Optimisation of compatibility for improving elongation at break of chitosan/starch films

When chitosan/starch films were used as agricultural mulch films, the problem of rupture often occurred. In order to improve the elongation at break, chitosan/starch blend films were prepared by casting with different formulations (different ratios of chitosan to starch, different plasticizing components and different plasticizer ratios) in this research. The elongation at break of the film reached up to 104.1% when chitosan was plasticized with 10% glycerol and 0.94% ethylene glycol alone and then mixed according to a 1 : 0.6 chitosan–starch ratio. The fact that plasticizing starch, plasticizing chitosan or co-plasticizing starch and chitosan made a big difference to the mechanical properties of the films was discovered for the first time. The films with different plasticizing components were characterized by their mechanical properties, crystal structures and surface morphologies. Mechanical properties of the films were related to their crystallinity. The higher the crystallinity, the higher the elongation at break. Plasticizing starch alone facilitated the formation of hydrogen bonds and massive structures. Plasticizing chitosan alone was beneficial to the formation of network structures of the films and exhibited anti-plasticization at low plasticizer concentration.