(187b) Flame Retardant Siloxane Polymers Produced by Eco-Friendly Synthetic Methods

There is a
tremendous interest in the area of flame-retardant (FR) materials due to their
numerous applications in clothing, construction, aviation and
telecommunications.  Current flame retardant (FR) materials on the market are
based on halogenated polymers and additives that are either classified as
harmful/toxic or give off such products upon combustion.  While these materials
have offered cost-effective solutions for FR applications, there is now an
increased global emphasis on discontinuing the use of these materials and
replacing them with environmentally and human safe alternatives.  Thus, there
exists the need to develop a new generation of environmentally-safe, economical
polymeric FR materials with efficient FR performance.  Our work centers on the
creation of novel polysiloxane copolymers (PS) by incorporating additives (e.g.
boron, organoclays and fillers) through a facile, environmentally benign,
solvent-free synthetic approach.  It is well-known in the literature that boron
is inherently thermally stable, environmentally safe and has extreme durability
to air oxidation.  Furthermore, boroxo silanol derivatives, used as
ceramic precursors, exhibit efficient FR properties.¹     We
have synthesized boron containing polysiloxane copolymers (polyborosiloxanes -
PBS) without the use of solvents.  Several different terpolymers,
consisting of a boronic acid (PBA) and an aromatic dianhydride (Oxy or DAH) at
various PBA/dianhydride molar feed ratios, have also been synthesized.  PBS
terpolymers have exhibited efficient flame and thermal properties with a
decomposition temperature (T_d) of 400-430ºC and a heat release
capacity (HRC) of 170-250 J/g-K.  Concurrently, PS-organoclay nanocomposites
have been synthesized.  When polymers are combined with small amounts of
organoclays, they can exhibit improved thermal, mechanical and FR properties.² 
Here, polysiloxane copolymers containing Oxy or DAH have been blended
with three different organoclays and two different fillers.  PS-organoclay
nanocomposites exhibit a T_d of 400ºC and an HRC of 160-200
J/g-K.  A synergistic approach is being employed to determine if further
enhancement of the FR properties can be achieved by creating PBS terpolymer organoclay
nanocomposites.  PS-filler blends created to determine the influence of
fillers such as cellulose and chitosan on thermal and flame retardant properties
will also be discussed.  The eco-friendly synthesis of PS-based nanocomposites
and blends and resulting flame retardant and thermal properties represent an
opportunity for a new generation of environmentally and human safe FR polymers
for military and civilian applications.

 [1] (a) Armitage, P.; Ebdon, P.R.; Hunt, B.J.; Jones
M.S.; Thorpet, F.G. Polymer Degradation and Stability, 1996, 54, 387. (b)
Martín, C.; Ronda, J.C.; Cádiz, V. PolymerDegradation and Stability, 2006, 91,
747.

[2] A.B. Morgan and C.A.Wilkie, (Eds.) Flame Retardant
Polymer Nanocomposites, Wiley-Interscience, New York, 2007.