Studies on tack of pressure–sensitive adhesive tapes

Abstract

SynopsisI t has been found that tack values of pressure-sensitive adhesives are dependent on the surface energies for adherends. The parabolic curves with maxima are obtained from the plots of tack values versus crit,ical surface tensions for the substrates. The maximum occurs a t the region where the two surface tensions are almost similar. On the other hand, tack is measured as a dynamic value indicated as the force necessary to deform the adhesive mass. To explain why the tack values is controlled by the surface character of the adherend, a mechanism is proposed for adhesive bond breaking. Primarily, bonding occurs by wetting the surface with adhesive. When the adhesive bond breaks by external force, unbonding proceeds from the viscoelastic deformation of the adhesive mass around the wetted spots on t,hc surface of the adherend. A? the total area of wetted spots is determined by surface energy, the tack value is dependent on the crib ical surface tension of the adherend.

How does tack depend on time of contact and contact pressure?

“…The distribution cp( z ) is then given by With this distribution, the total area of contact and the total load are given by A,,, = naR ( 8 ) P,,, = nEa3/'R'/'. (9) From these two expressions, one can easily obtain the relationship between load and area: which gives the well-known Greenwood result that the area of contact and the applied pressure are proportional to each other. 13 The important result that should be emphasized in our context is that for a given surface, A is inversely proportional to the elastic modulus E and proportional to the applied pressure.…”

Materials Science of Pressure‐Sensitive Adhesives

“…However, the correlation was less well established for PSAs. Toyama and co-workers studied the probe tack and peel strength of a poly(?z-butyl acrylate) on a variety of substrates and analyzed the dependence of their data on the surface energy of the adherends (Toyama et al, 1970). They found a maximum in the peel strength when the surface tensions of the adhesive, y a , and of the adherend, y s , were closely matched and argued that in this situation the interfacial energy is minimum.…”

Peel Morphology of Acrylate Adhesive Polymers

“…For example, Toyama et d Z 8 found that tack and peel adhesion were influenced by the difference between the surface tensions of the adhesive polymer and adherend. The pattern of peel morphology may, therefore, also be related to the difference between the surface tensions of the acrylate polymers.…”