High-performance biodegradable poly(vinyl alcohol)/starch composites via alkaline-regulated crystalline engineering

Abstract

The increasing demand for environmentally-friendly products has led to a growing focus on the development of high-performance biodegradable materials. However, achieving a balance between mechanical strength, water resistance, and biodegradability remains a challenge. Herein, the successful preparation of exceptional biodegradable poly(vinyl alcohol) (PVA)/starch (ST) composites using alkaline-regulated crystalline engineering is reported. The findings demonstrate that the alkali promotes ST gelatinization while inhibiting its recrystallization, resulting in improved compatibility and good dispersion in the PVA matrix. In contrast, the alkali enhances the crystallization of PVA, thereby improving the composites' water resistance. The composites exhibit outstanding mechanical properties, with a strain at break of approximately 400 % and a toughness of 54 MJ/m3, surpassing most reported works. Even in high humidity and water environments, the composites maintain their mechanical strength, with a strength of 13 MPa after soaking in water for 1 d, significantly higher than films without the addition of alkali. Moreover, the composites exhibit excellent biodegradability, with a degradation rate exceeding 40 % after a 60-d natural soil burial test. The flame retardancy is also greatly enhanced, with a limiting oxygen index (LOI) of 30 %. This study offers a promising avenue for the development of high-performance biodegradable materials such as dip-coating fabric, fire retardant coating, and industrial packaging.