Novel polymer nanomaterials for food packaging based on modified cellulose nanofibres

Nanocomposite materials based on polymers and various types of nanoparticles or -fibres have gained much interest lately as packaging materials, coatings, wound healing bandages, etc. Microfibrillated cellulose (MFC) with a thickness of 1–50 nm and a length of several μm (regarded as a nanomaterial) has been surface modified using its large number of hydroxyl groups. A wide variety of new functionalities have been introduced, both reactive groups as epoxy, amines, succinic and maleic acid for covalent introduction to matrix materials and hydrophobic compounds such as octadecylamine and poly(styrene-comaleic anhydride) for enhanced compatibility with the matrix. These modified MFC may be added to various different commonly used polymers in food packaging, e.g. PE, PP, PS, or paper, both to bulk materials and films to introduce new and improved properties. The strength of base paper increased significantly when coated with a layer of less than 10 % of MFC, whether pure or surface modified, and the air permeability decreased dramatically. Special focus will be given to antimicrobial MFC materials for use in food packaging. The challenge with antimicrobial packaging materials is often possible leakage to the food and/or fast wash-out with only temporary effect. Quaternary C18 ammonium ions were covalently attached to MFC. These functional groups disrupt the cell membrane of the bacterial cells through physical and ionic phenomena and will kill bacteria attached to the packaging material. These modified MFC are promising candidates as fillers for novel food packaging nanocomposite materials, combining antimicrobial activity with increased strength and decreased permeability due to fibre reinforcement.