The investigation is concerned with strategies to reduce losses in medium compressive strength during corrugating.
Medium handsheets with a non-random fiber orientation were made using a NSSC pulp and different levels of synthetic fiber addition, including glass and Kevlar pulp, at two levels of wet pressing. Corrugating was performed using a concora fluter, and compressive strength measurements were made in the tip and flank regions of the corrugated medium.
Forming losses are reduced by increased wet pressing with a greater improvement in the flank than the tip region of the flute. A small reduction in tip forming losses is found, for a given furnish when a film forming latex is used. However, a greater reduction is evident when a non-film forming latex is employed.
Forming loss measurements were also made on non-bonded and bonded laminates. The non-bonded laminates resulted in much lower forming losses, while the heat-activated laminates resulted in large forming losses similar to those found with conventional medium.
These experiments suggest that forming losses can be reduced if cost-effective systems are designed which do not activate until the fluting process is complete.