Polyurethane

Increased volume of PUR foam

To achieve a constant foam density, the increase of PUR density due to addition of calcium carbonate is balanced with the quantity of water used in the composition (taking into consideration the limitation specified for safety reasons) and/or with a blowing agent (carbon dioxide). At the end, a larger volume of PUR foam (+14%) is prepared with the same quantity of organic raw material, achieving a cost saving. Finally the saving is generated by two facts:

• partly substitution of expensive polymeric materials by mineral additive
• reduction of foam cell wall thickness to keep the overall foam density constant

Improved cooling conditions

During production, the good thermal conductivity of the calcium carbonate ensures a better distribution and a better discharge of heat produced during exothermic reactions.

Nucleating effects on foam cells

The mineral modifies the polyol rheology and creates a nucleating effect, producing PUR cells with a narrow size distribution. A better processability is observed especially when the foam is expanded with carbon dioxide. The feel of the foam is also positively changed.

Positive contribution on mechanical properties

Calcium carbonate brings stiffness to the wall of the PUR cells. The compression properties of PUR foams modified with fine calcium carbonate are improved by maintaining tear resistance. Fine and well dispersed calcium carbonate increases compression load and characteristics of PUR foam. For standard PUR formulation, tear resistance is maintained up to 15phr of calcium carbonate (15 parts of mineral for 100 parts of polyol). Tear resistance value depends upon wall thickness (density) and the foam composition (cross-linking additive).