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Quantification of acid diffusion in fluoroplastic materials
KTH, School of Chemical Science and Engineering (CHE).
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Kvantitativ analys av syradiffusion i fluorplaster (Swedish)
Abstract [en]

To improve the service reliability of polymeric materials used in corrosive environments more corrosion data such as diffusion of acids is needed. The aim of this research was to investigate the diffusion of acids mainly in fluoroplastic materials by optimizing quantitative and qualitative methods to measure the diffusion. It was found that ion chromatography could be used to measure the acid concentration found inside the different polymers by desorption into a water solution. The amount of ions was then recalculated and presented as gacid/gpolymer. The polymeric materials were exposed in hydrochloric acid, nitric acid, hydrobromic acid and mixed acid. Very large spreading was seen within each series for the polymers in the different acids resulting in very high standard deviations on the concentrations of acids. The cause of the spreading was not found,  but analyses on the acid concentration using inductively coupled plasma (ICP) verified the large spreading seen from the ion chromatograph and conclusions were drawn that the ion chromatography did not cause the spreading. Changes to the experimental procedure were made but did not resolve the problem. The solubility of hydrogen chloride was measured in the fluoropolymers: perfluoroalkoxy (PFA), polyvinylidene fluoride (PVDF) and ethylene-chlorotrifluoroethylene (ECTFE) and compared to the polyolefins: polyethylene (PE) and polypropylene (PP). It was found that the polyolefins had the highest solubility of hydrogen chloride and ECTFE had the lowest. Chlorine dioxide solubility in PVDF was established through a different approach, the LGB-method, but the problem with spreading was seen on these results as well. An indicator technique was used to calculate diffusion rates of HCl in polypropylene samples with successful results. However, the indicator technique did not work for the ECTFE samples.

Place, publisher, year, edition, pages
2014.
Keyword [en]
Fluoroplastics, Acid Diffusion, Ion-chromatography, Desorption, Solubility
National Category
Polymer Technologies
Identifiers
URN: urn:nbn:se:kth:diva-158714OAI: oai:DiVA.org:kth-158714DiVA: diva2:778861
Available from: 2015-01-12 Created: 2015-01-12 Last updated: 2017-08-29Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
  • harvard1
  • ieee
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  • vancouver
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  • de-DE
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  • Other locale
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