Metallurgical modifications and residual stress in welded steel with average carbon content

Welded joints of metallic materials are subject to residual stress and metallurgical transformations, in particular in the thermally affected zone (TAZ), with the possible formation, especially in steels with a high carbon content, of brittle structures and a loss of tenacity. The loss of tenacity in the TAZ facilitates the formation of cracks and possible brittle fracturing or failure, following the progressive propagation of the cracked zone. Moreover, residual stresses may cause premature failure in structural elements as they have an influence on the conditions of collapse, for example on account of instability of the compressed members. In this work, the order of magnitude of residual stress is estimated for a specific case, identifying by means of an empirical–experimental approach, the portion of material more susceptible to the formation of cold cracks under the combined effect of residual stress and brittleness of the microstructure.     

Hollow polymeric nanostructures—Synthesis, morphology and function

The development of reliable synthetic routes to polymeric nanostructures of well-defined composition, morphology and function is of scientific importance and technological interest. The generation of functional hollow polymeric nanostructures, hollow nanospheres and nanotubes in particular, can be achieved through direct and template-directed synthesis, core-shell precursors, and self-assembly of copolymers and polymer conjugates, as well as from dendrimers. The ability to prepare precursor macromolecules of well-defined structure and architecture has been substantially enhanced by recent advances in controlled radical polymerizations. The application and potential application of the hollow polymeric nanospheres and nanotubes as nanoreactors, and in diagnostics, encapsulation, controlled release, and other stimuli-responsive systems are also described.     

Polymeric pH-sensitive membranes—A review

Significant progress has been achieved in recent years in the field of pH-sensitive membranes. In many cases, pH-sensitive membranes are systems for which the flux, membrane pore size, and solute rejection ratio may be manipulated by changing the pH. This review summarizes recent developments covering the preparation, pH-responsive properties, and applications in various disciplines. The pH-sensitive groups and the evaluation parameters for pH-sensitive membranes are reviewed and discussed. A variety of preparation methodologies, including blending, pore-filling, surface-grafting, and surface-coating techniques are described, and some of their salient features are highlighted. The flat-sheet form and hollow-fiber form pH-sensitive membranes are reviewed. Membrane pore size change and electroviscous effect are discussed. Furthermore, future perspectives of pH-sensitive membranes are discussed.     

含氟乳液用于石膏保温材料的改性研究

为解决石膏材料易吸水的问题,采用核壳型乳液对传统石膏进行改性,改变石膏制品内表面的孔隙结构,降低石膏样品的吸水率,提高其抗压、抗折强度及孔隙率,减少石膏制品的导热率。研究了在不同添加量下,各添加剂对石膏密度、吸水率、力学性能(抗压强度、抗折强度)和导热率的影响,得到的最佳配比为:氟壳层乳液含量为5%,减水剂为总量的0.5%,缓凝剂的取量为0.2%时,所制备的石膏防水效果为最佳。     

（MMA／PMOE）共聚物交联改性研究

分别采用交联剂N,N′-亚甲基双丙烯酰胺(MBA)、二甲基丙烯酸乙二酯(EGDMA)对[甲基丙烯酸甲酯(MMA)/磷酸甲基丙烯酰氧乙基酯(PMOE)]共聚物进行改性,研究了改性材料的弯曲性能、维卡软化温度及吸水性。结果表明,(MMA/PMOE)共聚物经交联改性后材料的弯曲强度随着交联剂含量的增加而先提高后降低,维卡软化温度随着交联剂含量的增加而先升高后降低,以EGDMA为交联剂时材料的吸水率较低,EGDMA的加入并不影响(MMA/PMOE)共聚物作为特殊光学功能材料的应用。     

MMA涂料氧阻聚问题解决方案探讨

研究氧阻聚的机理、抑制或消除氧阻聚的方法与措施对提高MMA涂料产品质量有着重要的意义。本文分析了MMA涂料固化过程发生氧阻聚的机理,并介绍了隔绝氧气、添加氧清除剂或者链转移剂、引入气干型基团抑制氧敏感性、增加辅助成膜体系等抑制或消除氧阻聚的方法与措施。