Preparation and characterization of modified and unmodified carrageenan based films

Seaweed is a green, abundantly available, and inexpensive source of polysaccharide that can be obtained from the sea. In this work, seaweed was introduced as a potential raw material for the production of a biopolymer-based film. A seaweed-derived biopolymer, carrageenan, with or without alkali modification was investigated for its physical, mechanical, and water vapor barrier as well as thermal properties. The effects of chemical modification on the properties of carrageenan were also further studied by Fourier Transform Infrared Spectroscopy (FTIR) analysis. Results showed that chemically modified carrageenan film exhibited better thermal stability, water vapor barrier property and less hydrophilic as compared to the native seaweed and unmodified carrageenan films. Nevertheless, its mechanical properties (except elongation at breaks) were among the lowest. FTIR analysis indicated that alkali modification of carrageenan capable of removing the hydroxyl and sulfate ester groups in carrageenan structure and meanwhile, forming 3,6-anhydrogalactose, which could improve the flexibility of the film. Moreover, the heating temperature also significantly impacted the properties of the film. As a result, by using carrageenan as a renewable feedstock with or without chemical modification was shown its feasibility on the production of biopolymer film possessed interesting properties. (paper)