McBain and Hopkins

McBain and Hopkins [2], in their classical scientific study, argued that the surface roughness of a porous material was the basis of mechanical adhesion , its being... 

Packham, D.E. and Johnston, C., Mechanical adhesion were McBain and Hopkins right An empirical study. Ini. J. Adhes. Adhes., 14(2), 131-135 (1994). 

Most historical surveys treat the work of McBain and Hopkins in 1925 as the earliest application of modern scientific investigation to the study of adhesion [9]. McBain and Hopkins considered that there were two kinds of adhesion, specific and mechanical. Specific adhesion involved interaction between the surface and the adhesive this might be chemical or adsorption or mere wetting. Specific adhesion has developed into the model we today describe in terms of the adsorption theory. 

In contrast, mechanical adhesion was only considered possible with porous materials. It occurred whenever any liquid material solidifies in situ to form a solid film in the pores. They cite as examples adhesion to wood, unglazed porcelain, pumice, and charcoal. For McBain and Hopkins mechanical adhesion was very much a common sense concept, It is obvious that a good joint must result when a strong continuous film of partially embedded adhesive is formed in situ. ... 

Given that the roughening of surfaces often has a beneficial effects on adhesion, how can it be explained It might have been sufficient in 1925 for McBain and Hopkins [9] merely to assert that the mechanism of adhesion to a porous surface was obvious, but the wide range of experimental examples known today demands a more detailed discussion of the mechanisms involved. This, in turn, requires a critical examination of the common sense terms surface and roughness. ... 

Serious scientific concern with fundamental adhesion is usually dated back to the classic work of McBain and Hopkins in the 1920s, and various theories were advanced during the middle part of the last century. There was a strong tendency during much of this period to regard different theories as rival explanations of the same phenomena, rather than as complementary aspects of a broader rationalization. Much of the literature of the that time, and even some of the literature today, reflect this approach, and therefore it is appropriate in this chapter first to consider different theories individually. A synthesis will be given in the conclusions. 

Thus, the basic ideas, related by McBain and Hopkins in the 1920s, underlying both the adsorption and mechanical theories of adhesion still provide useful models for rationalizing observations in adhesion science. Two further adhesion theories, the electrostatic and diffusion theories, emerged from the Soviet Union in the middle of the twentieth century. We now turn to consider them, and how they are regarded today. 

Koh SK, Park SC, Kim SR, Choi WK, Jung HJ, Pae KD (1997) J Appl Polym Sci 64 1913 Leadley SR, Watts JF (1997) J Adhes 60(1 ) 175-196 McBain JW, Hopkins DG (1925) J Phys Chem 29 188 Packham DE (1998) The mechanical theory of adhesion-a seventy year perspective and its current status. 

---