Relationship between the cohesive strength and the tack of elastomers

AbstractThe autohesion (tack) and cohesion of a random styrene‐butadiene elastomer have been examined as a function of test temperature and speed using a T‐peel geometry. Both properties have been reduced to a single master curve by horizontally shifting the data with the same set of shift factors. The cohesive strength increases with increasing reduced test rate RaT and appears to approach a plateau at the highest rates. Tack also increases with RaT but decreases abruptly at a critical rate and peeling the occurs in a stick‐slip fashion. Tack again increases at sufficiently high test rates. In the range of rates where tack is maximized, its value is essentially the same as its cohesive strength. Above or below this range, tack is substantially less than the elastomer's cohesive strength. Mechanisms are proposed to explain why relative tack (i.e., tack divided by cohesive strength) is not a simple measure of the extent of completion of a tack bond and may indeed be equal to one in spite of incomplete tack bond formation.