cross-linking and solvent treatment of pei membranes · 2017. 11. 18. · cross-linking results...
TRANSCRIPT
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Cross-Linking Results
Cross-Linking and Solvent Treatment of PEI Membranes Connor Seacat · Griffin Karr · Michael Wales · Mary Rezac
Background
Membranes are used for separating gasses.
The polymer that we are constructing our membranes from is polyetherimide (PEI).
Solvent treatments intend to increase selectivity of the membranes and cross-linking prevents membranes from becoming plasticized. Plasticization occurs when gasses absorb into the membrane in large quantities and disrupt the packing of the polymer chains causing the membrane to lose its selective permeability.
Research Objective
Key Findings
Methods
XRD and FTIR data indicate that we effectively crosslinked the membranes.
Most solvents negatively affected the membranes’ gas selectivity. 1-Heptanol and n-Amyl alcohol showed improvements to the selectivity of the membranes.
GPU= %&'()*@-./01*2∗.4)*∗5**6/1*77(1*
Membranes were gas flux tested before and after each treatment.
Gas permeability was calculated by:
Peaks shifting right indicate decreased d-spacing due to cross-linking.
Amorphous halo shifting left indicates swelling of polymer chains.
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30050070090011001300150017001900
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cm-1
FTIRDataOfEthyleneDiamine
0Hr
5Hr
8HrImide
Amide
Amide
Imide
Imide
Imide bands:(1) ≈1770 cm-1(2) ≈1700 cm−1(3) ≈1340 cm−1
Amide bands: (1) ≈1645 cm-1(2) ≈1530 cm-1
Solvent Treatment Results
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He/N
2Selectivity
PermeanceHe
He/N2SelectivityvsPermeanceofHe
1-Butanol
n-Amyl
1-Heptanol
1-Octanol
Hexadecane
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0 1 2
He/N
2Selectivity
Treatment
He/N2SelectivityvsNumberofSolventTreatments
1-Butanol
n-Amyl
1-Heptanol
1-Octanol
Hexadecane
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0.005
0.01
0.015
0.02
0.025
1-Butanol n-Amyl 1-Heptanol 1-Octanol Hexadecane
MassS
olvent/M
assP
olym
er
VaporSorptionofPEIFilm
GasSupply
GasSelector
FeedPressureKnob
FeedPressureGauge
RetentateValve
MembraneHolder
VacuumValve
VacuumPump
PressureTransducer
Ballast
Membranes were prepared by dissolving PEI in a solvent solution and then casting that solution onto a glass sheet.The membranes were thenprecipitated in a bath of acetone and dried.
Use diamines to cross-link PEI membranes through vapor exposure and liquid baths in alcohol-diamine solutions.
Treat PEI membranes with various solvents to heal imperfections and increase the selectivity of He to N2 and He to O2 gasses through the membranes.
Determine most effective solvents and treatment styles.
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ryUnits
2Theta(Degrees)
1,3-diaminopropaneXRD
Unmodified PEI 2hr(T1)diaminopropane 2hr(T2)diaminopropane
4hr(T1)diaminopropane 4hr(T2)diaminopropane 8hr(T1)diaminopropane
8hr(T2)diaminopropane
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ryUnits
2Theta(Degrees)
EthylenediamineXRD
Unmodified PEI 2hr(T1)ethylenediamine 2hr(T2)ethylenediamine
4hr(T1)ethylenediamine 4hr(T2)ethylenediamine 8hr(T1)ethylenediamine
8hr(T2)ethylenediamine
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ryUnits
2Theta(Degrees)
1,3-Cyclohexanebis(methylamine)XRD
Unmodified PEI 2hr(T1)cyclohexanebis 2hr(T2)cyclohexanebis
4hr(T1)cyclohexanebis 4hr(T2)cyclohexanebis 8hr(T1)cyclohexanebis
8hr(T2)cyclohexanebis
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ryUnits
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1,3-diaminobutaneXRD
Unmodified PEI 2hr(T1)diaminobutane 2hr(T2)diaminobutane
4hr(T1)diaminobutane 8hr(T1)diaminobutane 8hr(T2)diaminobutane
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δh
(δd^2+δp^2)^.5
δhvs(δd^2+δp^2)^.5
PEI
methylenechloride(1)
methylenechloride(2)
water(1)
water(2)
methanol
ethanol
1-propanol
2-propanol
1-butanol
Heptane
Toluene(1)
Toluene(2)
p-xylene(1)
p-xylene(2)
Solubility parameters and sorption data were used to predict the effects of the solvent.
FTIR Data for Ethylene Diamine