38
Y. Qin et al.
using the software of JMicrovision. Note: all the investigated PET specimens were
entirely flat during the measurements, therefore, a 2D image analysis was sufficient
for revealing the S R of the specimens.
2.8 Thermogravimetric Analysis
A thermogravimetric analyzer (TGA Q5000, TA Instruments, USA) was employed
to explore the thermal stability of PET melt-spun fibres. The measurement was
conducted in a nitrogen atmosphere, where the scan heating rate was 10 °C/min
with an investigated range from 25 to 800 °C.
2.9 Size Exclusion Chromatography
In order to reveal the weight-average molar mass M w , number-average molar mass
M n , and polydispersity M w /M n of all the investigated materials, size exclusion measurements (GPCmax, Malvern) with triple detection were conducted. The PET was
dissolved in HFIP as solvent at 50 °C for 2 h at a concentration of 2 g/L, in order to
provide a complete dissolution of PET before conducting the measurements. With a
flow rate of 0.8 mL/min, the GPC measurements were performed at a temperature
of 35 °C.
Melt-spun fibres subjected to a higher processing temperature of 280 °C were
analyzed as well to evaluate the thermal degradation behaviour.
2.10 Rheological Characterization
The rheological properties of all the PET materials in oscillatory shear were investigated using an ARES rheometer (TA Instruments, USA) in the plate-plate geometry.
Through this type of rheometer may only be available at a low angular frequency
(<100 rad/s), it still can provide the critical rheological information corresponding to
the polymer molecular structure [41]. The dried PET materials were previously hot
compression at 270 °C under vacuum to produce cylindrical specimens with 2 mm in
thickness and 25 mm in diameter. For all the prepared specimens, dynamic mechanical measurements in the air were performed at 270 and 280 °C, respectively, at the
frequency ranging from 100 to 0.1 rad/s. A deformation amplitude of 10% in the linear viscoelastic zone proved previously by a strain amplitude sweep measurement,
was used for all the specimens in this study.
Y. Qin et al.
using the software of JMicrovision. Note: all the investigated PET specimens were
entirely flat during the measurements, therefore, a 2D image analysis was sufficient
for revealing the S R of the specimens.
2.8 Thermogravimetric Analysis
A thermogravimetric analyzer (TGA Q5000, TA Instruments, USA) was employed
to explore the thermal stability of PET melt-spun fibres. The measurement was
conducted in a nitrogen atmosphere, where the scan heating rate was 10 °C/min
with an investigated range from 25 to 800 °C.
2.9 Size Exclusion Chromatography
In order to reveal the weight-average molar mass M w , number-average molar mass
M n , and polydispersity M w /M n of all the investigated materials, size exclusion measurements (GPCmax, Malvern) with triple detection were conducted. The PET was
dissolved in HFIP as solvent at 50 °C for 2 h at a concentration of 2 g/L, in order to
provide a complete dissolution of PET before conducting the measurements. With a
flow rate of 0.8 mL/min, the GPC measurements were performed at a temperature
of 35 °C.
Melt-spun fibres subjected to a higher processing temperature of 280 °C were
analyzed as well to evaluate the thermal degradation behaviour.
2.10 Rheological Characterization
The rheological properties of all the PET materials in oscillatory shear were investigated using an ARES rheometer (TA Instruments, USA) in the plate-plate geometry.
Through this type of rheometer may only be available at a low angular frequency
(<100 rad/s), it still can provide the critical rheological information corresponding to
the polymer molecular structure [41]. The dried PET materials were previously hot
compression at 270 °C under vacuum to produce cylindrical specimens with 2 mm in
thickness and 25 mm in diameter. For all the prepared specimens, dynamic mechanical measurements in the air were performed at 270 and 280 °C, respectively, at the
frequency ranging from 100 to 0.1 rad/s. A deformation amplitude of 10% in the linear viscoelastic zone proved previously by a strain amplitude sweep measurement,
was used for all the specimens in this study.