Ethanol-NaOH solidification method to intensify chitosan/poly(vinyl alcohol)/attapulgite composite film

Chitosan/poly(vinyl alcohol) (CS/PVA) films have recently attracted considerable attention. However, CS/PVA film has a significant flaw. It may swell in an aqueous solution and then lose its mechanical strength. Many efforts have been engaged to strengthen the CS/PVA film by adding various reinforcing materials, but the effect of different post-processing methods on the crystallization and mechanical behaviors of the film was rarely investigated. In this study, we have introduced natural nanoscale attapulgite (APT) into CS/PVA film to enhance its mechanical properties. Based on this, the resultant CS/PVA/APT nanocomposite film was further treated with a solution of NaOH and ethanol to regulate the crystallization degree of the polymer chains. The results reveal that the APT nanorods that are uniformly dispersed in the CS/PVA matrix can form a stronger hydrogen-bonding network with the polymer chains to improve the thermal stability and tensile strength. After treatment with NaOH and ethanol, the crystallization degree of the nanocomposite film was greatly enhanced, which caused an evident improvement in its mechanical properties. This method provides a simple and green approach to enhance the mechanical properties of polymer-based films.