Amorphous polyamide m‐xylylenediamine‐adipic acid‐isophthalic acid copolymer (MXD6I): Evaluation of oxygen barrier property and free volume in high humidity condition. (5th January 2022) - Yamanaka, Masaki
Abstract: To get insights into the excellent gas‐barrier properties of amorphous polyamide m ‐xylylenediamine‐adipic acid‐isophthalic acid copolymer (MXD6I), free‐volume hole size and thermophysical properties of MXD6I were evaluated. The results from positron annihilation lifetime spectroscopy (PALS) showed that the free‐volume hole size of MXD6I—which was estimated from the ortho‐positronium ( o ‐Ps) lifetime and o ‐Ps intensity—remained almost unchanged even with a high water‐absorption rate. This indicates that no significant structural changes occurred in MXD6I. In contrast, the free‐volume hole size of the semicrystalline polyamide MXD6 significantly increased due to water absorption. The glass transition temperature ( T g ) of MXD6I decreased due to water absorption, but it remained higher than the ambient temperature. The molecular motion of MXD6I is likely to be limited even under high humidity conditions; therefore, nanoscale structural changes such as crystallization are unlikely. We found that the stable gas‐barrier properties of MXD6I can be attributed to its amorphous nature and a high T g even in a water‐saturated state.