Effect of triglyceride on the microstructure and gas permeation performance of Pebax-based blend membranes

Abstract A series of Pebax 2533/triglyceride (20 wt%) blend membranes were prepared to study the influence of triglyceride structure on Pebax-based membrane for the first time. The microstructure and morphology of blend membranes were characterized by XRD and SEM. The interaction and compatibility between Pebax and triglyceride were characterized by ATR-FTIR and DSC. The mechanical property of Pebax/triglyceride blend membrane was tested by universal testing machine. The thermal stability and the triglyceride content in blend membranes were characterized by TGA. Pebax showed relatively high compatibility with tripropionin (TPP), tributyrin (TBT) and tricapronin (TCP) and Pebax/triglyceride blend membranes showed reasonable mechanical property. The thermal stability of the Pebax/triglyceride blend membranes increased with the increase of triglyceride alkyl chain and Pebax/TCP blend membrane showed the highest thermal stability. For gas permeation of Pebax/triglyceride blend membranes, it relied on the combined action of ester group concentration, plasticization of triglyceride and volume resistance of alkyl chain. CO2 permeability of Pebax/triglyceride blend membranes all increased in comparison with Pebax membrane. However, due to the decline of ester group concentration and the increase of volume resistance with the increase of triglyceride alkyl chain, the degree of CO2 permeability enhancement of blend membranes decreased with the increase of alkyl chain length of triglyceride, that was Pebax/TPP > Pebax/TBT >Pebax/TCP. More specifically, for Pebax/triglyceride blend membranes, diffusion coefficients were the major factors contributing to the improvement of CO2 permeability. While solubility coefficients were the major factors to determine the trend of CO2 permeability. Thus, Pebax/TPP blend membrane showed the highest CO2 permeability of 566 Barrer with moderate CO2/N2 selectivity of 25 at 35 °C. While Pebax/TCP blend membrane showed constant CO2 permeability around 508 Barrer within 120 h gas permeation testing.