Measuring Paper Friction: Testing Conditions and Papermaking Factors, 1996 Finishing and Converting Conference Proceedings

J.D. McDonald, M.F. Gratton and A. Ménard

Pulp and Paper Research Institute of Canada

G.E. Sherson - Noranda Technology Centre

P.L. Ko - National Research Council of Canada

Four different instruments were used to determine the effect of measurement conditions on paper to paper coefficient of friction. We found that the coefficient of friction is independent of normal pressure (2.0 to 480 kPa) and speed (0.6 to 1000 mm/s). Coeffi-cient of friction increases significantly with increasing relative humidity. These findings suggest that TAPPI standard methods for coefficient of friction give friction values that can be applied to higher normal loading conditions such as within a paper roll, and at high surface speeds, such as in a winder nip. Calendering and the addition of flotation de-inked pulp lower the coefficient of friction. Although the changes are not large for practical changes in operating conditions, they could have a significant effect on the formation of defects such as crepe wrinkles when the coefficient of friction is already low. Increasing the moisture level of the web increases the coefficient of friction which means that variations in moisture could have an important role in friction related defects at the ends of the paper reel and edge rolls in the winder, where the moisture level is difficult to control.