ðð CD-PET
is a Cationic Dyeable Polyester.
ð It
is also known as Basic Dyeable Polyester.
ð It
is modified polyester.
ð In normal polyester, there are no sites for ionic
dyes. So, it can only be dyed by disperse dyes.
ð Compared to ionic dyes, disperse dyes have
smaller molecular extinction coefficients and lower build-up property.
ð So these dyes cannot give bright and deep
colours.
ð Moreover, fastness to sublimation and wet
treatments of disperse dyes are relatively poor compared to other classes of
dyes.
ð In order to avoid these problems, cationic
dyeable polyester(CD-PET) was developed.
Modification
Process (Manufacturing of CD-PET)
ð Co-polymerisation of an isophthalic acid
component containing a sulfonic acid group makes it possible to use cationic
dyestuffs for polyester staple fibres and filaments.
ð Generally, the sodium salt of 5-sulfo-isophthalic
acid (Na-SIPA) is used as CD co-monomer.
ð A cationic or basic dyestuff contains amines or
ammonium groups or quaternary nitrogen-heterocyclic.
ð Dyeing of CD-PET is an ion exchange process.
ð The sodium cations (Na+) from CD-PET are
substituted by the bigger dye cations, whereas the sodium ions enter into the
dye bath.
ð Thus, PET is chemically modified in a manner that
cationic dyestuffs can form a chemical complex with the fibre.
ð The chemistry of producing CD-PET is complicated.
ð The reason for difficulty is the acidic character
of Na-SIPA, especially in connection with hydrolytic or glycolytic conversion.
ð Therefore, after direct addition of this salt
into the PET esterification stage, the diethylene glycol (DEG) would reach a
high level because ether formation is acid-catalysed.
ð Additionally, the acidic character enhances the
TiO2 agglomeration.
ð The result is
difficulty in the spinning process, and an excessively low melting point of
CD-PET
Chemical
Structure
|
Density (g/cc)
|
1.45 – 1.49
|
|
|
Tenacity (g/d)
|
Dry
|
3.8 – 4.2
|
|
Wet
|
3.8 – 4.2
|
|
|
Breaking Elongation (%)
|
Dry
|
21 – 40
|
|
Wet
|
21 – 40
|
|
|
Elastic Recovery (%)
|
At 2%
|
90 – 92
|
|
At 5 %
|
75 – 85
|
|
|
At 10 %
|
45 – 60
|
|
|
Stiffness (g/d)
|
15 – 35
|
|
|
Moisture Regain (%)
|
65 % RH
|
0.8
|
|
90 % RH
|
1.1
|
|
|
Melting Point (ºC)
|
210 – 220
|
|
|
Softens at (ºC)
|
175 – 190
|
|
Chemical Properties
(1) Effect
of Acid:-
·
CD-PET fibre shows good
resistance to organic acids.
·
The fibre also exhibits
good resistance to inorganic acids at room temperature.
·
Only with concentrated
sulphuric acid, the fibre partially degrades.
(2) Effect
of Alkalis:-
·
The fibre is quite
resistance to weak alkalis at room temperature.
·
At 97ºC, 1 N NaOH
solution, fibre surface degrades due to saponification.
·
Ammonia will causes
aminolysis and loss in strength.
(3) Effect
of Bleaching agents and Solvents:-
·
The fibre has excellent
resistance to bleaching agents and organic solvents.
·
The fibre is swollen or
dissolved by phenols, chloroacetic acid, chlorophenols.
(4) Effect
of Sunlight:-
·
The fibre, on direct
exposure to sunlight, loses its strength and weakness.
(5) Dyeability:-
·
This fibre is specially
modified for dyeing with cationic dye.
·
So basic (cationic)
dyes are mostly used to dye CD-PET.
Applications
ð
Knitting: suede-imitation, plush fabric for home
textile , sportswear
Woven: peach skin
velvet
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