Improvement in the Fock test for determining the reactivity of dissolving pulp

The Fock test is widely used for assessing the reactivity of dissolving pulp. The objective of this study was to modify the method to improve the repeatability of the test. Various parameters that affect the repeatability of the Fock test were investigated. The results showed that Fock reactivity is dependent on testing conditions affecting the xanthation between cellulose and carbon disulfide, such as the moisture content of the pulp sample, sodium hydroxide (NaOH) concentration, xanthation temperature, carbon disulfide dosage, and xanthation time. The repeatability of the test was significantly improved using the following modified testing procedure: air dried sample in the constant temperature/humidity room, xanthation temperature of 66°F (19°C) in a water bath, xanthation time of 3 h, NaOH concentration of 9% (w/w), and 1.3 mL carbon disulfide.