The Ability to Absorb Oil

This property can be beneficial for hydrophobic plastics, such as polyolefins, as hydrophobic fillers can show a good interaction with the matrix. Also, hydrophobic fillers can very significantly influence the viscosity of the matrix, hence, its rheology and flowability. Fillers typically absorb oil in much higher quantities compared to water. Calcium carbonate absorbs 13-21% of oil, aluminum trihydrate absorbs 12-41% of oil, titanium dioxide 10-45%, wollastonite 19-47%, kaolin 27-48%, talc 22-57%, mica 65-72%, and wood flour 55-60%. Biodac absorbs 150% of oil by weight. 

Typically, if oil absorption is low, the filler does not change the hot melt viscosity much. Because of this, oil absorption test is often used to characterize the effect of fillers on rheological properties of filled plastics. 

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