| 1. |
- Jäverberg, Nadejda, 1977-, et al.
(författare)
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Dielectric Properties of Alumina-filled Poly (ethylene-co-butyl acrylate) Nanocomposites Part I - Dry Studies
- 2012
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Ingår i: IEEE transactions on dielectrics and electrical insulation. - 1070-9878 .- 1558-4135. ; 19:2, s. 383-390
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Tidskriftsartikel (refereegranskat)abstract
- The dielectric properties of poly (ethylene-co-butyl acrylate) with 13 wt% of butyl acrylate (EBA) filled with alumina nanoparticles were studied as a function of particle size, particle coating, filler content (2, 6 or 12wt%) and temperature. The particles were either unmodified or surface-treated with either aminopropyltriethoxy silane or octyltriethoxy silane. The complex permittivity was measured with frequencies varying between 1 mHz and up to 1 kHz at different temperatures (25, 45 and 65 degrees C). Measurements were performed in dry conditions. From the dielectric spectroscopy measurements it can be seen that the tan delta for the dry samples is almost independent of the type of the particle coating used. It does, however, depend on the particle size, filler content and temperature.
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| 2. |
- Jäverberg, Nadejda, 1977-, et al.
(författare)
-
Dielectric Properties of Alumina-filled Poly (ethylene-co-butyl acrylate) Nanocomposites Part II - Wet Studies
- 2012
-
Ingår i: IEEE transactions on dielectrics and electrical insulation. - 1070-9878 .- 1558-4135. ; 19:2, s. 391-399
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Tidskriftsartikel (refereegranskat)abstract
- The influence of moisture on the dielectric properties of different types of poly (ethylene-co-butyl acrylate) filled with alumina nanoparticles was systematically investigated by varying the type of aluminum oxide, particle surface treatment and filler content (2, 6 and 12 wt%). The nanoparticles were either unmodified or surface-treated with either aminopropyl triethoxysilane or octyltriethoxy silane. The complex permittivity was measured with an IDA200 dielectric spectroscopy analyzer at applied voltage of 200 V-peak with frequencies varying between 1 mHz and 1 kHz. The measurements were performed at 25 degrees C and relative air humidities of 24, 54 and 86 %. In order to expand the frequency range the HP 4284A precision LCR meter was used for measuring sample impedance at the frequency range of 100 Hz to 1 MHz. From the frequency dependence of dielectric losses it can be seen that absorbed water plays a significant role in determining the dielectric properties of the nanocomposites. The magnitude of tan delta seems to be determined primarily by the particle size and filler content, while the peak frequency is mostly influenced by the amount of absorbed water and the type of particle coating.
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| 3. |
- Nawaz, Sohail, et al.
(författare)
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Antioxidant activity in aluminium oxide - Poly(ethylene-co-butyl acrylate) nanocomposites
- 2012
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Ingår i: Polymer degradation and stability. - : Elsevier BV. - 0141-3910 .- 1873-2321. ; 97:6, s. 1017-1025
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Tidskriftsartikel (refereegranskat)abstract
- The antioxidant activity of Irganox 1010 (0.2 wt%) in aluminium oxide (2-12 wt%) - poly(ethylene-co-butyl acrylate) nanocomposites was studied. The aluminium oxide nanoparticles were in three different forms: uncoated and coated with either octyltriethoxysilane or aminopropyltriethoxysilane. The activity of the stabilizer in the nanocomposites was assessed by determining the oxidation induction time (OIT) using DSC. Composites with untreated aluminium oxide nanoparticles showed a much shorter OIT than the pristine polymer with the same overall antioxidant concentration indicating adsorption of the antioxidant onto the nanoparticle surfaces. The adsorption of antioxidant onto both uncoated and coated nanoparticles was confirmed by X-ray photoelectron spectroscopy. Composites containing coated nanoparticle fillers showed a significantly smaller depression of the OIT, indicating that the replacement of hydroxyl groups with organic silane tails decreased the concentration of available adsorption sites on the particle surfaces. Composites with a filler coated with a silane having terminal aliphatic amine groups showed an increased OIT with respect to that of the pristine polymer suggesting a synergistic on the stability effect between the antioxidant and the amine groups. The long-term activity of the stabilizer was assessed by measuring the OIT on samples after ageing in air at 90°C for 720 h. The decrease in OIT with increasing ageing time of the nanocomposites was slower than for the unfilled polymer. A possible interpretation of these data is that the antioxidant was slowly released from the adsorption sites on extended ageing.
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| 4. |
- Nawaz, Sohail, 1984-
(författare)
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Preparation and long-term performance of poly(ethylene-co-butyl acrylate) nanocomposites and polyethylene
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The current study discusses the preparation and long-term performance of polymer composites used for various purposes under different ageing conditions.The first part deals with the preparation and characterization of polymer nanocomposites based on poly(ethylene-co-butyl acrylate) (EBA–13 and EBA–28 with 13 and 28 wt % butyl acrylate, respectively) and 2–12 wt % (0.5–3 vol %) of aluminum oxide nanoparticles (two types with different specific surface areas and different hydroxyl-group concentrations; uncoated and coated with, respectively, octyltriethoxysilane and aminopropyltriethoxysilane). The nanocomposite with EBA–13 showed better overall nanoparticle dispersion while EBA–28 resulted in poor dispersion, probably due to insufficiently high shear forces acting during extrusion mixing which were unable to break down nanoparticle agglomerates.The activity of hindered phenolic antioxidant (0.2 wt%) in all EBA nanocomposites was assessed by determining the oxidation induction time using DSC. The composites containing uncoated aluminium oxide nanoparticles showed a much shorter initial OIT than the pristine polymer with the same initial concentration of antioxidant, indicating adsorption of antioxidant onto the nanoparticle surfaces. Composites containing coated nanoparticles showed a significantly smaller decrease in the initial OIT, suggesting the replacement of hydroxyl groups with organic silane tails, decreasing the concentration of available adsorption sites on the nanoparticle surfaces. The decrease in OIT with increasing ageing time in dry air at 90 °C of the nanocomposites was slower thanthat of the unfilled pristine polymer, suggesting a slow release of antioxidant from adsorption sites.The EBA nanocomposites exposed to liquid water at 90°C showed faster decrease of OIT than samples exposed to dry or humid air. The migration rate of antioxidant was controlled by the boundary conditions in the case of ageing in humid air and liquid water. The antioxidant diffusivity was lower for the composites containing uncoated ND than for the composites containing ND coated with octyltriethoxysilane or aminopropyltriethoxysilane.The migration and chemical consumption of deltamethrin DM, (synthetic pyrethroid) and synergist piperonyl butoxide from molded polyethylene sheets was also studied. Deltamethrin and piperonyl butoxide are often used for food storage and insect control purposes. DM showed no signs of crystallization and remained in a liquid state after being cooled to room temperature. Exposure of polyethylene compound sheets to liquid water (at 80 & 95 °C), caused degradation and hydrolysis of the ester bond in the DM, present in the prepared material, and generated species containing hydroxyl groups. Liquid chromatography and infrared spectroscopy showed a significant migration of the active species in liquid water, whereas in air at 80 °C (60 and 80 %RH) the loss of DM and PBO was negligible over 30 days.The long-term performance of medium-density polyethylene stabilized with six different phenolic antioxidants (0.1 wt%) in aqueous chlorinated media at 70 °C was studied. The results were compared with data for previously studied solutions of antioxidants in squalane (a liquid, low molar mass analogue of polyethylene). A linear relationship was established between the time to reach antioxidant depletion in polyethylene tape samples and the time in squalane samples. Infrared spectroscopy and scanning electron microscopy of drawn samples revealed the onset of surface oxidation and surface embrittlement in tape samples exposed beyond the time for antioxidant depletion.
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| 5. |
- Nordell, Patricia, et al.
(författare)
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Preparation and characterization of aluminum oxide-poly(ethylene-co-butyl acrylate) nanocomposites
- 2012
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 125:2, s. 975-983
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Tidskriftsartikel (refereegranskat)abstract
- This article describes the preparation and characterization of composites containing poly(ethylene-co-butyl acrylate) (EBA13 and EBA28 with 13 and 28 wt % butyl acrylate, respectively) and 212 wt % (0.53 vol %) of aluminum oxide nanoparticles (two types differing in specific surface area and hydroxyl-group concentration; uncoated and coated with, respectively, octyltriethoxysilane and aminopropyltriethoxysilane). A greater surface coverage was obtained with aminopropyltriethoxysilane than with octyltriethoxysilane. An overall good dispersion was obtained in the EBA-13 composites prepared by extrusion compounding. Composites with octyltriethoxysilane-coated nanoparticles showed the best dispersion. The addition of the nanoparticles to EBA28 resulted in poor dispersion, probably due to insufficiently high shear forces acting during extrusion mixing which were unable to break down nanoparticle agglomerates. The nanoparticles had no effect on the crystallization kinetics in the EBA13 composites, but in the EBA28 composites the presence of the nanoparticles led to an increase in the crystallization peak temperature, suggesting that the nanoparticles had a nucleating effect in this particular polymer.
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