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Biofilm adhesion on silicone materials
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Silicone composite high voltage insulators are sometimes contaminated by microorganisms in outdoor applications, which results in the insulator becoming conductive and thereafter failure of the insulators. In this work, it has been tried to develop silicone materials with antimicrobial properties. Silicone was blended with various antimicrobial agents. Affectivity and appropriate concentration of the biocides were decided through a fast test prior to the manufacturing of the samples.

Samples were aged according to an international biodegradation test. To study the extent of the growth on the samples’ surface visual analysis and scanning electron microscopy (SEM) were performed. Samples were studied for changes in surface properties and surface chemical composition with carrying out dynamic contact angle measurements and Fourier transform infrared spectroscopy respectively. Results from the biodegradation test showed some biocides could inhibit the fungal growth comparing the results for the reference samples. Biofilm formation resulted in changes in surface hydrophobicity and surface chemical composition.

Further, silicone materials were compounded with clay nanoparticles, which were modified with different organic compounds. Reference samples were manufactured with clay nanoparticles modified with a siloxane surfactant to make the dispersion of the particles into the silicone matrix easier. Clay nanoparticles were also grafted with two organic compounds with antimicrobial effect in order to synthesis organoclays, which have antimicrobial properties. Furthermore, grafting clay with these two compounds was also aimed to make the easy dispersion of the particles into silicone possible.

Nanocomposites compounded with antimicrobial clay nanoparticles as well as reference nanocomposites were tested with quick test for microbial growth. Changes in the clay particles morphology were examined with x-ray diffraction as well as SEM. Manufactured nanocomposites were also examined with x-ray and SEM to study the dispersion of nanoparticles into the silicone matrix. Changes in clay morphology were observed due to modification with organic compounds. Microbial growth was inhibited on some samples due to presence of antimicrobial organoclays.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011.
National Category
Textile, Rubber and Polymeric Materials
Identifiers
URN: urn:nbn:se:kth:diva-50053OAI: oai:DiVA.org:kth-50053DiVA: diva2:460931
Note
QC 20120120Available from: 2012-01-20 Created: 2011-12-01 Last updated: 2012-01-20Bibliographically approved
List of papers
1. Inhibition of biofilm formation on silicone rubber samples using various antimicrobial agents
Open this publication in new window or tab >>Inhibition of biofilm formation on silicone rubber samples using various antimicrobial agents
2011 (English)In: International Biodeterioration & Biodegradation, ISSN 0964-8305, E-ISSN 1879-0208, Vol. 65, no 8, 1111-1118 p.Article in journal (Refereed) Published
Abstract [en]

High-temperature-cured silicone rubber samples (silicone rubber (SIR) based on polydimethylsiloxane (PDMS)) and SIR samples containing three different antimicrobial agents, sodium benzoate (NaB), DCOIT (4,5 Dichloro-2-octyl-2H-isothiazolone-one) and p-aminobenzoic acid (PABA) were inoculated with fungal spore suspensions and incubated for 28 days at 29 +/- 1 degrees C and >= 90% humidity, according to the ISO 846:1997(E) protocol. Prior to the biodegradation test, a powder test was conducted to study the efficacy of the chosen antimicrobial compounds and to determine the correct concentration of the compounds for sample preparation. The extent of the microbial growth was studied visually and by Scanning Electron Microscopy (SEM). Changes in surface hydrophobicity and surface chemical composition were studied by contact angle measurements and Fourier Transform Infrared (FTIR) spectroscopy, respectively. Microbial growth and biofilm formation were observed on the surface of reference samples. DCOIT was the most effective antimicrobial agent, as demonstrated by the lack of microbial growth and unaltered surface hydrophobicity. On the surface of samples containing NaB, an initiation of microbial growth and therefore a slight change in surface hydrophobicity was observed. PABA did not inhibit the fungal growth.

Keyword
High voltage silicone rubber insulator, Biofilm, Biofouling, Antimicrobial agents, Biodegradation
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-50044 (URN)10.1016/j.ibiod.2011.09.001 (DOI)000297889000001 ()2-s2.0-80053376565 (Scopus ID)
Note
QC 20111205. Previous title: Biofilm formation on silicone rubber samples containing different antimicrobial agentsAvailable from: 2011-12-01 Created: 2011-12-01 Last updated: 2017-12-08Bibliographically approved
2. Design of antimicrobial silicone nanocomposites for high voltage insulation
Open this publication in new window or tab >>Design of antimicrobial silicone nanocomposites for high voltage insulation
(English)Manuscript (preprint) (Other academic)
Keyword
high voltage insulation, silicone/clay nanocomposites, organoclays, quaternary ammonium salts
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-38870 (URN)
Available from: 2011-09-01 Created: 2011-09-01 Last updated: 2012-03-20Bibliographically approved

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