Chemistry Reference
In-Depth Information
Finally, in the fourth way (fourth method) of obtaining a fullerene-containing
polymer composition, fullerene solution in o-dichlorobenzene (solution concen-
tration 20 mg) was introduced into the polymer solution (3 h after the introduction
of the imidizing mixture). In other words, it was done during PAA chemical
imidization but before polyimide was precipitated from the reaction mixture.
2.2. Methods
The melt viscosity of PI powders was determined in a rheogoniometer (designed
at the Topchiev Institute of Petrochemical Synthesis of Russian Academy of Sci-
ences) with a cone-plane geometry (the cone angle is 1°, plate diameter 40 mm) at
a constant shear rate of 10
-2
sec
-1
at a given temperature.
Differential scanning calorimetry (DSC) was performed using the DSM-2M
microcalorimeter (designed at the Institute of Biology, Russian Academy of Sci-
ences, Puschino) at a scanning rate of 10°C/min.
Powders of BTDA-DABP PI obtained by chemical and thermal imidizations
were molded as follows: First, discs 20 mm in diameter and 2-3 mm thick were
molded at room temperature and a pressure of 200 atm. The disc was placed in a
compression mold and heated without pressure to 320°C and maintained at that
temperature for 1 h. After heating, the compression mold was taken out of the
thermostat and the sample in the compression mold was subjected to a pressure of
150 atm. for 2-3 min. The compression mold was cooled to 60-70°C over 40 min
at a pressure of 100-150 atm. 5 mm wide, 2 mm thick and 18 mm long samples
were cut from molded disc. The samples were subjected to three-point bending
tests at a loading rate 1.3 mm/min. Bending strength σ
b
, Young modulus E, and
failure strain ε
max
were determined.
The thermogravimetric (TGA) analysis was carried out on a derivatograph
(MOM Company, Hungary) in a self-generated atmosphere (in other words, in the
atmosphere of volatile products released from the sample during heating); the
scanning rate was 10°C/min.
The tribological characteristics of moldings were determined on a Tribometer,
designed at the Institute of Problems of Mechanical Engineering, Russian Acad-
emy of Sciences; the testing configuration was “ring-ring”. A ring-shaped rotating
steel counterbody was in contact with a planar surface of the polymer ring cut
from molding. The variable parameters in friction and wear measurements were
contact pressure and sliding speed of the counterbody. The contact pressure
ranged from 1.7 to 6.7 MPa and the sliding speed of steel counterbody was 0.047
to 0.138 m/sec. The main parameters investigated were the coefficient of sliding
friction and wear (mass) for 10 min sliding at each nominal pressure in the tribo-
contact. The dimentionless wear rate
•
was
determined as the volume (V) of ma-
terial worn during a certain period of time (in our case 10 min) divided by the tri-
bological contact area (S) and the sliding path length (L), i.e.:
W
•
= V/SL [5].
Polymer particles formed during the experiment were also collected and analyzed
using a “Videolab” automated image processing system, designed at Moskow
W
Search WWH ::
Custom Search