Advanced Materials Research Vols. 11-12

Abstract: Thiirane is usually synthesized by epoxy resin, and there are considerable content of epoxy mixed in thiirane because of the poor yields. In this article, a novel separation method was used to get pure episulfide compound and epoxy compound from thiirane/epoxy resin synthesized in our lab. Furthermore, the perfect 1H NMR spectra of pure episulfide compound and epoxide compound were obtained. The quantitative analysis of content of epoxy groups in thiirane/epoxy resin was performed by using FTIR and was testified by 1H NMR. It was found that the analytical results of the conversion of epoxy groups by the two methods above coincided with each other well.

Abstract: The microstructure of the polyacrylonitrile (PAN) precursors can strongly affect the structure of the carbon fibers which determine the final mechanical properties of carbon fibers. The orientation factors ( n f
) of PAN precursors under different draw ratios were characterized by the birefringence (
n f ), which was obtained through polarized microscopy. The results show that the increasing of the draw ratio may enhance the degree of orientation, which can correspondingly improve the mechanical properties. However the increasing speed of the orientation factor slows down as the draw ratio reached to 8.

Abstract: Low molecular weight poly(butylene adipate) (PBA) was synthesized by melt polycondensation. The chain extension of the prepolymers was carried out using 2,2’-(1,4-phenylene)-bis(2-oxazoline) (PBOX) as chain-extender. The influencing factors including reaction temperature, oxazoline/-COOH molar ratio, and the molecular weight of prepolymers were studied. At the optimal chain-extending condition, PBA with Mn of 38583 and Mw of 125497 was prepared. The structure of the chain-extended PBA was also characterized by the FTIR and 1H NMR.

Abstract: Hydrogenation of neoprene (CR) latex was carried out by utilization of diimide with boric acid as a catalyst. Various hydrogenation conditions were studied and the hydrogenation degree could reach 48.1%. The most effective ratio of hydrogen peroxide/hydrazine hydrate was 0.8. The hydrogenation degree increased with increasing the temperature, the amount of boric acid and hydrazine hydrate. However, it decreased as prolonging the reaction time. The gel content was also investigated. Microstructure of hydrogenated neoprene (HCR) was characterized by IR and 1HNMR.

Abstract: A novel phosphazene cyclomatrix network polymer was synthesized via nucleophilic displacement of activated nitro groups of tri(4-nitrophenoxy)tri(phenoxy) cyclotriphosphazene with the hydroxyls of bisphenol A. Then, thermal properties of the polymer was investigated using dynamic thermogravimetric analysis (TGA) in air, pyrolysis and combustion experiments. According to the relation among the pyrolysis residue (CR) at 850°C, the char-forming tendency (CFT) of every structural unit in polymer and the limiting oxygen index (LOI), CFT of the structural unit (-P=N-)3 and the LOI of the polymer were calculated as 35.04 and 34.3 respectively, which provided theoretical parameter for designing the cyclomatrix- or cyclo- phosphazene polymers with highly thermal and flame-retardant properties.

Abstract: In this paper, the aging of an epoxy adhesive which is used to aluminum- aluminum composite joints in medium was studied by infrared spectroscopy (IR), scan electronic microscope (SEM) and shear strength test. In salt water, Na+ and Cl- can accelerate hydrolyzation of the adhesive and enhance water ingress ability in the adhesive. Shear strength tests indicate that the durability of the adhesive in salt water aging is lower than that in water. IR spectroscopy and SEM of the adhesive indicates that the salt water diffusion speed in the epoxy adhesive/ aluminumaluminum composite joints depends on not only temperature but also salt water aging time, and high temperature can accelerate the degradation of the adhesive in salt water.

Abstract: The rheological properties and viscoelasticity of PAN/DMSO solutions were studied by means of revolving rheometer under the scan modes of steady shear rate and dynamic frequency. The effects of shear rate and temperature of PAN/DMSO solution on its Non-Newtonian viscous index, zero shear viscosity, activation energy of viscous flow and modulus of the solutions were studied. It was found that PAN/DMSO solution is a kind of pseudoplastic fluid. And the more temperature of solution, the less Non-Newtonian viscous index at steady experiment curve, the less the loss modulus and storage modulus of solution at dynamics experiment curve. In addition, the liquidity and spinnability of the solution also increased when the temperature went up.

Abstract: Lithium rechargeable battery is a new type of battery developed in recent years. The studies on this system are naturally focused on the cathode material. The cathode material with conducting skeleton and energy-storing side lines was reported and a novel material carbyne polysulfide was studied. This paper was to explore a convenient approach for preparing carbyne polysulfide. The products obtained by co-heating polyvinylidene chloride(PVDC) and pulverized sulfur in ammonia environment was characterized by DSC /TG, IR, Raman spectrums and elemental analysis. And the product had been proved to have a sp2 hybride carbon skeleton with polysulfide attached on it, which resembles the theoretical structure of carbyne polysulfide. The material with favorable sulfur contents exhibited high specific capacity up to 705 mAh/g in the initial cycle and a stable reversible capacity approximately 420 mAh/g.

Abstract: Precipitate microstructures in Mg-2.0Gd-1.2Y-0.75Zn-0.2Zr alloy were investigated and the characteristic and mechanism of microstructure evolution in the alloy were discussed. Specific long-period 14H ordered stacking structure was formed at grain boundary of Mg matrix crystals by solution heat treatment at 773K and metastable β’ phase was formed during subsequent aging treatment at 498K in the Zn-added Mg-Gd-Y alloys. These structure and phase exist simultaneously at the peak-aged condition in the microstructure. Precipitate free zone (PFZ) of β’ phase does not exist at an interface between a 14H structure and Mg matrix inside the grain, however, PFZ exist near the edge of 14H structure at grain boundary. These results strongly suggest that high diffusion rate of solute atoms at grain boundary promotes the nucleation and growth of 14H structure.