Test Methods and Identification of Recycled Polyester
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3.3.1 Scanning Electron Microscopy
Scanning electron microscopy is a powerful technique used to examine the polyester
samples. Microscopic analysis is performed after the conformity of 100% polyester
by one of the traditional methods.
Microscopic visualization of the PET Microscopic visualization of the PET or
hollow fibers is possible using a polarized light microscope while in combination
with SEM. However, most of the synthetic fibers are produced round in shape. The
microporous round fiber cross-section can also be envisioned but not preferred. A
specialized section of other shapes with clefts like a typical slit, Y and T shape, circle
slit and hollow shapes have transpired for reasons, such as performance, comfort,
surface defect (pilling), readiness, bulkiness, tactility, processing, etc. Regular PET
types have round cross-section unlike others having core shapes [15]. The significant properties of cylindrical fibers such as pilling propensity, bending and stiffness,
inelasticity, friction, texture and softness are distinct from a linear cross-sectional
shape of fibers. The cores of hollow fibers provide information about the wall thickness/hollowness and thermal comfort of the PET. A compressed thick wall with four
channels can be seen and provide thermal protection.
3.3.2 Raman Spectroscopy
Adulterated textile can be examined using vibrational, rotational and low-frequency
modes of system using Raman spectroscopy. The r-PET is required to combat fraudulent fiber for which optical spectroscopy like IR spectroscopy is used. The rapid
identification offers qualitative and quantitative assessment of polyester samples
with reliable well-defined spectral structures. Such a molecular level identification
employs scatter light usually monochromatic in the infrared region and often lies on
the ultraviolet region. The shift occurs during molecular vibrations or interactions
that explicit energy further to provide information about the tested sample [16]. The
vibrational identification results in the fingerprint of identified molecular structure
that deals with the infrared analysis. Molecular identification includes density and
crystallinity with often less polar functional groups.
3.3.3 NMR Spectroscopy
A textile is subjected to NMR spectroscopic analysis via one among following chemical shift, Zeeman Effect or the Knight Shift effect in order to obtain molecular information. A physical state of textile is examined by the resonant frequencies developed
during analysis. Similarly, chemical and structural information of solid sample is
resulted from topologic and dynamic investigation. Three-dimensional structure of
molecules can be seen through low field NMR spectroscopy. Crystallization, spinning
and finishing ratio can also be evaluated [17].
79
3.3.1 Scanning Electron Microscopy
Scanning electron microscopy is a powerful technique used to examine the polyester
samples. Microscopic analysis is performed after the conformity of 100% polyester
by one of the traditional methods.
Microscopic visualization of the PET Microscopic visualization of the PET or
hollow fibers is possible using a polarized light microscope while in combination
with SEM. However, most of the synthetic fibers are produced round in shape. The
microporous round fiber cross-section can also be envisioned but not preferred. A
specialized section of other shapes with clefts like a typical slit, Y and T shape, circle
slit and hollow shapes have transpired for reasons, such as performance, comfort,
surface defect (pilling), readiness, bulkiness, tactility, processing, etc. Regular PET
types have round cross-section unlike others having core shapes [15]. The significant properties of cylindrical fibers such as pilling propensity, bending and stiffness,
inelasticity, friction, texture and softness are distinct from a linear cross-sectional
shape of fibers. The cores of hollow fibers provide information about the wall thickness/hollowness and thermal comfort of the PET. A compressed thick wall with four
channels can be seen and provide thermal protection.
3.3.2 Raman Spectroscopy
Adulterated textile can be examined using vibrational, rotational and low-frequency
modes of system using Raman spectroscopy. The r-PET is required to combat fraudulent fiber for which optical spectroscopy like IR spectroscopy is used. The rapid
identification offers qualitative and quantitative assessment of polyester samples
with reliable well-defined spectral structures. Such a molecular level identification
employs scatter light usually monochromatic in the infrared region and often lies on
the ultraviolet region. The shift occurs during molecular vibrations or interactions
that explicit energy further to provide information about the tested sample [16]. The
vibrational identification results in the fingerprint of identified molecular structure
that deals with the infrared analysis. Molecular identification includes density and
crystallinity with often less polar functional groups.
3.3.3 NMR Spectroscopy
A textile is subjected to NMR spectroscopic analysis via one among following chemical shift, Zeeman Effect or the Knight Shift effect in order to obtain molecular information. A physical state of textile is examined by the resonant frequencies developed
during analysis. Similarly, chemical and structural information of solid sample is
resulted from topologic and dynamic investigation. Three-dimensional structure of
molecules can be seen through low field NMR spectroscopy. Crystallization, spinning
and finishing ratio can also be evaluated [17].