A. Falsafi et al., DIRECT MEASUREMENT OF ADHESION BETWEEN VISCOELASTIC POLYMERS - A CONTACT MECHANICAL APPROACH, Journal of rheology, 41(6), 1997, pp. 1349-1364
We have measured the surface energies of several viscoelastic polymers
, using contact mechanics methods. The materials studied were diblock
copolymers of poly(ethylene)-poly(ethylene-propylene) (PE-PEP) having
different PE volume fractions and molecular weights. The materials exh
ibit differing viscoelastic relaxation functions in the bulk. Surface
energies were determined from contact mechanics experiments in the loa
ding mode, analyzed by incorporating the bulk viscoelastic effects int
o the Johnson-Kendall-Roberts theory of adhesive elastic contacts. The
samples were made of spherical caps of the materials formed by first
melting, and then cooling to room temperature. The measured values of
the surface energies are close to the reported value for that: of the
surface-active PEP block, based on prior contact angle measurements, i
ndicating that reliable surface energy values can be extracted from co
ntact mechanics experiments, suitably analyzed to account for viscoela
stic behavior. We believe that this method may be generalizable to sur
face and interfacial energy studies of a wide range of viscoelastic po
lymers. (C) 1997 The Society of Rheology.