Barrier Properties of Polylactic Acid in Cellulose Based Packages Using Montmorillonite as Filler

Polylactic acid (PLA) and montmorillonite (CB) as filler were studied as coatings for cellulose based packages. Amorphous (AM) and semi crystalline (SC) PLA were used at different concentrations according to a 2 x 6 x 3 full factorial experimental design. CB loading was three concentrations and coating was performed by casting. Contact angle (CA), water vapor (WVP) and grease permeabilities were measured for each resultant package and were compared to commercial materials (Glassine Paper, Grease Proof Papers 1 and 2 produced commercially). Significant differences were found and the main factors were the type and concentration of PLA. The best values were: for grease penetration, +1800 s; WVP from 161.36 to 237.8 g mu mkPa(-1)m(-2)d(-1) and CA from 69 degrees to 73 degrees for PLA-AM 0.5% and CB variable. These parameters are comparable to commercial packages used in the food industry. DSC revealed three different thermal events for PLA-SC and just T-g for PLA-AM. Crystallinity was also verified, obtaining a H-crys of 3.7 Jg(-1) for PLA-SC and 14 Jg(-1) for PLA-SC-BC, evidencing clay interaction as a crystal nucleating agent. Differences found were explained on terms of the properties measured, where structural and chemical arrays of the coatings play a fundamental role for the barrier properties.