Indi an Journal of Fibre & Tex tile Research Vol. 27. Dece mber 2002. pp. 335-34 1

Estimation of fibre maturity from micronaire value

G F S Hussa in", lanaki K LyeI'. Bindubala Singhvi & K R Kri shna lyer

Central Institute for Research on Cotton Technology. MalUnga, Mumbai 4000 19. India

Receil'ed 10 DClo/Jer 200 1; rel'ised receil'cd all d accepled 24 Decell/ber 2001

Cross-sectional perimeter. degree of thickening and mi cronaire va lues 1'01' 25 Indian cotton va rieti es covering thc entire spectrum of fincness level s have becn est imated . It is observed that for a given variety, the cross-sectional perimeter remains fa irl y constant irrespectivc o r the degree of maturat ion. Thi s leads to a direc t rel ationship betwccn thc micronaire val ue and the degree of thickening whi ch represent s the truc and botanical maturity fo r a given variety. It is also possible to poo l the va rieties ha ving peri meter within a spec ifi ed range and establish the relationship between mi cronai re va lue and degree of thickening for each perimeter range. The relat ionsh ips linking the above two parameters variet y-wise as well as perimetcr­wisc ha ve bccn prcse ntcd. Micronaire values for gradati on of va ricti es into three categories, namcly low, normal and hi gh, havc becn indicated.

Keywords : COllon. Fibre maturity. Micronaire

1 Introduction Maturity is defined or ex plained in terms of

secondary cell wall development i.e. the inward thickening of the fibre as the success ive layers of cell ulose are deposited during development after the fibre has attained its full length . This perspective views the maturity as a specific physiological attribute of the cotton fibre. Many textil e processing operations like carding, drawing, combing, spinning, dyeing and printing are sensiti ve to cotton fibre properties which are conceptuall y related to fibre development or maturity. Processing situations that have been shown to be dependent upon maturity include yarn strength , ya rn appearance, neps, imperfect ions, spinning efficiency, colour yield, shade repeats, baree' bands and undyed white specks 1.3.

Considerable misunderstanding persists about the true nature of fibre maturity. Raes and Verschrage4

have proposed probably the apt definition "the maturity of cotton fibre consists in defining it as the average relati ve wa ll thickness". Peirce and Lord) had proposed "degree or thickening" as a measure of

I maturity. The reciproca l of termed as the

o immaturity rati o, has been used by Hertel and Craven6

. The ratio of fibre width to the width of its lumen is yet another measure of maturit/.

., To whom allthc corrcspondence shou ld be addresscd. Phonc: 4 12 7273176 , 5 12 9979: Fax: 0091-022-4 13 0835;

E-mail: circot@vsnl.colll

Estab li shed techniques to eva luate the maturity may be divided into either direct or indirect. The direct approach in vo lves microscop ical observati ons to measure (i) the cell wall thick ness relative to the fibre diameters.9 , (ii ) the degree of thickening), and (iii ) the ratio of lumen width (L) to the wall thickness (W) of the fibres swollen in 18% NaOH 1o

.12

. However, approach (iii ) is presently the most popular and widely used one for the determination of maturity. Fibres irri gated with 18% NaOH are classified into di fferent groups, such as mature, half mature and immature, based upon the value of L I W. Maturity is expressed in terms of the percentage of matured fibres Pm (US standard ASTM to), maturity ratio Mr (Briti sh Standard Method 1t

) and maturity coefficient Me (CIRCOT Standard t

\ Some workers 5. 13. t4 have estab li shed formulae connecting 8, Mr. Pili and Me with each other.

The swoll en fibre technique, however, suffers from the drawback that a great deal of time and labour as well as eye strain is in volved. Tn add iti on, the maturity obtained after swelling the fibres in alkali may not represent the true botanical maturity . Raes and Verschrage l5 have demonstrated that swelling capacity of fibres in NaOH is not same for all cottons and hence the maturity va lue obtained by the swelling technique will grade the vari eti es (maturity scale) in an order di fferent from what ex ists before irri gati on with NaOH. Sheela el al. tli have unequivocall y demonstrated that the swollen fibre technique can lead to overestimation of maturity , especially in va ri eti es

336 INDIAN J. FIBRE TEXT. RES., DECEMBER 2002

that are basically prone to immaturity due to the simple reason that the immature fibres swell more than mature fibres and that the differential swelling is found to be variety dependent.

Indirect methods in volve the observation of some fibre characteristics that reflect the extent of fibre wall development or thickening such as birefringence ' 7. ' 9,

d b'I ' ~02 1 Ik I ' ' f I ??~J . yea I Ity- ' , a ' a I centn 'uge va ue --.- and air permeabilit/ 4

.32

. Of these, the approaches based on air permeabi lity are the most acceptable. Chapman.!.! had stated that causticaire fin eness and causticaire maturity of callan fibre could be predicted separately, yet simu ltaneously, accurately and rapidly with mi cronaire read ing by the aid of a conversion tab le provided the identity of vari ety is known.

Of late, the image analys is technique34-31i is slowly ga ining ground in the est imat ion of cotton fibre characteri stics such as ce ll wa ll thi ck ness, ri bbon width , maturity factor , maturi ty rati o, form factor, etc.

Pioneers In the interpretation of air flow measurements on fibre plugs were Hertel and Craven37 and Lord3x

. The rate of flow through the plug and, in turn, the micronaire va lue varies with the square of specific surface area. Specific surface area can be shown to be equal to M2 H." where the first term M depends upon the relative degree of wall thickening and the second term H" a measure of intrinsic fibre fineness which is directly proportional to fibre cross-sectional perimeter. If it is assumed that the perimeter for a given va riety remains constant , an assumption experimentally found true, then the micronaire va lue should direct ly reflect the fibre maturity . Lord38 had shown that as the fibre maturity decreases, the air permeability decreases more rapidly. In case of American cottons, certain

b· 3Y· . I I b d ar Itrmy Inl cronalre va ues lave een suggeste to denote the maturity of cotton; cottons having micronaire va lues less than 3.5 are considered as immature while those hav ing over 4.0 as matured . Cottons with micronaire va lues between the two can be mature or immature.

From the data collected on 20 Egyptian cottons (G.barbadense), Behear/o has reported a high correlation (r = 0.8156) between the degree of thicken ing (8 )directly measured from fibre cross­sect ions and the degree of thicken ing (8') calculated by using the expression 8' = Mie x 8 , where 8 is a constant equal to the inverse of P x K where P is fibre perimeter and K, the instrumental constant. He concluded that the micronaire va lue with sui table

constant 8 cou ld be used to determine the degree of wall thickening as the best est imate of maturity.

[n India, the innumerable varieties belonging to the fo ur major botanical species and hybrids having micronaire va lue as low as 2.4 and as high as 8.5 are grown. Indeed, the cross-sectional perimeter va lues of cottons grow n in India range from 45 /1m to 80 ~lm .

This wide spectrum of perimeter suggests the need to prescribe different cut-off micronaire va lu es to

different varieties to be class ified as matu re or immature.

Th is paper deals with the relat ionship between the degree of thi cken ing and the micronaire va lue variety­wise and perimeter range-wise. For each perimeter range, the micronaire val ues to grade the vari et ies into low, normal and hi gh categories have been indicated.

2 Mate"ials and Methods Twenty-five Indian cotton vanetles representi ng a

wide range of micronaire va lues were selected for the in vestigation . Table I shows the selected varieties and the range of micronaire values for each varietiy. From

Table I - Colton var ieties and their Illicronaire range

Variety Mi eronai re range

RCH 2.4 - 4.5

DCH .32 2 .5 - 3.0

Su rabhi 2.6 - 3.5

MCH .11 2.6 - 4.0

MCU.5 2.6 - 4.0

NHH .44 2 .7 - 4 .3

JKHY.I 2.7 - 4 .:1

Varaiaxill i 2.8 - 3.4

S.6 2.9 - 4 .2

LRA .5 166 3.3 - 4.7

G Co1.l 6 3.3 - 5.D

DHY.286 3.6 - 4 .5

G COLI 3.7 - 5.6

RS .875 3.8 - 5.6

G Cot DHy.7 3.9 - 5.6

HS .6 3.9 - 5 .8

F.846 4.0 - 5.6

H.1098 4.0 - 5. 1

Jayadhar 4.4 - 5.7

RST.9 4.6 - 6. 1

Digvijay 4.6 - 6.3

Wagad 4.8 - 6.6

RG. 8 6.4 - 8. 1

LD.327 6.7 - 8. 1

LD.49! 6.8 - 8.D

HUSSA IN el al.: EST IMATION OF FIBRE MATU RITY FROM MICRONA IRE VA LUE 337

each variety , about 5 lo ts, representing the entire spectrum of micronaire va lue of that vari ety, were chosen. Micronaire va lues were dete rmined by using the Sheffi e ld Micronaire adopting the procedure standardized at CTRCOT4 1

. Fibre maturity was

expressed in terms of the degree o f thi ckening (8) . For each sample, 200 cross-sectio ns were profi led . Us ing a planimeter the va lues of fibre outer c ross-secti onal area (A), perimeter (P) and lumen area (A') were

obtained. The degree o f thickening 8 was calcul ated by employing the following ex press ion:

8 = 4n( A - A' ) p 2

The mean values and CV O/O of 8 and P were arrived at.

3 Results and Discussion 3.1 Constancy of Perimeter

The cotton fibre is truly a remarkab le bio logical entity being formed fro m a sing le epidermal cell on the surface o f a fe rti lized cotto n seed . The development of cell into cotto n fibre takes place in two stages, namely ce ll e longation and ce ll wall thickening. The e longatio n pe ri od lasts for about 20

days after fl owering at which time the fibre compri ses

a thin primary ce ll wall (less than J /lm thick) enclos ing the protoplasm. The cell wall gradu all y thickens by depositi on of regular laye rs of cellu lose constituting the seco ndary wall. Many investigators 5.42.43 have confirmed that the cell wall di ameter (as

well as its perimete r) is determined earl y in the growth cyc le and is chi e fl y a geneti c character. Sreeni vasan et al. 44 monito red the structure and properti es of developing cotton fibres at very c lose inte rvals fro m J 8th day afte r fl owering and showed th at the pe rimeter o f cross-secti on remains almost constant, prov ing that there is very little change in the oute r tubu lar dimension of fibre w ith the increase in age.

Table 2 shows the pe rimeter values and CV O/O of the perimeter values for ten cotto n varieti es with w idely va rying mi cro naire va lues. Data given in the table c learl y confirm the fac t that the perimete r of a given variety remains fa irl y constant irrespecti ve of the degree of maturatio n. For instance, in the case of variety S .6 whil ~ the mi cronaire va lue varies from 2.9 to 4.2, its perimeter re mains fairly co nstant (5 J .05

/lm) and shows neg lig ible vari ati on, the C VO/O be ing

Table 2 - PcrimClcr valLlcs of ca lla n varictics

Variety Perimeter, ~1l11 Mcan CV% pcrimetcr, ~1l11

Surabh i 46.83 43.57 46. 11 44.55 44. 11 45.03 3.1

( 3.3) (3.2) (3.0 ) (2.7) (2 .6)

MCU.5 45 .92 45.84 46.43 45.84 46. 10 46. 11 46.04 0.5

(4.0) (3 .7) (3 .4) (3 .2) (2.9) (2.6)

RCH 46.90 46.80 46.00 46.20 48.1 0 46.60 46 .77 1.6

(4.5) (3.9) (3.4) (3 .2) (2.9) (2.2)

S.6 50.22 5 1.04 5 1.85 5 1.85 50.28 5 1.05 1.5

(4.2) (3.9) (3.5) (3.2) (2.9)

NHH .44 53.42 54.25 52 .54 5 1.03 52.83 50.54 52.44 2.7

(4.3) (4. 11 ) (3 .8) (3 .5 ) (3 .3) (2.7)

LR A.5 166 55.44 53. 11 55 . 15 55 .00 53. 10 53.35 54. 19 2.1

(4.7) (4.4) (4.2) (3 .9) (3.6) (3.2)

Digv ij ay 57. 18 56.2 1 58.23 55 .64 56.5 1 56.75 1.8

(6. 1 ) (5.9) (5 .5) (5.3) (4.7)

Jayadhar 56.85 58.96 58.33 58.37 57.7 1 5804 1.4

(5 .7) (5.5) (5.3) (4.9) (4.4)

RG.8 75 .03 72. 14 75.33 72 .5 1 73.6 1 75 .57 74.03 2.0

(8 . 1 ) (7.8) (7 .4) (7.0) (6.6) (6.4)

Wagad 8 1.65 8 1.47 82.32 79. 15 8 1.1 5 1.7

(6.6) (5.9) (5.6) (4 .8)

Figures in parcnthescs arc micronaire va lues.

338 INDI AN J. FII3RE TEXT. RES. , DECEMBER 2002

as low as 1.5. In the case of MCU.5, the CV% of perimeter is just 0.5. While the micronaire value of Wagad variety varies from 4.8 to 6.6, its perimeter

registers a fairly steady va lue of 8 1.1 5 ~Ul1 with CV% 1.7.

3.2 Relationship betwecn Micronairc Value and Dcgree of Thickening

The constancy of perimeter for a given variety should lead to direct relationship between micronaire va lue and degree of thickening. This is brought out clearly by ,. va lues between the two parameters shown in Table 3 for the twenty-five varieties included in the study.

Micronaire value and degree of thickening are highly corre lated (s ignificant at I % level) in all the varieties. This correlation leads to a linear equati on linking the two parameters. Eq uat ions fo r the different varIeties are presented in Table 3. These variety­speci fic equat ions can be used to evaluate the maturity of unknown sample of a given variety by conducting a simple micronaire test. The process of determination is very simple and quick. Over and above, the maturity va lue est imated through this procedure indica tes the true botanical maturity of the sample.

It is to be realised that the relationships between the micronaire value and the degree of thickening are different for di fferent varIeti es because their perimeters are different. It is, however, logical to presume that when the perimeters are close, the relationships will also be quantitatively sim i la r. Thi s paves the way fo r pooling varieties with in the narrow ranges of perimeter. in the present study, the entire

gamut of perimeter va ri ations (45 ~lm - 80 ~1l1 ) has been divided into four interval s, viz. 45-50 pm, S I-55

~lrn, 56-60 J..lm and 6 1 ~m and above. T he micronai re values and the corresponding val ues of degree o f th ickening of the vari et ies within each interva l arc pooled together and then the relations between the two quan titi es eval uated. Table 4 gives the values of correlation coefficien ts between micronaire and degree or thickening for the four chosen perimeter intervals. The strength of relationship between the two parameters is quite ev ident from very high val ues of correlation coefficients which are significant at 1% level. Therefore, the peri meter-based calibration g;'aphs can also be very well used fo r the purpose of determination of maturity f rom micronairc valuc. However, it is to be noted that these r values are somcwhat lower than the r va lues of variety-speci fic

Table 3 -Relal ionsh ip between Illi cronaire and degree of thicken i ng (Vari et y-speci fi e)

Variety

Surabhi

Vara laxmi

MCU.5

ReH

JKHY. I

G COl.1 6

RS.875

S.6

DCI-I.32

RST.9

NHHA4

F.846

1-1 . 1098

DHY.286

MCH.II

LRA.5166

HS.6

Digvijay

G COl. 17

Jayadhar

G Cot Dl-l y.7

LD.49 1

RG.8

LD.327

Wagad

Coefficient of Equ;Jti on between correlation (r) between Illi cronai re (M ic) and Illicrona ire and degree degree or thi ckening (8)

of thickening

0.997" 0=O.08:n Mic+0.3633

1.000" 8=0.0914 M ic+O.3383

0.996" 0=0.0762 M ic+OA2 17

0.96:l" 0=0.050 I Mic+OA802

0.990" 0=0.052:l Mic+OA854

0.96()" 0=(L0478 M ic+OA970

0.90 1" 0=0.0'i08 M ic+OA 182

0.937" 0=0.0495 Mic+OA850

0.994" 0=0.0575 Mic+OA I 85

0.990" 0=0.0377 Mic+0.522I

0.975" 0=0.0524 Mic+OA878

O.97J' 0=0.0369 M ic+0.53 12

0.989" 0=0.0.358 M ic+0.5 191

0.963" 8=0.0402 M ic+0.5363

0.996" 0=0.0567 Mic+OA693

0.988" 0=00365 Mic+O.5504

0.969" 8=0.(fl06 Mic+0.569

0.949" 8=0.0333 MiNO.5487

0.964" 0=0.0685 Mic+0.3454

0.980" 0=00793 Mic+0.29 14

0.980" 0=0.0 183 M ic+O.6:l52

0.957" 0=0.0494 Mic+0.3792

0.988" O=(L072:l M ic+O. 1860

0.91-:8" 0=(J.0497 Mic+OA065

0.968" 0=0.061-:5 M ic+0.1924

" Sign i ficant at 1 % leve l.

relati onship between the two tra its. T his is t'xpected to be so since the pcrimetcr-based relationship is arrived at by pooling variet ies of various leve ls or maturity. Perimeter-based ca libration graphs (M ic. vs 0) are depicted in Fig. 1.

The presen t study also reveal s the ro le of length of varIet tes in dec iding the relat ionsh ip betwecn micronaire and degrec of thickenillg. Tt is a wcll­known fact that the longer cottons are fi ner whereas the shorter cottons in general are coa rser. Data co llected in the present investigation seem to estab li sh that the longer cottons possess lower cross-sectional perimeter while the shortcr ones have higher cross­sect ional perimeter. The role of length in deciding the strength of re lationship between micronaire valuc and

HUSSAIN el al.: ESTIMATION OF FIBRE MATURITY FROM MICRONAIRE VALUE 339

degree of thickening can be gauged by the fact that there exists an excellent relationship between these two quantities when the cottons lying within a given perimeter range and having mean length within a specified range are grouped. Data presented in Table 5 demonstrate this observation clearly.

0.8

0.75 (a)

0.7

0.65

0 .6 Y ~ 0.0783. + 0.4001

R' = 0.7975 0.55

2.5 l.5 4.5

0.8

0.75 ( b)

0.7

0.65

0.6 • Y ~ 0.0451 x + 0.4996

• • R2 =O.7696 0> 0.55 c 'c ~

2 2.5 3 3.5 4 4.5 5.5 6

u 0.8 £ (c) a 0.75

'" ~ 0.7 2'

Cl 0.65 Y = 0.0638x ~ 0 .3729

R' = 0.8691 0.6

4 4.5 5.5 6 6.5

0.85

0.8 (d)

0.75

0.7

0.65

0.6

0.55 Y = O.0861x + 0.1049

R'.0.8804 0.5

4.5 5.5 6.5 7.5 8.5

Micronaire value

A comparison of r values in Tables 4 and 5 indicates that the relationships obtained from perimeter - length based pooling of varieties are stronger than those obtained from mere perimeter­based pooling. It is also be to noted that all the cottons

lying in the perimeter range 56-60 ,..un are of 2.5 % span length below 25 mm while those lying in the perimeter range 61 )..un and above are of length lesser than 20 mm.

An attempt has been made to arrive at micronaire values to grade varieties into three classes of maturity, viz. low, normal and high.

Making use of Lord's data45, Neelakantan46 has

deduced the following equation linking degree of

thickening (8) and Maturity ratio (Mr) :

8 = 0.575 Mr + 0.079

When Mr = I then 8 = 0.654. This value (8 = 0.654 ) can be treated ideal micronaire value for each vari ety.

Instead of having a fixed value for 8 it is decided to fix range for gradation. Accordingly, the samples having the mean degree of thickening 0.64 and less have been graded as low , those between 0 .65-0.70 as normal and above 0 .70 as high. From the calibration graph connecting the degree of thickening and micronaire value, the corresponding micronaire ran ge values have been arrived at.

Table 6 gives the micronaire values for each variety for classification into three categories of maturity . On the other hand, Table 7 gives the micronaire values corresponding to three categories of maturity for each perimeter range.

3.3 Anomalous Behaviour of Certain Collons Fig. I - Micronairc value liS degree of thickening for different

Among the twenty-five cottons taken for investigation , two cottons, namely G Cot DHy.7 and

perimeter range: (a) 45-50~1ll, (b) 51-55 ~lJn , (c) 56-60 ~m , and (d) 61 ~m and above

Table 4--Rclationship between micronaire and degree of thickening (Perimeter-based)

Perimeter range COllon varieties

~11l1

45 - 50 Surabhi. Varalaxllli . MCU.5 . RCH , JKHY.I

51 - 55 G Col. 16. S.6. DCH.32. RST.9, NHH .44. F.S46. H.I 098. DHY286, MCl--1I1. LRA.5166, HS. 6

56 - 60 Digvijay . G CoLl 7. Jayadhar

:::::6 1 LD.491 . RG.8. LD.327. Wagad

a Significant a t 1 % level.

Coefficient of correlation (r) between Illicronaire and

degree of thickening

0 .893"

0.877"

0.932"

0.938"

Equation betwecn Illicronaire ( Mic) and degree of thickening (8)

8 = 0.0783 Mic + 0.4001

8 = 0.0451 Mic + 0.4996

8 = 0.0638 Mic + 0.3729

8 = 0.0861 Mic + 0.1049

340 INDI AN J . FIBR E TEXT. RES., DECEMB ER 2002

Tablc 5 - Re lali onship belwee n mi cl'Onaire and degrce of thickening (Perimeter - lenglh based)

Pcrimcler 2.5 % Span lenglh Colton varie li cs range range III III Illm

45-50 30 -30 Va ra laxmi , Surabh i. MCU.5

45-50 2S-29 RCH , JKHY .I

5 I-55 27-28 S.6, MCII.II

5 I-55 25-26 NHH .44 , LRA.5 166, G CoL.l 6

5 I-55 23-25 I<ST.9, F.846, HS .6, H. 1098

56-00 22-23 D igvUay , Jayadha~ G COl.17

~ 61 19-2 1 LD.49I. LD. 327, Wagad

"Significant at] 'Yo leve l.

Tablc 6 - Micrllnaire valucs fo r malurit y g radalion ( Varie ty basis )

COllon VariclY

Su rabh i

Varalax mi

MCU.5

RCH

JKHY.I

G COl. 16

S.6

DCH.32

RST.9

NHH .44

F. 846

H.I098

DHY.286

MC H. II

LRA.5 166

HS.6

Digvijay

G Col. 17

Jayadh:.lr

LD.49 1

RG.8

LD.327

W:.lgad

Miel'Onairc va luc

Low Normal Hi gh

3. I and bc low 3.2~ 3.X 3.9 anc! above

3. I and below 3 . 2~ 3.8 3.9 anc! above

3. I anc! bc low 3.2 ~ 3.X 3.9 anc! above

3. I and be low 3.2 ~ 3.8 3.9 and above

3. I :.lnd below 3.2 - 3.R 3.9 and abovc

3.2 anc! below 3.3 ~ 4.4 4.5 and above

3.2 and below 3.3 - 4.4 4.5 and above

3.2 and be low 3.3 - 4.4 4.5 and above

3.2 and below 3.3 ~ 4.4 4.5 and above

3.2 :.l nd below 3.3 - 4.4 4.5 and above

3.2 and below 3.3 ~ 4.4 4.5 and above

3.2 and below :u ~ 4.4 4.5 and above

3.2 and bclow 3.3 ~ 4.4 4.5 and above

3.2 and below :u - 4.4 4 .5 and above

3.2 and be low 3.3 - 4.4 4 .5 and above

3.2 and below :U - 4.4 4 .5 and above

4.2 and below 4 .3 ~ 5. 1 5.2 and above

4.2 and bclow 4.3 - 5.1 5.2 and above

4.2 and below 4 .3 ~ 5. 1 5.2 and above

6.2 and below 6.3 ~ 6.9 7.D and above

0.2 and below 6.3 ~ 6.9 7.0 anc! above

6.2 and below 6.3 ~ 0 .9 7.D and above

6.2 and below 6 .3 ~ 6.9 7.0 and above

RS .875 , behave in a totally different manner. Though the variety-specific relationship between Mic and degree of thickening for these varieties are very strong (indicated by hi gh r values significant at 1% level) , these varieti es, when considered along with those havin g the same perimeter as well as the same mean length, pose some problems. For instance, the

Coeffic ienl of eorre lali on (1') between mieronai re and

dcgree of lhicke ning

Equalion lX' lween micl'Onai rc (M ic:) degrec of

lhi ekeni ng (8)

0.910"

0.937"

0.95 3"

0.9W'

0 .907"

0.932"

0.952"

8 = 0.0956 Mic. + 0.3407

0 = 0'()596 Mie. + 0.4706

8 = 0.05 16 M ie . + 0.4817

8 = 0.0458 Mi c. + D.5 137

8 = D.0374 Mie. + 0 .5253

8 = 0 .0638 Mic . + 0 .3729

8 = 0.0924 Mie. + O.D70D

Table 7- M iel'Onaire va lues :01' maluri lY gradal ion (Perimcler basis)

Peri meler MieJ'Onaire va lue range Low Normal Hi gh ~tlll

45 - SO 3. 1 and bc low 3.2 - 3.8 3.9 and above

51 ~ 55 3.2 and bc low 3.3 - 4.4 4 .5 and abovc

56 ~ 60 4.2 and be low 4.3 - 5. 1 5.2 and above

6 1 and abovc 6.2 and below 6.3 ~ 6.9 7.0 and above

micronaire va lues of RS .875 are too high for the measured degree of thickening while the reverse is the case with the vari ety G Cot DHy .7. It is well known that the micronaire value, which measures the res istance to air fl ow through a cotton plug of fi xed mass and dimension, depends upon the specifi c surface area of the fibres constituting the plug. The specific surface area is a fun ction of intri ns ic fineness (perimeter) and maturity (degree of thi ckening). However, it appears that apart from perimeter and maturity , some other traits of cotton fibres may playa role in resisting the air flow (i.e. micronaire value) . The present study has revea led that the length does influence the micronaire value. It is also possib le that factors like the number of convolutions may probably affect the flow of air through plug. Further detailed in vesti gation is required to ascertain these factors.

Variety-based and perimeter-based equations as well as calibration graphs can be used to determine the maturity of unknown sample of a given variety perimeter simply by conducting a micronaire test on the sampl e. The procedure is quick and the maturity thus estimated refl ects the true botanical maturity. The findings In this study have far reaching implicati ons 111 breeding research. Breeding

HUSSA IN e[ al.: ESTIMATION OF FIBR E MATU RITY FROM MIC RO NAIRE VALUE 34 1

programmes sho uld aim at "no rmal micronaire va lue" for each genotype depending on its intrinsic fin eness (perimeter). Micronaire value below thi s range could be indicati ve of nepping potential while those above would tend to reduce yarn CS P. Micronaire va lue plays a c rucial role in estimating the price of each vari ety . The lots hav ing micronaire value ass igned normal status through this in ves tigati on should fe tch higher price than the lots of the same va ri e ty w ith rnicronaire values ly ing in low or hi gh maturity groups.

4 Conclusions Constancy of cross-sec ti onal pe rimete r for a given

vari ety leads to a very stro ng re lati onship between the rnicronaire va lue and the degree o f thickening. Varieties hav ing perimete r w ithin a specified range can be pooled to establi sh the relationship between the micronaire value and the degree of thi ckening. It is a lso poss ible to ass ig n rni cronaire values fo r gradation of vari eti es into three categories, name ly low, normal and high.

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