Relationship between the Microstructure and Gas Transport Properties of Polyurethane/Polycaprolactone Blends

In this study, the relation between the permeation properties and structural characteristics of thermoplastic polyurethane based on polycaprolactone diol, TPU(PCL), and polycaprolactone (PCL) blends is investigated. for the purpsoes of this study, PU, PCL, and TPU/PCL blends containing 20 wt.% and 40 wt.% PCL were prepared via a solution blending method. The miscibility and good distribution of PCL in the soft segment of PU were represented by the reduced intensity of the band attributed to the NH band at 3400 cm^-1 in the Fourier transform infrared (FTIR) spectra. X-ray diffratcion (XRD) results indicated that the amorphous structure of TPU changed to a crystalline one when PCL was added. These results were further confirmed by FTIR and differential scanning calorimetry (DSC) analyses. The permeability of CO2, O2, N2, and CH4 gases at different feed pressures ranging from 12 to 16 bar were determined. A reduction in gas permeability due to the increase in PCL content was observed in the blends. However, gas selectivity did not change with addition of PCL.