The radiation crosslinking and scission of ethylene-propylene copolymers studied by solid-state nuclear magnetic resonance

Methyl groups from chain scission and H-crosslinks have been identified by solid-state nuclear magnetic resonance in amorphous ethylene-propylene copolymers containing 23 and 36 mole % propylene after γ-irradiation to 10 MGy at 30°C. G (scission) and G (crosslink) values determined from the n.m.r. spectra and by extraction are in agreement, which suggests that the crosslinks are not clustered. This may differ from the situation in polyethylene where there is a substantial crystalline content. G(S). G(X) and the ratio G(S)/G(X) increase with increasing propylene content of the copolymers.     

反应精馏法制备高纯度醋酸甲酯

在中试反应精馏塔中以浓硫酸为催化剂进行了醋酸与甲醇反应制备醋酸甲酯的试验。反应精馏塔的精馏段为填料,反应段为立体催化精馏塔板,采用连续操作,考察了回流比、甲醇进料位置、停留时间、催化剂用量对反应精馏的影响。试验结果表明,当回流比为1.2、甲醇进料位置为第11～15块塔板、停留时间为2.2～2.5h、催化剂与醋酸的质量比为1.07∶100时,塔顶醋酸甲酯的质量分数达到99.50%以上,醋酸的转化率达到99.85%以上。     

Photocatalytic degradation of methyl orange using heteropolytungstic acid-encapsulated TiSBA-15

Heteropolyphosphotungstic acid (H₃PW₁₂O₄₀) (HPA)-encapsulated titanium-supported SBA15 nanoporous materials (HPA-TiSBA-15) were synthesized as a new photocatalyst, and they were characterized by FT-IR and ³¹P NMR MAS spectroscopic methods. Their photocatalytic effects on degradation of methyl orange in water were investigated under natural conditions, and it was found that a 4-fold increase in the photodegradation rate is observed in the presence of HPA-TiSBA-15 as compared to the rate observed in the presence of titanium-supported SBA15 nanoporous materials (TiSBA-15) without HPA.     

Modelling thermal degradation of composite materials

A one–dimensional, transient thermal degradation heat transfer model for the response of composite materials when exposed to fire is presented. The model can handle layers of different materials. Material properties are functions of temperature. The reaction can be specified using Arrhenius‐type parameters or by inputting a density–temperature relationship determined by any experimental technique such as thermogravimetric analysis. The model is validated against the experimental data presented in Boyer's 1984 dissertation. Overall, the model provides excellent agreement with the experimental data. It is shown that very little difference is found between results arrived at by Arrhenius kinetics and results obtained by specifying the easier to measure density–temperature relationship. From this it is concluded that this technique is a viable alternative to Arrhenius‐type models. Copyright © 2006 John Wiley & Sons, Ltd.     

臭氧氧化-光催化降解水中的五氯酚

利用臭氧氧化-光催化技术降解水中的有机污染物五氯酚(PCP)。对比了紫外光照射、臭氧氧化、光催化、臭氧氧化-光催化4种方法降解PCP的情况。考察了臭氧氧化-光催化体系中臭氧流量、臭氧产量、PCP初始质量浓度、pH和CO23-等因素对PCP降解率的影响。实验结果表明,臭氧氧化-光催化法比单独使用紫外光照射、臭氧氧化、光催化法更能有效的去除PCP;增加臭氧流量和臭氧产量有利于提高PCP的降解率;降低PCP的初始浓度,PCP的降解率显著提高;pH对PCP的降解效果影响不明显;CO23-的存在显著降低了PCP的降解率。在臭氧氧化-光催化体系中,除臭氧直接氧化降解PCP外,臭氧与TiO2协同作用产生的.OH对PCP的降解也起到了重要作用。     

溶液中微量甲基异丁基酮的分析方法

研究了微量甲异丁基酮在氟氧铌酸（H2NbOF5)及氟钽酸（H2TaF7)溶液中存在的形式，找到利用碘仿-硫代硫酸钠联合滴定的方法，来标定微量甲基异丁基酮在H2NbOF5及H2TaF7溶液中的含量，本方法在钽铌冶炼过程中操作简便易行且结果重现性好。     

二氧化钛纳米晶的制备及光催化活性研究

本文用溶胶—凝胶法制备了不同晶相的TiO2纳米晶，将其负载于镍网上，以苯酚的降解为模型反应，研究对比了不同晶相TiO2纳米晶的光催化活性。结果表明，纯锐钛矿相的TiO2纳米晶的降解能力要强于锐钛矿与金红石混合相的TiO2纳米晶。     

The flame retardant mechanism of polyolefins modified with chalk and silicone elastomer

This paper presents the current understanding of the flame retardant mechanism of Casico?. The study includes the flame retardant effect of each individual component: ethylene–acrylate copolymer, chalk and silicone elastomer, as well as the formation of an intumescent structure during heating. The flame retardant properties were investigated by cone calorimetry and oxygen index tests. To obtain insight into the flame retardant mechanism, heat treatment under different conditions has also been performed. The results indicate that the flame retardant mechanism of Casico is complex and is related to a number of reactions, e.g. ester pyrolysis of acrylate groups, formation of carbon dioxide by reaction between carboxylic acid and chalk, ionomer formation and formation of an intumescent structure stabilized by a protecting char. Special emphasis is given to the formation of the intumescent structure and its molecular structure as evaluated from ¹³C MAS‐NMR and ²⁹Si MAS‐NMR, ESCA and XRD analysis. After treatment at 500°C the intumescent structure consists mainly of silicon oxides and calcium carbonate and after treatment at 1000°C the intumescent structure consists of calcium silicate, calcium oxide and calcium hydroxide. Copyright © 2003 John Wiley & Sons, Ltd.     

聚氨酯/聚(甲基丙烯酸甲酯-甲基丙烯酸丁酯)互穿聚合物网络聚合物的阻尼性能

采用本体聚合法合成出一系列阻尼性能良好的聚氨酯/聚(甲基丙烯酸甲酯-甲基丙烯酸丁酯)(PU/P(MMA-BMA))互穿聚合物网络(IPN)聚合物,通过动态力学分析方法表征了PU/P(MMA-BMA)IPN聚合物的阻尼性能。探讨了加入催化剂、高温后处理、交联剂用量及PU与P(MMA-BMA)的质量比对PU/P(MMA-BMA)IPN聚合物阻尼性能的影响。实验结果表明,经高温后处理后,以二月桂酸二丁基锡为催化剂、交联剂二乙烯基苯用量(占MMA和BMA的摩尔分数)为1.5%、PU与P(MMA-BMA)的质量比接近1或小于1时,PU/P(MMA-BMA)IPN聚合物具有良好的阻尼性能。     

Decreasing miscibility with greater heterogeneity in ternary polymer blend: poly(cyclohexyl methacrylate), poly(α‐methyl styrene) and poly(4‐methyl styrene)

A ternary blend system comprising poly(cyclohexyl methacrylate) (PCHMA), poly(α‐methyl styrene) (PαMS) and poly(4‐methyl styrene) (P4MS) was investigated by thermal analysis, optical and scanning electron microscopy. Ternary phase behaviour was compared with the behaviour for the three constituent binary pairs. This study showed that the ternary blends of PCHMA/PαMS/P4MS in most compositions were miscible, with an apparent glass transition temperature (T_g) and distinct cloud‐point transitions, which were located at lower temperatures than their binary counterparts. However, in a closed‐loop range of compositions roughly near the centre of the triangular phase diagram, some ternary blends displayed phase separation with heterogeneity domains of about 1 µm. Therefore, it is properly concluded that ternary PCHMA/PαMS/P4M is partially miscible with a small closed‐loop immisciblity range, even though all the constituent binary pairs are fully miscible. Thermodynamic backgrounds leading to decreased miscibility and greater heterogeneity in a ternary polymer system in comparison with the binary counterparts are discussed. © 2003 Society of Chemical Industry