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PTFE initiators : their influence on the physical properties of the polymer
Dissertation (MEng)--University of Pretoria, 2018.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2019
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| _version_ | 1867613518199521280 |
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| access_status_str | Open Access |
| author2 | Crouse, Philippus L. |
| author_browse | Crouse, Philippus L. |
| author_facet | Crouse, Philippus L. |
| collection | Thesis |
| dc_rights_str_mv | © 2019 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MEng)--University of Pretoria, 2018. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/71043 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:37:25.198Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2019 |
| publishDateRange | 2019 |
| publishDateSort | 2019 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/71043 PTFE initiators : their influence on the physical properties of the polymer Crouse, Philippus L. u11024969@tuks.co.za Puts, Gerard Jacobs Venner, William Victor UCTD Polytetrafluoroethylene (PTFE) Free radical polymerization Fluoropolymers Engineering, built environment and information technology theses SDG-08 Engineering, built environment and information technology theses SDG-09 Engineering, built environment and information technology theses SDG-12 Dissertation (MEng)--University of Pretoria, 2018. The Fluorochemical Expansion Initiative (FEI) program was implemented to encourage the local beneficiation of South Africa’s abundant fluorspar resources for the benefit of the economy. Fluoropolymer production was identified as an area in which technical expertise was decidedly lacking and which promised many opportunities for research and skills development. Polytetrafluoroethylene (PTFE), also commonly referred to by its DuPont trade name, Teflon™, is the most well-known of the fluoropolymers. It is decidedly beneficial to develop expertise in the area of synthesis and characterisation of fluoropolymers, particularly PTFE. This polymer is synthesised via free radical polymerisation of TFE and can be initiated by a number of free radical initiators. A commonly used initiator is ammonium persulfate (APS). PTFE produced in this way experiences significant discolouration when subjected to temperatures in the region of 380 °C during the moulding process. The cause of the discolouration is unreported in the scientific literature, despite this discolouration being general knowledge within the fluoropolymer industry. The research detailed herein was aimed at determining the cause of colour changes in thermally processed PTFE homopolymers. The research started with an in-depth review of the literature regarding the homopolymerisation of tetrafluoroethylene and included the types of end groups that could be formed from initiators as well as the infrared- and Raman spectroscopic identification of these end groups. PTFE was synthesised in an autoclave via aqueous conventional radical polymerisation using ammonium- and metal persulfates, H2O2, KMnO4 and di-tert-butyl peroxide, benzoyl peroxide as well as azo-based initiators. The synthesised PTFE was then subjected to differential scanning calorimetry, thermogravimetric analysis and Fourier-transform infrared- and Raman spectroscopy both before and after sintering. Care was taken to ensure the polymers were not contaminated with any initiator- or buffer residues. It was found that the discolouration is caused by the decomposition of carboxylate end groups at elevated temperatures which deposit carbon into the polymer matrix. It was found to be generally true that higher initiator concentrations lead to more discolouration, because of more carbon being deposited into the matrix by eliminated end groups. It was also found that the use of buffering agents and the type of buffering agent used influence the type of end groups formed on the polymer chains. mi2026 Chemical Engineering MEng Unrestricted SDG-09: Industry, innovation and infrastructure SDG-08: Decent work and economic growth SDG-12: Responsible consumption and production 2019-08-12T11:18:55Z 2019-08-12T11:18:55Z 2019/04/11 2018 Dissertation Venner, WV 2018, PTFE initiators : their influence on the physical properties of the polymer, MEng Dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/71043> A2019 http://hdl.handle.net/2263/71043 en © 2019 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | UCTD Polytetrafluoroethylene (PTFE) Free radical polymerization Fluoropolymers Engineering, built environment and information technology theses SDG-08 Engineering, built environment and information technology theses SDG-09 Engineering, built environment and information technology theses SDG-12 PTFE initiators : their influence on the physical properties of the polymer |
| title | PTFE initiators : their influence on the physical properties of the polymer |
| title_full | PTFE initiators : their influence on the physical properties of the polymer |
| title_fullStr | PTFE initiators : their influence on the physical properties of the polymer |
| title_full_unstemmed | PTFE initiators : their influence on the physical properties of the polymer |
| title_short | PTFE initiators : their influence on the physical properties of the polymer |
| title_sort | ptfe initiators their influence on the physical properties of the polymer |
| topic | UCTD Polytetrafluoroethylene (PTFE) Free radical polymerization Fluoropolymers Engineering, built environment and information technology theses SDG-08 Engineering, built environment and information technology theses SDG-09 Engineering, built environment and information technology theses SDG-12 |
| url | http://hdl.handle.net/2263/71043 |