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Selecting an ash test method T 211 vs T 413 vs T 244 can be confusing. This short write-up helps you understand which method is best for your needs.
IPS performs several different ash methods. In paper and polymers, the main purpose is to remove the bulk cellulose or polymer to determine the amount of mineral type components.
The cellulose is removed by gradually raising the temperature such that the cellulose or polymer decomposes without flaming (flame temperatures are much higher than 525°C.) After the cellulose is gone the sample is cooled in a desiccator (to prevent moisture pickup) and weighed. The weight of the residue is divided by the initial dry weight of the sample and reported as % ash.
The greatest advantage of ash at 525oC is that any calcium carbonate remains as the carbonate – it is not decomposed to calcium oxide.
Most clays will lose some of the moisture between the clay platelets. If the type of clay is known the percent ash can be corrected for this moisture loss.
Other minerals can decompose but they are not commonly found in paper and fiber type polymers.
This is the most common Ash test and gives a “non-cellulose” value.
The test is similar to the Ash at 525°C except the final temperature is 900°C.
Most minerals will decompose to their oxides e.g. CaCO3 will become CaO. Clays will typically be calcined (all moisture driven off and the clay platelets fused.)
This is the least common Ash test and is used only for special applications.
The ash from 525 or 900°C is treated with dilute acid to dissolve acid soluble components. The sample is filtered and washed to remove the acid solubles. The acid insoluble residue is ashed and weighed. That residue is reported as parts per million acid insoluble ash based on the original sample weight. It is often used to give an estimate of the silica content of pulp or paper even though other minerals can be present.
IPS defines sand as the acid insoluble ash, dispersed by sonication in water, which is retained on a Tyler 200 mesh screen (0.074 mm opening.) Sand is typically picked up from the soil during the handling of logs in the woods and at the pulp mill. Sand is thought to dull paper cutting devices (slitters and knives) faster than smaller particles.
Sand and acid insoluble Ash are similar but the sand determination utilizes screening so only particles >0.074 mm are quantified.
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