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 .     

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．     

电感耦合等离子体发射光谱法测定铀钼合金中钼EI北大核心CSCD

采用电感耦合等离子体发射光谱(ICP-AES)法测定铀钼合金中钼含量,考察了合金溶解、溶液中钼水解以及铀钼萃取分离等条件。确定溶液中H+浓度在3 mol/L时,铀钼合金在24 h内不会发生水解。选择发射波长202.031 nm为分析谱线。铀钼合金中钼含量在10~160μg/mL范围内呈线性关系,线性方程为y=3614.4x-1978,相关系数为0.9998,方法相对标准偏差小于1%。     

12-钼磷酸中水的存在状态及其热稳定性的质谱法研究

本文运用程序升温脱水-质谱计检测(TPD MS)和红外光谱测定(IR)法研究了12-钼磷酸(PMA)中水的存在状态及其热稳定性. 解迭了PMA的TPD MS谱, 发现PMA中存在有结合能量各异的7种水峰. 讨论了PMA中各种水的结合强度及其对Keggin结构稳定性的影响。     

高温熔融–电感耦合等离子体发射光谱法测定钼废渣中钼

通过优化高温熔融试剂和温度与分析谱线,建立了高温熔融-电感耦合等离子体发射光谱法快速测定钼废渣中钼含量的方法.准确称取0.10 g干燥钼废渣粉末,用2.5 g碳酸钠和1.0 g四硼酸钠混合熔剂于铂金坩埚中经920℃高温熔融15 min,以20 mL硝酸浸取并用水定容至200 mL.选择Mo 202.032 nm为分析谱...     

51VNMR研究磷钼钒系杂多酸的热稳定性

用NMR及IR、TG-DTA等手段研究具有Keggin结构的磷钼钒系杂多酸在空气中的热稳定性。实验结果表明:合成的杂多酸在各个Keggin单元中具有不同的钒含量。样品的热稳定性与其钒含量有关.随着钒含量的增加,keggin结构的热稳定性逐渐降低,但H_4PMo_(11)V_1O_(40)具有比H_3PMo_(12)O_(40)还要高的热稳定性。由于钒的取代,钼钒磷酸的热分解过程不同于钼磷酸。失去结构水使Keggin结构遭到破坏,但在室温下与水重新作用可使钼钒磷酸的Keggin结构恢复。     

杂多化合物催化性能的研究——第四周期过渡金属钼磷三元杂多化合物的合成及表征

本文用改进的方法成功地合成了以第四周期二价过渡金属离子取代12-钼磷杂多酸中的一个钼,并保持Keggin结构的五个新化合物:Na_5[PZ(H_2O)Mo_(11)O_(39)·5H_2O,其中Z分别为Mn、Co、Ni、Cu、Zn,并利用红外光谱及热分析等手段对合成产物的结构及热稳定性作了系统的研究,结果表明,合成产物与12-钼磷杂多化合物具有类似的结构,但合成产物的热稳定性明显低于12-钼磷杂多化合物。     

改进的钼酸铅重量法测定钼精矿中钼

钼精矿中钼的测定,部颁标准推荐用氧化性酸溶解样品,氨水分离铁的氧化物沉淀,滤液中钼用钼酸铅重量法测定.然后,碱熔酸不溶残渣,水浸熔块,用比色法测滤液中钼.两次测定之和为钼精矿中钼的含量.如此操作,手续较繁锁.本工作所改进的方法是用碳酸钠-硼酸钠于高温熔解,酸化熔块,加氨水除杂,用钼酸铅重量法测定滤液中钼.钼精矿中钼的含量测定,一次完成,手续得到了简化,节省了时间,降低了试剂、能源消耗,而所得结果与标准法测得值非常一致.1 试剂混合熔剂:碳酸钠与硼酸钠以2:1质量比在研钵中研匀     

钼和钨在氧化铝表面的分散特性

以低温(873 K)和高温(1173 K)焙烧的氧化铝为载体制备了一系列负载钼和/或钨催化剂,结合X射线衍射、红外光谱、氨溶实验、氢气程序升温还原表征以及 4,6-二甲基二苯并噻吩加氢脱硫性能评价,研究了钼和钨在氧化铝表面分散的特性. 结果发现,钼倾向与碱性羟基和中性羟基作用,而钨优先与中性羟基作用. 钼的引入促进了钨的还原. 氨溶后残余的钼钨物种虽然与载体的作用较强,但经焙烧后它们在载体表面重新再分散,达到新的热力学或能量平衡.     

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。     

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.     

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.     

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．     

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.     

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.     

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.     

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     

Thermal stability and ageing properties of sulphur and gamma radiation vulcanized natural rubber (NR) and carboxylated styrene butadiene rubber (XSBR) latices and their blends

The thermal stability of natural rubber (NR) and carboxylated styrene butadiene rubber (XSBR) latices and their blends was studied by thermogravimetric methods. Ageing characteristics of these latex blends were studied by applying hot air oven thermal ageing for seven days at 70 °C. The mechanical properties of the aged samples were studied. Thermal degradation and ageing properties of these individual latices and their blends were investigated with special reference to blend ratio and vulcanization techniques. As the XSBR content in the blends increased their thermal stability was also found to increase. Among sulphur and radiation-vulcanized samples, radiation cured possesses higher thermal stability due to the higher thermal stability of carbon-carbon crosslinks. DTG curves were used for the determination of different stages involved in the degradation. Activation energy for degradation was determined from Coats-Redfern plot. The properties of aged samples were found to decrease due to chain depletion. However, the moduli of XSBR and NR/XSBR blends were found to increase owing to the formation of crosslinks upon ageing.     

含三芳胺聚西夫碱空穴输送材料结晶性、热稳定性和传输性研究

采用缩聚反应合成了两种未见报道的含三芳胺聚西夫碱空穴输送材料（PC－1，PC－2），该材料具有非晶态结构、良好的热稳定性和空穴传输性，用IR，UV－Vis，^1H NMR对所合成的聚合物进行了表征；用XRD技术对在不同溶剂中得到的聚合物的结晶现象进行了研究；用热重分析（TG）和差热分析（DTA）技术对材料在氮气中的热稳定性进行了研究，并进一步用量子化学从头算方法，对电离热（Ip）和前线轨道能进行了计算，结果表明，用二甲苯为溶剂得到的聚合物无结晶现象，PC－1，PC－2均具有良好的热稳定性和空穴传输性。