Production of Starch/Gelatin Based Films Using the Extrusion Method and in-situ Enhancement of their Hydrophobicity

Document Type : Research Article


1 Department of Polymer Engineering, Faculty of Chemical Engineering, Tarbiat Modares University (TMU), Tehran, Iran

2 Polymer Engineering Department, Faculty of Chemical Engineering, Tarbiat Modares University, Tehran, Iran


Biodegradable films based on corn starch and bovine gelatin were prepared using a co-rotating twin screw extruder in the presence of water and sorbitol as a plasticizing pair. In order to improve hydrophobicity two reactive methods have been utilized: one, chemical bonding with paraffin wax via maleic anhydride and the other, acetylation through anhydride acetic. In both of the methods, the extruder has been used as a reactor. Then, biodegradable films from binary starch/gelatin and ternary starch/gelatin/paraffin grafted starch as well as starch/gelatin/anhydride acetic grafted starch blends were casted using the same extruder. The films were evaluated and compared in terms of mechanical and barrier properties using contact angle, water absorption, water vapor permeation tests. The results indicate that introducing paraffin grafted starch increases the hydrophobicity according to all three above-mentioned criteria, 28 ° increase in water contact angle, 9% decrease in water absorption and 4.2% decrease in water vapor permeation while the mechanical properties were comparable with the binary starch/gelatin film. On the other hand, in starch/gelatin/anhydride maleic films contact angle increased 21 ° and water absorption decreased 4.5% but the mechanical properties lost and water vapor permeation 3.5% boosted compared to the starch/gelatin films.


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