Submitted to: Polymers and the Environment
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/1/2004
Publication Date: 4/1/2005
Citation: Rutiaga, M.O., Galan, L.J., Morales, L.H., Gordon, S.H., Imam, S.H., Nino, K.A. 2005. Mechanical property and biodegradability of cast films prepared from blends of oppositely charged biopolymers. Polymers and the Environment. 13(2):185-191 Interpretive Summary: Many renewable polymers carry either negative or positive charge on their surfaces. In this study, advantage was taken to prepare thin films by blending polymers with opposite charges to obtain ionically crosslinked materials of improved properties. Results indicated that films made from anionic starch-chitosan had superior tensile properties due to the stable and stronger ionic bonds formed between anionic starch and positively charged groups in chitosan polymer. When exposed to compost, polymers in the film biodegraded as usual, indicating that ionic crosslinking did not interfere with polymer's inherent ability to biodegrade in nature.
Technical Abstract: About 50 mm thick cast films containing blends of oppositely charged biopolymers such as anionic starch-chitosan, and cationic starch-pectin were fabricated. The tensile strength and elongation at break (%) of the films were evaluated as well as their capacity to degrade in compost. The total mineralization of film by microorganisms in compost soil was also measured using respirometric techniques. In soil, films were recovered every 48 hours, and the degradation was assessed by their weight-losses, diminution of polymer's characteristic peak absorbance in Fourier transform infrared (FTIR) spectroscopy, and changes in the surface morphology via scanning electron microscopy (SEM). Anionic starch-chitosan films had much superior tensile strength and elongation compared to cationic starch-pectin, suggesting that the ionic bonds formed between anionic starch and positively charged groups in chitosan polymer were much more stable and stronger. Initially, both films lost about 36% weight within 96 hours, which also correlated well with the loss in the characteristic absorption peaks in the infrared region of the spectrum typical of biopolymers. Though, the rates of mineralization differed for two formulations, total mineralization (extent) for both films were achieved within 45 days.