Omya Calcium Carbonates significantly improve the stiffness of polypropylene and polystyrene, allowing for substantial reduction in sheet gauge while maintaining top load and thus leading to optimized formulation costs. Special grades are available for applications where high whiteness is required.
In polypropylene sheets, the stiffness and thermoforming properties are shifted towards polystyrene. The high thermal conductivity of Omya Calcium Carbonate allows to speed up extrusion, sheet processing and thermoforming. The rigid calcium carbonate particles lead to more isotropic physical properties, lower shrinkage and improved forming accuracy.
Overall, modification of thermoplastics with calcium carbonate offers the opportunity to significantly increase output – to an extent depending on the machine equipment and processing conditions. The introduction of calcium carbonate into
the polymer matrix reduces the amount of viscoelastic material in the formulation. Thus, it reduces typical viscoelastic phenomena, such as die swell, neck-in and shark skin. The mineral particles increase the internal shear forces, and therefore the melt viscosity. This improves the homogenization of the melt itself, and improves the dispersion and distribution of other additives.