New dispersion process for submicronic fillers in thermoplastics

Abstract

The addition of sufficiently small-sized fillers in thermoplastics is supposed to allow an increase in stiffness while maintaining a good resilience. However, it is often difficult to obtain a good impact resistance because the dispersion of fine fillers is not perfect - even using a powerful tool like a corotating twin screw extruder. This implies that the material will inevitably contain agglomerates that will cause a drastic drop in the material's resistance, bringing it down to the level of that of a coarse-filler containing material. CERDATO, jointly with APPRYL, has designed a patented process for the dispersion of fine fillers in an extruder that allows this problem to be solved. The originality of this process lies in the optimization of the deagglomeration of the filler before its feeding into the extruder. As an example, polypropylene/submicronic calcium carbonate compounds show a joint gain in stiffness and impact resistance, while a traditional incorporation process (fillers fed in the melt) leads to an important loss in impact resistance.