Indian Journal of Fibre & Textile Research Vol. 3 1 , June 2006, pp. 267-273

Varietal response of j ute fibres with varying meshiness to alkali treatment: Part I-Effect of alkali concentration and treatment temperature on

crimp development in jute fibres

R K Varshney"

Department of Textile Engineering, G iani Zai l S ingh College of Engineering & Technology, B athinda 1 5 1 00 1 , India

R K S ingh

Department of Textile Technology, The Technological Insti tute of Text i le & Sciences, B hiwani 1 27 02 1 , India

A K Sengupta

Ahmedabad Textile Industry 's Research Association, Ahmedabad 380 0 15, India

and

V K Kothari

Department of Textile Technology, Indian Institute of Technology, Hauz Khas, New Delhi 1 1 0 016 , India

Revised received 4 April 2005; accepted II April 2005

Alkali treatment of four varieties of jute fibres, namely W-4, TD-3, Desi and Mesta, with different meshiness levels has been carried out at three di fferent conditions of concentration and temperature, namely 9% conc.l2°C temp.(9/2), 1 8% conc.l30°C temp. ( 1 8/30) and 1 8% conc.l l OoC temp. ( 1 81 10) . Crimping behaviour in terms of decrimping extension, decrimping stress, decrimping energy and crimp stabi l i ty has been studied. I t is observed that under the condition 1 81 1 0, crimp development is max imulll because of its i nherent higher shrinkage potential. Decrimping energy is also found to be highest but the parameter crimp energy decay, having considerable practical i mportance and the indicator of crimp i nstabi lity, comes out to be higher. However, for all practical purposes, considering other technical aspects, 1 81 1 0 condition gives satisfactory results i n the crimp development.

Keywords: Decrimping, Hookean region, Jute, Load cycl ing, Meshiness index IPC Code: I n\. Cl .8 DOlF I 1 /00, D06M I I/OO

1 Introduction

Prickli ness and stiffness are the major characteristics of fabrics made from raw jute and i ts blends. As reported by several researchers 1 -8, alkal is especially the NaOH treatment gives more encouraging results to tackle these difficulties and has now been widely accepted. Macmillan and Sen7

reported the swelling of jute fibres wi th alkali treatment, result ing in the crimp generation wi th a number of changes both in the gross and the fine structure of the jute fibres . Lewin et al.2 concluded that no crimp is formed at NaOH concentration lower than 6% and the optimum temperature for the formation of crimps i s around 2°C. They observed maximum swel l ing at mercerization concentrat ion.

'To wholll a l l t h c c'()ITcspondcncc should b e addrcss.:d. E-mai l : rajecv_var:i I 1 l 1cy2002 @ v .. · \ • • < l . co . in

Various v iews regarding crimp generation, l ike partial non-uniform dissolution of chemical constituents 1 .9- 1 0 swell i ng of cel l wall w ith s imultaneous longitudinal contraction, have been put forward. Along with this the treatment conditions of NaOH solution has been suggested for crimp generation.2A,8 Crimp generation by alkal i treatment has been observed as a hope, which can make some value addition appropriate to the body wear requirements.

In the present work, the three conditions of NaOH bath of technical importance, i ,e. 9/2, I S/30 and I S/ l 0, have been adopted to study the behavioural response of jute fibres towards alkal ization, incorporating different varieties of jute at different meshiness levels so as to find out the most favourable condit ions of alkali treatment for imparting the characteri stics which can make it suitable for being spun i n l ( ) " y arn as wel i for blending with the natural and synthet i c fi bres .

268 INDIAN J. FIBRE TEXT. RES. , JUNE 2006

2 Materials and Methods

2.1 Sample Preparation

Four varieties of jute fibres viz. Desi , W -4, TD-3 and Mesta, with different meshiness indices (Table 1 ) were given alkali treatment at various concentrations and temperatures. The combinations were 1 8% NaOH at 30°C ( 1 8/30), 1 8% NaOH at 1 0°C ( 1 8/ 1 0) and 9% NaOH at 2°C (9/2).

2.1. 1 Combing

Jute reeds were combed with the help of two types of combs having the following specifi cations:

Coarse Comb

Length of teeth : 2 1 .26 mm Working w idth of teeth at tip : 1 .23 mm Working w idth of teeth at the bed : 1 .60 mm Fine Comb

Length of teeth : 1 3 .04 mm Working w idth of teeth a t the tip : 0.32 mm Working width of teeth at the bed : 0.72 mm

Combing was done by repeated cycles of combing ( 1 00 times i n both directions) ; in in i tial cycles, meshiness created h indrance in combing but after sometime smooth combing occurred. Hence, for each type of jute, three samples, namely uncombed (U), coarse

. combed (C) and fine combed (F), were

obtained.

2.1.2 Cutting of Reeds and Weighing

Uncombed, coarse combed and fine combed reeds were cut i nto 4 cm length with the help of a sharp

Table 1 - Specifications of raw material Jute Tenacity Breaking Degree of Mesh

cN/tex elongation combing density % loop

W-4 23.54 2 . l 6

TD-3 36.8 1 l .93

Desi 26. 1 9 2.2 1

Mesta 26.65 1 .50

Uncombed Coarse Fine S ingle fibre

Uncombed Coarse Fine Single fibre

Uncombed Coarse Fine S ingle fibre

Uncombed Coarse Fine S ingle fibre

ends/g

377 1 3 20067 3273

27926 1 5382 3233

23429 1 3038 1 9 3 1

23 1 76 1 5089 1 578

F ibre l inear

density tex

6.42 3.0 1 2.00 l .87

4 l .04 6.67 3.68 3.28

5.85 3.63 2.58 2.46

22.07 7.92 3.82 3.72

blade. Care was taken so that no s l ippage of fibres would be there, otherwise exact length would not be achieved. Weighing was carried out on electronic balance.

2.1.3 Treatment with Alkali

A series of NaOH solution of various concentrations was prepared. The jute samples made of 2g bundles were i mmersed i n unstretched state i n the alkali solutions a t a l iquor ratio o f 30: 1 under various temperature for a constant period of 45 min. After the alkali treatment, the treated jute bundles were washed thoroughly i n running water, soured with d i lute acetic acid ( 1 .5%) and further washed til l become neutral. The fibre bundles were then air dried and separated into s ingle fibre strands, hereafter called fibres.

2.1.4 Material Conditioning

All the measurements were taken i n a controlled air conditioned room at 70% R H and 25°C. This i s especially important as jute i s hygroscopic fibre and all i ts physical properties are influenced by the variation i n humidity.

2.2 Testing

2.2.1 Shrinkage

Extent of shrinkage was obtained as percentage length change due to alkali treatment of the known length of raw jute fibre.

2.2.2 Loss in Weight

Weight loss was obtained as percentage change i n weight o f fibres due t o alkali treatment o f the known weight of raw jute fibres.

2.2.3 Determination of Fibre Fineness

Fibre fineness was measured i n terms of l inear density of fibre. The l inear densities of the raw and alkali -treated jute fibres were determined by the gravi metric method of cutting, counting and weighing of 200 fibres.

I n case of alkali -treated fibres, crimps must be totally removed before cutting. For this purpose, individual fibres can be weighed by using paper clips wi th rider having a heavy enough load (0.5 g/den) . As jute i s a low extensible fibre, h igh-tension load should not change the value of denier but low pre-tension load wil l affect the denier.

2.2.4 Determination of Crimp Parameters

I t was found that w ith 9%(w/v) alkali treatment, the crimps developed were not observable w ith projected

VARSHNEY et al. : VARIETAL RESPONSE OF JUTE WITH VARYING MESHINESS TO ALKALI TREATMENT: PART I 269

image technique, so all that were measured by I nstron Tensile Tester using 20 mm gauge length, 5 mm/min crosshead speed, 1 0 gf ful l scale load and 200 mm/min chart speed. Fig . ! shows a typical load­elongation curve ONB (where elongation transformed into per cent) of a j ute filament treated with caustic soda solution. The total decrimping extension was determined by exttapolation. The l inear part NB of the curve ONB was extrapolated to cut the axis OX at Q. Then QM and MT were drawn parallel to OY and OX respectively . OT (or Pd) is the measure of decrimping load and OQ is regarded as decrmping extension. The parameters Hookean slope (9), load at a selected elongation, decrimping energy Ee, decrimping stress and crimp stability can also be obtained from Fig. 1 .

Energy of crimp or decrimping energy can be determined for each sample by traditional method of measuring the area under the load-elongation curve. Decrimping stress can be observed as decrimping I oad/ deni er.

Crimp stability was calculated in terms of per cent decay of decrimping energy in seven cycles of cyclic loading performed on the I nstron. Load cycle with load between 0 and average decrimping load was chosen and the decrimping energy of the ! 51 and the 71h loading cycles was used; the per cent change in the decrimping energy is regarded as a measure of crimp stabil ity.

3 Results and Discussion Table 2 shows the values of weight loss, length

contraction and crimp development on alkali treatment. When the jute fibres are subjected to alkali treatment, some structural transformation takes place as a result of irregular dissolution of alkal i soluble

T .... 0> E Q) o (; u.

y

UNCRlMPING REGION

T t------""7f.

o o

HOOKE AN REGION

1- -i B

HOOKEAN SLOPE

Extension (%) ---» x

Fig . l -A typical load-elongation curve of an alkali-treated single jute fibre

components especially the hemicellulose which is considered as the cementing material residing i n the i nterfibrillar region of jute fibre cells, leading to the release of the stresses which can cause the segmental shrinkage in the cellulose chains through disorientation and folding. Shrunk portion of the chains tries to take the shortest path and shifts to the center to attain the minimum energy level. Due to irregular distribution of lignin i n the gross structure of fibre and being resistant to swelling, the shrinkage wil l be irregular and multidirectional. This will cause buckling and bending of fibre at random places and in different orientations. Hence, the multidirectional and irregular differential cri mps are expected to generate. The extent of the crimps and their behaviour depend on the conditions of alkali treatment to different vanetles of jute under different levels of indi vidualization of fibres.

A consideration of the geometry of a fibre crimp is necessary to propound a rational explanation for the behaviour of a fibre during decrimping and thereafter. I n this connection, Evan ' s proposition I I would be appropriate to consider. Fig. 2 is the representation of a single crimp in the fibre which is under a small tension. The material at point B is in tension, but the material at poin t A is probably in compression initial ly. At C-C the material is in fairly uniform tension. The force at any extension (%) in the decrimping zone may be stated to be governed by this non-uniform distribution of stresses across the diameter of the fibre and along its length. But as the tension increases and the fibre comes in the straightened condition, the entire cross-section comes into tension and as a result, the tensile stress rises steeply signifying the linear Hookean region. Hence, the extensional profile of the crimped fibre finally takes the shape of a logarithmic curve as is evident from Fig. 1 .

I n the decrimping region, where the curve is sagging towards extension axis, the outside radius of a crimp may be considered to be lagging behind the inside radius along a force-extension curve by an extension dependent on the ratio of the radius of the crimp to fibre diameter while in the Hookean region, an increasing portion of the fibre flows. Hence, the force does not i ncrease as rapidly for the crimped fibre as for the uncrimped or comparatively less crimped fibre. This fact is sufficiently capable of explaining the shapes of the curves obtained for different alkali-treated jute samples ( 1 8/30, 1 8/ 1 0 and 9/2) as shown in Figs 3 and 4.

270 INDIAN 1. FIBRE TEXT. RES., JUNE 2006

Table 2-Effect of meshiness i ndex and treatment conditions on crimping behaviour of jute fibres

Sample ref. no.

S I S2 S3 S4 S5 S6 S7 S8 S9

Jute

W-4(U) W-4(U) W-4(U) W-4(C) W-4(C) W-4(C) W-4(F) W-4(F) W-4(F)

NaOH conc.

%

1 8 18 09 1 8 1 8 09 1 8 18 09

Temp. °C

30 10 02 30 10 02 30 10 02

Weight loss %

9. 1 5 7.10 5 .57 9.26 7.30 5.67 9.67 7.52 5.8 1

S I O TD-3(U) 1 8 30 6.79 Sl 1 TD-3(U) 18 10 5.51 S 12 TD-3(U) 09 02 4.68 S 13 TD-3(C) 1 8 30 6.85 S14 TD-3(C) 18 10 5.59 S 15 TD-3(C) 09 02 4.88 S 1 6 TD-3(F) 18 30 6.92 S17 TD-3(F) 18 10 5.89 S I 8 TD-3(F) 09 02 4.99

S 19 Desi(U) 1 8 30 8.86 S20 Desi(U) 18 10 6.06 S2 1 Desi(U) 09 02 5.0 I S22 Desi(C) 1 8 30 8.93 S23 Desi(C) 18 10 6.13 S24 Desi(C) 09 02 5.02 S25 Desi(F) 1 8 30 9.3 1 S26 Desi(F) 18 10 6.54 S27 Desi(F) 09 02 5 .45

S28 Mesta(U) 1 8 30 8.62 S29 Mesta(U) 18 10 7.52 S30 Mesta(U) 09 02 6.74 S3 1 Mesta(C) 18 30 8.88 S32 Mesta(C) 18 10 7.57 S33 Mesta(C) 09 02 6.86 S34 Mesta(F) 18 30 9.2 1 S35 Mesta(F) 18 10 7.71 S36 Mesta(F) 09 02 6.88

U- Uncombed, C-Coarse combed, and F-fine combed. Values in bold i ndicate most favourable conditions.

A Compression /.? � .

Fig .2- Stress i n a crimped jute fibre under smal l tension

At the Hookean region, the internal structure, apart from the physical crimp geometry, takes the center stage 111 influencing the mechanical (tensi le) behaviour. The chain of events described above

Length Decrimping Decrimping contraction extension stress

% % mN/tex

6.29 2.050 3.73 6.62 2. 1 16 3.56 5.02 1 .8 1 5 4.23 6.33 2.052 3 .63 6.80 2.275 3.51 5 . 1 2 1 .855 4. 1 6 6.38 2.056 3 .38 6.90 2.371 3.28 5 . 1 4 1 .9 1 2 4. 1 8

5.88 6.13 4.7 1 5.93 6.20 4.87 6. 1 2 6.22 4.97

6.78 7.27 5.0 1 6.89 7.75 5 .20 7.00 7.79 5.32

5 .88 6.21 4.35 5 .91 6.30 4.35 6. 1 3 6.50 4.44

1 .987 2.100 1 .860 2.030 2.180 1 .9 1 3 2.030 2.227 2.030

2.223 2.370 1 .6 1 9 2.225 2.440 1 .620 2.265 2.530 1 .700

1 .809 1 .882 1 .339 1 .960 1 .969 1 .409 2. 148 1.981 1 .577

2.09 2.01 2.09 2.09 1 .99 2.05 2.09 1.97 2.05

2.32 2.12 2.39 2. 1 5 2.l l 2.32 2. 1 2 2.07 2. 1 7

1 .82 1.51 1 .98 1 .8 1 1.46 1 .98 1 .74 1.46 1 .98

Decrimping energy �IN/tex

50.20 57.70 49.35 5 1 .27 59.37 49.86 58.21 76.05 52.92

1 9.7 1 26.72 20.89 1 9.96 27.52 22.95 2 1 . 1 3 29.54 24.29

3 1 .89 36.30 30.98 33.37 37.05 32.55 38.55 39.71 38.04

1 2.84 21.71 1 6.7 1 1 5 . 1 0 22.85 1 7 .38 1 7.64 26.36 1 9.92

Energy decay

%

2 1 .60 22.15 20.42 22.30 25.62 2 1 .34 3 1 .20 32.66 27.85

30.03 32.50 2 1 .59 30.60 35.03 24.64 32.23 36.45 27.6 1

1 6.37 18.03 1 5 .80 1 9.65 20.44 1 5 .90 20. 1 5 21.71 1 7 .4 1

1 8.84 21.54 1 3 .88 22.28 27.64 14.92 25.50 30.79 20.34

represents the conditions obtained at one cross-section of the fibre; other sections along the length of the fibre would be expected to experience the same effects but to a varying degree and not necessarily at the same time as those found at one particular section. This behaviour of the crimped fibre can be attributed to the iITegular structure of fibre resulted from the i rregular removal of alkal i soluble materials, l ike hemicelluloses, and i rregular arrangement of the insoluble component, l ike l ignin .

3.1 Shape of the Curve

Load-elongation curves characterize the crimps developed i'ri't

Jie 'fi8res as a cosequence of various

VARSHNEY el at. : VARIETAL RESPONSE OF JUTE WITH VARYING MESHINESS TO ALKALI TREATMENT: PART I 27 1

Fine combed

2 3 4 5 Extension (%)

7

Fig. 3- Load-elongation curves of di fferent varieties of jute at 1 8% NaOHI IO"C i n the decrimping zone under different combing conditions

changes taken place at micro as well as macro structure levels. The analysis of the decrimping curves reveals an i mportant fact that jute fibres of any origin behave in the same manner on alkali treatment at all the conditions (logarithmic curves) . This behaviour can be represented by the equation e = p log w + q between elongation e and the load w, where p and q are the constants (Lewin et al.\ Represen tative curves for all varieties can be drawn using the respective constants to explain the j ute fibre behaviour at different alkal i treatment conditions.

A typical representative curve is shown in Fig. I . The whole curve can be divided in to two regions: Hookean region and decrimping region. The reasonable explanation of the load-elongation curve can be given by considering the mechanism of elongation of the fibre.

Extension (%) )

Fig.4- General load-extension curves of alkali-treated jute fibres under different processing conditions (9/2- 9% NaOH, 2°C; 1 81 1 0- 1 8% NaOH, I OoC; and 1 8/30- 1 8% NaOH, 30°C)

It can be easily visual i sed that the extensional behaviour during the i ni tial stages of crimp removal i s controlled by fibre bending and extension and finally as the crimp removal approaches completion, the behaviour is controlled by the extensional modulus of the fibre. In decrimping zone, the curve for 1 8/ 10 has the shape more sagging than the curves for 9/2 and even 1 8/30 (Fig.4). In the Hookean region, where the curve gets almost s traightened with some angle to X-axi s i .e. extension axis , on moving from 1 8/ 10 to 9/2 through 1 8/30, the angle between the tangent to the curve and the extension axis (9) i .e . the ult imate modulus increases, indicating the effect of alkali treatment on rigidity of fibres. This typical behaviour (shape of curves) shows that the stress development i s slower i n 1 8/ 1 0 as compared to that in 1 8/30 and 9/2. More the shrinkage of fibres through chain folding more easier will be the stretching which, in turn, does not allow the forces to develop at a faster rate. This means that most of the force applied is absorbed by straightening of chains and hence, the stress development gets slower down i n 1 8/ 1 0. Figure 3 shows the comparative decrimping behaviour of all the varieties at different combed states under the most appealing condi tions of alkali i .e. 1 8/ 10, at which the maximum crimps are induced in the fibre. In 1 8/ tO, the t ie molecules wil l release the i n ternal stress mostly by disorientation, while i n 1 8/30, they have another option for doing so through segmental motion under higher thermal v ibration. Thus, the chain di sorientation is expected to be more in 1 8/ t O than i n 1 8/30 and hence more length contraction in 1 81 10.

3.2 Decrimping Extension

Decrimping extension means the extension In the fibres when the crimp approaches to zero under

272 I NDIAN J. FIBRE TEXT. RES., JUNE 2006

tensile loading. At higher concentration ( 1 8%), more shrinkage leads to more crimp development as compared to 9/2. Extension at 1 81 1 0 is even higher than that at 1 8/30 (Table 2).

Meshiness has a considerable impact on this parameter. I n meshed structure, the crimp development is rc <;tricted and the degree of combing is an important factor that faci l itates crimp generation. Decrimping extension for different varieties is given in the Table 2, which shows that W-4 and Desi have more crimp. While coarser varieties like TD-3 and Mesta experience l imited crimp formation .

3.3 Decrimping Stress

Decrimping stress (decrimping load/l inear density) results can be interpreted at physical or geometrical level and structural level.

The relation of decrimping stress with the crimp geometry of fibre is worth noting. It is clear from the interpretation of the views of various researchers including Samajpati et al. 8 and Chakravarty ' that the crimp developed in jute on alkali treatment is 3-dimensional crimp with varying crimp amplitude and crimp frequency. At 1 8/30 and 1 8/ 1 0, due to the occurrence of more swelling, differential shrinkage occurs extensively along the cross-section, resulting in development of crimps to a very large extent. The crimps formed are of larger helix radius. This is a simple applied mechanics principle that for the same material with the increase in helix or circular radius, the straightening becomes more easier (Fig. 5). The crimps developed at 9/2 are a combination of whole helices, semi circles and sometimes even a straight portion with overall very small helix radius. So, the response of this situation (9/2) towards the stress generation during straightening process of crimp is much significant and shows escalated stress generation . On the contrary, at 1 8/30 and 1 81 10, the crimp diameter or helix radius develops to a greater degree comparatively easy to be removed giving straight configuration to the fibre and experiences reduced decrimping stress.

F2 > F,

Fl ��>f 1 J-kl ix radius morc & crimps easy 10 remove

F2 �� F2 Helix radius less & crimps d i llicul l 10 remove

Fig 5- Decrimping force appl ied on fibres of d ifferent helix radius

Comparatively more strong conditions, by removing more hemicelluloses, leaves the fibrils in the less dense and less rigid condition and the stress transfer will be reduced. The presence of a little higher hemicelluloses at 1 81 1 0 in comparison to that at 1 8/30 does not help in generating higher decrimping stress. Higher length contraction at 1 81 10 will develop somewhat higher crimp and the stress transfer effect brought through the binding effect of hemicelluloses will be overcome by higher fibrillar disorientation. All varieties of jute under i nvestigation show a general trend of decreasing the decrimping stress with the i ncrease in degree of combing, because of the development of crimps under gradual reduction of restrictive forces. W -4 grade j ute has got the maximum decrimping stress although it is very flexible and soft. But the profile of crimps (lower helix radius) favours generation of higher decrimping stress. Desi also acquires second maximum decrimping stress. Being coarser fibres, Mesta and TD-3 develop very coarse crimps and more helix radius, which can easily be straightened out. Although due to higher denier, the decrimping force has been observed to be high but the i ntensity of force or specific decrimping stress comes out less.

3.4 Decrimping Energy The amount of energy to be absorbed by the fibre

during decrimping is dependent on the degree of extension and the decrimping force. In all the conditions of the alkali solution, reduction in meshiness will give rise to more energy absorption attributed to increase i n decrimping extension because in free state, the fibre is free to develop crimps. In 9/2, where decrimping extension is very small , the large decrimping force would compensate to bring decrimping energy to sufficiently high, intermediate between 1 8/30 and 1 81 1 O.

3.5 Crimp Stability

Crimp stability can be predicted in terms of energy decay in seven cycles of load cycling. If the process of cyclic loading is considered, it is found that the fibre is loaded upto decrimping load then returns to relaxation (zero load) . Keeping the ultimate load (decrimping load) constant in each cycle, the loss i n crimp will mean some degree of permanent set. During decrimping, the inside surface of the crimp undergoes extension and it will go on yielding until outer layer starts sharing load. So, the crimp stability largely depends on the state of cementing material and the degree of structural change occurred during chemical treatment.

VARSHNEY et al.: VARIETAL RESPONSE OF JUTE WITH VARYING MESHINESS TO ALKALI TREATMENT: PART I 273

At 9/2, remaining higher amount of rigid cementing material tries to bring the crimp back soon after the load disappears. At higher concentration i .e . 1 8%, second factor i .e. the change in structure, i s more significant. At low temperature of 1 0°C, relatively more residual cementing material compared to that at 30°C may help in providing higher ultimate stress (tenacity). The effect on crimp stability is relatively less because the bond reformation after treatment and drying occurs in the relatively more crimped, less ordered, less oriented configuration. The deliberation regarding behavioural difference towards crimp stability can further be extended in terms of the influence of thermal vibrations on bond breakage and reformation. Under lower temperature at 1 8/ 1 0, lesser bond breakage and reformation take place in comparison to 1 8/30.

As far as level of i ndividualization is concerned, the fine combed fibres comparatively can loose their structural identity more easily under tensile repetitive loading which is quite significant for consideration. TD-3 shows the highest energy loss, W-4 shows the second maximum energy loss, while Desi and Mesta show the minimum energy loss on repeated loading.

4 Conclusions 4.1 Generation of crimps in j ute fibres is due to the

partial dissolution of cementing material, causing some amount of length contraction. Under different conditions of alkali treatment, the crimps of different extents, shapes and sizes are generated. They are combination of waves, helices, semi-circles with multidirectional orientation. The removal of hemicelluloses leaves the shrinkage stresses inside the fibre which are irregular i n amount and direction. This differential shrinkage across the cross-section and along the length of fibres is responsible for producing this differential crimps.

4.2 At 9/2, almost non-observable crimps (by projected image techniques) with less waviness and more straightened portion are developed, while at

1 8/30 and 1 8/ 10, the crimp development is remarkable with quite discernible crimp helices and waves .

4.3 Decrimping extension and decrimping energy are maximum at 1 8/ 1 0 and minimum at 9/2 i n general; however, a t 1 8/30 these are intermediate between the two.

4.4 Trend of decrimping stress i s j ust the reverse of decrimping extension. At 1 8%, the crimps generate with more pliability which can easi ly be stretched. Crimps under 9/2 are somewhat more stiff.

4.5 The 1 8/ 10 condition shows minimum crimp stability towards tensile loading among the three conditions ; while it is maximum for 912 .

4.6 Meshiness i ndex considerably i nfluences the crimp development and the crimp behaviour. Individualization (removal of meshiness) through combing is advisable before actually giving alkali treatment. This i s especially important for unrestricted developments of crimps.

4.7 Although the crimp stability of W-4 is slightly less but i ts fineness, flexibility, crimp development and decrimping energy are sufficiently good i n comparison to TD-3 and Mesta, establishing its superiority.

References 1 Chakravarty A C, Texi Res J, 32 ( 1962) 525. 2 Lewin M, Shi loh M & Banababi, J, Text Res J, 29 ( 1959)

373. 3 Macmi l lan W G, Sengupta A B & Majumdar S K, J Text

Insl, 45 ( 1 954) T-703. 4 Roy M M, J Text Inst, 44 ( 1 953) T-44. 5 Sarkar P B, Mazumdar A K & Pal K B, J Text Inst, 29 ( 1 948)

T-44. 6 Mukherjee R R & Woods H J, J Text IIlSt, ( 1 950) T-4222. 7 Macmi llan W G & Sen M K, J Text IIlSt, 30 ( 1 939) T-73. 8 Samajpati S, Mazumdar A & Dasgupta P C, Texi Res J, 49

( 1 979) 8 . 9 Mazumdar A, Samajpati S, Ganguly P K, Sardar D &

Dasgupta P C, Text Res 1. 50 ( 1 980) 575. 10 Roy M M & Sen M K, J Text Illst, 43 ( 1952) T-396. I I Thomas F Evans, Text Res J, 24 ( 1 954) 637.