EFFECTS OF CHAIN PULL-OUT ON ADHESION OF ELASTOMERS

The effect of chain pull-out processes on adhesion has been examined for the case of an elastomer. A thin layer of polystrene-polyisoprene diblock copolymer was placed at the interface between a polystyrene-coated substrate and a lens-shaped block of cross-linked polyisoprene. The interface toughness was found to vary with the crack growth rate and the areal density of copolymer present at the interface. At high crack growth rates (0.05 mm/h) the toughness was increased by about a factor of 10 by the presence of 0.1 chain/nm2 at the interface. At lower rates the toughness varied linearly with crack velocity and showed a threshold toughness, as the velocity tended to zero, that increased with the areal density of copolymer. The experimental results are compared with the predictions of a number of recent models of chain pull-out.