EFFECT OF SUBMICRON-SIZE ADDITIVES ON THE FLOW PROPERTIES OF POLYAMIDE-6

The influence of submicron mineral additives on the rheological proper ties of polyamide 6 was investigated. Usually, after incorporation of increasing amounts of commercial fillers in the polymer matrix (partic le sizes in micron range), the viscosity is continuously increased whe n applying low shear rates due to higher friction in the sliding plane s. After intensive dispersion of submicron additives in ethylene glyco l by using polyethyleneimine as a cation-active dispersing agent, aggl omerate-free dispersions of all investigated additives were realized. Under standard conditions, the ethylene glycol/additive slurries were incorporated in the PA 6-matrix by using a twin screw extruder equippe d with a vacuum degassing stillhead to remove excessive glycol immedia tely. The expected effects characterized by improved intramolecular sl iding behaviour were found in different extents for TiO2, Al2O3, SiO2, clay and talcum. However, submicronized CaCO3 already restricted the intramolecular sliding in concentration ranges below 1 wt.-%. The anal ogous effect failed to appear when the same powdery additives were inc orporated in the polyamide 6-matrix by twin screw extrusion.