Nucleating activity of the quinacridone and phthalocyanine pigments in polypropylene crystallization

The nucleating ability of two organic pigments, quinacridone and phthalocyanine, in nonisothermal polypropylene (PP) crystallization was investigated. The investigations were carried out using DSC and polarizing microscopy. The efficiency of pigments in the nucleation process was determined in a simple test comparing the crystallization temperature of the PP‐containing pigments with respect to the pure polymer. Both pigments revealed good nucleating activity. In the presence of pigments the increment of the crystallization temperature and the increase of nucleation rate were observed. The nucleating efficiency of pigments was confirmed in investigations of the obtained structure. The nucleating activity of pigments was explained by their features fulfilling several requirements for good nucleating agents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3957–3964, 2003     

Spherulitic Growth of Apatite in a MgO─CaO─SiO2─P2O5 Glass

Differential thermal analysis, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, and transmission electron microscopy were used to study the crystallization of a glass with a composition of 11.2 wt% MgO, 40.5 wt% CaO, 33.3 wt% SiO₂, and 15 wt% P₂O₅. A two-phase "composite," which was composed of apatite and an intermediate phase (H-phase), was formed under appropriate heat-treatment conditions. The spherulitic morphology of apatite phase transformed from "open sheaf" into ellipsoidal as samples were heated to a higher temperature. These phenomena were due to the intermediate H-phase becoming unstable at this temperature so that the retardation effect on the apatite dendritic growth disappeared.     

Optimal temperature policies for catalytic transport reactors under periodic operation

The influence of inlet gas concentration cycling on the optimal temperature policy of catalytic transport reactors is studied theoretically. The model considered is based on plug flow of gas and catalyst particles with negligible interand intra-particle diffusional resistances and concentration dependent deactivation kinetics. To utilise the concentration of the reactant and the activity of the deactivating catalyst fully a proper temperature sequence along the reactor is needed. Thus, a general optimal temperature policy using the continuous minimum principle is derived for the reactor under periodic operation. The model equations are solved analytically for gas concentration, activity and temperature profiles. Resonance behaviour (maximum in conversion with pulse width) is obtained using the optimal temperature policy for certain sets of parameters. The effects of activation energy groups, reaction and deactivation constant groups and inlet temperature on the optimal temperature policy under periodic operation are evaluated. In all cases an improvement in conversion with the optimal temperature policy under periodic operation over that with an isothermal policy under periodic operation is obtained. A suboptimal policy, comprising constant temperature over different reactor sections, which is useful for implementation purposes is also discussed.     

Influence of composition and molecular mass on the morphology,crystallization and melting behaviour of poly(ethylene oxide)/poly(methyl methacrylate) blends

Results are reported on the influence of composition and molecular mass of components on the isothermal growth rate of spherulites, on the overall kinetic rate constant, on the primary nucleation and on the thermal behaviour of poly(ethylene oxide)/poly(methyl methacrylate) blends. The growth rate of PEO spherulites as well as the observed equilibrium melting temperatures decrease, for a given T_c or ΔT, with the increase of PMMA content.Such observations are interpreted by assuming that the polymers are compatible in the undercooled melt, at least in the range of crystallization temperatures investigated. Thermodynamic quantities such as the surface free energy of folding σ_e and the Flory-Huggins parameter χ₁₂ have been obtained by studying the dependence of the radial growth rate G and of the overall kinetic rate constant K from temperature and composition and the dependence of the equilibrium melting temperature depression ΔT_m upon composition, respectively.     

Bubble temperature data for phenol-alcohol systems: Phenol-I-Amyl alcohol and phenol-n-Amyl alcohol systems

In order to supplement the literature data on VLE, isobaric bubble temperature data were collected for the binary systems phenol-i-amyl alcohol and phenol-n-amyl alcohol over the entire composition range by indirect method using a standard Swietoslawski type ebulliometer. The measurements were made at three sub-atmospheric pressures. The experimental t-x data were correlated with both equation of state method and gamma-phi methods. In the former approach, the Soave equation of state is used, whereas in the latter case Wilson, NRTL and UNIQUAC equations are used.     

室温固化高温使用环氧胶粘剂的进展

本文介绍了室温固化高温使用环氧胶粘剂的主要成份、结构、性能及其特点，并对其存在的问题及未来的发展趋势化了简述．     

金沙江典型水库水温影响因素敏感性分析

在拱坝温度应力计算等领域,库水温是重要的边界条件,对其计算精度要求较高,尤其对于高拱坝上游库水温而言,需要进行详细研究。库水温的影响因素较多,如河道的类型、水库的来水流量、来水温度、气象条件等,如何合理考虑各项因素对库水温分布的影响,对于计算的精确度意义重大。利用横向平均的二维水动力模型来研究金沙江上向家坝、溪洛渡、白鹤滩、乌东德等4座水动力特征相似水库的水温时空动态分布,并以典型水库溪洛渡为例,对该水库的来水流量、来水温度和气象条件等因素进行敏感性分析。研究成果可为后续几座水库的水温计算分析提供参考。     

关于水泥窑低温余热发电有关问题的思考

根据多年从事水泥纯低温余热发电的实践经验,分析了单压系统、双压系统和闪蒸系统各自的优缺点;提出了统一考虑烧成系统和余热发电系统进行大系统优化的观点,着重就吨熟料烧成煤耗与发电量之间的最佳平衡点进行了分析;同时对如何进一步优化烧成系统和余热发电系统的设计提出了一些具体的建议。     

氨纶用聚酯二醇的研究

本文研究了聚酯二醇的生产工艺,重点研究了反应温度对生产工艺的影响以及原料已二酸与二元醇的投料比对产品酸值和羟值的影响,催化剂对产品质量的影响,并对产品着色原因进行了探讨。     

羟基磷酸钙结晶法回收大型水生植物发酵液中磷酸盐研究

为有效回收大型水生植物发酵液中磷,选择挺水植物西伯利亚鸢尾(Iris sibirica L.)和圆币草(Hydrocotyle vulgaris)进行发酵试验,分析不同pH值下发酵液中磷回收的效率和纯度,探索羟基磷酸钙(hydroxyapatite,HAP)结晶法回收水生植物发酵液中磷酸盐的可能性。结果表明:西伯利亚鸢尾和圆币草发酵液中钙磷摩尔数比分别为2.7和10,镁磷比分别为1.4和1.6,适合采用HAP法回收磷酸盐。不同水生植物发酵液调节pH值回收磷曲线相似,在pH为8.5时西伯利亚鸢尾和圆币草发酵液磷酸盐回收率分别达到89%和91%,产生的羟基磷酸钙沉降性能良好。X射线荧光光谱分析分析结果表明pH为8.5时沉淀物中P2O5质量分数超过25%,羟基磷酸钙为主要成分。pH调节超过8.5后沉淀物中碳酸钙含量会随着pH上升而不断增加,影响羟基磷酸钙的纯度,因此,回收磷酸盐适合的pH值为8.5。