Impact Resistance

The decisive advantage which results from the incorporation of ultrafine precipitated calcium carbonate in rigid PVC formulations relates to the significant improvement that is seen in the impact performance. This improvement is seen in rigid PVC compounds without the addition of any organic impact modifier. In the presence of both acrylic and CPE type modifiers, this improvement in the impact properties is repeated from the levels seen with the modifier alone. Whereas polymer modified compounds can display a sharp decrease in impact strength a low temperatures, the CPCC modified system possesses residual impact resistance even at low temperatures.

In contrast to organic impact modifiers precipitated calcium carbonate increases the E modulus of the extruded component and increases the impact strength without reducing the rigidity.
The explanation of this positive behavior can be found in both the processing improvements that synthetic calcium carbonate provides along with its ability to improve the dispensability of other components of the formulation i.e. organic impact modifiers. This improved dispersion and processing benefit also results in the reduction on the % reversion observed for the extrusion of a typical window profile formulation.

The more complete gelation that results from the inclusion of precipitated calcium carbonate provides a matrix that in comparison to natural calcium carbonates has fewer defect sites and opportunities for a crack propagation process leading to reduced mechanical properties. The micrographs show the differences in failure mode for PVC containing precipitated calcium carbonate from those containing a natural calcium carbonate derived by milling. It is possible to obtain ductile failures with reduced impact modifier levels by using precipitated calcium carbonate.

Abrasivity|Anti-sedimentation|Brightness|Neutralisation|Opacity|Porosity|Processing Aid|Rheology|Sheen|Stiffness|Surface Appearance|Washability|Weathering resistance