Physicochemical and barrier properties of polylactide films including antimicrobial additives

This study gives insight into basic physicochemical properties of new polylactide-based materials containing 1% wt of one of the three polyhexamethylene guanidine (PHMG) derivatives: PHMG stearate (LS), PHMG in granular polyethylene wax (LW) and PHMG sulfanilic acid salt (LA). The resulting materials after processing into films were studied by means of gel permeation chromatography (GPC); infrared spectroscopy (FTIR), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and thermogravimetry (TG). It was found that while PHMG does not react with the polymer matrix, compatibilizing additives such as sulfanilic acid, stearate salts and polyethylene wax interact with the polylactide. Sulfanilic acid initiates polymer crosslinking, stearate causes partial hydrolysis and polyethylene wax plasticises the polymer. LS composite shows the best barrier properties with a barrier characteristic of that of glass. The crystallinity of these materials decreases due to addition of PHMG with compatibilizing agent. The enthalpies of melting were found to be 21.5, 22.7 and 25.2 kJ/g for LA, LA and LW, respectively.