Adhesion between a Viscoelastic Material and a Solid Surface

Abstract

In this paper, we present a qualitative analysis of the dissipative processes during the failure of the interface between a viscoelastic polymer, characterized by a weak adhesion, and a solid surface. We reassess the "viscoelastic trumpet" model [P.-G. de Gennes, C. R. Acad. Sci. Paris, 307, 1949(1988], to express the viscous energy dissipated in the bulk as a function of the rheological moduli of the material, involving the local frequencies of sollicitation during crack propagation. We deduce from this integral expression the dhesion energy for different kind of materials: (i) we show that, for a crosslinked polymer, the dissipation had been underestimated at low velocities. Indeed, the interface toughness G(V ) starts from a relatively low value, G 0 , daue to local processes near the fracture tip, and rises up to a maximum of order G 0 (µ ∞ /µ 0 ) (where µ 0 and µ ∞ stand for the elastic modulus of the material, respectively at low and high strain frequencies). This enhancement of fracture energy is due to far-field viscous dissipation in the bulk material, and begins for peel-rates V much lower than previously thought. (ii) For a polymer melt, the adhesion energy is predicted to scale as 1/V . In the second part of this paper, we compare some of these latest theoretical predictions with experimental results about the viscoelastic adhesion between a polydimethylsiloxane polymer melt and a glass surface. In particular, the expected dependence of the fracture energy versus separation rate is confirmed by the experimental data, and the observed changes in the concavity of the crack profile are in good agreement with our simple model. More generally, beyond the qulitative and simple picture used for our approach, we expect our theoretical treatment to apply for relatively weak viscoelastic adhesives, for which the crack-tip dissipative term G 0 is weakly dependent on the fracture velocity.

Brittle fracture of polymer transient networks

“…Hence in all cases, ℓ is several orders of magnitude larger than L, ensuring that viscous effects are not relevant. This is consistent with the fact that at large distance the crack is parabolic and does not exhibit the x 3/2 scaling predicted by the viscoelastic trumpet model De Gennes (1996) and experimentally measured in the adhesive fracture of a polymer melt Saulnier et al (2004) and in polymer liquid under tension Huang et al (2016c). In addition, because the samples investigated here are very soft and strained elastically over very large deformation, they can be considered as hyperelastic.…”

The fingering to fracturing transition in a transient gel

“…2b). The parabolic shape over long distances suggests that this type of instability pattern can be considered as a crack, as observed for brittle solids [15][16][17] . Note that we find an overlap of the data for cracks with different radii of curvature spanning one order of magnitude, suggesting a universality of the shape.…”

Changes in materials properties explain the effects of humidity on gecko adhesion

“…Existing theories (Andrews, 1985;Hui et al, 1992;Saulnier et al, 2004) for the effect of viscoelasticity on the work of adhesion take  0 (tan, v c ), i.e. the influence of viscoelastic/rate effects is through a multiplicative function  that includes the viscoelastic and rate terms.…”

“…Assuming linear swelling with moisture in this dimension gives RϰRH. Next, following Saulnier et al (Saulnier et al, 2004), we take the -keratin to be a 'soft solid' and therefore have ϰv c tan 2 .…”