Synthesis of lignin nanoparticles employing acid precipitation method and its application to enhance the mechanical, UV-barrier and antioxidant properties of chitosan films

Lignin nanoparticles were obtained by a simple acid precipitation method from lignin KOH alkali solution and used as a reinforcing agent to prepare chitosan based lignin nanoparticles nanocomposite films. The effect of lignin nanoparticles concentrations (3, 5, 10, 15 and 30% v/v chitosan solution) on structural, mechanical, water vapor, ultra-violet light barrier, thermal and antioxidant properties of chitosan nanocomposite films was investigated. Particle size analysis reveals that the lignin nanoparticles are formed with an average size of 55 nm. The tensile strength and modulus were increased by 86 and 93%, respectively, in the presence of 15% of lignin nanoparticles compared to the values of chitosan film. The water vapor transmission rate of chitosan-lignin nanoparticles nanocomposite film reduced (32% for 15% LNPs) up to 15% concentrations. The ultraviolet barrier properties of the chitosan films were increased with an increase in the concentration of lignin nanoparticles. Lignin nanoparticles reinforced chitosan films were also significantly enhanced with antioxidant activity in comparison with neat chitosan film.