IndianJournalofFibre& TextileResearch Vol.22, March1997, pp. 53-60

Reactive behaviour of ramie fabrics pretreated with different swelling agents and their rub fastness property

n Oas,A K Samanta' & P C Dasgupta TextileChemistrySection,InstituteofJuteTechnology35, BallygungeCircularRoad,Calcutta700 019, India Received14 June 1995; first revisedreceived12 April 1996; secondrevisedreceivedandaccepted31 October1996 Scoured and bleached ramie fabrics were pretreated separately with four swe1lidg agents, viz. NaOH, EDTA, urea and phosphoric acid, and the consequent changes in tensile properties, extent of decrystallization, absorbency, uptake and fastness to washing light and rubbing for a monoch- lorotriazine (Cl. Reactive Orange 13) were evaluated. Pretreatment with 20% urea or 20% NaOH under slack condition resulted in a more desirable balance in the above-mentioned pro- perties including the improved dye uptake. Fastness to rubbing was poor and it was more pro- nounced at higher number of rub cycles. Both ring dyeing and higher coefficient of friction of ramie have been found to be responsible for this. To improve the rub fastness of reactive-dyed ramie fa- bric, post-treatment was carried out separately with catasoftener, silicone and polyethylene emulsion. Post-treatment with the last two finishing agents improved the rub fastness significantly on \both NaOH (slack) and urea (slack) pretreated and reactive-dyed ramie fabrics. Keywords: Dyeing, Polymeric finish, Ramie, Ring-dyeing, Rub fastness, Swellingpretreatment

1 Introduction are now banned in European countries for Recently, ramie has regained importance be- their carcinogenic nature or possible harmfulness cause of its increased share in the apparel and up- to human body. Therefore, reactive dyeing of ra- holstery textiles 1 in Asia and its sub-continents. mie becomes much important in today's context. Degummed ramie, in comparison with the rele- The present work was, therefore, undertaken to vant properties of cotton, is coarser, more heat- investigate the dyeing behaviour of ramie fabrics resistant, rapidly dryable, more durable, more lus- and their fastness properties when dyed with trous, more rigid, less extensible with highly crys- reactive dye with or without suitable pretreat- talline and highly oriented fine structure and has ments using different swelling agents and selective higher coefficient of friction, less moisture regain, post-treatments subsequent to dyeing of pretreat- higher tensile strength and improved wet ed ramie fabric. strength!", Highly crystalline and highly oriented fine structure of ramie makes the required dye 2 Materials and Methods diffusion difficult in comparison to that for cot- ton. In most of the cases, ring dyeing of ramie 2.1 Materials gives lower rub fastness. A few reports are avail- 2.1.1 Fabrics able on the rub fastness study for pure cellulosics" Scoured and bleached plain-woven ramie fabric but little information is available on such study having the following specifications was used: for ramie and that for reactive-dyed ramie pre- weight, 130 g/m-; warp, 52.9 tex; weft, 25.6 tex; treated with different swelling agents. Merceriza- ends/dm,190; and picks/dm, 230. For compara- tion of ramie as pretreatment before dyeing has tive purposes, plain weave cotton fabric having been investigated earlier by many workers-". Re- the following specifications was also used: weight, cently, Cheek and Rousellf-? have also made com- 109 g/m''; ends/dm, 315; picks/dm, 315; warp, 47 parative studies on the dyeing of mercerized ra- tex; and weft, 47 tex. mie, cotton and flax with low and high molecular weight direct dyes. But most of the azo direct 2.1.2 Dyes andChemicals A monochlorotriazine reactive dye (0 Reactive "Towhom allcorrespondenceshouldbeaddressed. Orange-13) obtained from a local dye supplier 54 INDIAN J. FIBRE TEXT. RES., MARCH 1997 was used after necessary purification. Sodium 2.2.3 Post-treatment with SoftenerlPolymeric Emulsions chloride, sodium hydroxide, sodium carbonate, The dyed fabrics were padded in a two-bowl urea, phosphoric acid, EDTA (disodium salt of laboratory padder containing 5% (solid basis) po- ethylenediamine tetraacetic acid), ammonium hy- lyethylene emulsion, adjusting the wet pick up at droxide, pyridine and acetic acid, all of AR grade, 80%. The fabrics were then touch dried at 80°C were used. for 10 min and further subjected to a higher tem- perature (110°C) treatment for another 5 min in a 2.2 Methods laboratory hot air-drying and curing chamber. 2.2.1 Pretreatment with Different Swelling Agents For silicone emulsion treatment, the fabrics The ramie fabric was pretreated by dipping in were similarly padded with 40 gIl silicone emul- 20% (w/w) aqueous solution of urea or in 15% sion containing 4 gIl zinc acetate, adjusting the (w/w) aqueous solution of EDTA, keeping the wet pick up at 80%. The fabrics were then touch material-to-liquor ratio (MLR) at 1:10, at room dried at 80°C for 10 min and cured in a laborato- temperature (30 ± 2°C) for 30 min after which it ry drying and curing chamber at 150°C for 4 min. was thoroughly washed with cold water and dried Catasoftener was applied by exhaustion process in air. on the fabrics by dipping the fabric pieces in a so- The phosphoric acid pretreatment of the ramie lution containing 2.5% (solid basis) catasoftener at fabric was similarly done with 81% (wIw) aque- pH 4 (adjusted by acetic acid), keeping the mate- ous phosphoric acid using same MLR and tem- rial-to-liquor ratio at 1:20. perature for 30 min. The fabric was then washed thoroughly with water, neutralized with dilute am- 2.2.4 Physical and Chemical Testings monium hydroxide solution, rinsed, washed and Absorbency of treated and untreated ramie fa- dried in air. brics was determined by measuring the iodine Caustic pretreatment of the experimental cotton sorption value (ISV) following the procedure de- and ramie fabrics was carried out by dipping the scribed by Marie'". X-ray crystallinity (%) of treat- fabric piece in 20% (w/w) aqueous NaOH for 30 ed and untreated (controJ) ramie as well as cotton min at room temperature (30 ± 2°C). The material- fibres was determined after separating the fibres to-liquor ratio was kept at 1:10. The fabric was then from the respective fabrics to obtain the wide washed with water, neutralized with 1.5% acetic angle diffraction pattern with rotation powder acid solution, rinsed, washed and air dried. Mer- method by nickel filtered CuKa radiation for 28 cerization of ramie fabric for extended time peri- values between 10° and 30°, and the crystalline od (30 min) was also done using the same caustic contents were evaluated using Segal's crystallinity liquor and same treatment condition but under index". Weight losses were determined by usual tension by dipping the pretensioned ramie fabric oven dry'weight basis. held on the pin of a celluloid frame throughout Area shrinkage of the fabrics was determined the treatment period and .the fabric was unloaded following the usual method described elsewhere". before air drying. The linear density (tex) of warp and weft yams of the untreated (control) and treated ramie 2.2.2 Dyeing with Reactive Dye fabrics was determined after separating the warp Dyeing of ramie and cotton fabrics with a reac- and weft yam from the corresponding fabric fol- tive dye (CI Reactive Orange-13) was carried out lowing the conventional procedure'? as given by using a material-to-liquor ratio of 1:50 and sodi- ASTM D1059-87. um chloride (70 gIl) and sodium carbonate (20 The coefficient of friction of treated and un- gIl) as additives to be added subsequently in the treated (control) ramie fibres was measured fol- dyebath. The dyebath was initially set at 50°C lowing the conventional procedure':' using an in- with dye and the material was put in the dyebath. clined plane fibre friction testing instrument. The temperature was gradually raised to 80°C Breaking load und breaking elongation of un- and then sodium chloride was added in three in- treated (control) and treated ramie fabrics were de- stalments within 30 min, keeping the dyebath termined'! as per IS: 1969-1968 using Zwick- temperature at 80 ± S°e. Finally, sodium carbon- 1445 CRT universal tensile testing machine. ate was added in two instalments and dyeing was The dye uptake of treated and untreated cotton continued for further 45 min. After the dyeing and ramie fabrics, expressed as mglg (dye in mili- was over, the material was rinsed cold, soaped gram per gram of fibre) was determined from the with 5 gIl commercial grade detergent at 50°C for difference of initial dye concentration taken in the 15 min, washed in cold water and dried in air. dyebath and the final dye concentration remained DASet al.: REACTIVEDYEINGBEHAVIOUROF RAMIEFABRICS 55 in the dyebath (including wash liquor) after ex- treatment where the change is insignificant. Both haustion. The dye concentrations were estimated the loss in breaking load and increase in breaking in the usual way" by the absorbence spectropho- extension must be viewed as a consequence of the tometry analysis using U-2000-Hitachi-UV-Vis effect of decrystallization, partial loss of orienta- absorbence spectrophotometer at the maximum tion and possible structural rearrangement .set af- absorbence wavelength of the respective dye solu- ter swelling. tion using a calibration curve prepared for this purpose. 3.1.2 FrictionalBehaviour Fastness to washing of the reactive-dyed ramie Table 1 shows that the frictional behaviour of fabrics was determined using ~ Launder-o-meter the ramie fibre remains almost unchanged irre- as per ISO- 2 wash method 16 and was assessed by spective of the type of swelling pretreatments, grey scale as per ISO-105-AD2 (loss of depth) and keeping the surface behaviour almost same. ISO-105-AD3 (staining). 3.1.3 Area Shrinkageand YarnLinear Density to rubbing was determined 15 The area shrinkage values of ramie fabrics pre- using SDL-electronic crockmeter as per IS: 766- treated with different swelling agents are given in 1956 and the grey scale as per ISO-105-AD2 Table 1. For each of the pretreatments, the area and AD3. Colour fastness to light was determined shrinkage value is higher than that for the control as per BS-1-6 : BOI-1978, using SDL-MBTF sample and it is maximum for PA pretreatment, Lamp-microscallight fastness tester". showing maximum relaxation. The changes in the KlS values computed by Kubelka-Munk equa- tex values of the warp and weft yams of the pre- tion 16 were obtained by measuring the reflectance treated ramie fabric are much in tune with the ul- of the dyed and subsequently rubbed fabrics on timate area shrinkage values obtained as a result Macbeth 2020 plus computer-aided reflectance of warp-way and weft-way yam shrinkage in the spectrophotometer using the necessary softwares. fabric, except in the case of phosphoric acid pre- treated sample, where the changes in the tex va- 3 Results and Discussion lues of the yams in both the directions are not commensurate with the extent of shrinkage. The 3.1 EffectofPretreatment withDifferentSwellingAgents on Mechanical Properties and Fine Structure lower extent of tex change, in spite of highest area shrinkage, in case of phosphoric acid treatment 3.1.1 BreakingLoad and Extension may be explained by some loss in mass from ra- From Table 1, it is observed that phosphoric mie' in PA treatment due to hydrolysis, supersed- acid (PA) pretreatment lowers the breaking load ing the effect of reduction in the length of the to the highest extent (29.7%). The best effect is yam by shrinkage. obtained in the case of NaOH (tension) pretreat- ment, where a measurable increase in breaking 3.1.4 DecrystaUization load is evident. In the case of EDTA and urea In all the pretreatments to ramie fabric, phos- pretreatments, the loss of breaking load is only phoric acid pretreatment results in maximum de- marginal. In all the pretreatments, breaking exten- crystallization, reducing the X-ray crystallinity sion increases, except for NaOH (tension) pre- from 63.3 to 39.2%. The extent of decrystalliza-

Table I-Effect of pretreatmentswith differentswellingagents on mechanicalproperties and fine structure of ramie Treatment Breaking Breaking Coefficient Area Lineardensityofyarn,tex Crystallinityi' load extension offriction' shrinkage % N % % Warp Weft Untreated (Control) 568.00 9.15 0.63 1.2 53.0 26.0 63.3 20%NaOH (tension) 583.21 8.93 0.64 6.0 54.3 26.6 53.2 20%NaOH (slack) 570.34 11.27 0.64 8.0 54.6 27.0 52.3 15%EDTA(slack) 558.24 12.23 0.63 11.0 55.0 27.8 51.3 20%Urea (slack) 519.68 15.52 0.61 18.0 55.4 28.5 46.1 81%Phosphoricacid(slack) 399.04 19.43 0.62 24.0 56.0 29.0 39.2 "Coefficientoffrictionfor controlcotton,0.24. bCrystallinityforcontrolcotton,63.0%. 56 INDIAN J. FmRE TEXT. RES., MARCH 1997 tion for different swelling pretreatments is in the noticeable increase in dye uptake when compared order: NaOH (tension)

Table 2-Effect of pretreatment with different swelling agents on absorbency, dyeability (reactive dyes) and dye fastness properties of ramie fabric ' , Treatment Absorbency Dye uptake Wash fastness R¥b fastness Light (Iodine sorp- mglg fastness tion value) 10 Cycles 100 Cycles mglg Staining" Staining" Ramie Fabric Untreated (Control) 28 7.2 S 5 3 4-5 2 4-5 3-4 20% NaOH (tension) 89 11.1 5 5 3-4 4-5 2-3 4-5 3-4 20% NaOH (slack) 99 13.6 5 4-5 4 5 3 4-5 3-4 15% EDTA (slack) 101 lS.2 5 5 3-4 5 2-3 4.5 3-4 20% Urea {slack) 121 19.2 5 5 4-5 5 3-4 4-5 3 81 % phosphoric acid (slack) 132 21.3 5 5 4-5 5 3-4 4-5 2 Cotton Fabric Untreated (control) 34 15.2 5 5 5 5 4-S 4-5 3-4 "Loss of depth or change in colour was assessed as per ISO 105 AD2 grey scale. "Staining was assessed as per ISO 105 AD3 grey scale. DAS et al: REACTIVE DYEING BEHAVIOUR OF RAMIE FABRICS 57

3.2.3.2 Light Fastness change in the K/S value of reactive-dyed cotton The light fastness of reactive dyes on both con- fabric almost ceases (curve 5) at about 20 rub cy- trol ramie fabric and control cotton fabric is al- cles, with no significant increase in the KlS value most same, showing that there is little effect of the of the corresponding stained abrader cloth (curve type of fibre. In the case of urea and phosphoric 8), indicating neither further dye transfer to acid pretreated and subsequently reactive-dyed stained abrader cloth on rubbing after 20 rub cy- ramie samples, the light fastness ratings are 3 and cles, nor loss of depth of shade (i.e. no alteration 2 respectively (Table 2). This may be attributed to of KlS values is observed for both the original the increased absorbency or accessibility in the dyed cotton and stained abrader cloth from 20 to non-crystalline region after decrystallization by 100 rub cycles). But in case of reactive-dyed ra- swelling agents, possibly facilitating the ease of mie, rubbing on the crockmeter up to 100 rub cy- diffusion of more moisture and oxygen for initiat- cles showed that though the transfer of dye onto ing the light fading mechanism'". stained abrader (ramie) cloth almost ceases (curve 4) after 20 rub cycles, but the loss of 3.2.3.3 Rub Fastness colour from original dyed ramie fabric continued Rub fastness ratings as assessed from the loss (curve 1) up to 100 rub cycles without further in- of depth of shade and from the extent of staining crease in stain on the abrader (ramie) cloth. This to the abrader cloth from ramie fabric are differ- loss of depth of shade of reactive-dyed ramie fa- ent, the former (loss of depth) being poorer in bric on rubbing was found to continue even with- each case (Table 2), while the corresponding data out any measurable loss of dyed fibre mass, as ex- in case of dyed control cotton fabric show the perimented separately (Data not shown here). same rub fastness rating on assessment by both These interesting observations about the rub the methods. However, on pretreatments with dif- fastness of reactive-dyed ramie fabric led us to ferent swelling agents, the poor rub fastness (as- sessed by loss of depth of shade) of ramie im- proves bymore than one unitfor phosphoric acid-and urea-pretreated and dyed ramie fabrics.This may be Romill Fobr ie attributed to mare diffusionand fixationofdyesto the core rather than surface after swellingpretreatments create easy dye diffusion facility and increased 2 dye-accessible sites on decrystallization by the 1 high swelling action of these two reagents. The ------"'-I'I---¥.' 4 other two swelling reagents, NaOH and EDTA, show little or marginal improvement in rub fast- ness (loss of depth) of ramie. However, when the NaOH pretreatment is carried out under slack condition, a small but measurable improvement in rub fastness (loss of depth) for reactive-dyed ra- Cotton Fobr ie mie is noticed (Table 2). Rub fastness ratings as- sessed from the extent of staining to the abrader cloth show almost no bearing on the type of pre- treatments done. On the extensive rubbing, i.e. for rubbing up to 100 cycles instead of 10 cycles, the rub fastness rating for reactive-dyed control ramie came down to 2 from 3 when assessed from the losss of depth of shade. But interestingly the rub fastness ratings assessed from the extent of staining to 20 30 40 so .00 abrader cloth for 10 rub cycles-and for 100 rub Number of rub eye'" cycles do not show any significantdifference. Fig. l-K/S values of reactive-dyed ramie and cotton fabrics Fig. 1 shows the KlS values of the reactive-dy- suQjected to different number of rubbing cycles vis-a-vis corresponding abrader cloth. (1 & S-without pyridine ex- . ed ramie and cotton fabrics as well as of the traction; 2 & 6-with pyridine extraction; 3 & 7-.brader corresponding stained abrader clothes for differ- cloth for pyridine-extracted samples; and 4 & 8- abrader ent number of rub cycles. It is observed that the cloth for without pyridine-extracted samples] 58 INDIAN J. FIBRE TEXT. RES., MARCH 1997 extend this study for Iinvestigating the causes and tive-dyed ramie fabric, continual loss of depth is remedies for this continual loss of depth of shade significant (curve 2). However, it is also observed without staining to the abrader cloth,particularly that the ultimate rate of decrease of KlS value, on on extensive rubbing. rubbing for 0 to 100 rub cycles, for pyridine-ex- tracted reactive-dyed ramie fabric .(curve 2) is 3.3 Causes of Poor Rub Fastness (Loss of Depth) of much lower than that found for the sample with- Reactive-dyed Ramie on E'lltensive Rubbing out pyridine extraction (curve v'I ). Also, the The observed poo~ rub fastness with continual abrader cloths for pyridine-extracted samples of loss of depth of shade without staining the abrad- both ramie and cotton show no significant changes in er cloth on extensive rubbing (20-100 rub cycles) KlS values on extensive rubbing (curves 3 and 1). for reactive-dyed ramie fabric may be due to any These observations establish that the poor rub one or possible combination of the followings: fastness of reactive-dyed ramie fabric is not go- (i) Relatively strongly held loose (unreacted) verned at least by relatively strongly held loose and hydrolyzed reactive dyes deposited on fabric (unreacted) or hydrolyzed reactive dyes deposited surface may show poor rub fastness on higher rub on ramie. It is already mentioned in the last para of cyc(.~e)sHi·igh11 er coeffi ci .entIff"0 . ncnon (063 . ) 0 f ranue. 3.2.3.3 that the loss of depth of shade of reac- (Table 1) with more irregular surface structure-? tive-dyed ramie fabric continued without any as compared to that of cotton (p.24) may produce measurable loss of dyed fibre mass and hence among higher abrasive force on the fabric surface during the above-said possible reasons, the reason (ii) extensive rubbing and may cause breaking and ul- may be considered to be negligible but there is timately loss of some ~yed fibre mass. every chance that phenomenon explained in the (ill) The same as in (ii) may also happen with- reason' (iii) may playa major role in this case. On out showing any loss of fibre mass, if the long-sta- microscopical examination, the presence of bro- ple ramie fibres (on the fabric surface) are torn or ken long-staple ramie fibre, anchored to the yarn broken on extensive rubbing, but still remain an- assembly even after 100 cycles of rubbing, indi- chored, holding the broken fibres at the other end cated that the reason (ill) is atleast partly respon- to the yarn structure in ramie fabric. The so sible for showing poor rub fastness (loss of depth) called free broken ends of the dyed ramie fibres of reactive-dyed ramie on extensive rubbing. with ring dyed cross-sections may be exposed to Microscopical examination of the cross-sections the dyed fabric surface and thereby may alter the of dyed control ramie showed ring dyeing effect, reflectance of the rubbed portion, showing the ap- which may ultimately cause exposition of the inner parent loss of depth without staining to the undyed layer on higher abrasion on extensive rubb- abrader cloth. ing and thus continual loss of depth of shade and (iv) In consequent to ring dyeing (as observed consequent change in K/S value may be ob- in microscopic examination) for highly oriented and served. Therefore, ring dyeing [reason (iv)] due to ordered structure of ramie fibre, the surface of the highly ordered and oriented fine structure of ra- ring-dyed ramie fibre is when abraded for mie is another factor responsible for such poor higher number of rub cycles, it may cause ex- rub fastness (loss of depth) on extensive rubbing posing of inner undyed layer progressively with without staining to the abrader cloth. the increase in rubbing cycles, which may lead to Therefore, it may be concluded that the reasons alteration of KlS valub of the rubbed portion of the (ill) and (iv) in mutual combination are responsi- dyed ramie fabric accordingly. ble for the poor rub fastness of dyed ramie, parti- To test if reason (i) has any bearing on the poor cularly on extensive rubbing, showing continual rub fastness, the pyridine-extracted reactive-dyed loss of depth of shade without increasing stain to ramie and cotton fabrics were also subjected to the abrader cloth. extensive rubbing (from 0 to 100 rub cycles) and The ring dyeing phenomenon can be reduced the corresponding changes in KlS values were by swelling pretreatment allowing more dye diffu- measured after 10, 20, 30, 50 and 100 rub cycles. sion, particularly when urea or phosphoric acid is The results are presented in Fig. 1 (curves 2 & 6). used as swelling agent, as discussed in 1st para of It is observed from Fig. 1 that the loss of depth of section 3.2.3.3. Phosphoric acid pretreatment shade, in terms of decrease in KlS value, on gives inferior mechanical properties of ramie and, rubbing for 0 to 100 rub cycles, is very marginal therefore, 20% urea or 20% NaOHpretreatment for pyridine-extracted reactive-dyed cotton sam- (under slack condition) may be considered as a ple (curve 6) while that for corresponding reac- prospective pretreatment for ramie, which is even DAS et al: REACTIVE DYEING BEHAVIOUR OF RAMIE FABRICS 59 better than NaOH pretreatment (under tension) or mercerization considering the overall balance 1·6 Pretreated with NaOH of mechanical properties, dyeability and dye fast- 1·4 ness (particularly rub fastness). "2

3.4 Effect of Selective Post-treatment with Different Softeners/Polymeric emulsions on Rub Fastness of Reactive-dyed Ramie Control To mitigate or reduce the poor rub fastness ~•• 0 "0 (loss of depth of shade) problem of reactive-dyed :> 1·8 ramie on extensive rubbing and consequent phe- ~ Pretreated with urea >C 1'6 nomenon explained in reason (ill) of section 3.3 .• attempts were made to suitably modify the sur- "4 ~ e face characteristic of 20% NaOH (slack) pretreat- '·2 ~ 7 ed and 20% urea pretreated ramie fabrics using '·0 ~S selective softeners/polymeric emulsions such as ~6 catasoftener, silicone emulsion and polyethylene 0-8 ~ Control emulsion. Relevant rub fastness results (after these 0 10 30 40 SO 100 post-treatments ),in terms of change in KlS values, 0 20 are graphicallypresented in Fig. 2. Numberof rub cycln Catasoftener (cationic softener) post-treatment Fig. 2-K/S values on extensive rubbing for differently finished (curve 2) on NaOH-pretreated (slack) and dyed ra- reactive-dyed ramie fabrics pretreated separately with aqueous mie, though deposited the fatty matters on the sur- solution of NaOH (20%) and urea (20%), both in slack condition prior to dyeing [Control-without any pretreatment or finishing face of the fibre to lubricate and soften the fibre post-treatment; I-NaOH-pretreated without any finishing post- surface it showed little improvement in rub treatment; 5-urea-pretreated without any finishing post-treat- fastness over slack-causticised ramie sample and at ment; 2 & 6-finished with catasoftener; 3 & 7-finished with sili- higher number of rub cycles, the improvement was cone emulsion; and 4 & 8-finished with polyethylene emulsion] very marginal as indicated by the corresponding curves 1 and 2. Catasoftener treatment on urea- can be considered to be a useful practical propo- pretreated ramie rather showed deterioration in sition if higher rub fastness is desired. rub fastness (corresponding curves 6 and 5), the reason for which is not understood from this 4 Conclusions study. Silicone finish suitable for producing a sof- 4.1 All the pretreatments, considered for the en- ter handle alongwith moderate film forming ca- hancement ·of accessibility, improve the reactive pacity showed a marked improvement (curves 3 dye uptake of ramie fabric to different extents. and 7) in rub fastness for both NaOH (slack) and Phosphoric acid though improves the accessibility urea-pretreated ramie, even on extensive rubbing. to the highest extent but results in high loss From Fig. 2, it may also be observed that polye- (about 30%) of tensile strength. Pretreatment with thylene emulsion, probably producing a smooth 20% NaOH or 20% urea under slack condition film over the fibre surface, showed orily marginal shows appreciable amount of decrystallization loss of KlS value at the rubbed portion for both [more than that obtained for NaOH (under ten- NaOH (slack) and urea-pretreated dyed ramie, re- sion) or mercerization process], considerable im- taining the physical appearance of the cloth al- provement in reactive dye uptake with low to most intact even after 100 rub cycles (curves 4 moderate strength loss, iridicating practical im- and 8). This further supports the view [reason (ill) portance for possible industrial application. in section 3.31 that the surface frictional behav- 4.2 Fastness to washing and light for reactive-dyed iour is one of the important factors responsible ramie are almost at par with those for similarly for poor rub fastness of reactive-dyed ramie fa- dyed cotton. However, the fastness to rubbing is bric which can be reduced by post-treatment with generally poor for ramie, particularly at higher silicone or polyethylene emulsion forming a soft number of rub cycles, in comparison to that for and smooth surface film over the dyed ramie sur- cotton. face. Therefore, post-treatment, either with sili- 4.3 Highly oriented and ordered structure of ra- cone or polyethylene emulsion, of reactive-dyed mie offers less dye accessibility (consequently less ramie fabric pretreated with either 20% NaOH or dye sites), resulting in (i) ring dyeing phenomenon preferably with 20% urea, both in slack condition, and (ii) high coefficient of friction of the ramie fi- 60 INDIAN J. FmRE TEXT. RES., MARCH 1997 bre, causing break of long-staple ramie fibre on References extensive rubbing without detaching from fabric; 1 Batra S K, in Handbook of fiber science and technology, these two reasons have been found to be the ma- Vol. 4, Fiber Chemistry, edited by M Lewin & EM jor responsible factors for lowering the rub fast- Pearce (Marcel Decker Inc, New York), 1985,727. ness of reactive-dyed ramie. 2 Dasgupta P C & Sen S K, Cellul Chern Technol; 10 (1976) 285. 4.4 Post-dyeing treatments with selective softeners 3 Nandi H K, Studies on outstanding feature of ramie as fi- or polymeric emulsions like silicone and polyethy- bre, yam and fabric (Directorate of Agriculture, Govt. of lene emulsion of suitably pretreated (particularly West Bengal, Calcutta), 1964, 185. 20% NaOH or 20% urea pretreatment under 4 Suganuma K & Kuno H, J Soc Dyers Colour, 102 (1986) slack condition at room temperature) ramie fabric 100. improve the fastness to rubbing significantly for 5 Marshall W, J Soc Dyers Colour, 40 (1924) 10. 6 Warwicker J 0, J Polym Sci, A2, 4 (1966) 571. reactive-dyed ramie fabric and these pre- and 7 Roy P K & Das B K, Text Res J, 47 (1977) 437. post-treatments may be considered useful for 8 Cheek L & Rousell L, Text Res J, 59 (1989) 478. practical application. 9 Cheek L & Rousell L, Text ResJ, 59 (1989) 541. 10 Nelson M, Rousella M A, Cangemi S J & Trouard P, Text Acknowledgement ResJ, 40 (1970) 872. The authors gratefully acknowledge the help 11 Segal L, Creely J J, Martina E (Jr) & Conrad C, Text Res J, 29 (1959) 786. rendered by Dr Swadesh Sett, College of Textile 12 Som N C & Mukherjee A K, Indian J Text Res, 14 Technology, Serampore, in determination of X-ray (1989) 164. crystallinity. They are also thankful to Dr U. Mu- 13 Annual book of ASTM standards; Section 7 (American khopadhyay, Dr D. Sur and Mr. D.K. Sinha of lIT for Society for Testing and Materials, Philadelpbia, USA), their advice, help and keen interest. The authors ex- 1987. press their indebtedness to the Ministry of Human Re- 14 Bandyopadhyay S B, Text Res J, 25 (1951) 9. source Department, Govt. of· India, and AICTE, 15 ISI (BIS) handbook of textile testing (Bureau of Indian Standards, New Delhi), 1986. Govt.of India, for grant in-aid to this department; 16 Trotman E R, Dyeing and chemical technology of textile the equipment purchased from these grants were fibres (Charles Griffin & Co. Ltd, London), 1975. very useful in this work. Allen N S, Rev Prog Color, (1987) 1761.