Morphology and mechanical properties of polyolefinic thermoplastic elastomer I. Characterization of deformation process

The structural origin of rubber elasticity in the polyolefinic thermoplastic elastomers composed of isotactic polypropylene (iPP) matrix and ethylene-propylene-diene rubber (EPDM) domains was investigated using scanning and transmission electron microscopes under uniaxial deformation and the computational analysis by a three dimensional finite element method. The rubber domains were dominantly deformed and elongated by accompanying localized yielding in iPP region between neighboring EPDM domains perpendicular to the stretching direction. The iPP region between adjacent EPDM domains in the stretching direction remained undeformed, suggesting that the undeformed iPP region plays the role in connecting rubber domains.     

马来酸酐接枝聚丙烯纤维的结构和性能研究

采用熔融纺丝法制备了马来酸酐(MAH)接枝聚丙烯纤维,考察了接枝纤维的力学性能和吸湿率以及马来酸酐的残留量。结果表明,马来酸酐接枝聚丙烯纤维的断裂强度比纯聚丙烯纤维的低,接枝率越高强度越低,断裂伸长率则相反;随着接枝率的增加,纤维的取向度也逐渐升高。与聚丙烯纤维相比,接枝聚丙烯纤维的吸湿率有了明显提高,在相同拉伸倍数下提高了3-5倍;MAH残留量相当于接枝率(0.73％)的3.7％,表明主要是接枝的马来酸酐改变了聚丙烯纤维的性质。     

40t/d PA6前聚合反应器设计简析

从设备与工艺两方面剖析了PA6生产前聚合反应器的设计。将反应器长径比例从原来的3:1改为10:1,并改进加热方式,优化结构设计,前聚合反应器设计为4段,各段间采用法兰连接,设计出生产能力40 t／d的前聚合反应器。     

氯乙烯聚合釜密封失效分析及技术改进

通过对氯乙烯聚合釜机械密封的失效分析 ,改进了该釜的密封结构 ,取得了良好的密封效果及经济效益     

Mechanical properties of high-strength concrete after fire

With compressive strength grade of C40, C60, and C70, respectively, normal-strength concrete (NSC) and high-strength concrete (HSC) were used to investigate compressive strength, splitting tensile strength, and bending strength after high temperature. The oil furnace is used in this study. Its temperature-time curve is close to standard curve, which conforms to Chinese standard GB/T 9978-1999. After being heated to temperatures of 200, 400, 600, 800, and 1000 °C, respectively, the mechanical properties of HSC were tested. The influence of temperature, water content, specimen size, strength grade, and temperature profiles on mechanical properties of HSC are discussed.     

Statistical Evaluation of Factors Affecting the Leaching Process of Waste Electrical and Electronic Equipment using Sodium Persulfate

Recycling of waste electrical and electronic equipment (WEEE) is important not only to reduce the amount of waste requiring treatment, but also to promote the recovery of valuable materials. Implementation of the European Directive on WEEE and recycling targets imposed in the European Union will require new processes to be developed and applied to recover metals from WEEE. This study aims to provide an alternative process for the dissolution of metals from WEEE which contains Cu and Zn based on our previous research. The effects of leaching parameters, such as temperature, Na₂S₂O₈ concentration, and leaching time, were separately investigated on leaching of copper, zinc, and brass (alloy composition ?35% zinc and 65% copper) in Na₂S₂O₈ solution (0.1, 0.2 and 0.3 M). Box–Behnken experimental design (BBD) method was used to determine the number and the condition of necessary leaching experiments. Statistical analysis of variance (ANOVA) was performed to see whether process parameters such as leaching time, temperature, and oxidant concentration are statistically significant or not on the leaching performance. Results show leaching time as the most influential factor in the dissolution process, for the first six models. Two extended models have been developed to optimize the parameters of the investigated process. In these models, we consider the metal composition as a model input next to the earlier investigated parameters. Optimal condition for maximum copper and zinc dissolution in Na₂S₂O₈ environment can be found for parameter values: temperature 45°C, oxidant concentration 0.1 M and leaching time 35 min.     

GRADIENT OF THE MECHANICAL MODULUS IN GLASS-EPOXY-METAL JOINTS AS MEASURED BY BRILLOUIN MICROSCOPY

The newly developed Brillouin microscopy is used for the first time to measure in situ the longitudinal elastic stiffness coefficient in the GHz-range inside of glass-epoxy-metal joints as a function of distance from the substrates. Interphases with a local variation of mechanical properties are quantitatively characterized. These interphases possess unexpected widths of tens to hundreds of microns. Inside the interphases, the spatial variation of the longitudinal stiffness coefficient depends on the type of substrate, on the curing conditions for the epoxy and probably on the distribution of internal stresses. The obtained spatial mechanical profiles provide valuable insight into the morphology-driven mechanics of the interphase, but additional information is needed for a full understanding of their physical and chemical origin. The presented results prove the sensitivity of the Brillouin microscopy; the elastic stiffness coefficients are detected with an accuracy in the subpercentage range. The spatial resolution is better than 10 µm.     

Effect of pigmentation on organic coating characteristics

The paper reviews the effects of pigmentation, i.e. type of pigment and pigment volume concentration, on organic coating characteristics, such as curing and film formation, mechanical properties, thermal expansion coefficient, glass transition temperature, stress development, physical ageing and water transport. The main families of pigments used in the fabrication of organic coatings and the effect of nanopigments incorporation in binders are also discussed.     

Brazing of ZrB2–SiC ceramic with amorphous CuTiNiZr filler

In the present work, amorphous CuTiZrNi foils with low melting point of 1133 K were synthesized using a melt-spinning method in argon atmosphere. A ZrB₂–SiC ultra high temperature ceramic was brazed at 1153–1253 K for 900 s. The wetting and spreading characteristics of amorphous alloy filler on the ceramic were studied with the sessile drop method. The reaction products between the ZrB₂–SiC ceramic and the CuTiZrNi filler were systematic studied by X-ray diffraction and scanning electron microscopy. Also, the formation process of interfacial product of joint was discussed. A maximum room temperature three-point bending strength of 210 MPa of the joint was obtained by reasonable processing. The high temperature strength of the joint was also studied, and the joint was found to exhibit a stable strength (240 MPa) at a high temperature of 873 K. The presence of refractory Ti₅Si₃ compound was believed to be contributed to the stable high temperature strength.     

Crystal structures and mechanical properties of M (Mg,Sr, Ba,La)xCa1−xB6 solid solution: A first principles study

First-principles calculations are performed in this work to study the effects of M (M=Mg, Sr, Ba, La) substitution in CaB₆. Both electronic structure and mechanical properties are examined. The current results indicate that the substitution of Ca by M atoms causes the lattice constants to scale linearly with the variation of x. The shear moduli of M_xCa_1−xB₆ are found to be related to the valence d-electron Mulliken charges in the lattice. The hardnesses of M (M=Mg, Ca, Sr, Ba, La)B₆ and their solid solution are calculated by analyzing the overlap populations of the B–B bonds in the solid solution system.