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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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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He/N

2Selectivity

Treatment

He/N2SelectivityvsNumberofSolventTreatments

1-Butanol

n-Amyl

1-Heptanol

1-Octanol

Hexadecane

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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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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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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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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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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