Starch-based nano-biocomposites: Plasticizer impact on the montmorillonite exfoliation process

The present paper analyzes the effects of the plasticizer nature on the clay exfoliation process into starch-based nano-biocomposites. The nano-hybrids have been elaborated by melt blending starch with different plasticizers, namely, glycerol, sorbitol and Polysorb®. In addition two types of nanofillers, natural montmorillonite (MMT-Na) and montmorillonite organo-modified with cationic starch (OMMT-CS) have been tested. Intercalated/aggregated and exfoliated morphologies were obtained with respectively MMT-Na and OMMT-CS as the nanofillers and glycerol as the plasticizer. Morphological analyses combined with uniaxial tensile tests have shown the negative effect of the sorbitol on the exfoliation extent into such nano-hybrid materials. Besides, thermo-mechanical analyses revealed the occurrence of a phase separation between domains rich and without nanofillers induced by the high plasticizer content of the starch formulations.