Zhang, Jie
(2006)
Teflon AF membrane transport of organic solutes.
Master's Thesis, University of Pittsburgh.
(Unpublished)
Abstract
Teflon AF 2400 membranes containing various weight percent FC-70 were cast from FC-72 solution. The membrane surface is hydrophobic as shown by contact angle measurement. Free volume in Teflon membranes was calculated by measuring the membrane density using the hydrostatic method. Differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) were conducted to study the thermal transitions of Teflon AF membranes. The glass transition temperature of Teflon membranes is -63 ¡ãC at 5 wt% FC-70 in comparison with 240 ¡ãC at 0 wt% FC-70. The permeability of Teflon membranes was investigated by transport experiments. The four probe solutes were toluene, ¦Á,¦Á,¦Á-trifluorotoluene, nitrobenzene and pentafluoronitrobenzene. The permeability coefficients of the probe solutes are found to be very sensitive to the FC-70 content and the temperature. The permeability coefficients of all solutes change with FC-70 in a similar way. They decrease initially as FC-70 content increases at low FC-70 concentration with reversal of this trend at higher FC-70 concentration, and decrease again and finally level off. Teflon AF membranes with less than 10 wt% FC-70 could be associated with the polymer¡¯s anti-plasticization, an effect indicated by a reduction in the free volume, a decrease in the glass transition temperature and a reduction in the partition ratio and permeability coefficient. Teflon AF membranes with 10 wt% FC-70 or more could be plasticized, resulting in lower glass transition temperature, higher free volume and higher permeability coefficient. Selectivity of the membranes was investigated for the pair ¦Á,¦Á,¦Á-trifluorotoluene/toluene and for the pair pentafluoronitrobenzene/nitrobenzene. It reaches a maximum at 10 wt% FC-70 for both pairs at 20oC. 10 wt% FC-70 is likely a turning point of plasticization, which is quite interesting since it is also related to the highest selectivity.Teflon AF membranes could also be plasticized by the organic liquid with which it is in contact. Chloroform seems to plasticize the membranes (they get pliable) and change the properties of the membranes to a less ¡®fluorous¡¯ environment. The concentration of FC-70 may change during transport experiments. We thus need to find a means to plasticize the films while keeping them fluorous.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
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| ETD Committee: |
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| Date: |
29 June 2006 |
| Date Type: |
Completion |
| Defense Date: |
3 February 2006 |
| Approval Date: |
29 June 2006 |
| Submission Date: |
21 February 2006 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
MS - Master of Science |
| Thesis Type: |
Master's Thesis |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
permeability; selectivity; FC-70; membrane transport; temperature effect |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-02212006-112911/, etd-02212006-112911 |
| Date Deposited: |
10 Nov 2011 19:31 |
| Last Modified: |
15 Nov 2016 13:36 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/6386 |
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