Thermomechanical and acidic treatments to improve plasticization and properties of chitosan films A comparative study of acid types and glycerol effects

Plasticized and unplasticized chitosan films were successfully prepared by thermomechanical treatment, as a possible alternative route to solvent casting method. Acetic acid and lactic acid were used as solvents and glycerol was used as plasticizer with a fixed concentration of 25 wt.-%. The properties of the prepared samples were investigated demonstrating the effects of acid type and the addition of glycerol. Microstructure analysis results revealed a homogeneous and cohesive matrix, indicating a smooth surface without pores, cracks and irregularities. Unplasticized samples with lactic acid showed lower stiffness, higher elongation at break, more thermal stability, higher water uptake and water vapor permeability compared to the samples prepared with acetic acid. The introduction of glycerol affected all properties of the samples, but the samples prepared with lactic acid were more influenced. The rheological and mechanical properties (tensile strength and elongation at break) were improved when glycerol was added, resulting in a ductile behavior with a small plastic deformation and higher elongation at break compared to unplasticized films. On the other side, thermal properties were negatively affected by a decrease in the thermal stability. The water uptake and WVP measurements verified that the hydrophilic character of the material was enhanced by the addition of glycerol

Ternary melt blend based on poly (lactic acid)/chitosan and cloisite 30B A study of microstructural, thermo-mechanical and barrier properties

International audienceIn this study, blends were developed based on poly (lactic acid) (PLA) containing chitosan (CHS) extracted in our laboratory and an organically modified montmorillonite (cloisite 30B) at different amounts from 1 to 4 (in wt.-%). Tensile samples were prepared using twin-screw extrusion followed by injection molding, and films were obtained by press compression. The morphological and mechanical results showed a phase segregation and poor adhesion between the polymers. Indeed, the elongation at break and thermal stability had undergone a major decrease when adding chitosan to the PLA matrix. Glass transition temperature (T-g), melt temperature (T-m) and recrystallization temperature (T-c) decreased with the addition of chitosan, whereby an increase in crystallinity indicated a nucleation effect showing the same results as with the addition of cloisite 30B. An interesting effect of cloisite 30B was found when it was incorporated into the PLA/CHS blend especially with respect to a 4 wt.-% of cloisite 30B amount. The loss of elongation at the break was partially compensated and the thermal stability and crystallinity were improved. The water vapor permeability (WVP) and water vapor transmission rate (WVTR) of PLA/chitosan blends were higher than those for the neat PLA. By incorporating the C30B into the PLA/CHS blends, very interesting and good barrier properties were recorded as compared to neat PLA and PLA/CHS composites