Metal ions increase mechanical strength and barrier properties of collagen-sodium polyacrylate composite films.

From the previous experiment, it was confirmed that the incorporation of 0.3 wt% sodium polyacrylate (PAAS) into collagen (Co) fibers can improve the mechanical properties and thermal stability of the composite films. In this study, Ca2+, Fe3+ and Ag+ ranging 0.001-0.004 mol/g were used to improve the properties of Co-PAAS blend films based on the rationale of their potential electrostatic interaction with these biopolymers. As expected, Zeta-potential film-forming solutions was decreased to some extent with the addition of metal ions. SEM images presented that the surface of the composites became coarser and internal structure became more stratified as metal ion contents increased. Tensile strength was increased by the addition of these ions with a varied optimal concentration: Ca2+ (0.003 mol/g), Fe3+ (0.002 mol/g) and Ag+ (0.001 mol/g). Water vapor permeability (WVP), solubility and light transmission value of films while causing film thickness no obvious change. In addition, the differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA) results indicated that the metal ions improved the thermal stability of the composite film. Therefore, Ca2+, Fe3+ and Ag+ with an appropriate addition amount can be used as a potential alternative to reinforce collagenous composite materials.