eprintid: 6386
rev_number: 4
userid: 6
dir: disk0/00/00/63/86
datestamp: 2011-11-10 19:31:43
lastmod: 2016-11-15 13:36:36
status_changed: 2011-11-10 19:31:43
type: thesis_degree
metadata_visibility: show
contact_email: jiz31@pitt.edu
item_issues_count: 0
eprint_status: archive
creators_name: Zhang, Jie
creators_email: jiz31@pitt.edu
creators_id: JIZ31
title: Teflon AF membrane transport of organic solutes
ispublished: unpub
divisions: sch_as_chemistry
full_text_status: public
keywords:  permeability; selectivity; FC-70; membrane transport; temperature effect
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.
date: 2006-06-29
date_type: completed
institution: University of Pittsburgh
refereed: TRUE
etdcommittee_type: committee_chair
etdcommittee_type: committee_member
etdcommittee_type: committee_member
etdcommittee_name: Weber, Stephen G.
etdcommittee_name: Michael, Adrian
etdcommittee_name: Curran, Dennis
etdcommittee_email: sweber@pitt.edu
etdcommittee_email: amichael@pitt.edu
etdcommittee_email: curran@pitt.edu
etdcommittee_id: SWEBER
etdcommittee_id: AMICHAEL
etdcommittee_id: CURRAN
etd_defense_date: 2006-02-03
etd_approval_date: 2006-06-29
etd_submission_date: 2006-02-21
etd_access_restriction: immediate
etd_patent_pending: FALSE
assigned_doi: doi:10.5195/pitt.etd.2011.6386
thesis_type: thesis
degree: MS
committee: Stephen G Weber (sweber@pitt.edu) - Committee Chair
committee: Adrian Michael (amichael@pitt.edu) - Committee Member
committee: Dennis Curran (curran@pitt.edu) - Committee Member
etdurn: etd-02212006-112911
other_id: http://etd.library.pitt.edu/ETD/available/etd-02212006-112911/
other_id: etd-02212006-112911
citation:   Zhang, Jie  (2006) Teflon AF membrane transport of organic solutes.  Master's Thesis, University of Pittsburgh.    (Unpublished)  
document_url: http://d-scholarship-dev.library.pitt.edu/6386/1/2006JieZhangThesis.pdf