Anchor and bridge functions of APTES layer on interface between hydrophilic starch films and hydrophobic soyabean oil coating

One of the well-recognized weaknesses of starch-based materials is their sensitivity to moisture, which limits their expanding applications. Natural materials, soyabean oils have been used as a coating for starch film, but the poor interface between hydrophilic starch and hydrophobic soyabean oil needs to be improved. In this work, (3-Aminopropyl) triethoxysilane (APTES) was used to reinforce the bonding between starch matrix and the coating of bio-based acrylated epoxidized soyabean oil (AESO). Study results show that APTES interacted effectively with both starch films via hydrogen bonding, and chemical bonds with AESO through the Michael addition reaction. Pull adhesion and cross-cutting tests demonstrated that the interfacial adhesion was significantly improved after treating their surface with APTES. The interfacial adhesion strength increased over 4 times after treating with 1.6 wt% APTES. The starch films treated with APTES and AESO coating were intact after soaking in water for more than 2 h. • Water resistant starch film coated with AESO-APTES double layers has been developed. • Interfacial adhesion between starch and AESO coating is significantly improved after surface treatment with APTES. • The WVP of starch film decreases after coating, especially the coating treated with APTES. • Mechanical properties of starch films are much more stable under high humidity conditions after double layer coatings.