Effect of biobased plasticizers, used as dispersing aids, on mechanical, rheological and thermal properties of micro fibrillated cellulose (MFC)/poly (lactic acid) (PLA) biocomposites over the time: how MFC controls the plasticizer migration?

Micro Fibrillated Cellulose (MFC) has gained interest both in academia and industry, but some critical issues must be overcome to exploit the industrial MFC/biocomposites uses. In particular, the first drawback is related to the MFC agglomeration during the primary processing. Encouraging results have been obtained using plasticizers, as dispersing aids, during the extrusion that optimizes the process parameters based on the variation of the melt viscosity. However, even if the plasticizer addition counterbalances the excessive biocomposite stiffness, caused by the addition of the MFC, its eventual migration from the finished product needs to be evaluated to avoid toughness reductions as well as environmental and health issues. In this work, the MFC role in controlling the plasticizer migration was evaluated by analytical modeling based on Fick's second law. The diffusion coefficient, D, over time was evaluated and correlated with the change in mechanical and thermal properties of cast extruded biocomposites. Mechanical and thermal data, analyzed over a 50-day time span, confirmed the expected benefits. The results obtained proved how the approach adopted in this study can be a valuable industrial manufacturing approach.