of metals with polymer matrix, what is consistent with the literature data [23]. From
the other hand, a secondary effect of the disperse filler in an already recycled MP in
the conditions of hard heat treatment, especially, if it is associated with mechanical
load, can be possible too.
The analysis of the results of conducted researches allows us to note the following
facts. Powdery metals are located in such a row because of the strength of catalytic
effect on the process of thermooxidative destruction of aromatic polyamide: Bronze >
Cu > Ti > Al > Ni. The metals are located in the same sequence by degree of their
influence on the IR spectrums of phenylone as it is showed in [22], i.e. the correlation
between thermal properties and structural transformations on molecular level is
observed.
Among the thermophysical methods, there are calorimetric and dilatometric ones
which are important methods for the researches of polymers. As it is known, thermal
expansion is typical for polymer materials when heated. This is due to the
anharmonisity of the vibrations of particles that make up the body and reflects the
forces which act between them, and due to the physical and chemical processes that
occur in it: vitrification, crystallization, stitching, softening etc.
In the equilibrium state solids occupy the volume that corresponds to the
minimum of free energy. At the temperature rises, the amplitude of the vibrations of
the atoms and their average displacement from the equilibrium position increase.
Consequently, the solid will change its sizes until its volume becomes so that it will
correspond to a minimum of potential energy. A qualitative characteristic of the
thermal expansion of polymers is the coefficient of thermal linear expansion which is
determined at the constant pressure [24].
Since polymers are characterized by a higher coefficient of thermal linear
expansion in comparison to other solids, the study of temperature dependence of these
coefficients is particularly important both for identification of temperature transitions
in polymers and for calculation of adjustments and allowances during the using of
parts.
Reducing the coefficient of thermal linear expansion leads to minimal shrinkage
of plastics when the temperature changes in the processes of manufacture or operation.
Also it can decrease the probability of cracking of materials under the influence of
temperature. It’s known [25] that the high values of the coefficient of thermal linear
expansion leads to some undesirable phenomena: residual stress appears and causes
the occurrence of significant thermoelastic forces which cause the destruction of the
composite material when the temperature rises.
The coefficient of thermal linear expansion was determined according to GOST
(State Standard) 15173-70 on the dilatometer DKV-5AM in the temperature range 293
– 1173 K.
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