Calcium carbonate has remarkably higher thermal conductivity as compared to the polymer (6 and 14 times higher than those of HDPE and PP respectively). This means that the heat generated during plastic processing is transmitted through the mixture more quickly allowing faster heat transfer in extruder (faster melting & more homogeneous melt temperature), leading to potential energy savings during extrusion.
Most common carrier resin in calcium carbonate filler masterbatches used for PE films, shopping and garbage bags as well as many others polyolefin products is LLDPE. A typical melt flow index (MFI or MFR) of a carrier resin ranges from 10 to 20 MI. Some master batches actually show higher MFI. Lower MFIs (1 to 2 MI) are also available though.
Cutting down production costs with CaCO3
Economical befenits of use of calcium carbonate concentrates are not limited with simple displacing of a filled polymer resin. In a real production a number of factors connected with CaCO3 usage would lead to cumulative cost savings.
Calcium carbonate (CaCO3) filler masterbatch (or filler master batch) is a concentrated mixture of calcium carbonate and other additives encapsulated during a heat (mainly extrusion) process into a carrier polymer resin which is then cooled and cut into granules (pellets) making CaCO3 masterbatch a solid additive for plastics. Since common CaCO3 MB was originally intended for filling plastics to replace a part of expensive carrier resin it is often called filler masterbatch or filler additive.