Water at the Polymer/Substrate Interface and Its Role in the Durability of Polymer/Glass Fiber Composites.
Water at the Polymer/Substrate Interface and Its Role in
the Durability of Polymer/Glass Fiber Composites.
(832 K)
Nguyen, T.; Byrd, W. E.; Alsheh, D.; Aouadi, K.; Chin,
J. W.
Durability of Fibre Reinforced Polymer (FRP) Composites
for Construction (CDCC'98), 1st International
Conference. Proceedings. August 1998, Canada,
Benmokrane, B.; Rahman, H., Editor(s)(s), 451-462 pp,
1998.
Keywords:
water; durability; building technology; bonding
strength; FT-IR; interface; polymer composite; composite
materials
Abstract:
Fiber-reinforced polymer composites are increasingly
used in offshore and civil engineering structures. In
these applications, composite material are often exposed
to aqueous environments. Water can reduce polymer
composite durability by affecting the matrix, the fiber,
and the fiber/matrix interface. This study investigated
the role of the polymer/substrate interfacial water
layer on the shear strength of polymer/glass fiber
composites. The thickness of the interfacial water
layer was measured by Fourier transform
infrared-multiple internal reflection (FTIR-MIR)
spectroscopy of an epoxy applied to a model siliceous
substrate. The shear strength of the composite was
determined from the short-beam test of unidirectional
composites made of E-glass fiber and the same epoxy
matrix. Both untreated and silane-treated siliceous
substrates and E-glass fibers were used. Little water
was observed at the interface of the silane-treated
specimens, but about 10 monolayers of water accumulated
at the epoxy-substrate interface of the untreated
samples after exposure to water. Shear strength loss of
the untreated composite was twice that of the
silane-treated material after a 3-month immersion in 60
deg C water. Further, the treated specimens remained
transparent but the untreated specimens became opaque
after water exposure. Evidence from mechanical and
spectroscopic analyses and visual observaton indicated
that water at the polymer/fiber interface was
responsible for the dfference in the loss of the shear
strength of the untreated and surface-treated
composites. Data on solubilities and diffusion
coefficients of water in the eopoxy for two exposure
temperatures and changes of epoxy glass transition
temperature and work of adhesion of epoxy/silica due to
water are presented.
