Meaning
Industrial polymer formulations face a rise in mineral inclusion defects when recycled feedstocks or excessive filler loading introduce unsanctioned particulate levels. Excessive calcium carbonate contamination alters the melt viscosity and compromises the mechanical integrity of moulded components. This phenomenon occurs when post-consumer streams are poorly sorted or when purge cycles fail to clear high-filler compounds from the extruder.
The limit of the condition is reached when the filler concentration exceeds the threshold that allows homogeneous polymer wetting.
Flow Hindrance
Extruder die blockages and screen pack blinding occur when these inorganic particles gather in the melt flow. High levels of calcium carbonate contamination raise the shear stress within the nozzle and cause severe melt fracture during high-speed injection cycles. This increase in flow resistance forces the moulding press to consume more energy to fill the cavities.
The thermal load also rises because of localized friction, which causes premature degradation of the surrounding polymer chains.
Structural Weakness
Moulded parts suffer from reduced impact strength when these foreign mineral particles act as stress concentration points. Unsanctioned calcium carbonate contamination creates structural weak spots that initiate microcracks under tensile stress. These fractures propagate rapidly along the boundaries between the resin and the non-bonded filler aggregates.
The finished product becomes brittle and prone to sudden failure under load.
Isolation Limit
Pyrolysis and ash testing offer a reliable method to isolate these mineral residues by burning off the organic resin matrix. When calcium carbonate contamination must be distinguished from functional mineral reinforcements, thermogravimetric analysis provides the precise decomposition temperature of the calcium salt. These tests cannot determine the original source of the filler once the part is formed.
