| abstract |
Biodegradable packaging films are provided. The film is made of a blend containing thermoplastic starch and polylactic acid. Starch is a relatively cheap natural polymer and is also renewable and biodegradable. Similarly, polylactic acid is a relatively inexpensive synthetic polymer and may be biodegradable and renewable while providing increased tensile strength to the film. While providing a good combination of biodegradability / regeneration and increased tensile strength, polylactic acid can also produce films that are relatively rigid and have relatively high stiffness (eg, high modulus of elasticity) and low ductility. Thermoplastic starch is softer than polylactic acid but is often difficult to melt process in film making processes and is very sensitive to moisture and water vapor, reducing its ability to be used as a single packaging film. In an effort to counteract the effects of such polymers, aliphatic-aromatic copolyesters are also used in the blends of the present invention. Such copolyesters are biodegradable, but they also have melting properties and ductility that make them excellent in the formation of films. Combinations of these polymers can achieve a good balance between biodegradability / regeneration, high tensile strength and good ductility (eg, high maximum elongation), but it is often difficult to achieve the exact set of mechanical properties still required for packaging films. . In this regard, the blend may contain a filler. Because of its rigid nature, the amount of filler can be easily adjusted to precisely match the blend to the desired degree of ductility (eg, maximum elongation) and stiffness (eg, modulus of elasticity). |