PLA/SiO2 composites: influence of the filler modifications on the morphology, crystallization behaviour and mechanical properties

Films of an architecturally modified poly(lactic acid) (PLAREx) with three different types of fumed silica nanofillers (SiO2) were processed through reactive extrusion-calendering in a pilot plant. The effects of the SiO2 type on both the dispersion and the crystallization behaviour under dynamic and isothermal conditions are investigated using transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The mechanical properties are assessed by tensile testing. TEM micrographs showed that the improved chemical affinity of both surface-treated SiO2 towards PLAREx end groups did not improve particle dispersion. DSC results revealed that untreated SiO2 nucleated PLAREx more efficiently than both surface-modified silicas. The activation energy for the isothermal crystallization process, as determined by an Arrhenius method, suggests that addition of untreated SiO2 enhances the crystallization rate of PLAREx. However, it seems that the tensile behaviour remained unchanged whether silicas were added or not.