Poly(vinyl alcohol)/Kaolin Barrier Films with Superior Dispersion Fabricated by Solid-State Shear Milling and Biaxial Stretching

Under the threat of environmental pollution caused by waste plastics, environmentally friendly and biodegradable materials with superior performance have attracted worldwide public attention. Herein, by combining solid-state shear milling (S3M) and biaxial stretching technologies, high-performance and environmentally friendly poly(vinyl alcohol) (PVA)/kaolin barrier films used for packaging were fabricated. The highly effective S3M technology simultaneously achieved the in situ exfoliation and superior dispersion of layered kaolin in the PVA matrix at ambient temperature. These kaolin nanoflakes featured a thickness of ∼3 nm and a width of ∼70 nm, thus effectively blocking the movement of PVA molecular chains and leading to the increase of glass transition temperature (Tg) as well as the initial degradation temperature of the PVA matrix. By further synchronously biaxial stretching, benefiting from the well-dispersed kaolin and the oriented PVA molecular chains, the obtained anisotropic composite film with 5 wt % kaolin exhibited extremely high yield strength (138.7 MPa), tensile strength (146.4 MPa), and Young's modulus (5.5 GPa), as well as excellent ultraviolet (UV) and oxygen barrier properties. This work not only highlights a novel strategy for achieving synchronous exfoliation and dispersion of layered clay minerals in a polymer matrix but also facilitates the green development of high-performance polymer-based films used for packaging.