The limiting viscosity number (CVN) is determined according to ISO 5351.

The limiting viscosity number is a measure of the average chain length of the cellulosic portion of pulps and provides information about possible fibre damage due to pulping and bleaching. This allows further properties in terms of strength and morphology to be assessed according to their potential.

The samples are torn into small squares, broken down (disintegrated) according to DIN EN ISO 5263-1 and dried in air. The dry matter content of the samples is determined according to ISO 638. From the prepared sample, the appropriate amount is weighed out according to ISO 5351 and shaken in CUEN solution until the sample is completely dissolved, avoiding oxygen (air) contact. Subsequently, the tempered sample and measured by means of Ubbelohde viscometer and the limiting viscosity number is calculated.