Dyeing of aramid fibers

DYING OF ARAMID FIBRES

BY: MUDDASSAR HASSAN

ROLL NO. 85

What are aramid fibers

These are also called aromatic polyamides Those polyamides,which have aromatic six

carbon rings in polymeric chain

Main types of aramid fibers

Technora (made by Teijin of Japan) Conex (made by Teijin) Kevler (made by Dupont) Nomex (made by Dupont)

Good Qualities of fibers

Good heat resistance High tenacity & modulus of rigidity Non flammability Greater sticking temperature Aramid dominate over glass fibers,and

carbon fibers in all over the world market Stiffest &Toughest than even carbon and

steel

High modulus five times greater than polyester

Excellent in tension Good chemical resistance Compactness and solidity of molecular

structure In dry air,at 260C Aramid shrink only 2% By Sputter etching, depth of shade

increased considerably

DISADVENTAGES

No substantivity to dyes No environment friendly Poor UV resistance Rapid loss of strength with flexing ,folding

&flogging Low light fastness,even spun dyed yarn Very expensive Poor in compression than glass

Main physical properties

Melting poit371C Tenacity 5.3gm\den at 65%RH&70F Specific gravity of fiber is 1.38 Tg 275C

Dying of nomex with Basic dyes

Fiber (2dtex\50mm) Fabric form GSM (265g\m

WashingNomex in fiber form are washed in Vald henriksen

FBK MACHINE.

In fabric form,Walter Franke dying apparatus

Recipe for washing

Nonionic surfactant 1g\l Trisodiun phosphate dodecahydrate1g\l Liqour ratio 30:1 Washing condition Start at 40C &temperature raised to80C for 30

min Rinsing with hot and cold for 10 min

Dying procedure

Polycolor zeltex AG machine, used for dying Resipe Dye 2% o.w.f (Special dye, CI Basic 41) Sodium nitrate 20g\l Career benzyl alcohol 70 g\l Acetic acid 2.5g\l (60%) Liqour ratio 20:1

After treatment process

Materials are treated with 2g\l nonionic surfectant for 20 min at 95C

Acetic acid added to maintain PH to 3 Hot &cold rinsing Fixation was carried out fir 30sec at 200C

Dyeing of Technora and conex with disperse dyes

Three commercial disperse dyes are used

1)Terasel yellow3GW(CI Disperse yellow54)

2)resolin red FB(CI Disperse Red 60)

3) Resolin blue FB (CI Disperse blue56)

DYING CONDITION

Temperature 190 &time 60 min

Dying machine

Mini –colour (Texam GIKEN)

Recipe

Disperse dye (4-24%o.w.f) Dispersing agent (Disper VG) Nonionic

surfectant 0.5g\l Acetic acid 0.2g\l & PH to4.2 Liqour ratio15:1 Dying temp is raised at 2degC\min Maintaining temp to 190C for 60 min Reduction clearing is carried out twice

Dyeing of Nomex type430filament yarn

Three commercial basic dyes are use for dying CI Basic blue54 (CIBB-54) CI Basic red29 (CIBR-29) CI Basic redGL22(CIBR22) Dyeing Procedure Weight of skein of yarn(2.5) Infinite Liqour ratio140:1 Commercial dyestuff (10% o.w.f)

Using no career Temperature of dying range of 80 to 100C

Approaches to improve dyebility of aramid fibers

More polar solvent Pretreatment of liquid ammonia Using benzyl alcohol as carrier

Pretreatment with liquid ammonia

Pretreatment fibers with liquid ammonia,substantivity towards basic dye increase quite significantly

Condition of pretreatment process Immersing 2.5g m-aramid in 100ml liquid

ammonia Time 10 min &at 40 C Rinsing with hot and cold water

Dependence of light fastness properties on pretreatment & dyeing procedure

CI Basic fastness to light A B C Yellow 28 3 3-4 4-5 Orange 22 1 3 4 Red46 1 2 3 Red29 1 4 4-5 Blue 49 1 3-4 3-4 A : Without pretreatment, dyed without career B : Without pretreatment,dyed with 70 g\l benzyl alcohol C : Pretretment with liquid ammonia,dyed without carrier

Conclusion

Pretreatment of aramid fibers with liquid ammonia can not only increase substantivity for basic dyes,but also light fastness properties, as comparing with those of fibers dyed conventionally with basic dyes using career benzyl alcohol

Effect of polar solvent on dyebility of aramid fiber

These are three high polar solvents Dimethyl formamide Dimethyl acetate Dimethyl sulfoide

These solvents provide chemical energy to fibers,permitting rearrangement of the polymer chain through breakage and reformation of interchain hydrogen bonding

Factor of changing solvent diffusion in nomex fiber

1)Molecular volume

Mol vol = Mol.wt\r * 10 24\N

Where r is density

N is Avogedro number

2)Temperature of corresponding to onset of shrinkage.

Exhaust dyeing of treated nomex yarns

Exhaustion of CIBB54 at 100C At 30 min Attaining max degree of structural modification Order of increasing exhaustion rate DMF<DMAc<DMSO In DMF,90% of dye liquor being exhausted after

4hours In DMAc&DMSO leads to very rapid exhaustion 95% of dye liquor being exhausted in 45 minutes

Untreated yarns dyed according to commercial dying procedure in presence of Dymex career resulted in low exhaution45% of dye liquor

Temperature dependence of exhaustion rate

With DMF A slight decrease in rate occurs when treatment temperature decreases from 100 to 50C

Considerable larger decrease in rate occurs on reducing temp of treatment to further to 40C

With DMAc major change in exhaustion rate occurs between samples treated at 82.2&75C

Influence of treatment time on exhaustion rate

An increase in treatment time, leads to faster exhaustion rate

Temp from 30 sec to 30 min,solvent diffusion And polymer interaction are considerably faster But exhaustion rate is unaffected Structural modification changes also depends on

treatment time

Conclusion

Optimum condition of dying 100c and 30 minutes then substrate is readily dyeable in atmosphere pressure

After solvent treatment ,loss of polymer chain orientation and \or formation of void takes place

Solvent treated fabric leads to attain greater dyebility at expense of initial modulus and tensile strength

Elimination of larger amount of careers

Lower dyeing temperature and shorter dyeing time (significant benefit)

Effect of varying liquid ammonia pretreatment time &dying temp

pretreatment time

Dying temp

inC

K\S VALUE

Wash fast-

-ness

0.2 130 12.1 3-4

5 130 12.4 3-4

10 130 10.8 3-4

30 130 11.0 3-4

30 100 10.6 3-4

Method of removing ammonia Rinsing Rinsing &drying Evaporation without rinsing Treatment Tensile strength Extension step mN\tex (%) A 270 48 B 230 64 C 213 47 D 222 27 E 243 43

A Raw fiber B; Pretreatment 15 min in liquid ammonia C; Pretreated fiber dyed with basic dye D; Untreated fiber dyed with

basic dye using benzyl alcohol E; Untreated fabric dyed with basic but without career( Effect of pretretment and dying method on fiber strength and extension)

Influence of sputter etching in shade of dyed fabrics

The aramid fabric Technora dyed with CI Disperse54 etc, are treated by sputter etching and argon low-temperature plasma

Sputter etching is effective I increasing color depth of dyed Technora

As a decrease of L* for blue and red dyeing and considerable increase in C*for all three colors

These effects on dyed Technora are slightly less with low temperature plasma treatment

No significant effect on CONEX FABRIC Basic purpose of sputter etching is to

produce deeper shade deeper and \or more vivid colors on dyed aramid fabric without actually increasing concentration dye

Technora caused by sputter etching is thought to be due to formation of Microcrates during treatment that severely restrict the reflection of incident light

Name of device used for sputter etching, Shinku-kiku RFS-200

Depth of shade is measured with colorEye MS2020 Spectrophotometer under illuminant D65 AND WITH 10 OBSERVER

Spectrophotometer calculate value lightness L* and color difference E in CIELAB color space

CONDITION OF SPUTTER ETCHING Pressure of 20 pa Power rating of 100 Wt Time of treatment from 30 to 300sec

References

JSDC Volume111 Mach 1995,page72 JSDC Volume 111 March 1995 ,page 111 TRJ April 1986, page 254 JSDC Volume 110 July\Aug , page228,1994 Encyclopedia of textile finishing by

H.K.ROUETTE Man made fibers, page408 By R.W.Moncrieff www.dupont product.com