Chemistry Reference
In-Depth Information
Figure 8.13 Tensile and flexural properties. (a) Strength and (b) modulus of the four
TO-based resins with different styrene concentrations.
TO-based polymer. The mechanical properties of TOPERMA polymers
(Figure 8.13) varied with styrene concentration in a different manner to the
changes seen in the SOPERMA and COPERMA polymers reported.
24
For
example, the flexural strength and modulus of the TOPERMA polymers had
their maximum values at a styrene content of 33 wt%, while the flexural
strength and modulus of both the SOPERMA and COPERMA polymers in-
creased with increasing styrene content. It was explained that these changes
were caused by their cross-link densities.
24
However, the variation of cross-
link density of those polymers did not match the changes in properties. It
seems that some other important factors affecting the mechanical properties
were neglected. From our transparency and SEM analysis, we believe that
the effect of phase separation is one of these important factors. Hence, the
mechanical properties of the four resins were explored, with respect the
effects of phase separation and cross-link density.
Figure 8.13 shows the changes in tensile and flexural strength and
modulus of the four resins with different styrene contents. These mechan-
ical properties reflect the stiffness of a polymer matrix. It was observed that
all these properties had a similar trend: increasing with the increase of
styrene content until 33 wt% styrene, then decreasing after this point. This
trend was similar to the change of phase separation, but did not agree with
the change of cross-link density. In other words, the phase separation seems
to have a more pronounced effect on the stiffness of the polymers, than the
cross-link density. The introduction of a second, rubber-like, oil-rich phase
improves the toughness of a polymer matrix but sacrifices its stiffness, while
the increase of cross-link density shows the opposite effect.
8,10,14,23,24,28
Due
to the absence of phase separation, the TOPERMA67-ST33 matrix achieved
