Caseinate based biodegradable films with improved water resistance
Résumé
Proteins are considered as an interesting alternative to traditional synthetic polymers in packaging applications. Sodium caseinate based films can be used in such area, but some of their properties need to be improved. The objective of this work was to improve water resistance of caseinate based films plasticized with triethanolamine (TEA). First, plasticized films were crosslinked by formaldehyde (HCHO) or by electron beam irradiation. The crosslinking efficiency was correlated to the decrease of protein solubility in water determined from a 280 nm absorbance method. The comparison between the two crosslinking methods showed that formaldehyde crosslinking was significantly more efficient than irradiation. The HCHO crosslinking technique was selected for the following of the study. Nevertheless, even for highly crosslinked samples, the plasticizer exuded out of the film. A second part of this work was focused on the effect of surface modification on plasticizer exudation in TEA plasticized caseinate films. Considering that silicone grease coating onto the film surface was able to control TEA exudation, surface modifying additives (SMA) based on NaCAS and organo-silicones were used to modify films surface properties. Surface wettability and energy were determined from contact angle measurements. TEA exudation ratios in water were also monitored for films containing SMA. SMA were less efficient in controlling TEA exudation rates but could significantly reduce surface energy to 42 mJ m2.