Biodegradable nanocomposite films based on amylopectin and chitosan

Sammanfattning: The use of disposable material is rapidly increasing, today the absolute majority of the material used for these application, i.e. food packages, are oil-based plastics such as polyethylene and polypropylene. Therefore it is of great importance to find alternative biodegradable materials made from renewable resources for this huge growing market. In the present thesis, work and research to develop and improve such materials are presented. Amylopectin and chiotsan are two interesting material choises for these applications. In this thesis serveral ways of improving amylopectin (AP) and chitosan films are presented, using either Na+-montmorillonite (MMT) or microfibrillated cellulose (MFC). A novel approach of using a water-soluble coupling agent to enchance the strength and stiffness of MMT/AP-composites by increasing the adhesion beween the matrix and the filler. The results from IR, mechanical and moisture absorption tests show that the coupling agent indeed improve the properties of the composite films. Studies on MFC/AP show that the MFC have a remarkable effect of acting as a reinforcing plasticiser creating a flexible material without the use of a plasticiser. Thermal measurements show that the MFC have a ability to bound water very tightly. This was further investigated with thermal analysis. Chitosan, another interesting “green material”, and the effect of using MFC and/or a well-known buffer treatment, to enhace the mechanical properties of chitosan films in dry and wet conditions have here been investigated. The addition of MFC prevented extensive shrinkage in the wet condition due to increased wet stiffness.