produces aggregates of low density, irregular shape, and a broad particle size distributions. When the coagulation is carried out in the reaction limited aggregation (RLA) regime, a coagulation time of about 1–120 sec, the system can be controlled by mixing to yield dense, spheroidal aggregates with a very narrow particle size distribution. The important variables in the RLA process for butyl acrylate/methyl methacrylate (BA/MMA) latexes were found to be mixing intensity, latex copolymer composition, and coagulation temperature. Dried aggregates formed in the RLA process were found to have excellent powder flow properties and low dustiness.     

超高相对分子质量聚乙烯纤维及其应用

本文介绍了超高相对分子质量聚乙烯(UHMWPE)纤维的制备方法及其发展现状，并简要概述了该纤维的结构、性能、改性方法及其在各领域中的应用。