Preparation And Properties Of Starch/Polyester Fully Biodegradable Composite Films

In the last decade,discarded non-degradable petrochemical plastics,specifically packaging films,have resulted in environmental problems worldwide.To minimize the environmental pollution caused by traditional plastics,the research and development of degradable materials for packaging have attracted considerable attention.Starch is a promising natural polymer that can replace traditional plastics in the packaging field because of its low cost,wide availability,renewability,and biodegradability.However,the poor mechanical properties and moisture resistance of starch films seriously limit their application as a commercial packaging material.In the present paper,starch/polyester trilayer composite film was prepared by three-layer co-extrusion blowing via screening the appropriate inner and outer layer formula,adjusting proper inner and outer layer formulations.The main findings are as follows:(1)The starch/polyester trilayer composite films with different inner and outer layer thickness were prepared by co-extrusion blowing.Scanning electron microscopy(SEM)results showed the successful fabrication of trilayer composite films.The crystallinity of trilayer composite films gradually increased as the thickness of Ecovio^?F2223 layer increased.The presence of Ecovio^?F2223 layer significantly increased the tensile strength and water contact angle of starch composite films.All trilayer composite films had lower water-vapor permeability than the starch film,and lower oxygen permeability than the Ecovio^?F2223 film.The trilayer composite films were degraded to a much greater extent compared with the Ecovio^?F2223 film.The weight loss of P10 trilayer composite films in soil in 120 days is about80%.(2)The performance of the composite films was significantly affected by the weight proportions of starch and poly(butylene adipate-co-terephthalate)(PBAT).The results showed that with the increase of PBAT content,the fluidity of starch/PBAT blends increased,and the modulus and composite viscosity decreased,and the hydrogen bonding was weakened.The mechanical properties and barrier properties of the starch films were significantly improved by adding PBAT.The maximum tensile strength and elongation at break of the starch/PBAT composite films in the longitudinal direction were 7.86 MPa and 532.4%,respectively.The minimum water-vapor permeability and oxygen permeability were 3.74×10^-11g·m^-1·s^-1·Pa^-1and 5.77×10^-15 cm²·s^-1·Pa^-1,respectively.(3)The extrusion blow molding process(traction speed and screw speed)affects the performance of starch trilayer composite film.With the increase of the traction speed,the tensile strength of the starch/PBAT trilayer composite films shows an increasing trend,while the elongation at break shows a reverse trend.The water vapor permeability decreased and the light transmittance increased.With the increase of the outer screw speed,the tensile strength and elongation at break of the starch/PBAT trilayer composite films increase,the water vapor permeability and the light transmittance decreased.SEM observed that the boundaries between layers of the film became obvious.