Keggin结构钼磷和钼硅杂多酸盐热稳定性研究

本文用TG-DTA、DSC热谱、变温红外光谱、X射线衍射和溶解性实验方法,对四十一种Keggin结构钼磷和钼硅杂多酸的碱金属、碱土金属、过渡金属、希土元素以及有机阳离子盐的热稳定性进行了系统的研究,初步讨论了影响热稳定性的因素。得到了一些有意义的结论。     

钼—桑色素的极谱波及其用于钨精矿中钼的测定

本提出了测定钼的新极谱体系，最佳底液条件为ｐＨ２．１的盐酸－２．３７×１０＾－６ｍｏｌ／Ｌ桑色素－０．１７２ｍｏｌ／Ｌ氯酸钠。极谱波峰电位为－０．４３Ｖ（ｖｓ．ＳＣＥ），钼（Ⅵ）浓度在１．０４×１０＾－９￣４．５９×１０＾－８ｍｏｌ／Ｌ范围内与波高有线性关系，检出限３．６７×１０＾－１０ｍｏｌ／Ｌ。方法简便，快速、准确，并已直接应用于钨精矿中微量钼的测定。     

甲基红在痕量钼的催化反应—示波极谱分析中的新应用

实验发现，在硫酸介质及加热下，痕量钼（Ⅵ）对硫酸联氨还原甲基红这一缓慢褪色反应具有强烈催化作用；甲基红在氢氮化钠介质中于－０．７０Ｖ．ＳＣＥ处产生一灵敏的示波极谱波。据此，本文采用固定时间法，用示波极谱法研究了利用这一新的指示反应催化测定钼的影响因素，建立了一个检出限和测定范围分别为０．８ｎｇ／ｍＬ和１．６～１００ｎｇ／ｍＬ钼的催化反应－示波极谱法，并用于测定矿石和钢样中的钼。     

漆酚钼螯合高聚物的合成及表征

采用漆酚与四氯氧化钼反应制得兼具螯合物特点和生漆固有性能的漆酚钼螯合高聚物 (PUM) .对不同反应条件下制备的高聚物的含钼量进行了测定 .并通过元素分析、红外光谱、电子顺磁共振谱、光电子能谱、质谱、高效液相色谱和热失重分析探讨高聚物的生成过程、结构特征和热性能 .结果表明 ,漆酚与四氯氧化钼首先发生氧化还原反应和配位反应生成螯合物 ,然后进一步聚合成为高聚物 ;该高聚物中存在漆酚钼螯合物结构单元且具有很好的热稳定性 ,其耐热性能比生漆和传统黑推光漆好得多 .     

微量元素钼的测定和钼酸锂的缓蚀研究

用ＥＤＴＡ滴定法测定了钼酸盐中的钼含量，用重量法研究了钼酸锂对炭钢的缓蚀能力，结果表明，当ＰＨ４时，０．０２－０．０７％钼酸锂对Ａ３钢片的缓蚀力为３６－７４．８％。     

催化动力学极谱法测定痕量钼

在稀Ｈ２ＳＯ４介质中，钼（Ⅵ）对硫酸联氨还原乙基橙的反应有强烈的催化作用。建立了催化动力学极谱法测定痕量钼的新体系，方法线性范围为２０－３００ｎｇ／ｍＬ，检出限为３．５４ｎｇ／ｍＬ。方法应用于尿中中钼的测定，结果满意。     

不同反荷离子的Keggin结构钼磷酸盐的热稳定性及其对异丁…

用共沉淀法制了以Ｋｅｇｇｉｎ结构为骨架的不同反荷离子钼磷酸盐，利用ＦＴＩＲ、ＸＲＤ等手段进行了表征。结果表明，Ｌｉ，Ｎａ，Ｋ，Ｃｓ分别作为反荷离子时的杂多酸盐的热稳定性依次增强，并考察了催化剂对异丁醛一步氧化制甲基丙烯酸的催化活性，其中Ｃｓ盐的催化活性最优。     

用~（31）P－NMR和IR谱研究MoDTP合成产物组分及反应机理

用~（３１）Ｐ核磁共振（ＮＭＲ）谱和红外（ＩＲ）光谱研究了二硫代磷酸钼（ＭｏＤＴＰ）合成产物组分含量、分子结构及其合成反应机理。结果表明，ＭｏＤＴＰ合成产物是由３７．２％的有机五价钼络合物、３５．１％的有机Ｐ＝Ｓ化合物和２７．７％的有机Ｐ＝Ｏ化合物等１４种成分组成，所含副产物或由原料带入，或因ＭｏＤＴＰ合成反应过程原料本身副反应伴随产生。     

Dawson结构钼钒磷杂多化合物对苯酚过氧化氢羟化作用的研究

Ｄａｗｓｏｎ结构钼钒磷杂多化合物对苯酚过氧化氢羟化作用的研究于剑锋，杨宇，吴通好，孙家锺（吉林大学化学系理论化学研究所，长春，１３００２３）关键词Ｄａｗｓｏｎ结构钼钒磷杂多化合物，苯酚羟化，过氧化氢苯二酚（ＤＢＨ）是重要的化工原料．由芳香化合物羟化制...     

Keggin结构钼系杂多蓝的离析和性质研究

本文报道了八种1:12系列钼系杂多蓝KyHzXMo_(12)O_(40)·nHp(X=Si,P,As,Ge)的制备和离析方法,并通过元素分析、电位滴定、极谱、循环伏安、红外光谱、可见-紫外光谱、X射线粉末衍射、XPS和~(31)PNMR对产物进行了表征。测定了四电子钼硅杂多蓝的单晶结构,确定了还原钼原子的位置是第三位、七位、八位、十位。实验结果表明,杂多蓝仍基本保持了Keggin结构。首次系统研究了八种杂多蓝固体的ESR谱,发现二电子、四电子杂多蓝比一电子杂多蓝具有更小的电子离域程度;热性质研究表明,固体杂多蓝随还原程度增大,热稳定性增强;研究其氧化还原性质发现,在不同介质中,杂多蓝的氧化序发生变化,极谱半波电位与杂原子电负性线性相关。并发现P和As的杂多蓝具有极强的抗酸解能力。     

The use of thermal analysis to study thermal processing effects on polypropylene

The thermal stability of a polypropylene copolymer has been examined at several stages during the processing of the material into its final product in order to obtain information on the influence of processing steps such as grinding and thermal heating on the expected lifetime of the material. Mass loss kinetics in an inert atmosphere were able to detect differences in thermal stability, but oxidative differential scanning calorimetry studies proved to be a more sensitive techiique. A comparative study of a specially prepared series of samples revealed the importance of additives on measured thermal stability and indicated that both mechanical and thermal processing can cause reduction in measured thermal stability.     

The effect of wood extractives on the thermal stability of different wood species

This study compares the thermal stability of different wood species, which is an important factor for the production of wood–polymer composites (WPCs), and investigates the effect of extraction on thermal properties. The chemical composition of four wood species – Quercus alba, Pinus radiata, Eucalyptus grandis and Acacia cyclops – has been determined, as the species is expected to affect the thermal stability of wood. Subsequently, the hot-water (HW) extractives, ethanol/cyclohexane (E/C) extractives and both extractives were eliminated from the wood via Soxhlet extraction and the thermal stability of the wood determined with thermogravimetric analysis (TGA) under identical conditions. The results suggest that a higher cellulose and lignin content leads to better thermal stability of wood in different temperature regimes. In all cases, the removal of extractives improved the thermal stability of the wood. The effect of combined extractions was more pronounced than of an individual extraction and E/C-extraction caused less improvement in the thermal stability of wood than HW extraction. The degradation of the investigated wood extractives occurred at low rates over a broad temperature range. Pure cellulose exhibited superior thermal stability compared to wood, but differences were observed between the investigated wood species.     

Effects of hydroxyvalerate contents in thermal degradation kinetic of cellulose acetate propionate/poly(3-hydroxyalkanoates) blends

Thermal stability of polymers is an important parameter that determines the application as well as the processing conditions. The green polymers have shown low thermal stability, such as the polyhydroxyalkanoates (PHAs). The PHAs with different comonomers containing hydroxyvalerate (HV) were studied. It was seen that the green polymer showed a fast thermal degradation process. The addition of the HV comonomer modified this profile and the thermal degradation kinetic. The blend prepared between the PHAs and other polymers can modify the thermal degradation process of the green polymers. In the present study, blends of cellulose acetate propionate and PHAs were prepared, and the thermal degradation kinetics of these blends were evaluated. It was observed that the cellulose acetate propionate (CAP) phase in the blends modified the thermal degradation process and kinetic profile of the PHA phase. In the blends, the thermal stability of the PHAs was slightly modified because of CAP reducing the reactivity of the PHAs. On the other hand, the thermal stability of the CAP phase in the blends is not largely modified by the PHA phase. However, the hydroxyvalerate comonomer decreases the reactivity of the CAP phase at the start of thermal degradation of the same. The interaction between the phases promotes the synergetic interaction, which slightly improves the thermal stability of the two polymers blends.     

聚丙烯成核剂成核效应及热稳定性研究

为表征在聚合物材料热加工成型过程中成核剂的成核效果的热稳定性，设计了用反复升降温ＤＳＣ实验，通过观察聚合物结晶温度和结晶热焓在反复升降温过程中的变化来考察成核剂的成核效率的稳定性．研究了碳酸钙、苯甲酸钠、对苯二甲酸和脂肪二元酸：庚二酸、辛二酸、壬二酸及其与碳酸钙组成的双组分成核剂对聚丙烯结晶成核效果的热稳定性．结果表明，高熔点物质碳酸钙、对苯二甲酸、苯甲酸钠的成核效果的热稳定性高，而脂肪二元酸的成核热稳定性低．庚二酸与碳酸钙组成的双组分成核剂的成核热稳定性高，但辛二酸、壬二酸与碳酸钙组成的双组分成核剂的成核热稳定性没有得到改善．这可能是由于庚二酸与碳酸钙之间存在某种相互作用，从而使成核效果得以稳定，而辛二酸、壬二酸与碳酸钙组成的双组分成核剂中，两个组分基本独立存在．     

Dehydrochlorination of Poly(viny1 Chloride) in Pyridine. III. Thermal and Mechanical Properties

The thermal properties of dehydrochlorinated PVC (DHPVC) were evaluated. From thermogravimetric analysis (TGA) and differential thermal analysis (DTA), a larger decrease in thermal stability of dehydrochlorinated PVC than of PVC was observed. Thermal stability of DHPVC increased continuously with an increase in dehydrochlorination temperature and dilution of the reaction solution during dehydrochlorination. However, with an increase in dehydrochlorination time, an increase in thermal stability after an initial drop was obtained. The highly cross-linked product separated from the reaction solution at higher dehydrochlorination temperatures showed a lower thermal stability than that of corresponding soluble DHPVC. The stress-strain behavior of dehydrochlorinated PVC samples was also studied.     

Poly(dimethylsiloxane)/palygorskite composites: preparation,characterization, and properties

Poly(dimethylsiloxane) (PDMS) composites were prepared by simple blending process using palygorskite (PG) or modified palygorskite (MP). This study has been designed to determine the influences of PG or MP on the thermal stability and the mechanical properties of PDMS composites. The thermal stability of PG and MP were also studied by thermogravimetric analysis (TGA). The results showed that MP had the similar thermal stability to PG, and PG or MP not only increased the thermal stability but also improved the mechanical properties of PDMS composites. Meanwhile, compared with PG/PDMS composites, MP/PDMS composites had better thermal stability and mechanical properties owing to the better dispersion of MP into the matrix, the stronger chemical interfacial interaction between MP and the matrix. Copyright © 2010 John Wiley & Sons, Ltd.     

Investigation of antioxidant and electron beam radiation effects on the thermal oxidation stability of low-density polyethylene

Effect of various antioxidants on the thermal oxidation stability of LDPE and X-LDPE has been investigated. To achieve this purpose, miscellaneous commercial grade antioxidants such as Irganox 1010, Irganox1076, Irgafos168, Irganox B225, and Chimassorb 944 were selected. Then, formulations based on different content of antioxidant were prepared. The samples were crosslinked by exposure to electron beam irradiation. To assess the thermal oxidation stability of samples, oxidation induction time (OIT) test was accomplished on both the irradiated and unirradiated specimens. Ageing tests were carried out in order to evaluate the thermal oxidation stability of irradiated X-LDPE. The results indicate that Irganox 1010 is the most effective antioxidant amongst the selected ones, concerning thermal oxidation stability of LDPE, before and after aging test.     

LiCoO2/LiNiO2/LiMn2O4材料安全性能的研究

随着锂离子电池的大型化,对电池安全性能的研究显得更为重要。锂离子电池的安全性有不同的测试方法,如进行过充试验和短路试验。在这些安全性试验中,以及在滥用中出现的安全性的问题,大多是由于电池内部温度升高,进而触发了大量放热的副反应[1],引起电池发生爆炸。本文通过对AA     

The influence of alkyl chain branching on smectic C formation

Fifty-five esters were prepared to show the effect of altering the point of alkyl chain branching on smectic C thermal stability. Six types of ester system were studied. Moving the position of alkyl chain branching away from the main molecular core enhanced smectic C thermal stability; after about the third carbon this effect was minimal. Extending the alkyl chain after the point of chain branching gradually lowered the smectic C thermal stability.     

Thermogravimetric analysis of thermal stability of poly(methyl methacrylate) films modified with photoinitiators

Films of poly (methyl methacrylate) (PMMA) were prepared by the addition of photoinitiator to the polymer. The influence of five organic photoinitiators on thermal stability of poly(methyl methacrylate) was studied by thermogravimetric analysis. Next, the PMMA films doped with these photoinitiators were UV irradiated and investigated in terms of changes in their thermal stability. It was found that the photoinitiators had accelerated thermal degradation of non-irradiated PMMA films due to the action of free radicals coming from the additives’ thermolysis. For UV-irradiated specimens, the effect of photoinitiator on PMMA thermal stability depended on the chemical structure of organic compound modifying the polymer. In general, thermal stability of irradiated samples was higher in the presence of additives. Thermal destruction of modified PMMA can be explained by the formation of resonance structures in aromatic photoinitiators and consumption of energy in dissipation processes.