The measurement results regarding the age-dependency of DP v and the number of cellulose chain scissions are compared to those obtained by glass capillary viscometry, showing a very good agreement. The rheometry method has been applied to 4 hygrothermally aged cellulose paper samples and the unaged counterpart. Also, rheometry measurements are less work-intensive than glass capillary viscometry measurements. Further, rheometry typically requires considerably less paper mass per test than glass capillary viscometry, which makes the method attractive for paper degradation studies with limited sample availability.

Rheometry allows to measure the viscosity for a range of shear rates, which results in multiple DP v evaluations per sample, and thus in statistically representative data from an individual test. The proposed methodology relies on the application of a shear flow in a thin film of cellulose solution to measure its dynamic viscosity, from which DP v can be subsequently derived in a straightforward fashion. The current study proposes an efficient, alternative method to evaluate DP v of cellulosic paper, which is based on rotational rheometry.

DP v can be deduced from the viscosity of dilute paper solutions, as typically measured through glass capillary viscometry. In paper degradation studies, the viscosity-average degree of polymerisation (DP v) is often used as a key indicator of the extent of degradation of cellulosic paper.

Constant viscosity test