Role of interfacial resistance to shear stress on adhesive peel strength

The adherence of an acrylic tape on silicone elastomers containing various quantities of a silicone MQ resin has been investigated by an instrumented peel test, along the lines of Newby and Chaudhury's work (Langmuir 1997,13, 1805-1809; Langmuir 1998,14,4865-4872), which gave the first evidence of in terfacial slip when a pressure-sensitive adhesive is peeled from a thin pol y(dimethylsiloxane) (PDMS) layer. In the present study, we show that the am plitude of interfacial slip movements is correlated to the composition of t he elastomer in MQ resin (small silica-like particles inserted into the ela stomer). High slip amplitudes are associated with low MQ resin content and result in weak shear deformations in the adhesive. Thus, depending on the c omposition of the elastomer, the peel energy is dominated either by frictio nal losses associated with slip at the interface (low MQ resin content) or by viscous dissipation due to shear deformations distributed in the volume of the adhesive (high MQ resin content). The transition between these two p rocesses depends on the contact time between the acrylic tape and the elast omer prior to peeling. The viscous and the frictional parts of the dissipat ed energy are quantitatively estimated from the observed displacements at t he interface and within the adhesive, the shear modulus of the adhesive, an d frictional laws determined from "pure" shear experiments. The computed en ergies can represent half of the measured peel energy for this adjustable s lip system. The understanding of the molecular mechanisms involved should h elp in the design of surfaces with adjusted adhesive properties.