Nodular Ductile Iron Microstructure consisting of nodular graphite in a pearlitic matrix surrounded by ferrite islands (bullseye graphite)
Filler (Ash) Content and Identification
An Ash test is used to determine if a material is filled. The test will identify the total filler content. It cannot identify individual percentages in multi-filled materials without additional test procedures being performed.
An Ash test involves taking a known amount of sample, placing the weighed sample into a dried / pre-weighed porcelain crucible, burning away the polymer in an air atmosphere at temperatures above 500°C, and weighing the crucible after it is has been cooled to room temperature in a desiccator. Ash residue remaining in the crucible is considered filler unless the residue is less than 1%. Residues of less than 1% are typically the result of additives that did not burn off.
The Ash test result is expressed as % ash. A magnified optical examination of the ash residue is performed to determine if the ash is glass, mineral, or a combination of both. The total ash content equals the weight of the ash divided by the weight of the original sample multiplied by 100%.
Identification of Filler
If the supplied material has mineral filler an FTIR analysis of the ash residue can help to further identify the type of mineral.
Smaller sample sizes:
TGA (Thermogravimetric Analysis) is an alternative method to determine filler content with smaller samples sizes.
