Meaning
A mineral additive increases the stiffness and reduces the cost of thermoplastic compounds without significantly altering the chemical structure. Incorporating calcium carbonate filler into a resin matrix improves the dimensional stability of injection moulded components. It is the most common inorganic material used to displace expensive virgin polymer in high volume production.
Volumetric Extension
The primary motive for adding the mineral is to increase the volume of the material at a lower price point. When calcium carbonate filler replaces a portion of the resin, the total density of the part increases while the raw material cost per kilogram typically decreases. This trade off is common in the production of garden furniture and automotive interior panels.
Processing Benefit
The presence of mineral particles changes the thermal conductivity of the melt. Because calcium carbonate filler helps the plastic heat up and cool down more rapidly, cycle times in the moulding machine are often reduced. Faster cooling allows the part to be ejected from the tool sooner, which increases the hourly output of a factory.
Mechanical Modification
Adding the mineral increases the flexural modulus of the final product. While calcium carbonate filler makes a part more rigid, it also reduces the impact strength and elongation at break compared to the unfilled base polymer. Proper particle size selection prevents the formation of internal stress concentrators that lead to premature failure.
Surface treatments on the filler particles can further improve the bond between the mineral and the polymer chains.
