Chemical cross linking modification of matrimid membranes using p-phenylenediamine for gas separation

Abstract

Para-phenylenediamine (1,4-diaminobenzene,/PD), for the first time was chosen as the cross linking reagent for Matrimid membranes. The modification was performed by immersing Matrimid membranes in 10%w/v /PD/methanol solution at ambient temperature for certain period of times. The FTIR spectra confirmed that the cross linking process had taken place, which indicates that imide groups were turned to amide groups during modification process. This study found that, there were no insoluble materials found from the gel test. This identified that most of diamines are only grafted onto the polyimides instead of developing the cross linking network. The gas transport properties of the pure and cross linked Matrimid membranes were investigated. The results showed that the cross linked Matrimid membranes decreases the O2 , N2 , CO2 and CH4 permeabilities compared to the unmodified membranes. Interestingly, the cross linked membranes showed an impressive enhancement of selectivity for O2/N2 from 6 to 10 with reasonable productivity and with only a small value increment for N2/CH4. In addition, the selectivity for C02/CH4 and C02/N2 were found to decrease compared to the unmodified membrane. This study concluded that the changes of imide groups to amide groups in the cross linking process has remarkable effects on gas separation properties of modified Matrimid since the chemical cross-linking modification by /PD display similar effects with the chemical cross linking modification that applied other types of diamines that performed complete cross linking process.