Chemistry Reference
In-Depth Information
oxybenzoic acid [37, 38]. The presence of fragments of
n
-oxybenzoic acid
in macromolecular chain of the polymer not only increases the thermal
resistance but improves the physic-chemical characteristics of polymeric
materials. Obtained polyesters, consisting of monomers of
n
-oxybenzoic
acid and
n
-dioxyarylene (of formula HO-Ar-OH, where Ar denotes bi-
sphenylene, bisphenylenoxide, bisphenylensulfone), possess higher break-
ing impact strength, than articles from industrial polyester [39]. The data
on thermogravimetric analysis of homopolymer of
n
-oxybenzoic acid and
its polyesters with 4,4′-dioxybisphenylpropane, tere- or isophthalic acids
are presented in Ref. [21]. The temperature of 10% loss of mass is 454,
482, 504 °C for them correspondingly.
Highly durable, chemically inert, thermo-stable aromatic polyesters
can be produced by interaction of polymers containing links of
n
-oxyben-
zoic acid, aromatic dioxy-compounds, for example of hydroquinone and
aromatic dicarboxylic acids [40]. Thermo and chemically resistant polyes-
ters of improved mechanical strength can be obtained by the reaction of
n
-
oxybenzoic acid, aromatic dicarboxylic acids, aromatic dioxy-compounds
and diaryl carbonates held in solid phase or in high-boiling solvents [41]
at temperature 180 °C and lowered pressure, possibly in the presence of
catalysts [42]. Some characteristics of aromatic polyesters based on
n
-
oxybenzoic acid are gathered in Table 7.1 [20].
As mentioned above, the thermal stability of polymers is closely tied
to the manifestation of fire-protection properties. Many factors causing the
stability of the materials to the exposure of high temperatures are charac-
teristic for the fire-resistant polymers too.
Thermally stable polyesters can be produced on the basis of
n
-oxy-
benzoic acid involving stabilizer (triphenylphosphate) introduced on the
last stage. The speed of the weight loss decreases two times, after 3 h of
exposure to 500 °C polymer loses 0.87% of mass [43].
The high strength high-modular fiber with increased thermo- and fire-
resistance can be formed from liquid-crystal copolyester containing 5-95
mol % of
n
-oxybenzoic acid.
The phosphorus is used as fire-resistant addition, in such a case the
oxygen index of the fiber reaches 65% [44].
A 40-70 mol % of the compound of formula Ас-
п
-С
6
Н
4
СООН are
used to produce complex polyesters of high mechanical strength [45]. The
polyesters with improved physic-chemical characteristics can be obtained
