In this study, a pad-steam process for treatment of polyester/cotton fabric with sodium hydroxide is developed and the effects of process parameters on selected properties of the fabric are  investigated. The results are compared with the conventional exhaustion process. Both processes improved the handle, dyeability and water absorption of the polyester/cotton fabric, but the pad-steam process has the advantages of less strength loss of the fibers, shorter treatment time, lower consumption of water and chemicals that make the process less hazardous to the environment

Aminoddin Haji

Firoozmehr Mazaheri

Reza M. A. Malek

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 Available on line at Association of the Chemical Engineers of Serbia AChE  www.ache.org.rs/CICEQ   Chem. Ind. Chem. Eng. Q. 17 (3) 359−365 (2011)  CI&CEQ  359  AMINODDIN HAJI1 REZA M.A. MALEK2 FIROOZMEHR MAZAHERI2 1Department of Textile, Birjand Branch, Islamic Azad University, Birjand, Iran 2Textile Department, Amirkabir University of Technology, Hafez St., Tehran, Iran SCIENTIFIC PAPER UDC 677.494.674:677 DOI 10.2298/CICEQ101205022H    COMPARATIVE STUDY OF EXHAUSTION AND PAD-STEAM METHODS FOR IMPROVEMENT OF HANDLE, DYE UPTAKE AND WATER ABSORPTION OF POLYESTER/COTTON FABRIC In this study, a pad-steam process for treatment of polyester/cotton fabric with sodium hydroxide is developed and the effects of process parameters on selected properties of the fabric are investigated. The results are compared with the conventional exhaustion process. Both processes improved the handle, dyeability and water absorption of the polyester/cotton fabric, but the pad-steam process has the advantages of less strength loss of the fibers, shorter treatment time, lower consumption of water and chemicals that make the process less hazardous to the environment. Key words: polyester; dyeability; weight reduction; cotton; sodium hydroxide.   Aside from the outstanding features of polyester fabrics such as tensile strength, dimensional stability, washability and abrasion resistance, certain drawbacks such as low water absorbency, pilling, and poor handle have also been reported. Blending po-lyester with cellulosic fibers is one way to overcome the drawbacks, so that better water absorbency, handle and much more comfort can be achieved [1]. Poly-ester/cotton fabrics are widely used in the textile in-dustry as they combine the advantages of both com-ponents that they are built of. By treating polyes-ter/cotton fabrics in alkaline conditions (using sodium hydroxide) further improvement in the fabric proper-ties can be obtained [2-5]. Alkali treatment of polyester fabric is a well- -known and conventional process in textile industry [3]. Sodium hydroxide can hydrolyze the ester groups in the polyester chains. Several researchers have found different mechanisms for alkaline hydrolysis of polyester fiber [1,2]. The weight reduction of polyester ranging between 15 and 30%, gives a silky handle, luster, soil repellency and anti static properties to the polyester fabric [4], and its stiffness, tenacity and elongation are decreased [4-6,12]. Although alkaline hydrolysis decreases the diameter of the fibers, the                                                  Correspondening author: A. Haji, Islamic Azad University, Ghaf-fari St., Birjand, Iran. E-mail: ahaji@iaubir.ac.ir Paper received: 5 December, 2010 Paper revised: 14 June, 2011 Paper accepted: 15 June, 2011 density of the fibers is not affected [7-11]. It has been stated by some researchers that the rate of polyester hydrolysis can be improved by using certain acce-lerants [13].  Xu and Yang have used the microwave irra-diation to increase the rate of hydrolysis of polyester with sodium hydroxide [14]. Raslan and Bendak have concluded that the use of sodium hydroxide in al-coholic media is more effective than sodium hydro-xide aqueous solution [15]. Konovalova has shown that magnetic activation of the water media can in-crease the hydrolysis rate of polyester [16]. Kimizu and co-workers have reported that under high pres-sure conditions (over 100 MPa) the decomposition of PET fabric will be resulted [17].  A wide range of studies has been carried out to investigate the effect of alkali on polyester/cotton fab-ric [18]. However, no one has worked on continuous processes such as pad-steam in this subject. In this study, a pad-steam process is proposed and com-pared with the conventional exhaustion method. Due to its lower costs, shorter required time, fewer che-micals used, much less environmental pollution and higher production [19], continuous processes can be a solution, as stated in this work. EXPERIMENTAL Materials Plain weave polyester/cotton (67/33) fabric (123 g/m², yarn count, Nm = 40, 50 warp/cm, 30 weft/cm) A. HAJI, R.M.A. MALEK, F. MAZAHERI: COMPARATIVE STUDY OF EXHAUSTION…  CI&CEQ 17 (3) 359−365 (2011)  360 was obtained from Brujerd Textile Co., Iran. Tinegal PAC (quaternary ammonium salt), Ultravon CN (non- -ionic surfactant) and Invadine VB (a weakly anionic wetting agent), Terasil blue BGE, Terasil black SRL- -01 (disperse dyes), Cibacron turquoise P-GR and Cibacron black P-GR (reactive dyes) was kindly sup-plied by Ex-Ciba, Iran. All other chemicals used in this work were laboratory grade reagents obtained from Merck. Methods To remove any natural or synthetic impurities, all fabric samples were scoured using a solution con-taining Ultravon CN (2 g/l) and sodium carbonate (1 g/l) for 20 min at 60 °C then rinsed and dried. Finally, the samples were heat set at 170 °C for 30 s in a laboratory stenter. The alkali treatment was processed by the fol-lowing methods:  1) Exhaustion. Like the conventional process, the samples were immersed in a sodium hydroxide solution (10 up to 40 g/l) at 50:1 liquor ratio. The initial temperature was 40 °C and the temperature was raised to boil in 30 min and then the boiling time was determined and reported. After the appropriate boiling time (1 h), washing, neutralization with 1% v/v acetic acid solution and final rinse of the samples followed.  2) Pad-steam. The samples were padded in a bath containing sodium hydroxide (5-30 g/l), Tinegal PAC, Invadine VB and urea, at 100% pick up. Steam-ing process at 120 °C was practiced. Then washing, neutralization and final rinse of the samples were followed. The weight loss (WL) is expressed as relative WL according to the equation:  WL = 100(W1 – W2/W1) where  W1 and W2 are the weights of the samples before and after alkaline treatment, respectively. Hydrolysis of PET can be controlled to affect fabrics at varying levels, i.e., from surface hydrolysis to extensive removal of the constituent polymer. In this study, to avoid from imposing significant changes in the bulk of PET fiber, and restrict the hydrolysis to the surface of the fiber, a weight loss between 15 to 20% has been considered as optimum weight reduc-tion value. Physical properties measurement The tensile strength of treated sample fabric was determined on an Instron tensile tester model TM-SM 1026 according to ASTM D5034-95 (2001) and wicking test was measured according to BS 3424: part 18, method 21A. Stiffness, or limpness, of a fabric can be deter-mined by measuring bending length. Flextural rigidity of fabric is proportional to the product of fabric arial density and bending length to the third power [9]. To determine fabric handle, bending length of the fabric was measured by a Shirley tester according to Booth [20], and the bending stiffness of the samples was calculated using the following equation: BS = 1000WC3 (1) where BS, W and C are bending stiffness, weight of 100 cm² of fabric in g and bending length in cm, res-pectively. Wicking test The experimental setup described in reference [21] was used for the measurement of vertical wicking of fabrics. The 1.5 cm×7 cm strips of samples were lowered to touch the water reservoir, at which mo-ment the timer was started, and the position of water front line (cm) over time was recorded [21]. Dyeing and color measurements Alkali treated and untreated PET/cotton fabrics were dyed using the following recipe. Padding at 75% pick up with a solution con-taining: 1 g/l disperse dye, 1 g/l reactive dye, 2 g/l Invadine LUN, 50 g/l urea, 5 g/l Invadine DP, 5 g/l Irgapadol MP and 15 g/l sodium bicarbonate, then drying at 110 °C and fixing at 210 °C for 1 min and fi-nally washing with 2 g/l Ultravon CN and 1 g/l sodium carbonate at 50 °C for 30 min and then rinsing tho-roughly. To affirm the effect of alkali treatment on dye ability of each fiber, pure cotton and PET fabrics of the same fibers as blended fabric were alkali treated and dyed with the same method. When dyeing cotton fabric, only the reactive dyes were used and only the disperse dyes were used when dyeing PET fabric. The reflectance of dyed samples and color co-ordinates CIE L*, a* and b* values were measured on a X-Rite CA22 spectrophotometer using illuminant D65 and 10° standard observer. It should be noticed that conditioning of the samples was performed according to ISO 139:2005 standard prior to all measurements. RESULTS AND DISCUSSION Effect of pad-steam method conditions on weight loss of PET/cotton fabric Figures 1 and 2 show the effect of sodium hyd-roxide concentration on weight loss percentage, with and without Tinegal PAC in two methods. It is obvious that weight reduction (%) is higher for exhaustion than A. HAJI, R.M.A. MALEK, F. MAZAHERI: COMPARATIVE STUDY OF EXHAUSTION…  CI&CEQ 17 (3) 359−365 (2011)   361pad-steam method at a certain alkali concentration, but it should be noticed that the treatment time is 1 h in conventional exhaustion method (compared to 5 min for pad-steam method). According to the figures 1 and 2, the presence of Tinegal PAC has an important role in weight loss of the samples and accelerates the process of alkali treatment. Tinegal PAC is a quater-nary ammonium salt with cationic charge, so it seems to be able to cover the negative group indicated in Figure 3, caused by the attack of alkali on the poly-ester chain, which provide further alkaline attack.  Figure 4 shows that the weight loss of sample increases with an increase in steaming time linearly. Physical properties of alkali treated PET/cotton fabric Figures 5 and 6 show the effect of steaming time and Tinegal PAC concentration on the tensile strength of alkali treated fabric with pad-steam method, res-pectively. It seems that the higher the steaming time the lower would be the tensile strength. Steaming time of five minutes at 120 °C resulted in the lowest loss of tensile strength and was considered as the op-timized steaming time. Increase in Tinegal PAC concentration over 2 g/l in the pad-liquor caused an increase in loss of fabric tensile strength. It can be seen from Table 1 that the exhaustion method (1 h) has a highly destructive effect on tensile strength of PET/cotton fabric compared with pad- -steam method (5 min) because of high degree of hydrolysis of PET fibers. Figure 7 shows the effect of weight loss percen-tage on bending stiffness of treated fabric in pad-steam051015200 5 10 15 20 25 30 35NaOH Concentration (g/l)Weight Reduction (%)Without Tinegal PACWith 2 g/l Tinegal PAC Figure 1. Effect of sodium hydroxide concentration on weight loss percentage in pad-steam method (5 min steaming time). 010203040500 1 02 03 04 05 0NaOH Concentration (g/l) Weight reduction (%) Without Tinegal PAC With 2g/l Tinegal PAC Figure 2. Effect of sodium hydroxide concentration on weight loss percentage in exhaustion method (1 h boiling time). A. HAJI, R.M.A. MALEK, F. MAZAHERI: COMPARATIVE STUDY OF EXHAUSTION…  CI&CEQ 17 (3) 359−365 (2011)  362  Figure 3. Polyester chain alkaline hydrolysis [18]. 1517192123252729310 5 10 15 20 25Steaming time (Min)Weight Reduction (%) Figure 4. Effect of steaming time on weight loss percentage in different steaming times. 05101520253035400 5 10 15 20 25Steaming time (Min)Tenacity Loss (%) Figure 5. Effect of steaming time on tenacity loss percentage of fabric in pad-steam method at 120 °C with 2 g/l Tinegal PAC. 0510152025303540012345Tinegal PAC concentration (g/l)Tenacity Loss (%) Figure 6. Effect of Tinegal PAC concentration on tenacity loss percentage of fabric in pad-steam method at 120 °C for 5 min. A. HAJI, R.M.A. MALEK, F. MAZAHERI: COMPARATIVE STUDY OF EXHAUSTION…  CI&CEQ 17 (3) 359−365 (2011)  363 method. Decreasing in bending stiffness is due to changing in handle properties of treated fabric. Decreasing in bending length of treated fabric might be due to the reduced diameter of fibers and thickness of fabric [22,23] after an increase in concentration of sodium hydroxide or presence Tinegal PAC in the pad-liquor. Table 1. Effect of two methods on tensile strength of PET/cotton fabrics (2 g/l Tinegal PAC) Method  Time, min  Reduction of tensile strength, %Pad-steam 5  20 Exhaustion 60  50.2 As shown in Figure 8, the water front line in the treated sample is pronouncedly higher than the un-treated one for both methods. This might be due to the increase of hydrophilic groups on the surface of PET fibers. The nucleophilic attack of NaOH on PET chains causes chain scissions at the ester linkages, producing carboxyl and hydroxyl polar groups, which lead to improved polarity and hydrogen bonding ca-pacity with water molecules, and thus better water wettability. Furthermore, the microscopic roughness caused on the surface of the fiber after removal of surface polymers can be responsible for better spread-ing of water over the fiber surface. There is no signi-ficant difference between water absorption of samples treated with two methods. According to the above-mentioned results, pad- -steam method was chosen as the preferred method for alkali treatment of PET/Cotton fabric and the dye-ing tests were performed only on pad-steam alkali 0100002000030000400005000019.5 20 20.5 21 21.5 22 22.5 23 23.5Weight Reduction (%)Bending Stiffness Figure 7. Effect of weight loss percentage on bending stiffness of fabric in pad-steam method at 120 °C with 2 g/l Tinegal PAC for 5 min.01234560 50 100 150 200Time (Sec)Water front line (cm)Untreated fabricAlkali treated fabric (pad-steam for 5 min)Alkali treated fabric(exhastion method for 60min) Figure 8. Wicking test results of untreated and alkali treated fabrics with two methods. A. HAJI, R.M.A. MALEK, F. MAZAHERI: COMPARATIVE STUDY OF EXHAUSTION…  CI&CEQ 17 (3) 359−365 (2011)  364 treated samples. To specify the effect of the alkali treatment of dye absorption of each fiber, pure cotton and PET fabrics of the same fibers as blended fabric were alkali treated and dyed with the previously men-tioned method. As shown in Table 2, the L* of dyed alkali treated PET/Cotton samples is less than dyed untreated fabrics indicating an increase in color depth of alkali treated fabric. This increase in dye absorption can be due to the caustification effect of the cotton part as well as the formation of terminal hydroxyl and carboxyl groups on the polyester surface. The in-crease for cotton portion is more than the PET portion as can be seen from Table 2. CONCLUSION Alkali treatment of PET/cotton fabric by exhaus-tion and pad-steam method was studied. Both me-thods lead to considerable weight reduction and strength loss of the fabric, which is higher in the case of ex-haustion method. Steaming or biling time, concen-tration of alkali and Tinegal PAC have largest effect on the amount of weight reduction in both methods. Alkali treatment by pad-steam method at 120 °C for 5 min reduces the weight of polyester/cotton fabric re-sulting in minimum loss of tenacity, increase in hydro-philicity and dye absorption and better handle of the finished fabric. Considering the reduced amount of water, alkaline conditions, time, energy consumption and environmental requirements, the proposed pro-cess seems to be more appropriate. REFERENCES [1]  E.P.G Golh, L.D. Vilensky, Textile Science, 2nd ed., Longman Cheshire, Melbourne, Australia, 1983, p. 187 [2]  R. Betschewa, P. Wangelov, Melliand Textilber. 70 (1989) 599-604 [3]  N. Kallay, Text. Res J. (1990) 663-668 [4]  R.T. Shet, S.H. Zeronian, Text. Chem. Color. 14 (1982) 11-16 [5]  J. Lee, Proceedings of the 3rd Asian textile Conference, Vol. 1, 1995, pp. 256-261. [6]  A. Khosravi, Dyeing Polyester and Cellulose Acetate, Jahad Daneshgahi, Tehran, 1994, p. 12 [7]  H.L. Needles, Text. Chem. Color. 17 (1985) 177-185 [8]  H.L. Needles, S. Holmes, J. Soc. Dyers Colour. 106 (1990) 385-388 [9]  M. Haghighatkish, M. Nouri, J. Appl. Polym. Sci. 72 (1999) 631-637 [10]  K.V. Datye, J. Soc. Dyers Colour. 107 (1991) 218-219 [11]  M. Haghighatkish, M. Yousefi, Iran. J. Polym. Sci. Technol. 1 (1992) 56-60 [12]  M.C. Yang, H.Y. Tsai, Text. Res. J. 67 (1997) 760-766 [13]  S.R. Shukla, M.R. Mathur, J. Appl. Polym. Sci. 75 (2000) 1097-1102 [14]  W. Xu, C. Yang, Color. Technol. 118 (2002) 211-214 [15]  W.M. Raslan, A. Bendak, J. Appl. Polym. Sci. 98 (2005) 1829–1837 [16]  M.V. Konovalova, Fibre Chem. 37 (2005) 93-96 [17]  M. Kimizu, Y. Shimbo, T. Abe, T. Hori, Seni Gakkashi 61 (2005) 109-114 [18]  M. Montazer, A. Sadighi, J. Appl. Polym. Sci. 100 (2006) 5049–5055 [19]  G. Kazakeviciute, V. Valiene, A. Abraitiene, Environ. Res. Eng. Manage. 28 (2004) 40-47 [20]  J.E. Booth, Principle of Textile Testing, 3rd ed., Butter-worth-Heinemann, London, UK, 1968, p. 334 [21]  A. Patnaik, R.S. Rengasamy, V.K. Kothari, A. Ghosh, Text. Prog. 38 (2006) 1-105 [22]  H. Tavanai, J. Text. Inst. 100 (2009) 633-639 [23]  F. Mousazadegan, S. Saharkhiz, M. Maroufi, J. Text. Inst. 101 (2010) 716-728.     Table 2. Color coordinates of untreated and alkali treated (pad-steam method at 120 °C for 5 min) polyester/cotton fabric dyed with blue and black dyes Fabric  L*  a*  b*  ∆E Polyester/cotton  alkali  treated-blue 53.73 -24.3 -27.4 5.013 Polyester/cotton untreated-blue  58.48  -24.4  -25.8 Polyester/cotton  alkali  treated-black  18.93 -1.08 -2.82 4.787 Polyester/cotton untreated-black  23.56  -1.97  -3.65 Cotton alkali treated-blue  48.45  -20.1  -24.9  5.52 Cotton untreated-blue  53.12  -22.5  -23.2 Polyester alkali treated-blue  63.15  -17.4  -33.4  2.7 Polyester untreated-blue  64.38  -18.6  -31.3         A. HAJI, R.M.A. MALEK, F. MAZAHERI: COMPARATIVE STUDY OF EXHAUSTION…  CI&CEQ 17 (3) 359−365 (2011)   365 AMINODDIN HAJI1 REZA M.A. MALEK2 FIROOZMEHR MAZAHERI2 1Department of Textile, Birjand Branch, Islamic Azad University, Birjand, Iran 2Textile Department, Amirkabir Univer-sity of Technology, Hafez St., Tehran, Iran NAUČNI RAD    UPOREDNO ISPITIVANJE METODA ISCRPLJI-VANJA I PAD-STEAM RADI POBOLJŠANJA NEKIH SVOJSTAVA (OPIPA, PRIJEMA BOJE I APSORPCIJE VODE) TKANINE OD MEŠAVINE POLIESTAR/PAMUK U ovom radu, razvijen je pad-steam process za tretiranje tkanine od mešavine polies-tar/pamuk natrijum-hidroksidom i istraživan uticaj parametara procesa na odabrana svoj-stva tkanine. Rezultati su poređeni sa konvencionalnim procesom iscrpljivanja. Oba pro-cesa su poboljšala opip, sposobnost bojenja i apsorpcije vode tkanine od mešavine poli-estar/pamuk, ali pad-steam proces ima niz prednosti, kao što su: manji gubitak jačine vlakana, kraće vreme tretiranja, manja potrošnja vode i hemikalija, koje proces čine ma-nje opasnim po životnu sredinu. Ključne reči: poliestar, sposobnost bojenja, smanjenje mase, pamuk, natrijum-hi-droksid.   

COMPARATIVE STUDY OF EXHAUSTION AND PAD-STEAM METHODS FOR IMPROVEMENT OF HANDLE, DYE UPTAKE AND WATER ABSORPTION OF POLYESTER/COTTON FABRIC

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