| Abstract: | In a study of pressure-sensitive adhesives prepared from mixtures of natural rubber and three different tackifying resins, it was shown that a tackifying resin may form either one- or two-phase systems with natural rubber. Measurements of the viscoelastic properties of the adhesives show that the effect of tackifying resins is to modify the viscoelastic properties so that the adhesive performance in bonding and unbonding is improved. It is suggested that a two-phase system is not necessary for good tack, and a theory based on a two-phase system cannot adequately explain the rate dependence of tack tests. Tack measured by the probe test is shown to be dependent upon a balance between the viscoelastic properties and the transition temperature of the adhesives. This theory is used to explain the effect of contact time, withdrawal speed, and resin softening point on the tack of adhesives. |
