Meaning
Chemical surface treatment applied to calcium carbonate or other mineral fillers to reduce surface energy and improve wetting by the polymer matrix. Applying a stearic acid coating prevents the agglomeration of fine particles during the compounding stage. This layer acts as an internal lubricant that lowers the viscosity of the melt and improves the mechanical properties of the finished part.
Surface Modification
The fatty acid molecules attach their polar heads to the mineral surface while the non-polar tails extend into the polymer. This arrangement creates a hydrophobic barrier that prevents the mineral from absorbing moisture during storage. It also facilitates the rapid dispersion of the filler into the resin, which reduces the energy consumption of the compounding extruder.
Processing Advantage
Treated fillers flow more easily through feeding systems and exhibit less friction against the metal surfaces of the moulding machine. A stearic acid coating reduces the torque required to process highly filled compounds, which protects the motor and gearbox from stress. This improvement in flow allows for faster cycle times and the production of parts with complex geometries.
Finished Property
Parts containing coated fillers often show better impact strength and a higher gloss finish compared to those with untreated minerals. The improved bonding at the interface between the filler and the resin prevents the formation of microcracks under stress. This stability ensures that the component maintains its performance throughout its service life in challenging environments.
