Polyamide 6/wollastonite composites: strength properties and their dependence on humidity and temperature

The use of wollastonite as a reinforcement for Ultramid 35 polyamide 6 (PA 6) composites was evaluated using various mechanical test methods. The results suggest that wollastonite acts as a reinforcement for PA 6 at concentrations in the range 25-40 wt.%, because it increases strength, stiffness and impact strength. Increases of 20-200% in these properties were obtained for these wollastonite concentrations. This reinforcing effect was observed when the composite was not exposed to any humidity or temperature treatment; such treatments were found to cause a deterioration in interfacial adhesion as concluded from scanning electron microscopy observations. In conclusion, it seems that the present surface treatment system of the wollastonite may be improved and so better the long-term properties of PA 6 /wollastonite composites in severe conditions. The short-term tests, however, show that the wollastonite reinforces PA 6, i.e. increases the strength, stiffness and impact strength when it is not exposed to any humidity or temperature treatments. 11 ref.--AA