Effect of Cross-Linking on Tack and Peel Strength of Polymers

In this work the influence of cross-linking on the adhesive fracture energy and the peel strength is studied choosing polydimethylsiloxane (PDMS) as a model polymer. A series of samples was prepared by electron-beam irradiation which covers the whole range from a viscoelastic liquid to a cross-linked rubber. The mechanical behaviour of these PDMS samples was characterized by mechanical spectroscopy. Tack measurements with an instrument described elsewhere⁵ and peel measurements show that the adhesive fracture energy after short contact times as a measure of tack and the peel strength have a pronounced maximum in the range above the gel point, where the PDMS consists of a very loose and imperfect network and a high fraction of soluble polymer. In this range debonding is connected with the formation of fibrillar structures within the polymer.