Softwood Kraft Digestion Yield and Carbohydrate Retention Physics
Softwood kraft yield optimization relies on balanced alkali profile splits that prevent carbohydrate peeling while sustaining delignification.
TAPPI T 230
Viscosity Method
A standardized testing method determines the viscosity of pulp by dissolving it in a cupriethylenediamine solution to evaluate cellulose degradation. In laboratory analysis, tappi t 230 provides a rapid and repeatable measure of the average molecular weight of the cellulose fibers. This standard is widely used in North American pulp mills.
Measurement Procedure
The test is performed by mixing a dry pulp sample with a specific concentration of the solvent and shaking it until the cellulose is completely dissolved. Under the rules of tappi t 230, the resulting solution is drawn into a capillary viscometer, and the time it takes to flow between two marks is measured. This flow time is converted to viscosity in centipoise, reflecting the length of the cellulose polymer chains.
Longer chains yield a more viscous solution, which correlates with higher physical strength in the final paper sheet.
Process Application
Pulp mills use this test to monitor the severity of chemical treatments like cooking and bleaching. When the viscosity measured by tappi t 230 drops below the limit, it indicates that the cellulose has been degraded, which will reduce the strength of the finished paper. This real time data allows process engineers to adjust chemical dosages or temperatures to maintain pulp quality.
By keeping the viscosity within a specific range, mills can ensure their pulp meets the strength requirements of high performance packaging boards.