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Surface modification of polymers using elemental fluorine
Dissertation (Ph. D.) -- University of Stellenbosch, 1995.
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867614038022684673 |
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| access_status_str | Open Access |
| author | Du Toit, Francois Johannes |
| author2 | Sanderson, R. D. |
| author_browse | Du Toit, Francois Johannes Sanderson, R. D. |
| author_facet | Sanderson, R. D. Du Toit, Francois Johannes |
| author_sort | Du Toit, Francois Johannes |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Dissertation (Ph. D.) -- University of Stellenbosch, 1995. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/54864 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:45:40.774Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/54864 Surface modification of polymers using elemental fluorine Du Toit, Francois Johannes Sanderson, R. D. Stellenbosch University. Faculty of Science. Dept. of Chemistry & Polymer Science. Polymers -- Surfaces Fluorine Fluorination Dissertations -- Polymer science Dissertation (Ph. D.) -- University of Stellenbosch, 1995. Polyethylene, polypropylene and propylene-ethylene copolymers were reacted with elemental fluorine under carefully controlled reaction conditions. During kinetic studies, these reactions were monitored in a thermobalance adapted to be compatible with fluorine gas. It was shown that surface fluorination of a hydrocarbon polymer occurred in two stages. During the initial stage, which was chemical reaction controlled, the progress of the reaction was unaffected by the presence of a yₛ reacted layer but was proportional to the available surface of the unreacted material. In the second stage, the reaction zone moved into the solid, leaving behind a partially fluorinated surface layer through which the fluorine gas had to diffuse in order to reach the inner unreacted core. The fluorination reaction was influenced by the fluorine concentration, treatment time, choice of diluting gas, fluorination temperature and reactor pressure. In addition, polymer structure, the deactivating effect of substituent fluorine atoms and side reactions, such as oxidation, also affected the kinetics of the fluorination reaction. Surface fluorination resulted in a decrease in the total surface tension of the polyolefins, and surface tension values that resembled those of fluoropolymers were obtained. During fluorination in the presence of oxygen (oxyfluorination) however, oxygen functionalities were introduced in the polyolefin surfaces which resulted in surface tension values as high as 55 mN·m⁻¹. The wettability of fluorine-treated surfaces depended on the choice of the diluting gas as well as on reaction variables. Studies of surface inversion of fluorinated and oxyfluorinated polyethylene showed that unlike traditional surface modification methods such as plasma treatment, fluorine-treated surfaces did not revert quickly to surfaces resembling untreated surfaces. Oxyfluorination improved the adhesion properties of polypropylene considerably and strong adhesive bonds could be prepared using conventional adhesives. Fluorination also improved adhesion of polypropylene, although to a less extent than oxyfluorination, which indicated that small amounts of oxygen were probably introduced during fluorination, even though reaction conditions were chosen to be substantially free of oxygen. Receding contact angle studies confirmed the presence of oxygen functionalities in fluorinated surfaces. Fluorination resulted in polyolefins having improved barrier properties against non-polar liquids such as petroleum. Barriers were obtained with polyethylene, polypropylene and propylene-ethylene copolymers. The thickness of the fluorinated layer and the choice of the diluting gas were important factors in the creation of effective barriers. Oxyfluorination of polyolefins resulted in the formation of oxygen barriers which offer considerable application potential in the packaging industry. In order to achieve the best barrier at economical treatment times, the oxyfluorination reaction was optimised with respect to reaction variables. Highly fluorinated, inert membrane systems were prepared by exposing polyvinylidenefluoride membranes to elemental fluorine. In order to eliminate the deactivating effect of the fluorine atoms already present in the molecular structure of the vinylidenefluoride monomer, reaction conditions were different from those normally employed for surface fluorination reactions. Doctoral 2012-08-27T11:36:46Z 2012-08-27T11:36:46Z 1995 Thesis http://hdl.handle.net/10019.1/54864 en Stellenbosch University 190 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Polymers -- Surfaces Fluorine Fluorination Dissertations -- Polymer science Du Toit, Francois Johannes Surface modification of polymers using elemental fluorine |
| title | Surface modification of polymers using elemental fluorine |
| title_full | Surface modification of polymers using elemental fluorine |
| title_fullStr | Surface modification of polymers using elemental fluorine |
| title_full_unstemmed | Surface modification of polymers using elemental fluorine |
| title_short | Surface modification of polymers using elemental fluorine |
| title_sort | surface modification of polymers using elemental fluorine |
| topic | Polymers -- Surfaces Fluorine Fluorination Dissertations -- Polymer science |
| url | http://hdl.handle.net/10019.1/54864 |
| work_keys_str_mv | AT dutoitfrancoisjohannes surfacemodificationofpolymersusingelementalfluorine |