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Title: Tetrafluoroethylene polymerisation : fundamentals of a complex industrial process
Author: Tomlinson, Martha
ISNI:       0000 0004 2739 4978
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2011
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This study was an investigation of the complex industrial PTFE polymerisation. Ex- periments were devised within the operating conditions to investigate the solubility of tetrafluoroethylene (TFE) in the hydrocarbon wax added to the polymerisation. Over the polyrnerisatlon pressures, the solubility of TFE in the wax varied from 5.6x10-2 mol dm-3 (1000 kPa) to 11.2x10-2 mol dm-3 (1310 kPa). The solubility was decreased by the pres- ence of ammonium perfluorooctanoate (APFO), a trend also observed for nitrogen. Four polytetrafluoroethylene (PTFE} polymerisations were performed to ascertain the effect of varying quantities of wax on the dispersion and polymer particles produced. No significant difference in molecular weight, particle size or particle crystallinity was observed. It has been proposed that the role of the wax is to aid solubilisation of TFE in the aqueous phase and it does play a pivotal role in the nucleation or growth mechanism of PTFE. It is theorised that PTFE particles change from rods to cobble-stone particles via a roll-up mechanism. Statistical analysis of the particle shapes and size was performed from electron microscopy images. No evidence for a roll-up mechanism was observed. The rate of polymerisation was investigated through a novel experimental procedure and the 1 st-order rate constant with respect to TFE was found to be of the order of 1 x 10-3 s-1. The addition of nitrogen to the autoclave reduced the rate of polymerisation substantially. 2,3,4,5,6-pentafluorostyrene (PFS) was chosen to develop a polymerisation recipe with the aim to mimic the PTFE polymerisation. A reproducible aqueous synthesis was developed and used to test fluorinated surfactants with and without the presence of wax. A method of determining the kinetics of polymerisation using gas chromatography-mass spectrometry was created. The addition of wax reduced the rate of all polymerisations as PFS was preferentially soluble in the wax over the aqueous phase.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available