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An oxide-alumina-silicacoating which would to improve the oxidation resistance of carbon fibers was prepared by sol-gel method. XRD and SEM were used to characterize the surface appearance and phase transition about the carbon fibers with oxide-alumina-silica coating. The oxidation resistance of carbon fibers was also analyzed with the DSC-TG and the isothermal oxidation experiment. It was shown that the antioxidant properties of the carbon fibers with oxide-alumina-silica coating improved significantly. The concentration of precursor sol had an influence on the coating of carbon fibers and the antioxidant properties of the carbon fibers with oxide alumina silica coating increased 300°C compared to uncoated ones.

A visible-light-driven photocatalyst Ag3PO4 was prepared by a novel precipitation- replacement process. The synthesized sample was cubic crystals with the bandgap of 2.16 eV. And most of the particles size was among 0.5~2 mm. The Ag3PO4 shows high photocatalytic activity for the degradation of methyl orange (MO) solution under the visible light (l>420 nm). The apparent ratio constant (kapp) value of Ag3PO4 was about 239 and 50 times that of P25 and C-TiO2, respectively.

A novel visible-light-active C-N-Cl-codoped TiO2 photocatalyst was prepared by a simple process. The as-prepared sample was characterized by XRD, XPS, and UV-Vis. The analysis results showed that the as-synthesized sample was anatase and possessed a narrow bad gap of 2.4 eV after the doping of carbon, nitrogen and chlorine. An obvious absorption for visible light was observed in the range of 400~700 nm for C-N-Cl-codoped TiO2. By degrading of methyl orange (MO) solution under the visible light (l>420 nm) irradiation, the synthesized photocatalyst showed 5 times photocatalytic activity than that of P25.

Mechanical properties have close relation with microstructure. Based on orientation of the molecule chain in fiber, they show a rapid increase in tensile properties. Nevertheless, block materials mainly gain rise of mechanical properties by blend or composite, it is hardly proposed on the self-reinforced materials by optimizing the microstructure. In this work, the structure and tensile properties of polypropylene (PP), treated at 105°C for 5min under different pressure, were studied with microscopy, differential scanning calorimetry (DSC). The variety of supra-structure that the spherulite deforms into ellipse even fractures piece in the pressure field adds to the mechanical properties. The orderliness of crystal increases with the pressure, and Tm is increased slightly from the original level.

An approach which formed sheet structure through plane compression processing in the bulk of polymer (polypropylene (PP)) was suggested and the strengthening mechanism was presented based on a series of experiment. The variety of super-molecular structure that the spherulite deformed into ellipse even fractures piece in the pressure field helped to increase the tensile performance. In the polar reign of spherulite, the lamellae underwent a slight deformation, and the lamellae broke into fraction and then slid each other along the flow direction in the equatorial region. Finally, the lamellae in the sample aligned along the flow direction, and the sheet structure which was packed each other by lamellae was built up by plane compression processing.

Mechanical properties have close relation with microstructure. Based on orientation of the molecule chain in fiber, they show a rapid increase in tensile properties. Nevertheless, block materials mainly gain rise of mechanical properties by blend or composite, it is hardly proposed on the self-reinforced materials by optimizing the microstructure. In this paper, a strengthening of PP was gained by uniaxial compression through small deformation of spherulite. A series of measurements were applied, including tensile test, polarizing optical microscope (POM) and differential scanning calorimeter (DSC). The results show that the tensile properties of polypropylene (PP) have a rapid rise. POM suggestes that the spherulite has deformed into ellipsoid even belt along the orientation of sample of PP, which plays an important role in self-reinforcing of PP. And the initial melt point displayed by DSC slightly decreases because of the partial ruptures of crystal phase.

In this study a solution-blend method is adopted to prepare conductive polyvinyl alcohol (PVA) and polyaniline doped with dodecyl benzene sulfonic acid (PVA/PANI-DBSA) blend films. Emeraldine base (EB)-type polyaniline (PANI) is dissolved in N-methyl-2-pyrrolidinone (NMP) and then blended with PVA/dodecyl benzene sulfonic acid (DBSA) solution by various amounts. The morphological structures and characterized of the films were observed via scanning electronic microscopy (SEM), thermogravimetric analysis (TGA) and X-ray powder diffraction (XRD). Electrical properties of the blends were characterized by means of electrical conductivity measurements. It is found that the electrical conductivity and the thermal degradation onset temperature of the PVA/PANI-DBSA blend film are increased as the amount of PANI-DBSA is increased.

The effects of the copolymerization system on the monomer reactivity ratios for a copolymer of acrylonitrile with N-vinylpyrrolidone was studied for contrast. The values of the monomer reactivity ratios were calculated by the Kelen–Tudos method. The reactivity ratios in the aqueous suspension polymerization system were similar to those in the solution polymerization system at polymerization conversions of less than 6% [reactivity ratio of acrylonitrile (rAN) = 0.438 ± 0.015, reactivity ratio of N-vinylpyrrolidone (rN-VP) = 2.28 ± 0.02]. As conversion of more than 12%, the changes in the monomer reactivity ratios became less prominent (rAN = 0.651, rN-VP = 1.98). In the water-rich reaction medium [H2O/dimethylsulfoxide (DMSO) > 60/40], the monomer reactivity ratios were approximately equivalent to those in the aqueous suspension polymerization system. In the DMSO-rich reaction medium (DMSO/H2O > 60/40), the reactivity ratios were similar to those in the solution polymerization system. With an increase in the polarity of the solvent, the values of the reaction ratios both decreased. The values of the reaction ratios gradually tended toward 1 with increasing copolymerization temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 422–425, 2003

Free-radical solution copolymerization of itaconic acid and acrylonitrile was carried out in DMSO using azodiisobutyronitrile as an initiator, changing the feed rate of itaconic acid. The resulting polymerization solution was spun to form polyacrylonitrile (PAN) precursors of carbon fibers. The precursors were treated with a CoSO 4 aqueous solution on-line. The structure and properties of untreated and treated PAN precursors and the resultant carbon fibers were characterized by SEM and TEM, a stabilization process, etc. It is suggested that CoSO 4 acts as a catalyst in the formation of a ladder structure and reduces the temperature of cyclization, and the carbon fibers developed from treated PAN fibers showed improvement in the tensile strength and the Young's modulus.

Direct melt/solid polycondensation of lactic acid (LA) was carried out to obtain high molecular weight poly(lactic acid) (PLA) by a process using various catalysts in the first-step melt polycondensation, and followed solid polycondensation by using p-toulenesulfonic acid monohydrate (TSA) as the catalyst in the second step. Effects of various catalysts and reaction temperature on the molecular weight and crystallinity of resulting PLA polymers were examined. It was shown that SnCl2·2H2O/TSA, SnCl2·2H2O/succinic anhydride, and SnCl2·2H2O/maleic anhydride binary catalysts should be effective binary catalysts to obtain high molecular weight PLA of more than 1.2 × 105. A conventional melt spinning method was used to spin PLA fibers, which displayed tensile strength of (382.76 ± 1.41) MPa and tensile modulus of (4.36 ± 0.07) GPa.