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Electrical Insulating Properties of Poly(Ethylene-co-Butyl Acrylate) Filled with Alumina Nanoparticles
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this work the electrical insulating properties of the nanocomposite materials based on poly(ethylene-co-butyl acrylate) filled with alumina nanoparticles are studied. The dielectric properties chosen for the evaluation are the dielectric permittivity and loss as well as the breakdown strength and the pre-breakdown currents. The reason for choosing these particular properties is partly due to the importance of these for the general electrical applications and partly due to the uncertainties involved for these particular properties of the nanocomposite materials.

The importance of moisture absorption for the dielectric properties is outlined in this work. All measurements were performed in both dry conditions and after conditioning of the materials in humid environment until saturation. The data for moisture absorption was taken from the water absorption study performed at the Department of Fibre and Polymer Technology, KTH.

The dielectric spectroscopy in frequency domain was employed for measuring dielectric permittivity and loss. Havriliak-Negami approximation was used for characterization of the measurement data and at the same time ensuring the fulfillment of the Kramers-Kronig relations. Results from the dielectric spectroscopy study in dry conditions suggest that dielectric spectroscopy can be used for evaluating nanoparticle dispersion in the host matrix, based on correlation between the morphology data obtained from SEM investigation and the scatter in the dielectric loss. The dielectric spectroscopy study performed on the nanocomposites after conditioning in humid environment showed that absorbed moisture has a distinct impact on the dielectric loss. Especially pronounced is its’ influence on the frequency behavior, when the dielectric loss peaks are shifted towards higher frequencies with increased moisture content. The nanocomposite materials characterized by higher specific surface area generally exhibit higher dielectric losses. Surface functionalization of the nanoparticles does not seem to have much influence on the dielectric loss in dry conditions. After conditioning in humid environment, however, the surface modification was shown to have a significant impact. Temperature is another significant factor for the frequency behavior of the dielectric loss: it was found that the studied nanocomposites can be characterized by Arrhenius activation.

The breakdown strength and pre-breakdown currents study outlined the influence of moisture as well. The study indicated that surface treatment of the nanoparticles can enhance properties of the nanocomposite materials, namely aminopropyltriethoxy silane was an especially successful choice:

• The highest breakdown strength was determined by the study for NDA6 material formulation in dry conditions.

• After conditioning in humid environment the NDA6 material continued showing the best breakdown strength among the nanocomposite mate rials, as well as this value was close to the breakdown strength of the reference unfilled material.

This study confirms the existence of the optimal nanofiller content or rather optimal specific surface area of the dispersed nanoparticles in the host matrix. The latter is supported by the comparison between the nanocomposites based on nanoparticles with two different specific surface areas, which shows that the dielectric properties worsen, i.e. the dielectric losses increase and the influence of absorbed moisture on the breakdown strength becomes more pronounced, for nanomaterials with larger specific surface area. The pre-breakdown currents were found to follow space-charge limited conduction mechanism reasonably well. The following conduction regimes were identified: constant region (likely due to measurement difficulties at low field strengths), Ohm’s regime, trap-filled-limit regime and trapfree dielectric regime. The breakdown usually occurred either during the trap-filled-limit regime, when the current increased dramatically for the small change in electric field, or during the trapfree dielectric regime. The threshold values between different conduction regimes seem to correlate well with the oxidation induction times (OIT), which in turn depend on the total specific surface area. The pre-breakdown currents tend to be highest for the materials filled with the untreated nanoparticles. Increased absorbed moisture content causes higher pre-breakdown currents for the nanocomposite materials, while for the reference unfilled material the pre-breakdown currents do not show such tendency. Generally it can be said that the repeatability in the measured data is higher for the nanocomposite materials in comparison to the unfilled host material, as was demonstrated by both dielectric spectroscopy and breakdown studies.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , xii, 70 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2013:005
Keyword [en]
nanocomposites, poly(ethylene-co-butyl acrylate), EBA, alumina, dielectric permittivity, absorbed water, humidity, temperature, dielectric spectroscopy, breakdown strength, pre-breakdown current
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-116862ISBN: 978-91-7501-647-4 (print)OAI: oai:DiVA.org:kth-116862DiVA: diva2:601059
Public defence
2013-02-27, F3, Lindstetsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20130207

Available from: 2013-02-07 Created: 2013-01-28 Last updated: 2014-02-11Bibliographically approved
List of papers
1. Dielectric properties of alumina-filled poly(ethylene-co-butyl acrylate) nanocomposites
Open this publication in new window or tab >>Dielectric properties of alumina-filled poly(ethylene-co-butyl acrylate) nanocomposites
Show others...
2010 (English)In: 2010 Annual Report Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), IEEE , 2010, 5724031- p.Conference paper, Published paper (Refereed)
Abstract [en]

The dielectric properties of poly (ethylene-co-butyl acrylate) with 13 wt% of butyl acrylate (EBA) filled with alumina nanoparticles (diameter < 50 nm) were studied as a function of particle coating and filler content (2, 6 and 12 wt%). The particles were either unmodified or surface treated either with aminopropyl triethoxysilane or octyltriethoxysilane. The complex permittivity was measured with an IDA200 dielectric spectroscopy analyzer at applied voltage of 200 Vpeak with frequencies varying between 1 mHz and up to 1 kHz at different temperatures (25, 45 and 65°C). Measurements are performed in dry conditions. Pure EBA shows two regions of frequency dispersion in the complex permittivity: a broad relaxation peak in the order of MHz and a characteristic low frequency dispersion that likely is a Maxwell-Wagner response due to a barrier blocking conduction process. Obtained data fits well to a sum of two Havriliak-Negami expressions. Adding nanoparticles to the EBA matrix changes the low frequency dispersion behaviour significantly. Differences in dielectric losses between nanocomposites with different surface treatment seem to be small. The differences in dielectric constant, however, are more pronounced and seem to indicate better dispersion with octylthriethoxysilane surface treatment.

Place, publisher, year, edition, pages
IEEE, 2010
Series
Conference on Electrical Insulation and Dielectric Phenomena. Annual Report, ISSN 0084-9162
Keyword
Behavioral research, Dielectric devices, Dielectric losses, Dispersions, Ethylene, Nanocomposites, Nanoparticles, Surface treatment
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-31435 (URN)10.1109/CEIDP.2010.5724031 (DOI)2-s2.0-79952934052 (Scopus ID)978-142449470-5 (ISBN)
Conference
2010 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2010; West Lafayette, IN; United States; 17 October 2010 through 20 October 2010
Note

QC 20110315

Available from: 2011-03-15 Created: 2011-03-15 Last updated: 2014-09-03Bibliographically approved
2. Influence of Moisture on Dielectric Properties of Alumina-filled poly(ethylene-co-butyl acrylate) Nanocomposites
Open this publication in new window or tab >>Influence of Moisture on Dielectric Properties of Alumina-filled poly(ethylene-co-butyl acrylate) Nanocomposites
2011 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

The dielectric properties of poly(ethylene-co-butyl acrylate) with 13 wt% of butyl acrylate (EBA) filled with alumina nanoparticles (average diameter of 25 nm) were studied as a function of particle coating, filler content (2, 6 and 12 wt %) and relative humidity of the environment used for sample conditioning. The particles were either unmodified or surface treated either with aminopropyltriethoxy silane or octyltriethoxy silane. The samples were conditioned at 24, 56 and 86 % RH in desiccators in room temperature using salt solutions until saturation was reached.

The complex permittivity was measured with an IDA200 dielectric spectroscopy analyzer at applied voltage of 200 Vpeak with frequencies varying between 1 mHz and up to 1 kHz at room temperature.

Dielectric losses measured for pure EBA in both dry and humid conditions show very small variations, while measurements performed on the nanocomposites exhibit distinct loss peaks that depend on the filler content, particle coating and humidity of the environment used for conditioning. The loss peak amplitude depends on the filler content, the shape is determined by the type of coating used and the loss peak frequency is defined by both humidity level and type of coating used.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-104478 (URN)
Conference
NORD-IS 2011: Nordic Insulation Symposium
Note

QC 20121116

Available from: 2012-11-16 Created: 2012-11-05 Last updated: 2013-02-07Bibliographically approved
3. Dielectric Properties of Alumina-filled Poly (ethylene-co-butyl acrylate) Nanocomposites Part I - Dry Studies
Open this publication in new window or tab >>Dielectric Properties of Alumina-filled Poly (ethylene-co-butyl acrylate) Nanocomposites Part I - Dry Studies
Show others...
2012 (English)In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 19, no 2, 383-390 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
nanocomposite, nanofillers, alumina, poly(ethylene-co-butyl acrylate)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-31437 (URN)10.1109/TDEI.2012.6180229 (DOI)000303069300002 ()2-s2.0-84860176248 (Scopus ID)
Note
QC 20120522Available from: 2011-03-15 Created: 2011-03-15 Last updated: 2017-12-11Bibliographically approved
4. Dielectric Properties of Alumina-filled Poly (ethylene-co-butyl acrylate) Nanocomposites Part II - Wet Studies
Open this publication in new window or tab >>Dielectric Properties of Alumina-filled Poly (ethylene-co-butyl acrylate) Nanocomposites Part II - Wet Studies
Show others...
2012 (English)In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 19, no 2, 391-399 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
nanocomposite, nanofillers, alumina, poly(ethylene-co-butyl acrylate), absorbed water
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-31438 (URN)10.1109/TDEI.2012.6180230 (DOI)000303069300003 ()2-s2.0-84860181612 (Scopus ID)
Funder
Swedish Research Council, IFA 2007-5095
Note
QC 20120525Available from: 2011-03-15 Created: 2011-03-15 Last updated: 2017-12-11Bibliographically approved
5. Dielectric breakdown strength of alumina filled poly (ethylene-co-butyl acrylate) nanocomposites
Open this publication in new window or tab >>Dielectric breakdown strength of alumina filled poly (ethylene-co-butyl acrylate) nanocomposites
2012 (English)In: 2012 Annual Report Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), IEEE , 2012, 323-326 p.Conference paper, Published paper (Refereed)
Abstract [en]

Dielectric breakdown strength of poly (ethylene-co-butyl acrylate) (EBA) nanocomposites filled with spherical alumina particles was studied as a function of particle coating and relative air humidity. The nanocomposites were prepared from a mixture of EBA formulations (13 wt% butyl acrylate groups content) and alumina powder. The particles were either unmodified or surface-treated with aminopropyltriethoxy silane or octyltriethoxy silane. The filler content studied was 6 wt%. Every material formulation was thoroughly examined under SEM in order to verify homogeneous particle dispersion. Two different relative humidities of air were used for conditioning the samples prior to testing: 0 and 86 % RH.

    The dielectric breakdown strength measurements were performed with a DC ramp of 1.2 kV/s. Ten samples were tested for each material formulation. Results were compared to the pristine EBA samples. Applying Weibull analysis to the measured data indicated a slight increase in breakdown strength for the dry nanocomposites filled with amino-treated particles as compared to the reference material in dry conditions. As expected, conditioning materials in humid environment had a negative impact on breakdown strength. This effect was more pronounced for nanocomposite materials, while the reference unfilled material was affected the least.

Place, publisher, year, edition, pages
IEEE, 2012
Series
Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP, ISSN 0084-9162
Keyword
Air humidity, Alumina particles, Alumina powder, Breakdown strengths, Butyl acrylates, Conditioning materials, Dielectric breakdown strength, Dry condition, Filler contents, Humid environment, Particle coatings, Particle dispersion, Reference material, Weibull analysis
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-104479 (URN)10.1109/CEIDP.2012.6378786 (DOI)000316899800075 ()2-s2.0-84872081304 (Scopus ID)978-1-4673-1252-3 (ISBN)
Conference
2012 IEEE Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2012; Montreal, QC;14 October 2012 through 17 October 2012
Note

QC 20121114

Available from: 2012-11-14 Created: 2012-11-05 Last updated: 2013-12-12Bibliographically approved
6. Prebreakdown Current and Breakdown Strength of Alumina-filled Poly(ethylene co-butyl acrylate) Nanocomposites: Part I - Breakdown Strength
Open this publication in new window or tab >>Prebreakdown Current and Breakdown Strength of Alumina-filled Poly(ethylene co-butyl acrylate) Nanocomposites: Part I - Breakdown Strength
(English)In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135Article in journal (Other academic) Submitted
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-117934 (URN)
Note

QS 2013

Available from: 2013-02-07 Created: 2013-02-07 Last updated: 2017-12-06Bibliographically approved
7. Prebreakdown Current and Breakdown Strength of Alumina-filled Poly(ethylene co-butyl acrylate) Nanocomposites: Part II - Prebreakdown Currents
Open this publication in new window or tab >>Prebreakdown Current and Breakdown Strength of Alumina-filled Poly(ethylene co-butyl acrylate) Nanocomposites: Part II - Prebreakdown Currents
(English)In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135Article in journal (Other academic) Submitted
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-117935 (URN)
Note

QS 2013

Available from: 2013-02-07 Created: 2013-02-07 Last updated: 2017-12-06Bibliographically approved
8. Influence of Applied Voltage and Temperature on the Current through the Alumina-filled poly(ethylene-co-butyl acrylate) Nanocomposites Under Constant Stress
Open this publication in new window or tab >>Influence of Applied Voltage and Temperature on the Current through the Alumina-filled poly(ethylene-co-butyl acrylate) Nanocomposites Under Constant Stress
(English)Manuscript (preprint) (Other academic)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-117936 (URN)
Note

QS 2013

Available from: 2013-02-07 Created: 2013-02-07 Last updated: 2013-02-07Bibliographically approved

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