Polymer composites containing chitosan and starch as biodegradable fillers

Blending (at 20 degrees C) of chitosan or potato starch as a biodegradable filler with the oligomeric matrix of a bioundegradable unsaturated polyester resin (UPR) or oligo(methyl methacrylate) (OMMA), Polimal 194-3, followed by polymerization of the matrix [induced in UPR and in OMMA by UV irradiation (0.5 h) and by benzoyl peroxide (2%, 60 degrees C, 4 h), resp.], yielded composites containing up to 15% (optimum) of chitosan or up to 40% of starch. Samples were prepared as films 20 to 50 mu m thick. The composites were heterogeneous with numerous starch grain inclusions evident in microscopic examination (Fig. 1). As the biodegradable filler content was increased, the breaking strength and the elasticity modulus of the composite decreased (Figs. 2 and 3); they rose considerably after the composite had been photo-hardened (UV, 3 h) (Fig. 4). DSC (DuPont instrument, -3 degrees C to 200 degrees C, 10 degrees C/min) thermograms showed the polymerization of the OMMA matrix to PMMA to be accelerated by the fillers used (Fig. 7).