Mechanical and permeability properties of biodegradable extruded starch/polycaprolactone films

Barley starch and glycerol were mixed with polycaprolactone (PCL)powder in various combinations and plasticized in a twin-screw extruder. When possible, extrudates were processed into films in a single-screw extruder and subjected to an orientation process with the aim of improving the water durability and mechanical strength of the starch films. The mechanical properties, water vapour and oxygen permeabilities, sorption isotherms and solubility of the processed films were studied. The films containing 20 percent or more PCL achieved a tensile strength of 20 MPa or higher. Orientation of the film still further improved the tensile strength, and also the water vapour and oxygen barrier properties. With PCL contents of 0-20 percent the starch/PCL films proved to be excellent oxygen barriers. Increase in PCL content beyond this impaired the oxygen barrier properties, whilst improving the water barrier properties.