Mechanical properties of gelatin nanocomposite films prepared by spreading: effect of montmorillonite concentration

摘要

The use of nanoparticles as reinforcement loads may be an interesting alternative to improve the properties of gelatin films. Thus, the objectives of this study were the development of nanocomposite gelatin-based films by spreading, and the study of the effect of the nanoparticle concentration on the mechanical properties of those films. The nanocomposite-forming solutions (NFS) were prepared with 5g gelatin/100g NFS, 30g glycerol/100g gelatin and 0, 5 and 10g montmorillonite (MMT)/100g gelatin. The NFS were applied on the support using an automatic spreader (spreader height= 1.5 mm; spreader speed= 35 mm/s; base temperature= 20°C) and dehydrated at 30°C. The nanocomposite films were characterized immediately after drying (DN), and after 7 days-conditioning (CN) in 58% relative humidity at 25°C, to determine the mechanical properties by tensile tests, moisture, thickness and phase transitions by differential scanning calorimetry (DSC). The increase in MMT concentration (CMMT) increased the thickness of the films, with slightly higher effect for the CN than for the DN, and provoked decrease in the moisture of films as function of CMMT. Regarding the mechanical properties, the tensile strength of the DN and CN increased with CMMT, indicating reinforcement of the biopolymeric matrix by the nanoparticle load. Similar behavior was observed for the elastic modulus. The lower values of resistance and rigidity for the CN must be attributed to the plasticizing effect of the absorbed moisture during conditioning. Besides, the elongation at break (%) increased with the CMMT for the DN but decreased for the CN. The nanoparticles affected the phase properties, which demonstrated the plasticizing effect of the absorbed moisture, according to the DSC results. Thus, the montmorillonite contributed to reduce the susceptibility of the nanocomposite material to the environmental relative humidity, and to enhance the mechanical properties, notably resistance and rigidity.