The effect of nanoparticle content and size on the morphology and crystallization behavior of poly(lactic acid)/silica nanocomposites

Poly(lactic acid) (PLA)/silica nanocomposites with different filler loading and two different primary particle size of the filler were prepared by using a twin-screw extruder followed by injection molding. Morphological investigations showed, depending on the filler size and filler content, good dispersion with average agglomerate sizes of 38-60 nm. The spherulite growth and crystallization behavior of the nanocomposites discovers that smaller particles and a low filler loading leads to the fastest crystallization. The behavior can be explained by the fact that the small agglomerates and individual particles, visible in a standard Scanning Electron Microscope (SEM) are most frequently in this case. These particles serve as heterogeneous nucleation agents finally resulting in a fast crystallization of the PLA nanocomposite.