It is well known that the properties of polymer compounds depend in a complicated manner both on the choice of the raw materials and the compounding technology. Consequently, any change in the formualtion or the processing parameters will affect not one but all properties. Within this complex scheme, mineral components have traditionally been given secondary consideration. This is somewhat surprising as the interface between mineral and matrix critically influences some important material properties. Examples are reported pertaining to the effect of particle size distribution on the viscosity (processibility) of a minerally flame retarded epoxy compound and of the dependence of some mechanical properties of an EVA compound from the filler level. In the latter case it was observed that e.g. the elongation at break decreases along a sigmoid curve as the filler level increases. Consequently, there is little loss of performance up to a critical level at which point the properties deteriorate rapidly upon further increasing the filler level. The influence of various surface treatments on the elongation at break and on the processibility (represented by the MVI) is shown. While the silane treatments S 11 and S 41 both improve the elongation at break and the processibility, the polymer coating P 14 largely enhances the processibility but yields a compound with a 30% reduced elongation. A close cooperation between compounder and mineral producer will expedite the development of improved (mechanically as well as economically) compounds.
