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Publications (4 of 4) Show all publications
Sanchez, C., Wåhlander, M., Karlsson, M. E., Quintero, D. C. M., Hillborg, H., Malmström, E. & Nilsson, F. (2019). Characterization of Reduced and Surface-Modified Graphene Oxide in Poly(Ethylene-co-Butyl Acrylate) Composites for Electrical Applications. Polymers, 11(4), Article ID 740.
Open this publication in new window or tab >>Characterization of Reduced and Surface-Modified Graphene Oxide in Poly(Ethylene-co-Butyl Acrylate) Composites for Electrical Applications
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2019 (English)In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 11, no 4, article id 740Article in journal (Refereed) Published
Abstract [en]

Promising electrical field grading materials (FGMs) for high-voltage direct-current (HVDC) applications have been designed by dispersing reduced graphene oxide (rGO) grafted with relatively short chains of poly (n-butyl methacrylate) (PBMA) in a poly(ethylene-co-butyl acrylate) (EBA) matrix. All rGO-PBMA composites with a filler fraction above 3 vol.% exhibited a distinct non-linear resistivity with increasing electric field; and it was confirmed that the resistivity could be tailored by changing the PBMA graft length or the rGO filler fraction. A combined image analysis- and Monte-Carlo simulation strategy revealed that the addition of PBMA grafts improved the enthalpic solubility of rGO in EBA; resulting in improved particle dispersion and more controlled flake-to-flake distances. The addition of rGO and rGO-PBMAs increased the modulus of the materials up to 200% and the strain did not vary significantly as compared to that of the reference matrix for the rGO-PBMA-2 vol.% composites; indicating that the interphase between the rGO and EBA was subsequently improved. The new composites have comparable electrical properties as today's commercial FGMs; but are lighter and less brittle due to a lower filler fraction of semi-conductive particles (3 vol.% instead of 30-40 vol.%).

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
field grading nanocomposites, non-linear resistivity, reduced graphene oxide (rGO), HVDC, SI-ATRP surface modification
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-252652 (URN)10.3390/polym11040740 (DOI)000467312900169 ()31022914 (PubMedID)2-s2.0-85065904341 (Scopus ID)
Note

QC 20190610

Available from: 2019-06-10 Created: 2019-06-10 Last updated: 2019-06-10Bibliographically approved
Nikjoo, R., Taylor, N., Edin, H., Hollertz, R., Wåhlander, M., Wågberg, L. & Malmström, E. (2017). Comparison of Oil-impregnated Papers with SiO2 and ZnO Nanoparticles or High Lignin Content, for the Effect of Superimposed Impulse Voltage on AC Surface PD. IEEE transactions on dielectrics and electrical insulation, 24(3), 1726-1734
Open this publication in new window or tab >>Comparison of Oil-impregnated Papers with SiO2 and ZnO Nanoparticles or High Lignin Content, for the Effect of Superimposed Impulse Voltage on AC Surface PD
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2017 (English)In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 24, no 3, p. 1726-1734Article in journal (Refereed) Published
Abstract [en]

Surface discharge behavior of modified oil-impregnated paper (OIP) with nanoparticles (NPs), has been investigated under AC voltage with superimposed impulses. Surface Partial Discharges (PD) can develop at an oil-paper interface and lead to its degradation. Modified paper, made from fibers with adsorbed nanoparticles, can affect the partial discharge behavior of a paper in combination with oil at the interface between oil and fibers. Papers with two different concentrations (2 wt% and 6 wt%) of silica (SiO2), and paper with silanized zinc oxide (ZnO) nanoparticles (1 wt%) have been studied. Papers with SiO2 NPs showed lower impulse-induced surface PD activity. However, thorough purification during the production of SiO2 filled papers was necessary to achieve a good performance. With less purification, paper with 2 wt% of SiO2 did not show such significant improvements. Paper with 6 wt% of SiO2 NPs showed a large number of AC surface PDs, but low influence of impulse voltage on subsequent PD. Papers containing 1 wt% of silanized ZnO showed reduced relative permittivity, but no significant difference in surface PD behavior. The effect of high lignin content in Kraft paper has also been studied. Paper with higher lignin content showed better surface PD characteristics under the impulse. Paper with low concentrations of pure SiO2 NPs, and paper with high lignin content thus appear good candidates for further studies to improve the surface PD behavior of OIP.

Place, publisher, year, edition, pages
IEEE, 2017
Keywords
Nanoparticles, SiO2, silanized ZnO, superimposed impulse, oil-impregnated paper, lignin
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-211614 (URN)10.1109/TDEI.2017.006053 (DOI)000405000300046 ()2-s2.0-85022338626 (Scopus ID)
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy StorageSwedish Energy Agency
Note

QC 201708010

Available from: 2017-08-11 Created: 2017-08-11 Last updated: 2017-08-11Bibliographically approved
Wåhlander, M., Nilsson, F., Carlmark, A., Gedde, U. W., Edmondson, S. & Malmström, E. (2016). Correction: Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states. Nanoscale, 8, 13522-13522
Open this publication in new window or tab >>Correction: Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states
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2016 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 8, p. 13522-13522Article in journal (Refereed) [Artistic work] Published
Abstract [en]

Correction in Figure 8 for ‘Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states’ by Martin Wåhlander, et al., Nanoscale, 2016, DOI: 10.1039/c6nr01502f

Keywords
graphene oxide matrix free shape memory effect
National Category
Polymer Technologies
Research subject
Chemistry; Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-193105 (URN)10.1039/C6NR90136K (DOI)
Projects
Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage
Note

QC 20160929

Available from: 2016-09-28 Created: 2016-09-28 Last updated: 2017-11-21Bibliographically approved
Wåhlander, M., Nilsson, F., Carlmark, A., Gedde, U. W., Edmondson, S. & Malmström, E. (2016). Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states. Nanoscale, 8, 14730-14745
Open this publication in new window or tab >>Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states
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2016 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 8, p. 14730-14745Article in journal (Refereed) Published
Abstract [en]

We demonstrate a novel route to synthesise hydrophobic matrix-free composites of polymer-grafted graphene oxide (GO) showing isotropic or nematic alignment and shape-memory effects. For the first time, a cationic macroinitiator (MI) has been immobilised on anionic GO and subsequently grafted with hydrophobic polymer grafts. Dense grafts of PBA, PBMA and PMMA with a wide range of average graft lengths (MW: 1–440 kDa) were polymerised by surface-initiated controlled radical precipitation polymerisation from the statistical MI. The surface modification is designed similarly to bimodal graft systems, where the cationic MI generates nanoparticle repulsion, similar to dense short grafts, while the long grafts offer miscibility in non-polar environments and cohesion. The state-of-the-art dispersions of grafted GO were in the isotropic state. Transparent and translucent matrix-free GO-composites could be melt-processed directly using only grafted GO. After processing, birefringence due to nematic alignment of grafted GO was observed as a single giant Maltese cross, 3.4 cm across. Permeability models for composites containing aligned 2D-fillers were developed, which were compared with the experimental oxygen permeability data and found to be consistent with isotropic or nematic states. The storage modulus of the matrix-free GO-composites increased with GO content (50% increase at 0.67 wt%), while the significant increases in the thermal stability (up to 130 °C) and the glass transition temperature (up to 17 °C) were dependent on graft length. The tuneable matrix-free GO-composites with rapid thermo-responsive shape-memory effects are promising candidates for a vast range of applications, especially selective membranes and sensors.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2016
Keywords
graphene oxide, macro-initiator, ARGET ATRP, shape memory, isotropic, nematic, well-dispersed, orientation, matrix-free
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-193102 (URN)10.1039/C6NR01502F (DOI)000381442500006 ()2-s2.0-84981501478 (Scopus ID)
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy StorageEU, European Research Council
Note

QC 20160929

Available from: 2016-09-28 Created: 2016-09-28 Last updated: 2017-05-30Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3310-9964

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