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Standard: |
TAPPI |
Method: |
TAPPI T 413 |
Title: |
Ash in wood, pulp, paper and paperboard: combustion at 900°C |
The TAPPI T 413 Ash 900°C method for determination of ash can be applied to all types of wood, pulp, paper and paperboard.
A test specimen is ignited in a muffle furnace at 900°C. A separate test specimen is analyzed for the percentage moisture. The resulting weight of ash and moisture level in the sample are used to calculate the percentage ash present at 900°C on a moisture-free sample basis.
The ash content of the sample may consist of: various residues from chemicals used in its manufacture, metallic matter from piping and machinery, mineral matter in the pulp from which the paper was made, and filling, coating, pigmenting and/or other added materials. The amount and composition of the ash is a function of the presence or absence of any of these materials or others singly or in combination. No specific qualitative meaning is attached to the term “ash” as used in this test method. Where a further qualitative examination of the ash is desired, IPS can provide semi-quantitative inorganic chemical composition with Energy Dispersive X-ray Spectroscopy or quantitative analysis of heavy metals by ICP.
The combustion of cellulose to form volatile combustion products occurs at about 300°C. For papers or pulp containing no added fillers or coatings, ignition at either 525°C or 900°C will yield essentially identical results of a few tenths percent ash or less. Examples of such papers include “ashless” filter papers manufactured for chemical analysis, or dissolving grade pulps.
For samples containing fillers, coatings or pigments which undergo negligible change in weight upon ignition of either 525°C or 900°C, such as the oxides of silicon or titanium, and where other fillers, coatings or pigments are known to be absent, ignition at either temperature may be taken as a semi-quantitative measure of the percentage of such material present in the sample.
In most cases, the ash content of paper and paperboard will contain inorganic residues from the pulp, inorganic residues from paper making chemicals, and loading or filling materials deliberately added. In such cases, the significance of the ash level determined will vary depending upon which ashing temperature is used and the identity of the materials added.
For papers containing only cellulose and calcium carbonate, ignition at 525°C will remove cellulose, and moisture, but will leave as ash the calcium carbonate essentially intact. Ignition at 900°C will convert the calcium carbonate to calcium oxide. In such cases, these methods may be used in conjunction to provide a good estimate of added calcium carbonate levels.
For papers containing cellulose and clays or materials of indefinite composition and/or variable thermal decomposition, significance of ash level may require significant confirmation regarding the materials added, qualitative analysis of the ash as described in T 421, or both, and even then care in determining data significance will be required.
The user of this test method must confirm that 525°C is the correct ashing method to use and the significance of results based on an understanding of the composition of the sample ash and the information desired. This method may be used in conjunction with TAPPI T 413 “Ash in Wood, Pulp, Paper and Paperboard: Combustion at 900°C” for a more comprehensive understanding of the non-cellulosic materials present in the sample.
To perform adequate testing, at least two and half grams of sample will be needed. This ensures that a duplicate can be run for each sample. If sample availability is limited, testing can be performed using less sample or as a single determinant. For the determination of ash by combustion at 525°C, see TAPPI T 211 “Ash in Wood, Pulp, Paper and Paperboard: Combustion at 525°C.”
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