1 research outputs found
AFM Probing of Polymer/Nanofiller Interfacial Adhesion and Its Correlation with Bulk Mechanical Properties in a Poly(ethylene terephthalate) Nanocomposite
The interfacial adhesion between
polymer and nanofiller plays an
important role in affecting the properties of nanocomposites. The
detailed relationship between interfacial adhesion and bulk properties,
however, is unclear. In this work, we developed an atomic force microscopy
(AFM)-based abrasive scanning methodology, as applied to model laminate
systems, to probe the strength of interfacial adhesion relevant to
poly(ethylene terephthalate) (PET)/graphene or clay nanocomposites.
Graphite and mica substrates covered with ∼2 nm thick PET films
were abrasively sheared by an AFM tip as a model measurement of interfacial
strength between matrix PET and dispersed graphene and clay, respectively.
During several abrasive raster-scan cycles, PET was shear-displaced
from the scanned region. At temperatures below the PET glass transition,
PET on graphite exhibited abrupt delamination (i.e., full adhesive
failure), whereas PET on mica did not; rather, it exhibited a degree
of cohesive failure within the shear-displaced layer. Moreover, 100-fold
higher force scanning procedures were required to abrade through an
ultimate “precursor” layer of PET only ∼0.2−0.5
nm thick, which must be largely disentangled from the matrix polymer.
Thus, the adhesive interface of relevance to the strength of clay–filler
nanocomposites is between matrix polymer and strongly bound polymer.
At 90 °C, above the bulk PET glass transition temperature, the
PET film exhibited cohesive failure on both graphite and mica. Our
results suggest that there is little difference in the strength of
the relevant interfacial adhesion in the two nanocomposites within
the rubbery dynamic regime. Further, the bulk mechanical properties
of melt mixed PET/graphene and PET/clay nanocomposites were evaluated
by dynamic mechanical analysis. The glassy dynamic storage modulus
of the PET/clay nanocomposite was higher than that of PET/graphene,
correlating with the differences in interfacial adhesion probed by
AFM