Advanced Materials Research Vol. 900

Abstract: In order to improve thermal stability of Poly (Vinyl Chloride), a kind of thermal reversible cross-linking agents, the end cyclopentadienyl ethanethiol salts, sodium cyclopentadienyl ethyl mercaptan (CPD-C₂H₄SNa) was synthesized in this paper. The DSC results proved that the prepared CPD-C₂H₄SNa has obvious thermal reversible characteristics and the thermal reversible temperature was at 177 °C. The effects of cross-linking agent amount, cross-linking reactive time and temperature on flexible PVC compounds were evaluated through gel content testing. It was showed that the cross-linking agent with 3 Phr is optimum for PVC compounds. Moreover, both the cross-linking reactive time and temperature has effects on gel content of PVC compounds. The gel content of CPD-C₂H₄SNa cross-linked PVC compounds reaches maximum at 76% for 20 min at 160 °C.The static thermal stability of flexible PVC was measured according to congo red method. The results showed that the thermal stability of PVC compounds was enhanced with increasing cross-linking agent amount.

Abstract: The application of elastomeric coatings for improving the ability of already existing structures to dissipate the energy released by impact events has been investigated by many researchers in the past decade and is today an area of considerable interest. In recent years, polyurea has been successfully applied as a coating material for enhancing the impact protection of buildings and it has also demonstrated a considerable improvement of the survivability of metallic and non-metallic structures subjected to severe shock and impact loading conditions. Given its remarkable properties in terms of impact energy mitigation, life endurance and corrosion resistance, this material is currently of interest for its application in many fields of engineering. This paper presents and discusses the results of the mechanical characterization conducted on a polyurea elastomer fabricated following two different procedures and subjected to varying strain rates of compression load. The tests were conducted to verify the sensitivity of the material behavior to the varying loading conditions and to verify how the fabrication of the material in the laboratory can influence the test results.

Abstract: The research progresses about polyolefin catalyst systems in recent years are summarized. Focusing on the type and properties of the catalytic polymerization of the olefin polymerization catalyst, including typical Ziegler-Natta catalysts, metallocene catalysts and post-transition metal catalyst system. Then the new post-transition metal catalyst is introduced.

Abstract: Water-soluble phenolic resin was prepared using sodium hydroxide and ammonia as catalysts. The molecular structure of water-soluble phenolic with different molecular weight was studied by infrared spectrum and the mechanism was discussed. The results show that addition reaction and polycondensation synchronize in the reaction process, while addition reaction dominates in the early stage while polycondensation dominates in the later stage.

Abstract: 1-Bromohexadecane (BHD) and N-Methyl diethanol amine (MDEA) are applied as reactants, to synthesize the surfactant hexadecyl methyl dihydroxyethyl ammonium bromide (HMDAB). The product was analyzed by IR,¹H NMR and MS. The best reaction conditions are obtained by single feature experiment method: 110°C, molar ratio of reactants n (BHD):n (MDEA) = 1.1:1, reaction time 110min, and scale up in a 10 L reactor in similar condition. Finally the surface tension of 24.8 mN·m^-1 was identified, showing that the HMDAB has good solubilization, foaming and emulsifying properties.

Abstract: The PEEK/PEI/PES plastic alloys were processed by twin-screw extruder at 370°C separately with five mass ratios of 70/30/0, 70/25/5, 65/30/5, 60/30/10, The solvent resistance were investigated by experiments, their results showed that the concentrated H₂SO₄ resistance of alloy plates had been improved by alloying in 6h, the acetone resistance of mass ratio of 70/25/5 is preferably, increasing the content of PES, the acetone resistance becomes relatively stable, in addition, the chloroform and N, N-dimethyl formamide resistance of mass ratio of 70/25/5 is also preferably, and the polarity of the reagent has a limit influence on solvent resistance of plastics alloy materials.

Abstract: In the zinc hydrometallurgy process, iron is usually present in leach solutions and its elimination is a major operational problem. The first step of iron removal is iron oxidation by MnO₂, but this process have some disadvantages such as the cost is relatively high and decreased the current efficiency in the electro-winning stage. In this paper, a new iron oxidation process in zinc leaching solution by ozone oxidation was conducted and evaluated. The results showed that Fe²⁺ concentration decreased from 7.45 g/L to 0.51 g/L in 80min at pH 3. Oxidation of Fe²⁺ by O₃ is controlled by chemical reaction. O₃ dissolve rate, pH and initial iron concentration are key parameters for this process. Our finding indicated the potential application of O₃ oxidation in iron removal process of zinc hydrometallurgy.

Abstract: The corrosion behaviors of peak-aged Mg-7Gd-5Y-1Nd-0.5Zr alloys in CO₂ atmosphere under different relative humidity were investigated by OM, SEM. The weight loss rates, corrosion morphology and residual mechanical properties were also analyzed. The corrosion rates of specimens in CO₂ atmosphere at 70% relative humidity were highest than others. Relevancy of the influence factors included relative humidity and concentration of CO₂ were researched. The results show that relative humidity and concentration of CO₂ in the environment both played an important role in corrosion behaviors.

Abstract: The solidification behaviors of Sn-Zn alloy under rotating magnetic field (RMF) with different magnetic intensities and different rotating frequencies were investigated, and the velocity of the convection induced by RMF was calculated. It is found that the trunk length of the precipitated phase reduces with the increase of magnetic intensity and rotating frequency, and the precipitated-phase distribution is more uniform. The tangential rate increases with increasing the magnetic intensity and rotating frequency, and reaches the maximum value at about 0.55r0. All the results indicate that the solidification microstructure is attributed to the effect of RMF on the nucleation, temperature fluctuation and fluid convection in the solidification process. It predicts that RMF presents obvious advantages on controlling solidification microstructure.