Cure and Properties of Thermosetting Materials at the Nanoscale

1
Cure and Properties of Thermosetting Materials at
the Nanoscale
Sindee L. Simon, Chemical Engineering, Texas Tech
University

• Nanoscale constraint is known to have a
  significant impact on the thermal properties of
  materials. Such changes are particularly
  important for the use of thermosetting materials
  in nanoelectronic applications, as well as for
  the use of nanoparticle-thermoset composites.
  However, although thermosetting resins have been
  cured in the presence of nanoparticles and
  nanotubes, cure of thermosetting resins under
  well defined nanoscale constraints has not been
  previously documented. Hence, in this project,
  we investigate the isothermal curing of a
  thermosetting resin, bisphenol M dicyanate ester,
  which trimerizes to form a polycyanurate network
  material, in the nanopores of controlled pore
  glass matrices.
• We find Tg depressions for both the bisphenol M
  dicyanate ester monomer and the polycyanurate
  networks confined in both silanized (hydrophobic)
  and native (hydrophilic) nanopores. The
  depression is only a few degrees for the monomer,
  whereas a Tg depression of approximately 60 K is
  observed for the "fully-cured" network in both
  silanized and native 11.5 nm pores. Two Tgs are
  also observed in all of the native pores and in
  the smallest silanized pores.

Nanoscale constraint is also found to
significantly accelerate the reaction kinetics of
bisphenol M dicyanate ester as shown in the
figure at the right, where the rate of increase
in the limiting fictive temperature (Tf', which
is approximately equal to Tg) is plotted as a
function of cure time for resin cured in
silanized nanopores. In native pores, the
reaction is accelerated even more.
Interestingly, nanoscale constraint does not
affect the network structure of the polycyanurate
formed. This conclusion is based on the fact
that the normalized Tg versus conversion
relationship, the gelation point, and the sol
fraction versus conversion relationship are the
same for resin cured in nanopores as for resin
cured in the bulk state.