95
8 . Figure 3. Thermomechanical graphs of non-crystalline (1), crystalline (2)
and reticulated (3) polymers:
T
sh
- glass transition
temperature;
T
k
- crystallization temperature;
T
t
- temperature of adhesiveness;
T
k
- chemical decay (destruction) temperature;
I, II, III - areas of glassy (1), high elasticity (II) and viscous (III) states.
High elasticity is only high characteristic of polymers,
these materials can
undergo large elastic deformations.
A sticky state is similar to a liquid with high viscosity.
Linear or branched polymers can change from one physical state to another
with temperature changes.
Polymers with a spatial structure (with a network structure) exist only in the
glassy state. Orientation can be strengthened. In this case, the polymer in a highly
elastic or viscous state is gradually deformed and a certain order appears in the
structure of the polymer.
In uniaxial deformation, fibrous, pipe-like products are
obtained, in biaxial deformation, films are obtained. In the process of orientation,
the strength of the polymer increases.
The strength of amorphous polymers
decreases
over time, because the phenomenon of disorientation occurs over time
under the influence of temperature.
The mechanical properties of polymers are also affected by the time and rate
of exposure to the powder. Under the
influence of an external force, the
macromolecule of the polymer is straightened, elongated, the links shift and twist.
The passage of such changes depends on time, therefore,
when evaluating the
properties of polymers, it is necessary to take into account the effect of temperature
and time on them, in other words, the relaxation property of the polymer should be
taken into account.
