Chemistry Reference
In-Depth Information
increases the cost of the latter. Consequently, the aromatic inhibiting flame
additions are necessary for creating thermally and fire resistant polymeric
materials. The introduction of such agents in small amounts would not
diminish properties of polyesters.
Accounting for the aforesaid, one can assume that the chemical modi-
fication of known thermally resistant polyesters, by means of introduction
of solider component (halogen-containing
n
-oxybenzoic acid) can help to
solve the problem of increasing of fire safety of polyesters without wors-
ening of their properties. It is obvious [49] that to replace one should in-
tentionally use bromine atoms, which are more effective in conditions of
open fire compared to atoms of other halogens.
So, as it comes from the above, the reactive compound involving halo-
gens are widely used for imparting fire-protection properties to aromatic
polyesters, as well as oligomer and polymeric antipyrenes.
The liquid-crystal polyesters (LQPs) became quite popular within the
last decades. Those differ in their ability to self-arm, possess low coef-
ficient of linear thermal expansion, have extreme size stability, are very
chemically stable and almost do not burn.
LQPs can be obtained by means of polycondensation of aromatic oxy-
acids (
n
-oxybenzoic one), dicarboxylic acids (iso- and terephthalic ones)
and bisphenols (static copolymers) and also by peretherification of poly-
mers and monomers.
Depending on the degree of ordering, LQPs are classified as smec-
tic, nematic and cholesterol ones. Compounds, able to form liquid-crystal
state, consist of long flat and quite rigid, in respect to the major axis, mol-
ecules.
LQPs can be obtained by several cases:
• Polycondensation of dicarboxylic acids with acetylic derivatives of
aromatic oxy-acids (
n
-oxybenzoic one) and bisphenols.
• Polycondensation of phenyl esters of aromatic oxy-acids (
n
-oxyben-
zoic one) and aromatic dicarboxylic acids with bisphenols.
• Polycondensation of dichloranhydrides of aromatic dicarboxylic ac-
ids and bisphenols.
• Copolycondensation of dicarboxylic acids, diacetated of bisphenols
and/or acetated of aromatic oxy-acids (
n
-oxybenzoic one) with poly-
ethyleneterephthalate.
Liquid crystal copolyesters have been synthesized [50-56] on the ba-
sis of
n-
acetoxybenzoic acid, acetoxybisphenol, terephthalic acid and
