Abstract
A commercial tackmeter of Pickup type was employed to investigate the autohesion characteristics for raw rubbers by measuring the maximum tack strength and the wet area printed on the peeled surface under various experimental conditions. Three portions of different dullness spaced concentrically in the wet surface were usually distinguishable and their areas were found in general to be directly proportional to one another.
The wet area, S, as well as the maximum tack strength, F, increased exponentially with time of contact, but seemed to level off finally. Thus we obtained the following empirical equations,
S=S∞(1-e-tp/τp),
F=F∞(1-e-tp/τp),
where S∞, F∞ and τp are the constants independent of time of contact, tp.
Comparison of those time-dependent data on tack with the relaxation moduli obtained from the separate measurements on the same sample suggests that the both processes are being governed by the mutual factor, the mobility of rubber molecules. It was then found that the dependence of the maximum tack strength on the rate of separation could reasonably be understood when the penetrated chain of the partially diffused molecule through the contact surface acts as a viscoelastic body.
