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Use of essential oils for the prevention of biofilm formation on silicone rubber high voltage insulators
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. Univ Skovde, S-54128 Skovde, Sweden.ORCID iD: 0000-0002-5394-7850
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.ORCID iD: 0000-0002-2139-7460
2015 (English)In: Polymers from Renewable Resources, ISSN 2041-2479, Vol. 6, no 4, 119-136 p.Article in journal (Refereed) Published
Abstract [en]

The prevention of biofilm formation on high voltage insulators is important to avoid changes in the surface properties of the material and the subsequent failure of the application. Antimicrobial silicone rubber samples were prepared by the addition of thymol and eugenol to Sylgard 184 to determine the possibility of using natural antimicrobial agents present in essential oils in materials used for high voltage insulators. The antimicrobial effects of thymol and eugenol were studied for different fungal strains and for green algae identified in the biofilms formed on insulators in Tanzania, Sri Lanka and Sweden. It was successfully demonstrated that samples containing high amount of eugenol and different concentrations of thymol could inhibit the fungal growth of strains from Sri Lanka and Tanzania and the growth of green algae. The growth of strains from Sweden was also suppressed. The addition of eugenol to the material resulted in a noncrosslinked system and therefore, the antimicrobial effect of the additive in the material could not be assessed. The addition of thymol did not significantly influence the thermal and mechanical properties of Sylgard184. Although thermal analysis revealed that a large amount of the antimicrobial agent was lost during sample preparation, the materials were effective against microbial growth, even at low thymol concentrations.

Place, publisher, year, edition, pages
Rapra Technology Ltd. , 2015. Vol. 6, no 4, 119-136 p.
Keyword [en]
Algae, Biofilms, Elastomers, Electric insulation, Electric insulators, Essential oils, Microorganisms, Phenols, Rubber, Silicones, Thermoanalysis, Anti-microbial effects, Biofilm formation, High voltage insulators, Microbial growth, Natural-antimicrobials, Sample preparation, Silicone rubber, Thermal and mechanical properties
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-174283Scopus ID: 2-s2.0-84952893692OAI: oai:DiVA.org:kth-174283DiVA: diva2:858505
Note

QC 20170111

Available from: 2015-10-02 Created: 2015-10-02 Last updated: 2017-03-24Bibliographically approved
In thesis
1. Prevention of Biofilm Formation on Silicone Rubber Materials for Outdoor High Voltage Insulators
Open this publication in new window or tab >>Prevention of Biofilm Formation on Silicone Rubber Materials for Outdoor High Voltage Insulators
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Microbial colonization on the surface of silicone rubber high voltage outdoor insulators often results in the formation of highly hydrated biofilm that influence the surface properties, such as surface hydrophobicity. The loss of hydrophobicity might lead to dry band formation, and, in the worst cases, flashover and failure of the insulator.

In this work, the biocidal effects of various antimicrobial compounds in silicone rubber materials were determined. These materials were evaluated according to an ISO standard for the antimicrobial activity against the growth of aggressive fungal strains, and microorganisms that have been found colonizing the surfaces of outdoor insulators in several areas in the world. Several compounds suppressed microbial growth on the surfaces of the materials without compromising the material properties of the silicone rubber. A commercial biocide and thymol were very effective against fungal growth, and sodium benzoate could suppress the fungal growth to some extent. Thymol could also inhibit algal growth. However, methods for preservation of the antimicrobial agents in the bulk of the material need to be further developed to prevent the loss of the compounds during manufacturing. Biofilm formation affected the surface hydrophobicity and complete removal of the biofilm was not achieved through cleaning. Surface analysis confirmed that traces of microorganisms were still present after cleaning.

Further, surface modification of the silicone rubber was carried out to study how the texture and roughness of the surface affect biofilm formation. Silicone rubber surfaces with regular geometrical patterns were evaluated to determine the influence of the surface texture on the extent of microbial growth in comparison with plane silicone rubber surfaces. Silicone rubber nanocomposite surfaces, prepared using a spray-deposition method that applied hydrophilic and hydrophobic nanoparticles to obtain hierarchical structures, were studied to determine the effects of the surface roughness and improved hydrophobicity on the microbial attachment. Microenvironment chambers were used for the determination of microbial growth on different modified surfaces under conditions that mimic those of the insulators in their outdoor environments. Different parts of the insulators were represented by placing the samples vertically and inclined. The microbial growth on the surfaces of the textured samples was evenly distributed throughout the surfaces because of the uniform distribution of the water between the gaps of the regular structures on the surfaces. Microbial growth was not observed on the inclined and vertical nanocomposite surfaces due to the higher surface roughness and improved surface hydrophobicity, whereas non-coated samples were colonized by microorganisms.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xi, 67 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:51
Keyword
High voltage insulator, silicone rubber, biofouling, biofilm, biocide, superhydrophobicity, self-cleaning, hierarchical roughness
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-174091 (URN)978-91-7595-694-7 (ISBN)
Public defence
2015-10-23, K1, Teknikringen 56, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20151002

Available from: 2015-10-02 Created: 2015-09-30 Last updated: 2015-10-02Bibliographically approved

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Karlsson, SigbrittStrömberg, Emma

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