有机高分子吸湿材料的吸附模型与机理

选聚丙烯酸钠(PAA)、聚丙烯酰胺(PAM)、丙烯酸-甲基丙烯酸共聚物P(AA-MA)、丙烯酸-丙烯酰胺共聚物P(AA-AM)、丙烯酸-甲基丙烯酸-丙烯酰胺共聚物P(AA-AM-MA),系统研究其吸湿过程和机理。吸湿性能的测试结果表明,硅胶和分子筛10 h内便饱和,有机高分子吸湿材料仍能持久吸湿,其饱和吸湿容量比硅胶提高至少6%以上,比分子筛提高至少50%以上,吸湿速率快于硅胶和分子筛。吸附动力学实验表明,有机高分子吸湿材料的吸湿主要遵循准二级动力学模型,吸湿率受湿度和高分子树脂自身的吸附性能影响。Freundlich吸附等温模型证实有机高分子吸湿材料吸湿并非单层吸附,而是物理吸附和化学吸附同时发生,且多以化学吸附为主。热力学分析得该吸湿过程为吸热反应且可自发进行。     

温敏型聚合物P(NIPAM-co-AAc)制备过程中单体竞聚率的测定

以过硫酸铵为引发剂,采用半间歇式无皂乳液聚合法合成了P(NIPAM-co-AAc)共聚物,采用化学分析法测定了不同单体配比下共聚物的组成,采用FR法、KT法及YBR计算法得到单体竞聚率。结果表明,异丙基丙烯酰胺与丙烯酸共聚的单体竞聚率分别为0.4416和0.2558,两种单体都倾向于与另一种单体聚合形成交替共聚物。     

聚丙烯酸-甲基丙烯酸-丙烯酰胺P(AA-MA-AM)三元共聚物的合成及其吸湿性能研究

以丙烯酸、丙烯酰胺和甲基丙烯酸为单体,N,N’-亚甲基双丙烯酰胺为交联剂,过硫酸钾为引发剂制备P(AA-AM-MA)高分子吸湿材料。系统研究单体浓度、单体配比等因素对其吸湿性能影响。根据正交实验,P(AA-AM-MA)最高吸湿率达0.95g/g。应用Sigma Stat 3.5进行多元线性回归分析得各因素与吸湿率的数学关联式,吸湿量直观分析表明,六因素影响吸湿性的主次顺序:脲含量>中和度>单体浓度>单体配比>交联剂浓度>引发剂浓度。     

不同结构高吸水树脂的制备与性能研究

采用水溶液聚合法,以丙烯酸、丙烯酰胺和2-丙烯酰胺基-甲基丙磺酸为反应单体,制备了3种高吸水树脂聚丙烯酸-丙烯酰胺(P(AA-AM))、聚丙烯酸-2-丙烯酰胺基-甲基丙磺酸(P(AA-AMPS))和聚丙烯酸-丙烯酰胺-2-丙烯酰胺基-甲基丙磺酸(P(AA-AM-AMPS)),系统考察了反应条件对高吸水树脂吸水和吸盐水性能的影响,并研究了3种高吸水树脂在不同浓度的KCl、CaCl2和FeCl3中的吸水性能。结果表明:反应条件对不同高吸水树脂吸水性能的影响具有相同的趋势,但不同高吸水树脂的最佳反应条件不相同,P(AA-AM)、P(AA-AMPS)和P(AA-AMAMPS)的最佳反应条件分别为:中和度75%、65%和80%;交联剂用量都为单体总质量的0.02%;引发剂用量为单体总质量的0.20%、0.24%和0.20%;不同高吸水树脂受离子溶液的影响程度不同,P(AA-AM)CaCl2>KCl。     

光敏引发AM/DAC共聚的竞聚率测定和序列分布

以丙烯酰胺(AM)和丙烯酰氧乙基三甲基氯化铵(DAC)为单体,2,2’-偶氮二异丁基脒盐酸盐(V-50)为光敏引发剂,在紫外光照射下进行水溶液聚合,采用Fineman-Ross、Kelen-Tudos及Yezrielev-Brokhina-Roskin法计算了单体竞聚率,得出光敏引发条件下,AM和DAC的竞聚率分别为2.2784和0.3836。分析了单体组成、共聚物瞬时组成随转化率变化的关系及共聚物主链的序列长度分布,得出采用AM起始物质的量比为0.8且总转化率在80%以下的合成工艺条件,可得到组成相对均一的AM/DAC共聚物。运用差示扫描量热仪对共聚物结构进行分析表征,表明所得聚合物是AM/DAC共聚物。     

丙烯酸-甲基丙烯酸共聚物的合成和吸湿性能

采用甲基丙烯酸(MAA)、丙烯酸(AA)为聚合单体,以亚硫酸氢钠-过硫酸铵为引发剂,采用水溶液聚合法制备了聚丙烯酸-甲基丙烯酸P(AA-MAA).系统地研究了单体浓度、单体配比、反应温度等各项聚合条件对聚合物吸湿性能的影响.在T=20℃、RH=90%条件下,与传统的硅胶、分子筛等吸湿材料的吸湿性能进行了对比.结果表明,硅胶和分子筛在10h内已经逼近吸湿平衡点,而P(AA-MAA)的吸湿率明显＞80%且仍未达到其最大吸湿容量.在吸湿性能测试的各个阶段,P(AA-MAA)的吸湿率是它们的5倍以上,明显优于传统的硅胶和分子筛.红外光谱分析证实了P(AA-MAA)共聚物的生成.     

紫外光敏引发丙烯酰胺/甲基丙烯酰氧乙基三甲基氯化铵共聚反应的动力学

单体丙烯酰胺(AM)和甲基丙烯酰氧乙基三甲基氯化铵(DMC)通过2,2’-偶氮(2-脒基丙烷)二氢氯化物(V-50)引发,在紫外光的作用下合成P(AM-co-DMC)共聚物。通过毛细管膨胀计法测定了其反应动力学。随着单体浓度、引发剂浓度、反应温度的升高,反应速率也随之增加。在控制低转化率的条件下,以Fineman-Ross、Kelen-Tudos及YezrielevBrokhina-Roskin法计算了单体竞聚率。得出了在紫外光与引发剂共同作用下,AM和DMC共聚单体的反应级数为2.2502,引发剂的反应级数为0.5032,反应活化能为38.1920kJ/mol,AM和DMC的竞聚率分别为2.3398和0.2849。     

丙烯酰胺与顺酐的共聚合反应及其产物的特性研究

考察了丙烯酰胺与顺丁烯二酸酐的共聚反应的条件,测定了单体的竞聚率。用ＩＲ、ＳＥＭ对共聚物的结构进行了表征,研究了其结构与性能的关系,得到了单体转化率高,性能好的吸水性材料。     

不同聚合方法下p(AM/NaAMPS)聚合物微观结构的研究

采用溶液聚合和反相微乳液聚合方法对丙烯酰胺(AM)和2-丙烯酰胺基-2-甲基丙磺酸钠(NaAMPS)在较低单体浓度下进行共聚。计算得出两种方法中单体AM、NaAMPS的竞聚率;溶液中r_(AM)=0.30,r_(MADQUAT)=1.31;微乳液中r_(AM)=0.63,r_(MADQUAT)=1.12。并用测得的竞聚率数据,通过计算机程序计算共聚物的瞬时组成、平均组成,研究在溶液和反相微乳液中合成共聚物的组成及序列分布的不同,研究结果表明微乳液聚合得到的聚合物的平均组成更均一     

聚丙烯酰胺及其多孔材料吸湿性功能研究

以丙烯酰胺(AM)为单体,N,N’-亚甲基双丙烯酰胺为交联剂,亚硫酸钠-过硫酸铵为引发剂,采用水溶液聚合法制备聚丙烯酰胺(PAM)吸湿材料。系统研究了单体浓度、交联剂用量和水解度等聚合条件对其吸湿性能的影响。吸湿实验表明,PAM的吸湿性能优于传统的无机吸湿材料硅胶和分子筛。采用聚乙二醇(PEG)、碳酸钙(CaCO3)两种致孔剂合成多孔PAM,并与PAM的吸湿性能进行对比。实验结果知PAM/PEG的吸湿速率比PAM提高50%以上,吸湿容量也显著提高;而PAM/CaCO3的吸湿效果并不理想。热失重分析TGA得出PAM/PEG比PAM的热稳定性稍稍降低,而PAM/CaCO3的热稳定性则稍稍提高。     

热交换器的分类及优缺点分析

热交换器是将不同温度介质之间的热量通过热传导的形式,由高温介质传递给低温介质,使介质达到生产所需温度的工艺设备,也可作为一种节能设备使用.通过对不同热交换器的结构分析,总结不同热交换器的优缺点、适用环境,为生产工艺设计人员及设备制造单位在选择可降低能耗、提高效率的设备上提供参考.     

聚苯胺及其复合物的制备和结构及形貌分析

通过化学氧化法分别制备盐酸,盐酸和十二烷基苯磺酸,碳纳米管(MWNTs-COOH)掺杂的聚苯胺,利用红外光谱,紫外光谱,扫描电子显微镜和透射电子显微镜对所制备聚苯胺的结构和形貌进行分析。分析不同掺杂物对聚苯胺的结构和形貌的影响;同时研究了超声波作用对聚苯胺形貌以及聚苯胺包裹MWNTs-COOH情况的影响。     

Modelling and computation of curing and damage of thermosets

The curing of thermosets is a complex process involving the transition from a fluid into a (visco-) elastic solid. This phase transition comes along with an increase in stiffness and a volume shrinkage of the polymer. The latter may lead to severe residual strains and stresses, which in turn can cause damage in the final, usually quasi-brittle material. In this contribution a constitutive model is developed which takes into account the curing of a thermosetting material together with the process-induced damage as resulting from curing shrinkage. The curing of the material is governed by a phenomenological hypoelastic constitutive equation which includes temporal evolutions for stiffness and volume shrinkage. Thermal and viscous effects are neglected in the present study. An isotropic gradient-enhanced damage model is adapted to describe the damage evolution. The curing-damage model is implemented into a finite element code and numerical examples for thermosetting materials demonstrate that the proposed model is capable to predict cure-induced damage in thermosets.     

Thermodynamic similarity and prediction of the properties and characteristics of substances and processes

Principles of the theory of thermodynamic similarity are considered in application to all aggregate states of a substance, including phase transitions, and to the change in dissipative structures in open systems.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 5, pp. 709–716, November, 1987.     

Mechanisms of Corosion and Oxidation of Metals and Alloys

Selected topics in field of the study of the mechanisms of corrosion and of oxidation of metals or alloys are presented. The first part reports a new model for the mechanism of the breakaway oxidation of ferritic stainless steels in water vapour. The second part is devoted to the physico‐chemical aspects of oxidation and presents experimental methods useful in the kinetic modelling applied to two alloys, the zircalloy‐4 and an AlMg5 % in the liquid state. In the third part the physical and numerical modelling of the stress corrosion cracking behaviour in face‐centered cubic (fcc) alloys is detailed, which enables the study of the influence of macroscopic parameters (such as the temperature or hydrogen activity) on the fracture process.     

碳化硼陶瓷增韧补强和致密化研究现状及其展望

碳化硼陶瓷具有极高的硬度,然而其低韧性、低抗弯强度、难以致密化限制了它的广泛应用.已有一些研究集中于碳化硼陶瓷增韧补强和致密化,对这一方面国内外研究进展进行了归纳与评述,阐明各种增韧补强和致密化方法的优缺点,提出碳化硼陶瓷增韧补强和致密化研究值得发展的一些方向.     

Measurement and analysis of elastic and anelastic properties of alumina and silicon carbide

Measurements of dynamic Young's modulus, E, and damping as a function of temperature, T, were made for alumina and silicon carbide. The Young's modulus data were compared with some from the literature, and analysed in terms of a theoretical framework relating the Debye temperature, θD, with the elastic constants. For both materials this analysis yielded a ratio T₀/θ_D which was near 0.4, where T₀ is an empirical fitting constant for the plot of (E(0)−E)/T versus 1/T (E(0) is the value of E at 0 K). The analysis of the damping data in terms of an Arrhenius type dependence led to effective activation energies near kT, where k is Boltzmann's constant. This revised version was published online in November 2006 with corrections to the Cover Date.     

Preparation and characterization of phosphate and arsenate apatites of strontium and their solid solutions

Samples of phosphate and arsenate apatites of strontium and six of their solid solutions, spread over the entire compositional range, were prepared by a wet method. They were characterized by chemical, X-ray, electron microscopic and infrared analyses. The validity of Vegard's law established the homogeneity of the solid solutions.     

检定和校准证书的异同与应用

本文介绍了检定和校准以及证书的两点相同、五点不同之处,说明了对检定证书和校准证书的正确应用。