Studies on Recycled Polyester
43
evaluated, and the double-log plot of the zero shear viscosity η 0 as a function of the
weight-average molar mass M w is shown in Fig. 4. The fitted lines are the best fit
using Eq. (11), which present good agreements with the measured data points.
Figures 5 and 6 show the storage modulus G
and loss modulus G
as a function
of frequency ω for five materials at two experimental temperatures. As expected,
all the materials indicate the linear molecular chain, considering that the molecular
chains are completely relaxed and present characteristic behaviour in the terminal
zone, where G
is proportional to ω
2 and G
proportional to ω [48]. Additionally, the
relationship between the microstructure of polymers or blends and the slope in the
plot of storage modulus G
and loss modulus G
has been investigated by Han et al.
[51–53]. As acceptable for low frequency even if applying a simply Maxwell-model
for first approximation, generally the majority of isotropic homogeneous polymer
melts and solutions show a slope of 2 in the logarithmic plot of G
against G
, which
corresponds well to this work. It should be pointed out that due to the resolution
of the rheometer used, data points of G
were dominated by the noise at a lower
frequency.
It can also be observed that the storage modulus G
and loss modulus G
at a
lower temperature of 270 °C in Fig. 5 presents the same trend with the zero shear
viscosity η 0 as provided in Table 7. For rPET-B and vPET-1 with the similar zero
shear viscosity η 0 , they also have almost exactly the same value of storage modulus G
and loss modulus G
at the same frequency. With respect to the storage modulus G
and loss modulus G
at the higher temperature of 280 °C, the curves of vPET-2 and
vPET-3 are coinciding; simultaneously, the curves of rPET-B, vPET-1 and rPET-A
are overlapping considerably (see Fig. 6). That is to say, at higher temperatures,
the difference of the storage modulus G
and loss modulus G
between different
materials becomes insignificant. Furthermore, with the increase of temperature, a
slight drop of the storage modulus G
, as well as the loss modulus G
of all the
materials is also observed as shown in Fig. 7.
Fig. 4 Zero shear viscosity
η 0 versus weight-average
molar mass M w for three
virgin PET materials at two
temperatures. The lines are
the best fit using Eq. (11)
43
evaluated, and the double-log plot of the zero shear viscosity η 0 as a function of the
weight-average molar mass M w is shown in Fig. 4. The fitted lines are the best fit
using Eq. (11), which present good agreements with the measured data points.
Figures 5 and 6 show the storage modulus G
and loss modulus G
as a function
of frequency ω for five materials at two experimental temperatures. As expected,
all the materials indicate the linear molecular chain, considering that the molecular
chains are completely relaxed and present characteristic behaviour in the terminal
zone, where G
is proportional to ω
2 and G
proportional to ω [48]. Additionally, the
relationship between the microstructure of polymers or blends and the slope in the
plot of storage modulus G
and loss modulus G
has been investigated by Han et al.
[51–53]. As acceptable for low frequency even if applying a simply Maxwell-model
for first approximation, generally the majority of isotropic homogeneous polymer
melts and solutions show a slope of 2 in the logarithmic plot of G
against G
, which
corresponds well to this work. It should be pointed out that due to the resolution
of the rheometer used, data points of G
were dominated by the noise at a lower
frequency.
It can also be observed that the storage modulus G
and loss modulus G
at a
lower temperature of 270 °C in Fig. 5 presents the same trend with the zero shear
viscosity η 0 as provided in Table 7. For rPET-B and vPET-1 with the similar zero
shear viscosity η 0 , they also have almost exactly the same value of storage modulus G
and loss modulus G
at the same frequency. With respect to the storage modulus G
and loss modulus G
at the higher temperature of 280 °C, the curves of vPET-2 and
vPET-3 are coinciding; simultaneously, the curves of rPET-B, vPET-1 and rPET-A
are overlapping considerably (see Fig. 6). That is to say, at higher temperatures,
the difference of the storage modulus G
and loss modulus G
between different
materials becomes insignificant. Furthermore, with the increase of temperature, a
slight drop of the storage modulus G
, as well as the loss modulus G
of all the
materials is also observed as shown in Fig. 7.
Fig. 4 Zero shear viscosity
η 0 versus weight-average
molar mass M w for three
virgin PET materials at two
temperatures. The lines are
the best fit using Eq. (11)