Indi an Journal or Fibre & Textile Research Vol. 27, Dece mber 2002, pp. 352-357

Elastic recovery properties of polyester jet-spun yarns

G K Tyag i", A Goyal & A Patnaik

The Technological Institute or Tex tile & Sc iences, Bhiwani 12702 1, India

Received 19 April 200 1; revised received alld ({ccepted 25 September 2001

The relationship between magnitudes or the instrumental measure ment or the elastic recovery properties and some yarn parameters has been studied. In general, the coarse yarns have low immedi ate elastic recovery, hi gh delayed e lastic recovery, and a large permanent se t than the rine yarns prepared under the identi ca l process ing conditions. The use or higher first nozzle pressure and main draft produces hi gh immedi ate e lasti c recovery but low del ayed e lastic recovery and permanent set. Both amplitude and rate or extcnsion produce a large variation in the e lasti c recovery prope rties, the magnitude being depe ndent mainl y on processing ractors.

Keywords: Air-jet spinning , Elasti c recovery , First nozzle pressurc, MJ S ya rn

1 Introduction The increas ing popul arity of air-Jet spinning

technology and its ability to produce fine yarns for certain substrates has created a need to expend its range. Thi s new technology offers significant advantages in respect of processing speed, production cost, and some potentia l benefits in weaving. When air-jet spun yarn is used', the improvement in warp and filling stops can be up to 25 .5% and 55% respectively . A comprehensive bibliography of the literature in thi s fi e ld is available in a recent pUblication2

. Much of this literature is focused on the dependency of yarn properties on important fibre and process parameters3

.6

. However, there is no report on the e lastic recovery properti es of air-jet spun yarns. A better understanding of the clastic paramete r would he lp in engineering yarns for specific end uses. Thi s is because the manufacturing of textile mate ri al involves a long process of transformation in which the textile substrate is subjected to different kinds of stress which give ri se to inte rnal tensions that ease with the time. This increases the vari ation in dimensions, resulting in the rejection of the substrate for the application for which it is destined . Thi s paper reports the findings of an ex ploratory study of the elastic recovery characteristics of polyester jet-spun yarns produced by varying first nozz le pressure and main draft.

a To whom all the correspondcnce should be addrcsscd. Phone : 42561; Fax: 0091-01664-43728; E-mail: tit s intr@nde.vsnl.net.in

2 Materials and Methods 2.1 Preparation of Yarn Samples

Polyeste r staple fibre of the length 51 mm, fineness 1.67 dtex, tenacity 31.75 cN/tex and breaking ex tension 30.8% was processed on a Lakshmi Riete rs' blow room line and carded on a MMC card. The card s liver was given three passages on a Lakshmi Riete rs drawframe DO/2S to produce finisher sliver of 2.7 ktex. Thi s slive r was spun into 11.8 and IS.5 tex yarns on a Murata air-jet spinner (Mode l MJS S02) with total draft of 229 and 145 respective ly using a machine speed of 200 m/min and a feed ratio of 0.9S. First nozzle pressures of 2.0, 2.5 and 3.0 kgf/cm2 and main drafts of 30.91, 35.77 and 41.55 were used for producing nine samples for each yarn count.

2.2 Tests

The e lasti c recovery paramete rs or th e ya rns were determi ned us ing lnstron tensi Ie teste r (Model 44 1 I) as pe r the ASTM standard, 500 mm test specimens be ing e longated at extension rates of 50, 100 and 500 mm/min . The immediate e lastic recovery (l ER), de layed elastic recovery (DR) and permanent set (PS) were obtained fo r initial extension leve ls of 2, 4 and 6%. For each se lected level of extension , the yarns were allowed to fully re tract and then relaxed for 3 min, and the variations in extension were observed. Fig. I shows the typical load \IS. extension in an e lastic recovery measuremene. OA is a load extension curve obtained as a consequence of the initial extension of the specimen up to a pre-determined level COL). The cross-head of the In stron is then

TYAG I el (/1.: ELASTIC RECO VERY PROPERTI ES O F POLYESTER JET-SPUN YARN S 353

returned to its initial pos ition and the yarn recovery curve AS is traced out. The extension leve l at te x12 gf load is taken as a measure of immediate elastic recovery (LS ). The cross-head is kept at zero for 3 min and then extended till it crosses the te x12 gf load line at point C. E lastic recovery parameters we re ca lculated using the fo llowing express io ns :

~----------------------~A

L

Extension, nun Fig. I- Load-extension curve used for de termination o f c last ic recovery parameters

Table I - Analys is of va ri ance resul ts fo r e lastic parameters

Process Dcgree of F-ratio

variables frcedom Immediate Dclayed Permanent e las ti c c lastic se t

rccovery recovery

A 45 1.39" 16.96" 540.54"

B 127.96" 2 1.97" 70.54"

C 85.76" 8.69" 58 .8 1"

D 1020.75" 48.78" 993.95"

E 470.87" 69.59" 78 .1 7"

A*B 0. 17h 6.32h 16. 131>

A*C OA5 h 0 .60b 2.76"

A*D 85 .58" 70.76" 0. 19h

B*C 2 .07" O.Ol b 2.76h

B*D 3.33h 1.3 1 h I.oi'

C*D IAOh 1.6i' 0. 131>

A*E 0. 3i' 3.461> 4.3i'

B*E 9.66" 2.84b 1.86b

D*E I 109.60" 32. 16" 1.69h

Error 5

" S ignifi cant at 99% confidence level; :lJld h Non-s ignifi cant at 99% confidence leve l. A - Yarn linear density; B - First nozzle pressure; C - Main draft ; D - Amplitude o f ex tension; and E - Ex tension rate .

Immedi ate e lasti c reco very (IER), % = [BLlOL]x lOO

De layed e lasti c recovery (DR), % = [BCIOL]x IOO

Pe rmane nt set (PS), % = [OCIOL]x lOO

3 Results and Discussion The influe nce of ex perimental variab les, v iz. first

nozzle pressure, ma in draft and amplitude and rate of extension, on e lasti c recovery properti es was assessed using the analys is o f variance (T able 1) at 1 % level of significance. Only the first o rder interactio ns were considered.

3.1 Infl uence of Ampli tude and Rate of Extension on Immediate Elastic Rec:overy

Fi gs 2-7 show the recovery responses of the po lyester MJS yarns produced with d iffere nt f irst nozzle pressure and main draft. In a ir-j et spinning, the yarn linear de nsity is a hi ghly significant facto r fo r immedi ate elas ti c recove ry, de layed e las ti c recovery and permane nt set, as has been obse rved using the stati sti ca l analys is ANOV A (T able I). Fi g. 2 shows that the highest immedi ate e lasti c recove ry is 83.4% fo r 11.8 tex yarn at 41 .55 ma in dra ft and 3 .0 kgf/cm2 first nozzle pressure. The lower immedi ate elasti c recove ry of 45 . 1 % be longs to 18 .5 tex a t 30.9 1 main draft and 2.0 kgf/cm2 first nozzle pressure. The first nozzle pressure is an ano ther hi ghl y s ignificant fac to r fo r immedi ate e lastic recovery because it increases the inc ide nce of wrapper fibres which exerts more rad ia l pressure o n the core fibres , resulting in a compact packing . It is no teworthy that the change in ma in draft o ffe rs s ig ni ficant advantage in respect o f immed iate e las ti c recovery; the lo wer immedi ate e lasti c recovery correspo nds to lowe r main dra ft a nd increases consistently with the inc rease in main d raft.

It can be seen from Fi g . 2 that the cho ice of ex tension ra te s ignificantl y a ffects the immed iate elastic recovery. The immed iate e lasti c recovery, in genera l, registers lower va lues w ith decreas ing ex te nsion ra te . Such a behav io ur of immedi ate e las ti c recovery could be asc ribed to the unique structural features o f MJS yarns. At low ex te nsion rate, the phe no menon of stress- re laxation predo minates during the actu al stre tching time whic h impairs the recovery characteri sti cs

8. The immedi ate e las ti c recovery of

MJS yarn s is a lso influe nced by the amp litude of ex te nsion. It is evide nt from Fig. 3 that the immedi ate e las ti c recovery s ignificantly decreases with the increase in amplitude o f exte nsio n. However, the decrease in immedi ate e lasti c recovery with the inc rease in amplitude of ex te nsion is less marked in

354

100

INDIAN J. FIBRE TEXT. RES. , DECEMBER 2002

First nozzle pressllre, 2.0 kg/crn'; Extension, 2'),.

-+-1 1.8 1e x.30 .91 MD __ 18.5 tex. 30.91 MD

___ 11.8 tex . 35 .77 MD ~ 18.5 tex. 35 .77 MD

-.-- 11.8Iex.41 .55 MD ____ 18 .5 lex. 41 .55 MO

80 t-

= 60 r ;;--, ..... (1)

> o () Q) ..... 40 I

100 r--------------------------------------------------------~

~ >.. (1)

> o o (1) .....

80

60 ·

40

100

80

60

o 40 ~

Ul ro 100 <l)

(1)

w -0

(1) 80

= E

60

40

Main drafl .\ 1.55: Exlension. 2% -+-1 1.8 lex . 2.0kg/cm ___ 11 .8 tex, 2.5kg/c m -,-- 11 .8 tex. 3 .0kg/cm

__ "~"o~om

50 100 500

Extension rate, mm:!l1lin.

Fig . 2- Influc ncc of cXlension rale on immcdiatc clast ic recovery

First nozzle pressure. 2. 1l kg/clll ': Extension mle. 50 11lIIlh nill

-+- 11 .8 tex. 30 .9 1 MD -- 18.5 'e x, 30 .91 MD

___ 11.8 lex . 35 .77 MD ~ 18 .5 lex. 35.77 MD

M'l ill dra ft. 41 .55: E."tc il s ion rat e. 50 mill/ mi ll -+- 11 .8 tex. 2.0kg/cm ___ 11.8tex . 25kg/cm - -18.5 tex. 2.0kg/cm -,-1 8.5 tex , 2.5kg/cm

2 4

Amplitude of extension, %

-.-- 11.8 lex. 41 .55 MO ____ 18.5 tex. 41 .55 MO

-.-- 11 .8 tex 3.0kg/cm ___ 18.5tex.3.0kg/c m

6

Fig. :I-Influence of amplitude of ex tens ion on immcd iatc elastic recovcry

TYAGI el al.: ELASTIC RECOVERY PROPERTIES OF POLYESTER JET-SPUN YARNS

40 -.---------------------------------------------------------~

30

6 20 <!)

> o <.) <!) ..... <.) 10

'.c ~ 40 <!)

'l::l <!)

>. ~ 30

<!)

o

.... ..0 0 ....

20

10

40

30

>-. 20

~ > o <.)

Firsl nozzle pressure. 2.0 kg/CII12: E.'\ lcnsion. 2'%

__ 11.8 lex, 30 .91 MD _ _ 18.5 tex, 30.91 MD

-a-l1 .8tex, 35 .77 MD ____ 18.5 l ex, 35 .77 MD

Main dra fl. 41.55: E.\1Cnsion. 2'%

-+--.11 .8 tex , 2.0kg/cm ____ 11 .8 tex , 2.5kg/cm - - 185 tex , 2.0kg/cm -,- 18.5 tex, 25kg/cm

50 .100

Extens ion rate, mm/min

__ 11 .8 tex, 41 .55 MD __ 18.5 tex, 41 .55 MD

__ 11 .8 tex , 30kg/cm __ 18.5 tex, 3.0kg/cm

500

Fig. 4--lnfluence of extension ratc on delaycd clastic rccovcry

FirSI nozzle pressure. 2.0 kg/em': E,\ lcIISioll ra lc, 50 mill/ min

__ 11.8 t9x,30.91 MD ~11 . 8Iex, 35 .77 MD __ 11.8 Icx , 41..55 MD

_ _ "~~5~le:x~, ~35~.~77~M~D~~;;;.~ ________ ~1~8.~:~le~x, 41 .55 MD

~ 10 .L-______ ~ __________________ ~ __________________ ~L_ ______ ~

"-' 40 If)

ro <!)

'l::l <!)

~ 30 <!)

o

20 .

10

Maill draft. 41 ,55: E.\1ension r(l IC. 50 lIun/ min __ 11 .8 Iex , 2.0kg/cm -- 18.5 tex. 2.0kg/crn

~ 11 8lex, 2.Skg/cm -.- 18.5 tex, 2.5kg/cm

2 4

Amolitude of extensiol1_ %

-.- 11.81ex 30kg/c lll __ 18.5 tex , 3.0kg/cm

6

Fig, 5- ln flucncc of amplitude of cx tcnsion on delayed elastic rccovcry

355

356

~

OJ (/J

---c: <V . c: C1:1

8 .... <V

0...

INDIAN J. FIBRE TEXT. RES., DECEMBER 2002

40 .r=----~----------~----------------------------~ First nOL7.1 c pressure. 2.0 kg/e ill ' : E.\ tension. 2'X,

30

20

10

-.- 11.8 tex . 30 .91 MO _ _ 18.5 tex , 30.91 MO .

____ 118 tex, 35.77 MO --11-18.5 le x. 35.77 MD

__ 11 .8 le x, 41 .55 MD ____ 18.5 tex , 41.55 MD

o L-______ L-______________ L-______________ L-____ ~

40 .r-------------------------------------------~

3 0

20

10

o

40

30

20

10

0

40

30

20

10

0

a

M;lin draft. 41.55: E"tellsion, 2'X,

-+- 11.8 tex . 2.0kglcm __ 11 .8 tex . 2.Skglcm - - 18.5 lex , 20kglc m ___ 18.5 tex, 2.5kglcm

50 100

Extension rate, mm/min

--.- 11 .8 tex . 3.0kglcm ___ 18.5 tex , 3.0kglr. m

500

Fig . 6- ln llucncc of cxtens io n rate o n pe rmanent se t

fo ils! nozzle pressure. 2.0 kg/em: ; Extension rate, 50 nlm/ min -+- 11 .8 lex, 30.91 MD __ 11.8 le x, 35 .77 MD _ _ 18.5 lex , 30.91 MD ______ 18.5 tex , 35 .77 MD

Main dr<lft, 41. 55 ; Extension rate, 5tl mtrl/ min

0

-+- 11.8 tex ,' 20kglc m __ 11 .8tex, 25kglcm __ 18.5 lex , 2.0kg/cm ~ 18.5 (ex, 2,5kglcm

2 4

Amplitude of extension, %

__ 11.8 lex, 41 .55 MD ___ 18.5 tex. 41.55 MD

--.- 11,8 le x 3.0kg/cm _ _ 18 .5 lex , 3 .0kglcm

6

Fig . 7- lnllucnce o r amplitude o r cxte ns io n o n pe rmane nt set

TYAGI et al.: ELASTIC RECOVERY PROPERTIES OF POLY ESTER JET-SPUN YA RNS 357

the yarns produced with higher first nozz le pressure. This is expected due to the hi gher incidence of wrapper fibres which restri cts the process of disintegration of the yarn structure during stretching.

3.2 Influence of Amplitude and Rate of Extension on Delayed Elastic Recovery

Figs 4 and 5 depict the delayed e lasti c recovery of different MJS yarns. In genera l, the yarns produced with lower main draft ex hibit hi gher de layed e lasti c recovery , followed by the yarns produced with hi gher main draft. According to the ANOV A results, first nozzle pressure is a hi ghly significant factor affecting delayed e lasti c recovery. The de layed e lastic recovery has a tendency to decrease with the increase in first nozz le pressure (Figs 4 and 5). This suggests that the yarns should be spun with hi gh first nozzle pressure to keep the delayed elastic recovery low. The increase in extension rate further reduces delayed e lasti c recovery , the latter however re fl ects no consistent trend in respect of yarn linear density and amplitude of ex tension.

3.3 Influence of Amplitude and Rate of Extension on Permanent Set

Permanent deformation (Fi gs 6 and 7) generall y seems to be larger for coarse yarns but it tcnds to decrease when the extension rate increases and, at the same time, when amplitude of extension decreases. Thi s is quite understandable in the I ight of the fact that these parameters result in increased immediatc elastic recovery. The use of lower first nozzle pressure and main draft leads to a larger permanent deformation. The increased permanent deformatio n

with lower va lues o f first nozzle press ure and main draft can be attributed to the lack of suffic ient transverse forces as a result of improper forma tion of wrappers, causing more core fibres to s li p than to break.

4 Conclusions Both ex tens io n rate and amplitude of extension

exert significant influence on immed iate e las ti c recovery , which tends to inc rease when the extension rate increases and decreases when the amplitude of ex tension increases. The immedi ate e lasti c recovery increases marked ly with the increase in both first nozzle pressure and main draft.

Lowest de layed e last ic recovery and permanent deformation are observed at a first nozzle pressure of 3.0 kgf/cm2. However, the de layed e lastic recovery and permanent deformation increase when the ya rn linear density inc reases and , at the sa me time. when main draft and ex tension rate decrease. The increase in amplitude of ex tensio n increases permanent deformation of the s truc tures, but its e ffect o n the delayed elastic recovery is not clear.

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80. 4 Artzt p, Steinbach G & St ix C. /111 Te.11 BIIII, 38(2) ( 1992) 5. 5 Tyagi G K. Kau shik R C 0 & Sa lohotra K R. /Ildiall J Fibre

Text Res, 20 ( 1995) 2 14. 6 Lawrence C A & Baqui M A , Text Res J, 61 ( 199 1) 123. 7 M anich A M & Castellar cle M D. Tnl Res J. 62 ( 1992) 196. 8 Guthrie J C & Norm an S. J Te.\t 111 .1'/, 52 ( 1961 ) T sm.