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Abstract:
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Nomex, which was introduced by E.I. DuPont de Nemours
and Company in the late 1940's, was developed to meet the
need for improved fiber durability and functionality at
high temperatures. Nomex is a non-melting polymer which
does not support combustion, only begins to char at 700 °F
and has been found in end-use products ranging from hot gas
filtration bags to productive clothing.
A major problem with Nomex is that it is extremely
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difficult and expensive to dye. The inherent chemical
structure and high glass transition temperature prevents
most dyes and carriers from penetrating into the compact
structure. Currently, the recommended dyeing procedure for
Nomex is limited by the necessity for high concentrations
of carrier, high temperature for a prolonged period of
time, difficulty in removal of the carrier, and a decrease
in the flame resistance characteristics due to residual
carrier in the fiber.
Because of the difficulties in dyeing Nomex, many
companies are having to buy solution dyed Nomex to meet the
appropriate specifications for the desired end-uses. The
buying of solution dyed Nomex increases the price of the
final product, eliminates the capabilities for style and
color changes, and eliminates the ability for quick response.
This work evaluated eight solvents, at two dyeing
times, two concentrations of solvent, with and without t he
addition of sodium nitrate, and were dyed according to t he
aqueous dyeing procedure. The dyeings were conducted on a
single primary dye shade and on a trichromatic dye shade .
In addition, the solvents were evaluated by treatment o f
the Nomex prior to dyeing.
Results from the aqueous dyeing procedure indicated the
solvent Acetophenone (Dymex) gave the highest increase in
depth of shade followed by Methyl Benzoate and N-Cyclohexyl-
2-Pyrrolidone. In addition, longer dyeing times,
higher concentrations of solvents, and the use of sodium
nitrate added to the dyebath allowed for a significant
increase in dye uptake. The remaining solvents, DMF, DMSO,
Sulfolane-W, Antiblaze 19T, and Antiblaze 100 had virtua lly
no effect on increasing the depth of shade.
The solvent pretreatment prior to dyeing revealed t hat
the treatment of Nomex with the solvents DMF, DMSO, and
Methyl Benzoate significantly increased the depth of shade
to near that of the dyeing conducted by the aqueous process
using the solvent Acetophenone (Dymex). Further research
of the pretreatment procedure may produce a dyeing
procedure which overcomes the disadvantages of the current
aqueous dyeing procedure.
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