Handbook of Adhesives and Sealants

Theories of Adhesion 551.0015Cosine θ0.90.8 c30Contact angle θ (degrees)0.74514 18 22 26 30Surface tension (dynes/cm) at 20°CFigure 2.3 Zisman plot for determining critical surface tension of polytetrafluoroethylene.Test liquids are n-alkanes. 5Substitution of the Young equation into the Dupre equation results inthe Young-Dupre equation that states:WA LV(1 cos ).This equation relates a thermodynamic parameter, W A , to two easilydeterminable quantities: the contact angle and the liquid-vapor surfacetension. For conditions of perfect wetting (cos 1):W 2 WA LV C2.2.4 Bond failure energyBond failure energy is composed of two parts: a reversible work ofadhesion and an irreversible work of adhesive deformation. Thus, thestrength of styrene-butadiene rubber adhesive depends on two components:a viscoelastic energy dissipation term, which is a function oftest rate and temperature, and the intrinsic failure energy whichagrees closely with the work of adhesion, W A , when bond failure isapparently interfacial.