Design and development of Schiff's base (SB)-modified polylactic acid (PLA) antimicrobial film for packaging...

SB compounds were synthesized from (para, ortho, meta)-phenylenediamine as a cross-linking agent through vanillin. The chemical structure of the formed SB complexes is confirmed by FT-IR spectroscopy. Among the three complexes, para-phenylenediamine (p-SB), possessing a stable resonance structure with the lowest steric repulsion, was obtained in the highest yield of 87%. Hence, the present work focused on reducing the brittle behavior and improving the antimicrobial activity of PLA by reacting it with p-SB. FT-IR investigation revealed the existence of an intermolecular hydrogen bonding between PLA and SB, which led to an increased toughness in the PLA-p-SB complex. This is further confirmed through SEM analysis. The tensile and contact angle measurements determined an improvement in mechanical properties and hydrophobic nature of the PLA-p-SB film. DSC results demonstrated an increase in flexibility, which indicated a 10 °C reduction in glass transition temperature (T _g) of PLA-p-SB films. The antimicrobial activity of the PLA-p-SB films had a maximum of 15 mm zone of inhibition, which was found to be more effective than the neat PLA film. PLA-p-SB coating on Kraft paper showed improved mechanical and barrier properties than neat PLA coatings and could be tried as a possible replacement for conventional synthetic packaging materials.