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TAPPI T 236 Kappa number






Kappa number of pulp


TAPPI T 236 applies to many kinds of chemical, semi-chemical, unbleached and semibleached pulps within the kappa number range 1 to 100. Above a kappa number of 100, precision of the test may decrease, and the relationship between kappa number and lignin content may decrease, depending mainly upon the wood species from which the pulp is made. There is no general and unambiguous relationship between the kappa number and the content of lignin of other organic impurities in a particular pulp. The relationship varies according to the wood species and the pulping and delignification procedures used during the pulping process for a specific pulp. Kappa number is essentially a straight line relationship with both klason lignin and chlorine number for pulps below 70% total pulp yields. The percentage of klason lignin in a pulp sample whose kappa number is determined by the procedure in this standard test method may be approximated using the following equation: Lignin level (%) = Kappa number × 0.13. If the kappa number is to be used to determine a precise numerical value regarding the amount of lignin present in a specific pulp of interest, a more precise relationship can be established by testing the specific pulp of interest. As written, this standard is intended for use in the laboratory testing of pulps. It is recognized, however, that kappa number is widely used as an in-process test in the pulp and paper mill, in some cases with modifications


The level of lignin and other impurities in pulp is very important in pulp production, as it is directly related to the amount and type of bleaching chemical required to produce a finished pulp of specified end use properties, particularly pulp brightness. Kappa number may be used as a specification for pulp used in various end use paper products such as bag papers, printing and writing papers and others.


The equivalent of 15 grams oven-dried sample is required at a minimum to perform proper testing of the sample. The amount of sample used may need to be increased to ensure that 50% of the permanganate is consumed by the test specimen. Test is run as a single determination, per the method. Duplicate determination can be done at additional cost if requested by the client. If sample is limited, a test can be run via TAPPI UM 246 Micro-Kappa number where the sample size can be limited to three grams.

Please note:

IPS cannot sell or otherwise provide standards, specifications, or test procedures to third parties.