Chemistry Reference
In-Depth Information
Starting with these and mutually complementing the properties, materials
of high operation properties, and thermo-stable plastics of constructional
assignment in the first turn, have been produced.
Some widely used and attractive classes of polymers of constructional
assignment are considered in detail below.
7.3
AROMATIC POLYESTERS OF
N
-OXYBENZOIC ACID
The
n
-hydroxybenzoic (
n
-oxybenzoic) acid has been extensively used at
polymeric synthesis for the improvement of thermal stability of polymers
for the last years [18, 19]. The aromatic polyester “ECONOL,” homo-
polymer of poly
n
-oxybenzoic acid, possesses the highest thermal resistant
among the all homopolymeric polyethers [20] and attracts attention for the
industry.
The poly
n
-oxybenzoic acid is the linear high-crystalline polymer
with decomposition temperature in inert environment of 550 °C [20]. Be-
low this point decomposition goes extremely slow. The loss in weight at
460 °C in air is 3% during 1 h of thermal treatment and than number is
1% at 400 °C. The CO, CO
2
and phenol are released when decomposing
in vacuum at temperatures 500-565 °C, the coke remnant is of almost
polyphenylene-like structure. It is assumed [27], that decomposition starts
from breaking of ester bonds. The energy of activation of the process of
fission of up to 30% of fly degradation products is 249,5 kJ/mol. The fol-
lowing mechanism for the destruction of polymer has been suggested:
The high ordering of polymer is kept till temperature 425 °C. The equi-
librium value of the heat of melting of polymers of
n
-oxybenzoic acid is
found to be 5.4 kJ/mol [21].
Several methods for the producing the poly
n
-oxybenzoic acid have
been proposed [20, 23-30], which are based of the high-temperature poly-
