The Structure and Properties of Ultrathin Films Blended from Nanofibrils of Natural Fibers.

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In this study, a new type of the biodegradable ultrathin films have been developed using natural nanofibrils (NFs), and the surface-structure of their ultrathin films and mechanical properties are analyzed. Three kinds of natural fibers, wood pulp (bleached kraft pulp, cellulose), chitosan (commercial grade) and collagen (cow hide waste) were used as raw materials. A small commercial grinder with a specially designed disk was used to nanofibrillate the natural fibers. All the materials were controlled as a slurry containing 90 - 99 % water. The diameter of their NFs from wood pulp was about some nanometer and the diameter of the some ones from chitosan and collagen were some ten nanometer. A new type of ultrathin film was made from the water suspension of NFs. The thicknesses of these films were from about some hundreds nanometer to about some tens nanometer, being homogeneous, strong and translucent. The ultra thin films of three kinds of NFs were easily obtained by this water-suspension method without using an organic solvent. Each NFs in ultrathin films is oriented to parallel to its surface plane by structural analysis. The formation process of their ultrathin films was made by microfibrillating the NFs, and then their networks of microfibril were compared with the ordinary films of solvent-cast method. Now, we are able to prepare thin hybrid films which are expected for many uses. The thin film from the mixture of wood pulp, chitosan and collagen was about 1.5 times of that of print grade paper and about 2 times of that of polyethylene. These values of the films are sufficient for practical use.