Preparation of graphene oxide-silica nanohybrid/poly(lactic acid) biaxially oriented films with enhanced mechanical properties

Poly(lactic acid) (PLA) biaxially stretched films and graphene oxide-silica nanohybrids (GO-SiO2)/PLA nanocomposite biaxially stretched films (PGSi) with different stretching ratios were prepared by simultaneous biaxial stretching. The structural changes during biaxial stretching have a direct impact on the properties of the biaxially stretched films. Therefore, this work mainly studies the effect of the presence of filler (i.e., GO-SiO2) on the structural evolution of PLA during biaxial stretching, and establishes a bridge between structural changes and property changes. Through wide-angle X-ray diffraction (WAXD) and atomic force microscopy (AFM), it was found that GO-SiO2 facilitates the isotropic orientation of molecular chains during biaxial stretching and attenuates the degree of preferred orientation. As a result, the mechanical properties of PGSi biaxially oriented films are inferior to those of PLA biaxially oriented films. However, the synergistic effect of the excellent barrier property of GO-SiO2 and biaxial stretching make the barrier property of PGSi biaxially stretched films even better. In addition, when the tensile force is stronger than the interfacial force between GO-SiO2 and PLA, GO-SiO2 will precipitate out of PLA under the condition of a large stretching ratio, resulting in the generation of defects, which is not conducive to the improvement of PLA performance.