A method of measuring tackiness

For measuring the tackiness of viscous materials to the solid surface, we designed an attachment to the tensile tester driven with constant speeds. Blends at high molecular weight polyisobutylene with low molecular weight polyisobutylene or with a hydrogenated rosin were used as samples. The maximum force fb at the time tb of the force‐time relation recorded on a chart was determined as a measure of the tackiness. The relation between fb and tb satisfies the equation fb ∝ tb−1/2 derived by Eley. The fb depends on the time tc and the pressure pc at contact, the temperature and the rate of sepration, r, and the rosin content of the sample. The activation energy, obtained from the slope of plots of fb against the reciprocal of the absolute temperature shows a value of 2–6 kcal/mole, which is similar to the activation energy of the viscous flow. To decide whether the failure occurs at the interface or within the adhesive itself, fb was measured with cylinders made of various materials such as polytetrafluoroethylene, polyethylene, poly(methyl methacrylate), and brass.