A study of the morphology and energetics of fracture can shed some light on adhesion . Two approaches are made and both lead to the same general conclusions . In the first, the fracture of liquids of increasing viscosities or their cavitation leads to the ideas that fracture of polymers is governed by flaws or imperfections, not by molecular parameters. The second approach is that of Griffith, who postulated his now famous ‘crack theory’. The fracture of materials is again seen as a statistically controlled process dependent on the presence of flaws. Qualitatively, it is known that fracture of paper is explicable by stochastic considerations, too; however, quantitatively, the crack or flow theory fails.
In order to explain the mechanical failure of paper, it becomes necessary to apply the statistical approach to the bonds between the molecules . These are the hydrogen bonds joining cellulose molecules together. It is found that, if a variance is assumed to exist around the mean value of the bond energy, the rupture energy of paper can be related to its content of hydrogen bonds. Thus, the adhesion of the elements of paper is quantitatively explicable in terms of characteristics of this bond.