Meaning
Chemical decomposition process where calcium carbonate releases carbon dioxide to form calcium oxide at elevated temperatures. In polymer analysis, calcite decarboxylation occurs between 600 and 850 degrees Celsius. Mass changes during this reaction influence the accuracy of mineral filler measurements.
Thermal Threshold
The reaction initiates at a specific heat level determined by the atmospheric pressure and the purity of the sample. While most organic polymers decompose below 550 degrees Celsius, calcite decarboxylation requires high energy to break the chemical bonds within the mineral. Laboratories must calibrate their equipment to account for this secondary weight loss.
Analytical Interference
Failure to distinguish between the loss of polymer and the loss of gas from the filler results in an incorrect ash content reading. When calcite decarboxylation happens during a test, the recorded weight of the inorganic residue is lower than the actual mineral loading. Technicians use isothermal holds or corrective factors to reconcile the mass of the remaining calcium oxide with the original calcium carbonate.
This precision ensures that the reported filler percentage matches the technical datasheet of the compound.
Processing Consequence
Thermal instability of the filler at extreme extrusion temperatures can lead to the formation of voids or surface blisters in the final part. Because calcite decarboxylation generates gas, any processing temperature that approaches the decomposition point risks structural failure. Moulders monitor the melt temperature to prevent the unwanted release of carbon dioxide inside the barrel.
