Miscible oriented poly(vinyl alcohol)/starch blend film for biodegradable disposable packaging

Ecofriendly packaging materials are anticipated to serve as an alternative to traditional polyolefin materials for alleviating environmental pollution. In this work, miscible oriented poly(vinyl alcohol) (PVA)/soluble starch packaging films were fabricated via melt processing and hot stretching, overcoming the issues of phase separation and poor mechanical strength. Soluble starch with a high amylose content exhibited excellent miscibility with PVA, endowing the blends with a visible light transmittance of approximately 80%, and resulting in disrupted crystallization and reduced melting points. Benefiting from their microscopic homogeneity, the blends could be subjected to hot stretching to compensate for the deficiency in the mechanical properties. After being stretched to 3.5 times, the tensile strength of the blend film with 20 wt% starch increased from 21.1 MPa to 121 MPa, which was attributed to the formation of denser hydrogen bonding network, an increase in crystallinity, and generation of a preferred orientation structure. Preliminary aerobic biodegradation and soil burial tests demonstrated the biodegradability of the PVA/soluble starch blends, showing that microbes thrived by using the blend film as their sole energy source. The PVA/soluble starch blend film addresses the key chanllenge of phase separation, exhibiting great potential in the application as environmentally friendly packaging materials.