Effect of filler morphology and surface chemistry on the rheological properties of filled polypropylenes

The effect of filler size, shape and surface chemistry is investigated for mineral‐filled polypropylene. Viscosity, first normal stress difference and dynamic properties are all considered. It is shown that, other things being equal, viscosity decreases as filler size increases, the filler surface is made hydrophobic or the shape of the filler is changed from ‘blocky’ to ‘platey’. The first normal stress difference is found to be relatively insensitive to such changes.