Zein/hydroxypropylcellulose Biofilms with Hydrophilic and Hydrophobic Montmorillonite Clays

This study analyzed the changes in the structural, morphological and mechanical properties of Biofilm A (46.1% zein/30.8% hydroxypropylcellulose/23.1% propylene glycol) and Biofilm B (53.8% zein/23.1% hydroxypropylcellulose/23.1% propylene glycol) when 0.5%, 1% or 2% Cloisite Na+ (NaMt) and 1% Cloisite 30B (C30B) were added to the systems. Infrared spectroscopy showed clay particles interact with the polymeric matrix mainly via hydrogen bonds between silanol and amide/hydroxyl groups from minerals and polymers, respectively. X-ray diffraction and small angle X-ray scattering patterns indicated clays were exfoliated in both formulations with 0.5% NaMT and 1% C30B, or presented larger lamellar spacing on biofilms containing 1% or 2% of hydrophilic clay compared to pure clays. Scanning electron micrographs showed clay were incorporated into the polymers at low clay content and presented some aggregates at 2% NaMt. Mechanical tests showed that Biofilms B had better mechanical properties compared to Biofilms A, and Biofilms B with 1% NaMt presented the highest value of tensile strength. Moreover, the addition of organophilic clay in both formulations produced nanocomposites with good mechanical properties. These results showed clays are strategic to obtain nanocomposite films with interesting physical and chemical properties.