Possible use of methylbenzenes as electrolyte additives for improving the overcharge tolerances of Li-ion batteries

Based on the voltammetric behaviour of a series of methyl-substituted benzenes in 1M LiPF₆/EC-DMC electrolyte, xylene was selected and tested as an electrolyte additive for overcharge protection of Li-ion batteries. From the overcharge curves, CV behaviour and SEM observations of the cells in the presence of xylene, it was found that the additive can polymerize at the overcharged voltage to form a dense layer of isolating polymer film at the cathode surface, which blocks off further oxidation of the electroactive material and electrolyte and, therefore, improves the overcharge tolerance of the Li-ion battery. In addition, the xylene additive has shown only a slight influence on the cycling behaviour.     

Preparation,characterization, and adsorption properties for metal ions of a novel chelating resin containing sulfoxide and diethylene glycol

A novel chelating resin containing sulfoxide and diethylene glycol, poly{4‐vinylbenzyl‐[2‐2‐(hydroxyethyl)ethoxyl]sulfoxide} (PVESO) was synthesized using chloromethylated polystyrene (PS‐Cl) as material. Its structure was characterized by elemental analysis, infrared spectra, and scanning electron microscopy (SEM). The adsorption capacities of the resin for Hg²⁺, Ag⁺, Cu²⁺, Zn²⁺, and Pb²⁺ at various pH values were determined. The maximum adsorption capacities for Hg²⁺ and Ag⁺ were 1.56 and 0.75 mmol g^?1 respectively. The resin had high selectivity for Hg²⁺ and Ag⁺ over the pH range 1.0–7.0. The adsorption capacities for Hg²⁺ and Ag⁺ under competitive condition were also determined by batch experiment method. In addition, the adsorption kinetics of the resin towards Hg²⁺ at different temperatures was also investigated. The results showed that the adsorption rate was governed by film diffusion at 20°C and 25°C, by particle diffusion at 30°C and 35°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 6054–6059, 2006     

Biaxial orientation in LLDPE films: Comparison of infrared spectroscopy,X‐ray pole figures,and birefringence techniques

In this study, linear low‐density polyethylene films were produced using different processes (film blowing and biaxial orientation) and processing conditions. The orientation of the films was characterized in terms of their biaxial crystalline, amorphous, and global orientation factors using birefringence, tilted incidence polarized Fourier Transform Infrared Spectroscopy (FTIR), and X‐ray diffraction pole figures. Evaluation of a simplified FTIR procedure without the use of the tilted method for the determination of crystalline orientation factors proposed in the literature is also evaluated and assessed. The results indicate that FTIR overestimate the crystalline orientation factors, particularly for the crystalline a‐axis. Significant discrepancies are also observed for the b‐axis orientation, which may be due to an overlap of the amorphous phase contribution. Those differences are larger for films with low orientation, such as blown films. Amorphous phase orientation from FTIR depends on the band used and is not necessarily in agreement with that determined from the combination of X‐ray and birefringence. The simplified FTIR procedure is proven to be inadequate in the case of linear low‐density polyethylene blown films studied having a random lamellar crystalline morphology. POLYM. ENG. SCI. 46:1182–1189, 2006. © 2006 Society of Plastics Engineers.     

Influence of the components in the flow properties and physical aging of spray coating PVC plastisols

A study of the rheological properties and aging characteristics of 15 poly(vinyl chloride) (PVC) plastisols formulated for spray coating is made. The influence of the PVC type, plasticizer, filler, diluent, and thixotropic agent is analyzed and discussed in terms of the yield stress value, a shear thinning index, and an aging characterizing parameter.     

Influences of zinc oxide and an organic additive on the electrochemical behavior of pure aluminum in an alkaline solution

The corrosion behavior of pure aluminum in inhibited and uninhibited 4 MKOH was investigated by means of hydrogen collection, polarization curve measurement and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion of pure aluminum was greatly inhibited by the addition of ZnO and dimethyl amine epoxy propane (designated as DE). EIS and EDAX analyses revealed that ZnO produces its effect by depositing on the aluminum surface, which increases the overpotential of hydrogen evolution. It was also found that the addition of DE could greatly improve the deposition of zinc layers.     

Structure and properties of polyimide‐bonded magnets processed from prepolymers based on diacetyl derivatives of aromatic diamines and dianhydrides

We report a novel method of polyimide (PI) synthesis from prepolymers based on dianhydrides and diacetyl derivatives of aromatic diamines that facilitate the preparation of a melt processable mixture at 300 ± 10°C of the prepolymer and magnetic Nd‐Fe‐B alloy to provide PI‐bonded magnets with enhanced properties. It is shown that chemical structure of the prepolymers strongly influences viscosity behavior via crystallization of the oligoimide in the melt, leading to formation of PI with rigid‐rod like structure. This structural ordering of the prepolymers based on diacetyl derivative of diamine used in this study, if not controlled, leads to exponential increase of melt viscosity with time, making it practically impossible to prepare melt processable mixture of the magnetic particles and the PI prepolymers at elevated temperatures. The results obtained demonstrate that appropriate dianhydrides and diacetyl derivatives of diamines that do not lead to crystallization of oligoimides in prepolymer mixture can be used under controlled processing conditions to prepare melt‐processable PI‐bonded magnets containing rigid‐rod like PI structure that significantly increases thermal stability of the magnets. The temperature dependencies of the magnetic properties of the PI‐bonded magnets under conditions that they are likely to encounter during their service life were found to be remarkably similar to that of commercial thermoplastic magnets such as injection‐molded nylon magnets. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 478–485, 2006     

Zinc hydroxystannate and zinc stannate as flame‐retardant agents for flexible poly(vinyl chloride)

The flame‐retardant and smoke‐suppressant properties of inorganic tin compounds such as zinc hydroxystannate (ZHS) and zinc stannate (ZS) were investigated in a comparison with alumina trihydrate, magnesium hydroxide, and Sb₂O₃ through the limiting oxygen index test and smoke density test. The flame‐retardant mechanisms were studied through the char yield test, SEM, quantitative analysis, thermogravimetry and differential thermal analysis. The thermal degradation in air of flexible PVC treated with the above compounds was studied by thermal analysis from ambient temperature to 800°C. The results showed that tin compounds such as ZHS and ZS could be used as a highly effective flame retardant for flexible PVC, and it appears that the tin compound may exert its action in both the condensed and vapor phases, but mainly in condensed phases as a Lewis acid. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1469–1475, 2005     

Low-Temperature Dielectric Properties of Ceramic Potassium Tantalate (KTaO3)

Dielectric properties of KTaO₃ ceramic fabricated by both conventional sintering and sintering followed by isostatic hot pressing (HIP) were measured at T =4.2 to 300 K over a frequency range from 400 Hz to 4 MHz. The weak field response shows a faint peak near 10 K which has a clear relaxation character, as in high-purity single crystals. The general response is well reproduced by the Barrett function, but additional polarizability with relaxation character is also in evidence at higher temperatures. No dielectric hysteresis was observed at high fields for cycling frequencies down to 0.04 Hz anywhere in the temperature range.     

Photocross-linking of low-density polyethylene. III. Supermolecular structure studied by SALS

The supermolecular structure of photocross-linked polyethylene (XLPE) has been studied by small-angle light scattering (SALS). The data show that the spherulitic structure of XLPE gradually deteriorates with increasing degree of cross-linking and increasing irradiation temperature from well-developed spherulites to rodlike aggregates and disordered lamellar structures. A photocross-linked sample of PE has lower crystallinity, smaller crystallites, and smaller spherulites than does the original sample. At high degrees of cross-linking, the SALS patterns show little or no spherulitic structure. Results with photocross-linked polyethylene demonstrate that the overall effect of cross-linking on the morphological structure is similar to that of an increase in molecular weight of the polymer. © 1993 John Wiley & Sons, Inc.     

Photoinitiated crosslinking of ethylene‐vinyl acetate copolymers and characterization of related properties

Photoinitiated crosslinking of EVA in the presence of benzophenone (BP) as photoinitiator and triallyl isocyanurate (TAIC) as crosslinker and characterization of the related properties have been studied by gel determination, heat extension, DSC, DMTA, TGA, and mechanical measurements. The photoinitiated crosslinking efficiency of the EVA‐BP‐TAIC system and various factors affecting the crosslinking process, such as photoinitiator and crosslinker and their concentrations, irradiation temperature, and irradiation atmosphere were studied in detail and optimized by comparison of gel contents. The results show that the EVA samples with a thickness of 1 mm are readily crosslinked to a gel content of above 80% with 5 s UV‐irradiation under optimum conditions. The data from the heat extension and DSC show that the crosslinking density of photocrosslinked EVA increase and their crystallinities decrease with increasing the UV‐irradiation time. At the same time, photocrosslinking of EVA leads to a lowering of the melt temperature and a decrease of heat of fusion. The DMTA results show that photocrosslinking increases the amorphous phase and storage modulus of the crosslinked EVA, but does not change the glass transition temperature. The data from TGA and mechanical tests give evidence that the thermal stability and mechanical properties of photocrosslinked EVA samples are much better than those of the uncrosslinked EVA. POLYM. ENG. SCI., 47:1761–1767, 2007. © 2007 Society of Plastics Engineers