-
06/2010;
-
[show abstract]
[hide abstract]
ABSTRACT: Composition comprises at least one polycarbonate and at least one isoindole 1,3-dione derivative (I). Composition comprises at least one polycarbonate and at least one isoindole 1,3-dione derivative of formula (I). R 1-R 6, R 1 3-R 1 6H, (pseudo)halo, OH, NH 2, NO 2, 1-20C alkyl, 1-20C cycloalkyl, 2-20C alkenyl, 2-20C alkynyl, 1-20C aryl, 1-20C alkoxy, 1-20C acyl, 1-20C aldehyde, 1-20C carboxylic acid, 1-20C carboxylic acid ester, amide or acyl halo; m, n : 0-10; and T 1, T 2organic group. Independent claims are included for: (1) the isoindole 1,3-dione derivative (I), where m and n are 1-10 and T 2 is phenoxy phenyl moiety of formula (II); (2) a polymer element comprising the composition; (3) preparing the polymer element from the composition by pressing, scraping, spreading, centrifuging, spraying, extrusion, blow molding and/or compacting; (4) an electret element comprising the polymer element that is charged; (5) preparing the electret element, comprising producing the polymer element and charging it; and (6) electromechanical converter comprising the polymer element or the electret element. R 6 1-R 7 4H, (pseudo)halo, OH, NH 2, NO 2, 1-20C alkyl, 1-20C cycloalkyl, 2-20C alkenyl, 2-20C alkynyl, 1-20C aryl, 1-20C acyl, 1-20C aldehyde, 1-20C carboxylic acid, 1-20C carboxylic acid ester, amide or acyl halo.
Ref. No: EP2159222 (A1), Year: 03/2010
-
[show abstract]
[hide abstract]
ABSTRACT: The influence of physical aging on the electret properties before corona charging of three amorphous polymers, polyetherimide (PEI), poly(phenylene ether) (PPE), and polystyrene (PS), as well as with blends of PPE and PS, was investigated. The degree of aging was monitored by determining the enthalpy relaxation h using differential scanning calorimetry (DSC). The electret performance was evaluated by isothermal potential decay (ITPD) at elevated temperatures and by thermal stimulated discharge (TSD) measurements. It was demonstrated that physical aging below the glass transition temperature substantially improves the electret performance of amorphous polymers by reducing the free volume and thus hindering charge motion. As an example, the performance of nonaged PEI was improved by physical aging at 200 °C for 4 days from 18 to 95% retained charge after 24 h at 120 °C. A similar beneficial influence of physical aging on the charge storage capability was achieved using blends of PPE with PS.
J. Polym. Sci. B: Polym. Phys. 03/2010; 48:990-997.
-
[show abstract]
[hide abstract]
ABSTRACT: The performance of a polymeric electret material depends on many parameters, and besides chemical structure, charging conditions, and application temperature, other factors, such as grade, manufacturer, processing history, and additive package, are critical. Commercial polyetherimide (PEI) Ultem®1000 films exhibited satisfying electret properties as revealed by an isothermal potential decay (ITPD) to 75% of the initial surface charge after 24 h at 90°C. It was found that after purification by reprecipitation this value drops to 34% and that the same PEI synthesized by two different methods revealed to be a very poor electret with charge retention of almost zero. Assuming that an additive in the commercial material might be responsible for this behavior, we identified an organophosphonite which is commonly used as antioxidant in high-temperature polymers. We incorporated this additive by melt compounding into purified PEI and found a dramatic increase in charge retention to 79% of the initial charge at an additive load level of 0.5 wt %. By immersing Ultem®1000 films in water, the electret behavior was further improved and almost 100% charge retention was achieved.
J. Appl. Polym. Sci. 03/2010; 115:1247-1255.
-
[show abstract]
[hide abstract]
ABSTRACT: An electret is a dielectric material exhibiting a quasi-permanent electric charge. The aim of this work is to give access to polycarbonate (PC) electret materials with a distinctly improved electret performance. In this context, the charge storage capabilities of corona charged films of several PC grades were investigated by isothermal potential decay measurements at 90°C. The most promising PC grade was further improved by a new class of bisimide additives. The best additive at the most efficient concentration in combination with a physical aging step yielded excellent PC electrets maintaining almost their complete applied charge even at 90°C.
Macromol. Chem. Phys. 01/2010;
-
[show abstract]
[hide abstract]
ABSTRACT: The charge decay in isotactic polypropylene (i-PP) films of 50 µm thickness, containing three kinds of additives, namely a trisamide, a bisamide and a fluorinated compound, with concentrations in the range 0.004–1 wt% was studied. Compression molding was used to produce the films. The samples were either surface-charged by a corona method or volume-charged by mono-energetic electron beams of different energies, having penetration depths up to 6 µm. In all cases, surface potentials of about 200 V were chosen. After charging the films, the decay of the surface potential was studied either by an isothermal discharge method at 90 °C or by thermally stimulated discharge measurements. The results show a dependence of the decay rate on the kind of additive used, on additive concentration and on the energy of the injected charges. In particular, for samples with fluorinated additives, the stability of the surface potential decreases markedly with increasing electron energy, while such a dependence is very weak for samples containing the bisamide additive and does not exist at all for samples with the trisamide additive. These observations are tentatively explained by the radiation-induced generation of relatively mobile negative ions originating from the bisamide and fluorinated additives.
J. Phys. D: Appl. Phys. 02/2009; 42:065410 (8pp).
-
8th International Technical Symposium on Polyimides & High Performance Functional Polymers (STEPI 8), Montpellier, France; 06/2008
-
Advanced Functional Materials 08/2007; 17(14):2336 - 2342. · 10.18 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The aim of this work was to establish and better understand the structure-property relationship of fluorinated arom. poly(ether imide)s (PEI) with respect to their electret performance. Therefore two series of PEIs with increasing fluorine content were synthesized. All PEIs are amorphous materials with glass transition temps. above 220 Deg. Thin films with thicknesses around 100 micro m were compression molded and corona charged, and isothermal surface potential decay was investigated at 90 Deg as an accelerated test for the electret performance. In comparison to the corresponding non-fluorinated PEI, an improvement of up to thirty-fold was achieved by the incorporation of trifluoromethyl moieties. Out of the investigated fluorinated PEIs, the polymer with the best charge storage performance maintained 87% of the initial surface potential charge after annealing at 90 Deg for 24 h. It was also found that, within the investigated series, the highest fluorine content does not necessarily result in the best charge-storage properties.
Macromol. Chem. Phys. 05/2007; 208:1522-1529.
-
[show abstract]
[hide abstract]
ABSTRACT: In the present work, the development of cellular films by stretching isotactic polypropylene (i-PP) filled with NA11 (2,2'-methylene-bis-(4,6-di-tert-butylphenyl)-phosphate) particles and hollow glass spheres is reported. Morphology, electret properties and piezoelectric activity are investigated. An enhancement of the charge storage stability for the cellular films is due to the formation of cavities, which retard the drift of charges through the volume of the film. Furthermore, the cellular stretched i-PP films with hollow glass spheres were made piezoelectric by suitable corona poling method. Films were stretched to draw ratios of 3.5:3.5 (medium stretched) and selected samples were drawn to ratios of 5:5 (highly stretched). The applied draw ratio was found to directly influence the cavity formations and by this the electret and piezoelectric properties. Excellent electret properties were obtained in the case of highly stretched i-PP films containing 10 wt% of NA11, known as a nucleating agent additive for i-PP. Additionally, piezoelectric activity (d<sub>33</sub>=179 pC/N) was observed in these films. i-PP films with glass spheres showed piezoelectric coefficients between 17 and 170 pC/N, depending on glass sphere size and concentration as well as on draw ratio
IEEE Transactions on Dielectrics and Electrical Insulation 11/2006; · 1.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Isotactic polypropylene (i-PP) films containing additives such as the commercial α -nucleation agent NA11 and the anorganic filler particles CaCO3 and Al2O3 were biaxially stretched. As a result, the films assume a cellular morphology with oblong cavities extending in the direction of the film elongation. In the present study, stretched films of 50 µm thickness with additive concentrations of 0.05–10 mass per cent were charged with a corona method to potentials of 400 or 500 V. The stability of the charges was tested isothermally at temperatures of 90 and 120 °C and by means of thermally stimulated discharge (TSD) experiments. The isothermal measurements show, for the above additives with concentrations higher than about 0.3%, a reduction of the charge decay with increasing additive concentrations. Compared with reference films of pure PP, the potential decay of the films containing additive concentrations of 10% is significantly reduced. Correspondingly, the TSD measurements indicate a shift of the main discharge peak to higher temperatures up to the melting temperature. Generally, the voiding and thus the stability also increases with the stretching ratio. These improvements of the charge stability are attributed to the barrier effect of the cavities. The results are of interest with respect to the various applications of PP electrets, such as ferroelectret devices and air filters.
Journal of Physics D Applied Physics 01/2006; 39(3):535. · 2.54 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Here we report the processing of cellular, high-temperature polymers for electret applications based on polyetherimide (PEI) and polyetheretherketone (PEEK). The two approaches were utilized to improve the electret properties by insertion of cavities are the physical batch foaming process using carbon dioxide as the blowing agent and the stretching of polymeric plates containing suitable particles, which allows the manufacturing of porous films. The electret properties of foamed PEI and PEEK as well as stretched PEI containing NA11 particles are characterized by isothermal charge decay measurements at 90°C after corona charging to surface potentials of about 400V. Investigation of the cellular morphologies was achieved by scanning electron microscopy (SEM) and micro-computertomography (μCT). As result, the cellular films show a clear improved charge storage behaviour compared to the compact films. The best results were achieved with porous PEI films, prepared by stretching and after twofold charging.
Applied Physics A 01/2006; 85(1):87-93. · 1.63 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Isotactic Polypropylene (i-PP) films containing additives such as the commercial α-nucleation agent NA11 and the anorganic filler particles CaCO<sub>3</sub> and Al<sub>2</sub>O<sub>3</sub> were biaxially stretched. As a result, the films assume a cellular morphology with oblong cavities extending in the direction of the film elongation. In the present study, stretched films of 50 μm thickness with additive concentrations of 0.05 to 10 mass percent were charged with a corona method to potentials of 400 V or 500 V. The stability of the charges was tested isothermally at temperatures of 90 °C and 120 °C and by means of thermally stimulated discharge (TSD) experiments. The isothermal measurements show, for the above additives with concentrations higher than about 03 %, a reduction of the charge decay with increasing additive concentrations. Compared to reference films of pure PP, the potential decay of the films containing additive concentrations of 10 % is significantly reduced. Correspondingly, the TSD measurements indicate a shift of the main discharge peak to higher temperatures up to the melting temperature. Generally, the voiding and thus the stability also increases with the stretching ratio. These improvements of the charge stability are attributed to the barrier effect of the cavities. The results are of interest with respect to the various applications of PP electrets, such as ferroelectret devices and air filters.
Electrets, 2005. ISE-12. 2005 12th International Symposium on; 10/2005
-
[show abstract]
[hide abstract]
ABSTRACT: Cellular polymer films are suitable for electret and piezoelectric applications. Considerable attention is currently focused on thermoplastic polymer foams such as isotactic polypropylene (i-PP). The cellular morphology leads to barrier effects effectively improving the charge storage stability. However, the application of neat cellular polypropylene electrets is limited due to their relatively low working temperature. Therefore, new research activities are mainly focused on processing of cellular high temperature polymers such as polyetherimide (PEI). A promising approach is a physical batch foaming process using carbon dioxide as a blowing agent, which allows the manufacturing of thin cellular films. The control of the cellular morphology plays an important role with respect to the charge storage behavior and is influenced by the processing parameters such as blowing agent concentration or foaming temperature. Investigations of the cellular morphologies are achieved by scanning electron microscopy (SEM). Electret properties are characterised by potential decay measurements at 90°C after corona charging to surface potentials of about 400 V. In general, such cellular films show improved charge storage behavior in comparison to the compact materials.
Electrets, 2005. ISE-12. 2005 12th International Symposium on; 10/2005
-
[show abstract]
[hide abstract]
ABSTRACT: The synthesis and characterization of liquid-crystalline precursor polymer solutions[1] for polyimides permit for the first time the preparation of bulk- and surface-oriented polyimide thin films from the nematic lyotropic state by shear. A special shearing technique was developed and optimized to orient viscous solutions into thin films with thicknesses below 100 nm. The films produced were thermally imidized and characterized by polarized light microscopy, as well as polarized FTIR and UV-vis spectroscopy before and after imidization. The dichroic ratios (DRs) before imidization were determined as 5 by FTIR, and 4.5 by UV-vis spectroscopies. After imidization the DRs increased to 14 and 7, respectively. The shear-oriented layers possess a surface profile in the form of striations, which was characterized by mechanical surface scanning and atomic force microscopy (AFM). The profile height was determined in the nanometer range in contrast to the profile distance in the micrometer range, thus the latter is a magnitude larger than the film thickness. To quantify and compare the orientation potential of the obtained orientation layers, cells with a liquid-crystalline host and a dichroic azo dye as guest were prepared. Interesting for this class of rod-like polyimides is that layers, which were cast from low concentration isotropic solutions and rubbed, exhibited an almost doubled DR of 15 compared to analogously prepared alignment layers based on commercial flexible polyimide systems (DR = 8).
Advanced Functional Materials 05/2003; 13(5):387 - 391. · 10.18 Impact Factor
-
Advanced Materials 04/2002; 14(8):577 - 581. · 13.88 Impact Factor
