Structural evolution and barrier properties in biaxially stretched polyethylene terephthalate/hydroxy-terminated polybutadiene films

This paper aims to investigate the crystallization and barrier properties of oxygen-scavenging polyethylene terephthalate films (OSP) at different stretching ratios and stretching rates. The results show that with the increase of the stretching ratio, more regular lamellar crystal was formed in the biaxially stretched OSP films, and the amorphous phase thickness between lamellae and the long period decreased. The presence of oxygen scavenger acted as heterogeneous nucleation, further promoting the crystallization of the OSP films. This was conducive to prolong the diffusion path of gas molecules through the film. Furthermore, the increase of the stretching ratio expanded the "active"oxygen barrier area of the oxygen scavengers. Thus, the barrier performance of the biaxially stretched OSP films was improved significantly. In addition, the variation of crystallinity and properties of OSP films with the stretching ratio was consistent with the variation with the stretching rate, but the stretching ratio had a greater impact. It was also found that the increase of the stretching ratio and the introduction of oxygen scavenger both increased the stretching strength of the OSP films, while the biaxially stretched OSP film maintained good optical properties.