Date of Award


Degree Name

Bachelor of Science


Pulp and Paper Technology


This study was carried out to evaluate the effect on the ply-bond strength of the moisture content of the plies of a multi-ply sheet at the time of joining.

Two-ply sheets were formed with the plies at various moisture contents at joining. The resulting ply-bonds were evaluated by three methods, viz. Instron peel, Mullen ply-bond, and z-direction tensile. Each method showed the same trend of ply-bond strength dependence on moisture and within the range of experimental error the average values of the three techniques correlated well.

This study showed that the moisture content of the plies at joining is extremely critical in the ply-bond strength of paperboard. The practical minimum moisture content at which a ply-bond was possible was 20%. There was a gradual increase of ply-bond strength with increasing moisture content of the plies until a critical moisture range of 85 to 90% was reached. In this narrow range of moisture content the ply-bond strength increased two to fourfold. Once the critical range of moisture content was exceeded, no further increase in ply-bond strength occurred because the failure of the two-ply assembly occurred within one of the plies. This was confirmed by experiments which showed that the single ply (intraply) strength was of the same magnitude as the two-ply bond strength.