Chemistry Reference
In-Depth Information
and structure, are a function of its type, structure and content of both phas-
es, nature and value of interphase actions and manner the phases are linked
in the system.
The progress in the area of TPE is connected with the research oriented
to improve thermal stability of the rigid phase (higher T
g
) and to increase
chemical resistance as well as thermal and thermo-oxidative stability of the
elastic phase [2]. A specific group among the TPE described in the litera-
ture and used in the technology are microheterogeneous mixes of rubbers
and plastomers, where the plastomer constitutes a continuous phase and
the molecules of rubber dispersed in it are cross-linked during a dynamic
vulcanizing process. The dynamic vulcanization is conducted during the
reactive mixing of rubber and thermoplast in the smelted state, in condi-
tions of action of variable coagulating and stretching stresses and of high
coagulating speed, caused by operating unit of the equipment. Manner of
producing the mixtures and their properties as well as morphological traits
made them be called thermoplastic vulcanizates (TPE-V) [9, 10]. They are
a group of “customizable materials” with configurable properties. To their
advantage is that most of them can be produced in standard equipment
for processing synthetics and rubbers, using the already available genera-
tions of rubbers as well as generations of rubbers newly introduced to the
market with improved properties. A requirement of developing the system
morphology (a dispersion of macromolecules of the cross-linked rubber
with optimum size in the continuous phase of plastomer) and achieving an
appropriate thermoplasticity necessary for TPE-V are the carefully select-
ed conditions of preparing the mixture, (temperature, coagulation speed,
type of equipment, type and amount of the cross-linking substance). When
selecting type and content of elastomer, the properties of the newly cre-
ated material can be adjusted toward the desirable direction. Presence of
the cross-linked elastomer phase allows for avoiding glutinous flow under
the load, what means better elasticity and less permanent distortion when
squeezing and stretching the material produced in such a manner as com-
pared to the traditional mixtures prepared from identical input materials,
each of which produces its own continuous phase. With the dynamic vul-
canization process many new materials with configured properties have
been achieved and introduced to the market. The most important group of
TPE-V, which has commercial significance, are products of the dynamic
vulcanization of isotactic polypropylene (iPP) and ethylene-propylene-
diene elastomer (EPDM). It is a result of properties of the PP and EPDM
