A Molecular Theory of Tacky Adhesion

Adhesive force fa acts on the adherend surface through pseudo links and is given by a product of wetting force W/l and the fraction of links of about 10−2. W is a wetting energy of about 101—2 cgs-unit and l is a length of a segment of 1 nm in the adhesives polymer and fa is about 106—7 cgs-unit or 1—10 kg cm−2. On peeling a tape of pressure-sensitive adhesives, the adhesives layer is expanded and voids and fibrils are often formed. The shear forces in fibrils are integrated to give the peeing force P. The layer is deformed to give a concaved shape expressed with a catenary curve. In this model, P increases with increasing the relaxation time τ, thickness h, velocity v, and decreasing the peeling angle θ. P is expressed as P = (0.7 fa/sin/θ)/(1/h + 1/τv). For the tensile test in parallel plates, the thickness is expanded uniformly and P = fa(1 + τv/h). For the shear test, the cohesive rupture occurs and P = ηv/h, η being viscosity.