NC State
L.S. Nordman. Bonding in paper sheets. In Fundamentals of Papermaking Fibres, Trans. of the Ist Fund. Res. Symp. Cambridge, 1957, (F. Bolam, ed.), pp 333–347, FRC, Manchester, 2018.


The bond strength has been defined as the energy required to break the bonds in a bonded area of unit size. A determination of the bond strength thus involves measurements of energy as well as of surface areas. Several methods for measuring the bonded area are reviewed and their limitations are discussed. For investigations carried out in the Finnish Pulp and Paper Research Institute, the optical method based on the Kubelka-Munk theory was employed. Following the concept that microbreaks occur in a test strip during loading, the increase in the scattering coefficient of a sample subjected to a tensile test is believed to be caused by the breaking of bonds. A number of qualitative tests revealed a strong similarity between bond breakage and stress/strain behaviour of the test strip. Quantitatively, the bond strength was determined from the slope of the line depicting the relationship between the increase in scattering coefficient and the irrecoverable energy loss in a straining/destraining cycle. The bond strength as found to be dependent on pulp quality. The values for the bond strength thus obtained agree as to the order of magnitude with other values reported in publications.

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