The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform

M Srinivasan - One of the best experts on this subject based on the ideXlab platform.

  • synthesis and characterization of Polyamideimides by direct polycondensation with triphenyl phosphite
    European Polymer Journal, 1993
    Co-Authors: D Venkatesan, M Srinivasan
    Abstract:

    Abstract Two diimido-dicarboxylic acids, bis-4-[N-(4-carboxy phthalimido)phenyl]sulphone(I) and bis-4,4′-[N,N′-(4-carboxy phthalimido)]azobenzene(II), were synthesized and aromatic Polyamideimides were obtained from them by direct polycondensation with various aromatic diamines using triphenyl phosphite. Since these polymers incorporate preformed imide groups, they did not pose the common problems encountered in imidization of polyamic acids. The polymers were characterized by inherent viscosity, i.r. spectra, elemental analysis, X-ray and thermal methods.

  • synthesis and characterisation of Polyamideimides from bis 4 trimellitimidophenyl sulfone
    Polymer International, 1992
    Co-Authors: D Venkatesan, M Srinivasan
    Abstract:

    Polyamideimides [COPh(CO) 2 N-PhSO 2 Ph-N(CO) 2 PhCONHArNH] n (Ar= PhOPh, PhPh, C 10 H 6 , C 5 H 3 N, PhN=NPh, PhCONHCO, PhOPhC(CH 3 ) 2 PhOPh, PhOPhSO 2 PhOPh) have been synthesised by the interaction of a number of aromatic diamines with an imidedicarboxylic acid. Since these polymers incorporated a preformed imide group, they did not pose the common problems encountered in imidisation of polyamic acids. They were synthesised by low temperature (<5 o C) polycondensation, in 75-92% yields and had viscosities in the range 0.18-0.39 dl/g and very high solubility in polar aprotic solvents

D Venkatesan - One of the best experts on this subject based on the ideXlab platform.

  • synthesis and characterization of Polyamideimides by direct polycondensation with triphenyl phosphite
    European Polymer Journal, 1993
    Co-Authors: D Venkatesan, M Srinivasan
    Abstract:

    Abstract Two diimido-dicarboxylic acids, bis-4-[N-(4-carboxy phthalimido)phenyl]sulphone(I) and bis-4,4′-[N,N′-(4-carboxy phthalimido)]azobenzene(II), were synthesized and aromatic Polyamideimides were obtained from them by direct polycondensation with various aromatic diamines using triphenyl phosphite. Since these polymers incorporate preformed imide groups, they did not pose the common problems encountered in imidization of polyamic acids. The polymers were characterized by inherent viscosity, i.r. spectra, elemental analysis, X-ray and thermal methods.

  • synthesis and characterisation of Polyamideimides from bis 4 trimellitimidophenyl sulfone
    Polymer International, 1992
    Co-Authors: D Venkatesan, M Srinivasan
    Abstract:

    Polyamideimides [COPh(CO) 2 N-PhSO 2 Ph-N(CO) 2 PhCONHArNH] n (Ar= PhOPh, PhPh, C 10 H 6 , C 5 H 3 N, PhN=NPh, PhCONHCO, PhOPhC(CH 3 ) 2 PhOPh, PhOPhSO 2 PhOPh) have been synthesised by the interaction of a number of aromatic diamines with an imidedicarboxylic acid. Since these polymers incorporated a preformed imide group, they did not pose the common problems encountered in imidisation of polyamic acids. They were synthesised by low temperature (<5 o C) polycondensation, in 75-92% yields and had viscosities in the range 0.18-0.39 dl/g and very high solubility in polar aprotic solvents

In Kyu Moon - One of the best experts on this subject based on the ideXlab platform.

  • second order nlo Polyamideimides based on functionalized stilbene derivatives direct polycondensation and characterization
    Polymer, 1998
    Co-Authors: In Kyu Moon
    Abstract:

    Abstract Polyamideimides having nonlinear optical (NLO)-active chromophores were synthesized by direct polycondensation of 4-[N,N′-bis(2-aminoethyl)amino]-4′-nitrostilbene (DANS-diamine) with oxy-bis[N-(4-phenylene)trimellitic imide] (BCI), N-(3-carboxyphenyl)-trimellitimide (BTI) and trimellitic anhydride chloride (TMAC). The direct polycondensation of NLO Polyamideimides without a curing step may ameliorate the optical property of NLO polymers by reducing the optical propagation loss. The resulting polymers were highly soluble in aprotic polar solvents such as DMF, DMAc, NMP, etc. The NLO Polyamideimides exhibited the inherent viscosity range of 0.14–0.33 dl g−1. Molecular structural characterization for the resulting polymers was achieved by 1H n.m.r., FTi.r. and u.v.-visible spectroscopies. The glass transition temperature for the resulting NLO Polyamideimides was in the range 142–224°C and they showed thermal stability up to 260°C. The polymer solutions could be spin coated onto indium—tin-oxide (ITO) glass or quartz disc substrates to form optical quality thin films. The electro-optic coefficients (r33) at the wavelength of 1.3 μm, measured by a simple reflection method, for polymer thin films poled around the glass transition temperature were in the range 1.9–7.4 pm V−1.

  • thermally stable 2nd order nlo Polyamideimides based on functionalized stilbene derivatives
    Molecular Crystals and Liquid Crystals, 1997
    Co-Authors: In Kyu Moon
    Abstract:

    Abstract The Polyamideimides having NLO-active chromophores were synthesized by the condensation polymerization of DANS-diamine with trimellitic acid chloride. The polymer was characterized by IR, NMR, UV, DSC, and TGA. The polymer was highly soluble in nonpolar aprotic solvents such as DMF, DMAc, NMP, etc. The polyme was easily spin-coated on a silicon wafer, indium-tinoxide (ITO) coated glass, quartz discs, and NaCl substrates, forming the good quality of thin films. The electro-optic coefficent of r33 at the wavelength of 1.3 μm for polymer thin films poled around the glass transition temperature of 142 °C measured by simple reflection method was 5.4 pm/V.

D.l. Schweickart - One of the best experts on this subject based on the ideXlab platform.

  • High temperature breakdown strength and voltage endurance characterization of nanofilled polyamideimide
    IEEE Transactions on Dielectrics and Electrical Insulation, 2012
    Co-Authors: Linda S. Schadler, A. M. Travelpiece, Christopher Calebrese, Keith J. Nelson, D.l. Schweickart
    Abstract:

    For high temperature wire enamel application, the dielectric properties of nanoscale silica and alumina filled polyamideimide were characterized as a function of filler loading, and temperature. It was found that although the dc breakdown strength improved for both composite systems, only the alumina also exhibited an increase in ac breakdown strength. In addition, the voltage endurance at elevated temperature in both a needle/plate and twisted wire geometry was improved over a narrow range of filler loading (5-7.5 wt%). At room temperature, pulsed electroacoustic analysis (PEA) data does not indicate any difference in space charge buildup in the composite for fields up to 25 kV/mm over a period of 2 h. This is in contrast to other nanocomposite systems, which tend to show mitigation of space charge buildup with the addition of nanoparticles. Dielectric spectroscopy shows that the addition of nanoparticles increases the real permittivity above that expected for volumetric mixing rules. This enhancement is associated with high effective permittivity interfacial areas. No systematic changes in losses in the frequency range between 10-4 and 105 Hz were seen. The results suggest that carrier scattering is the primary mechanism leading to the improved breakdown strength.

  • Polyamideimide-alumina nanocomposites for high-temperatures
    2010 10th IEEE International Conference on Solid Dielectrics, 2010
    Co-Authors: Christopher Calebrese, J. Keith Nelson, Linda S. Schadler, D.l. Schweickart
    Abstract:

    Metal oxide nanoparticles have been shown to improve the dielectric breakdown strength of insulating polymers. Polyamideimide is a material of practical use for high temperature insulation, and nanoparticle fillers show promise in improving the high temperature stability and dielectric breakdown strength. This work demonstrates the effect of 40–50 nm alumina nanoparticles on the improvement in AC breakdown strength of polyamideimide at elevated temperature and characterizes related electrical properties to gain insight into the mechanisms leading to this improvement. Breakdown tests were performed at temperatures up to 300 °C. The buildup and movement of space charge as a function of filler loading was measured at room temperature using pulsed electroacoustic analysis. Dielectric spectroscopy was used to measure the permittivity at temperatures up to 300 °C. In addition to improving the dielectric breakdown strength, alumina nanoparticles also improved the resistance to thermal degradation, which should allow operation of the composites at temperatures above the operating temperature of the base resin.

  • Dielectric integrity of silica-PAI nanocomposites at elevated temperature
    2009 IEEE Conference on Electrical Insulation and Dielectric Phenomena, 2009
    Co-Authors: A. M. Travelpiece, J. Keith Nelson, Linda S. Schadler, D.l. Schweickart
    Abstract:

    It has been shown that in many cases, the addition of nanoscale metal oxide fillers to polymers leads to an improvement in dielectric breakdown strength at room temperature. However, in some cases electrical insulation is exposed to elevated temperatures. A thermally stable polymer material, such as polyamideimide (PAI), is desired for these applications. For this reason, breakdown strength measured at elevated temperatures is required, since this property is expected to degrade with an increase in temperature. The addition of nanoparticles has been shown to increase PAI decomposition temperature and is also expected to mitigate the effect of increased temperature on dielectric properties. In this paper, AC and DC breakdown strength of PAI and nanosilica filled PAI are reported at room temperature and elevated temperatures. (200–340°C) Test temperatures were well below the decomposition range of polyamideimide as measured by thermogravimetric analysis (TGA). Silica composites at all loadings (whether treated or untreated) were shown to have a higher AC and DC breakdown strength at elevated temperatures than unfilled material. Dielectric spectroscopy results are also presented.

Stephen Gray - One of the best experts on this subject based on the ideXlab platform.