The relationship between chemical microstructure, crystallinity, mechanical properties, and CO2/N2 gases permselectivity of thermoplastic polyurethane membranes

Abstract

In this study, thermoplastic polyurethane (TPU) with 30%wt hard segment content (HSC) was synthesized using isophorone diisocyanate (IPDI), 1, 4-butanediol (BDO) as the chain extender, and polycaprolactone (PCL) with three different molecular weights (2000, 4000, and 10000) as polyols. Fourier-transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (H-NMR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analysis were used to evaluate the chemical microstructure and physical characteristics of polycaprolactones (PCLs) and thermoplastic polyurethanes (TPUs). The results showed that the crystallinity and the glass transition temperature (Tg) of TPUs became different depending on the molecular weight of the PCL soft segments. A tensile strength was used to evaluate the mechanical properties of TPUs. It was observed that increasing the molecular weight of PCL decreased the elongation at break and increased the ultimate tensile strength. The permeability of CO 2 and N 2 gase over wide ranges of pressure (3 to 9 atm) was examined, and the permselectivity of the membranes was determined. It was concluded that an increase in the feeding gas pressure led to an increase in the gas permeability of all samples. It was observed that in TPU samples, the increase in the molecular weight of PCLs led to a decrement in selectivity and an increase in permeability of CO 2 and N 2 gas.