Durable Hydrophobic Treatment of Cotton Fabrics with Glycidyl

Research Note pubs.acs.org/IECR

Durable Hydrophobic Treatment of Cotton Fabrics with Glycidyl Stearate Emil Ioan Muresan,†,* Gina Balan,‡ and Vasilica Popescu‡ †

Faculty of Chemical Engineering and Environment Management, ”Gheorghe Asachi” Technical University, 73 Boulevard Mangeron, Iasi-700050, Romania ‡ , Faculty of Textiles, Leather Engineering and Industrial Management, ”Gheorghe Asachi” Technical University, 53 Boulevard Mangeron, TEX 1 Building, Iasi-700050, Romania ABSTRACT: Glycidyl stearate (GS) obtained by reaction of sodium stearate with epichlorohydrin in the presence of dimethylformamide (DMF) was used for durable hydrophobic finishing of cotton fabrics. The presence of glycidyl stearate on hydrophobic treated cellulose fiber was put into evidence by FTIR, SEM, and EDX analyses. The hydrophobicity of the treated sample was assessed by determination of the water contact angles and absorption times of the water drops. The effects of glycidyl ester concentration, temperature, and duration of curing treatment on hygroscopicity, air permeability, whiteness, and tensile strength were evaluated. The best results regarding the use of glycidyl stearate as a hydrophobization agent (water contact angle is 152, absorption time of water drop is 200 min) were obtained for the samples treated with 60 g/L glycidyl stearate and 10 g/L NaOH at 120 °C condensation temperature for 20 min. The durability of hydrophobic treatment was also examined.

1. INTRODUCTION

2. EXPERIMENTAL PART 2.1. Materials. Sodium stearate was purchased from Sigma Aldrich Co., dimethylformamide from Fluka, Lavotan DSU from Bezema, Tween 80, epichlorohydrin (1-chloro-2,3-epoxypropane) and NaOH from Merck. All the chemicals were used without previous purification. Desized, scoured, and bleached 100% cotton fabric (170 g/m2) was used in this study. 2.2. Synthesis of Glycidyl Stearate (GS). Sodium stearate (27,325 g) was treated with epichlorohydrin (7 mL) in the presence of DMF (120 mL) and heated under stirring at 105 °C for 5 h. The final reaction mixture was vacuum filtered, washed with distilled water (60 °C), and vacuum-dried on a rotavapor. The yield of glycidyl stearate determined by Jay method was 25.6 g.24 The obtaining reaction of 2,3-epoxypropyl stearate (glycidyl stearate) is shown in Scheme 1. 2.3. Obtaining of Emulsions and Treating of Cotton Fabric. The emulsions used to treat the cotton fabric were obtained by mixing glycidyl stearate (20, 40 and respectively 60 g/L) with 2% aqueous solution of nonionic tenside (Tween 80) at 70 °C. The treatment of cotton samples was carried out in two steps. In the first stage the impregnation with emulsion at 70 °C was performed, followed by pad squeezing (in order to remove the excess of emulsion). In the second step the fabric treated with emulsion was impregnated in NaOH solutions (5, 10, and respectively, 15 g/L), pad squeezing (squeezing degree, 100%), rolling, wrapping in polyethylene sheet, maintaining for 6 h at room temperature, drying for 20 min at 70 °C, and curing at variable temperatures and durations. In the presence of NaOH catalyst, glycidyl stearate reacts with OH functional groups of cellulose resulting an ether linkage (Scheme 2).

Materials based on cellulose fibers are interesting because of their broad field of applications including clothes, medical textiles, technical textiles, and in-door or out-door textiles. Various chemicals have been used to confer hydrophobicity to textile substrates. These include waxes, aluminum and zirconium soaps, metal complexes, and pyridinium compounds.1 The disadvantages of these compounds are the low washing fastness and the low permeability to air and vapors. Hydrophobic cotton fabrics were obtained using hydrophobic compounds such as silicones2−4 and fluorocarbon compounds.5−10 Fluorocarbon compounds were widely used due to their ability to provide good performance in water and oil repellence. However, disadvantages posed by fluoroalkyl compounds are the high costs, the potential risk for human health in case of skin contact, and environmental concerns. The fluoropolymer repellent in combination with different monomers with a reactive group or fluorocarbon copolymer/SiO2 materials were used to treat cotton fabrics in order to obtain sustainable hydrophobicity.11−15 In recent years, the studies regarding the modification of hydrophobicity for the woven cellulosic fibers focused on the use of hybrid organic/ inorganic materials elaborated through sol gel routes.16−22 Dankovich and Ksich studied hydrophobic modification of cellulose fibers with triglycerides of vegetable oils.23 To obtain sustainable hydrophobic surfaces by a chemical reaction between cellulose hydroxyls and reactive groups of some hydrophobic compounds is the most desirable. The objectives of this paper are the synthesis of glycidyl stearate and its application on cellulosic fibers fabrics in order to confer them hydrophobic properties. Glycidyl stearate was obtained by the reaction between sodium stearate and epichlorohydrin. The treating of cotton fabric was performed using a padding technique. Properties evaluation and surface characterization of treated samples were reported. © 2013 American Chemical Society

Received: Revised: Accepted: Published: 6270

January 21, 2013 April 11, 2013 April 20, 2013 April 20, 2013 dx.doi.org/10.1021/ie400235u | Ind. Eng. Chem. Res. 2013, 52, 6270−6276

Industrial & Engineering Chemistry Research

Research Note

Scheme 1. Obtaining Reaction of Glycidyl Stearate

Scheme 2. Reaction of Glycidyl Stearate with Cellulose Fiber

Table 1. Hydrophobic Properties of Fabric Samples treatment conditions sample no.

glycidyl stearate (g/L)

untreated sample 1. 20 2. 40 3. 60 4. 40 5. 40 6. 40 7. 40 8. 40 9. 40 a

NaOH (g/L)

curing temperature (°C)

curing time (min)

contact angle (degrees)

absorption time of water droplet (min)

spray rating

10 10 10 5 15 10 10 10 10

120 120 120 120 120 110 130 120 120

20 20 20 20 20 20 20 10 30

a 139 146 152 139 152 128 151 128 151

b 109 179 200 158 174 76 199 69 198

0 70 100 100 90 100 50 100 50 100

Cannot be measured. bAbsorption time of the water droplet for the untreated sample is 2 s.

2.6. Analyses. 2.6.1. FTIR. FTIR analyses were carried out on a multiple internal reflectance accesory (SPECAC, USA) with ATR KRS-5 crystal of thalium bromide-iodide, having 25 reflections and the investigation angle of 45°. This accessory device was attached to the FTIR IR Affinity-1 Shimadzu (Japan) spectrophotometer; the spectra registration was realized with 250 scans in the range of 4000−2800 cm−1 and the range of 1800−500 cm−1, respectively. 2.6.2. SEM and EDX. A Quanta 200 3D Dual Beam electron microscope was used, which is a combination of two systems (SEM and FIB), by which three-dimensional images could be obtained by sending an electron beam on the untreated and treated samples. Moreover, by using the X-ray radiation with dispersive energy (EDX), the elemental analyses were possible

The treated samples were washed with 2% Lavotan DSU (30 min at 70 °C), rinsed with distilled water at 70 °C and then dried. 2.4. Evaluation of Hydrophobicity. The hydrophobicity of treated samples was put into evidence through the values of contact angle that the water drop form with the surface of treated samples and by the time where a drop of water placed at the fabric surface is completely absorbed by this. Static water contact angles of the sample surfaces were measured at 22 °C in ambient air using an automatic contact angle goniometer equipped with a flash camera (model DSA 100, Kreuss, Germany) applying a sessile drop method. For determination of water absorption time (according to AAATC Test Method 79) 10 droplets of water were poured with a micropipet on the surface of treated samples from a distance of 2 cm. The average volume of water droplet was about 30 μL. The droplets were placed in different places on the surface of the fabric; the final result regarding the water absorption time by the fabric was considered as an average of 10 measurements. The water repellency of treated fabrics was additionally assessed by spray tests according to AATCC Test method 22-2010. The treated samples were laid 15 cm under a spray nozzle at a 45° angle and 250 mL of water was poured onto the fabric through the spray nozzle. The duration of exposure was 30 s. The wetting surface of the treated samples was compared with AATC photographic standards (spray rating “0” indicates complete wetting, where ratings of 50, 70, 90, and 100 indicate the gradual increase in resistance to wetting with water). 2.5. Durability of Hydrophobic Treatment. The durability of hydrophobic treatment was assessed by the values of water droplets absorption times on the surface of hydrophobic treated samples. These values were determined after each washing cycle. The washings were carried out at 60 °C for 30 min, according to the standard test EN ISO 105-CO6:1999.

Figure 1. Photographs of water droplets placed on the surface of treated samples (sample numbers correspond to those indicated in Table 1). 6271

dx.doi.org/10.1021/ie400235u | Ind. Eng. Chem. Res. 2013, 52, 6270−6276


Research Note

where Pa is air permeability, p is pressure to whom the air is passed through the fabric, expressed in mm H2O, V is air flow rate (L/h) that passes through a certain surface of the fabric, and A is air absorption surface. 2.6.4. Hygroscopicity. Hygroscopicity (samples capacity to retain water vapors) was determined according to Standard EN ISO 12571:2000 using the following equation: H = 100

for the identification of surface characteristics and a high resolution chemical analysis. 2.6.3. Air Permeability. The measurements for air permeability of treated and untreated samples were carried out on ATL-2 Metrimpex Hungary apparatus according to Standards ASTM D 737-96. The air permeability is calculated with the following equation: 3

(2)

3. RESULTS AND DISCUSSIONS The main parameters (NaOH concentration, glycidyl stearate concentration, curing temperature, and curing time) that

2

(m /min·m )

(%)

where H is the hygroscopicity, Wu is the mass of the wet sample (stored for 24 h in atmosphere with 100% relative humidity), and Wc is the mass of the conditioned sample (stored for 24 h in standard atmosphere with 65% relative humidity). 2.6.5. Whiteness. The whiteness values for the treated samples and for the blank sample were determined on a Spectroflash 300 DATACOLOR spectrophotometer, using the Micromatch 2000 program. 2.6.6. Tensile Strength. The tensile strengths of treated and untreated fabrics were determined on warp direction with a Zwick, Roell 2005, Germany 2008 dynamometer according to DIN EN 13934-1 133 standard.

Figure 2. Profile of a water droplet on the treated cotton.

V Pa·p = 60·A

Wu − Wc Wc

(1)

Figure 3. Effect of working parameters on durability of hydrophobic treatment. 6272



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Figure 4. The FTIR spectra of untreated cotton sample (1), hydrophobic treated cotton sample (2), and glycidyl stearate (3). For spectra 3, sample 2 was treated with 40 g/L glycidyl stearate and 10 g/L NaOH, for 20 min at 120 °C and then washed.

influence the hydrophobic treatment and characteristics of treated fabric were studied. 3.1. Evaluation of Treated Samples Hydrophobicity. Hydrophobic treatments were carried out using emulsions prepared according to the procedure described in paragraph 2.3. For the samples treated in this way, the contact angles between the fabric surface and water droplets, the absorption times of water droplets deposited on the fabric surface, and spray ratings were determined. The results obtained are presented in Table 1. The measurements of contact angles were performed 20 s later after the water drops were placed on the cotton fabric. To highlight the hydrophobicity of treated samples, Figures 1 and 2 are show the photographic images of water drops for which the wetting angles were read according to Table 1, and the profile of a 30 μL water drop at different times since its deposition on the fabric surface. The hydrophobicity gained by textile material can be explained by the presence of glycidyl stearate hydrocarbon chains inserted through the etherification reaction between −OH groups from cellulose and the oxirane ring of glycidyl stearate in the presence of NaOH as catalyst. The highest values for the water contact angle, absorption time of water droplets, and for spray rating were obtained for high glycidyl stearate concentration, high temperature, and long curing time. 3.2. Durability of the Hydrophobic Treatment. To assess the durability of hydrophobic treatment, samples were subjected to repeated washings. After each washing/drying cycle, the absorption times of water droplets deposed on the sample surface (that represent the mean value of 10 measurements) were determined. The results obtained are shown in Figure 3. The maintaining of water droplets absorption times (after repeated washing cycles) at approximately constant values proves the

durability of hydrophobization treatment carried out with glycidyl stearate for curing temperatures higher than 120 °C and curing times higher than 20 min. Durability of treatment, respectively, the good fixing capacity of glycidil stearate at the optimized reaction conditions, is explained by formation of ether linkages between the oxiranic ring of glycidyl stearate and OH groups of cellulosic fiber. Curing temperatures lower than 120 °C and curing times lower than 20 min do not favor the efficient fastening of glycidyl stearate and therefore the absorption time of water droplets decreases after the first washing cycles. 3.3. Analyses. 3.3.1. FTIR Analyses. Figure 4 are shows the FTIR-ATR spectra of glycidyl stearate, an untreated cotton sample, and a hydrophobic treated cotton sample. The etherification reaction of glycidyl stearate with the HO groups of cellulose is proven by the disappearance of peaks from 1047, 987, 941, 875, and 717 cm−1 (characteristic to epoxy group from stearate) and by an increase of intensity of peaks at 1053 cm−1 and 1029 cm−1 typical for etheric C−O bonds.25 The grafting of glycidyl stearate on cellulosic fiber is also highlighted by the appearance of peaks from 2916 cm−1 and, respectively, 2850 cm−1 that correspond to symmetric and antisymmetric stretching of the CH2 group from the hydrocarbonate chain of glycidyl stearate and by an absorption band located at 1739 cm−1 that corresponds to the esteric group of glycidyl stearate (FTIR spectra of treated cotton sample, curve 2 from Figure 4). 3.3.2. SEM and EDX Analyses. By means of electron microscope, advanced qualitative (using EDX 32/SEM) and quantitative analyses were carried out (Figure 5). The SEM image shows the surface morphology of treated and untreated cotton samples. As can be noticed from Figure 5a, the untreated cotton fibers have a smooth surface, while the presence of hydrophobic product can be noticed on the surface of treated fibers (Figure 5b). 6273



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Figure 5. SEM and EDX analyses. The analyzed sample was treated with 40 g/L glycidyl stearate and 10 g/L NaOH, for 20 min at 120 °C and then was washed. MF = magnitude factor.

3.4. Features of Treated Materials. The chemical compounds used for treatments (glycidyl stearate and NaOH), the temperature, and the treating period can modify the properties of cotton fabric. For this reason the effect of these parameters on air permeability, hygroscopicity, whiteness, and tensile strength of treated cotton fabric were also studied. The values obtained for treated and untreated samples are presented in Table 2. 3.4.1. Hygroscopicity. The decrease of hygroscopicity for treated samples is mainly due to screening of hydrophilic groups by hydrophobic chain from glycidyl stearate. The hygroscopicity values are consistent with those obtained for the water droplets absorption times and for the water droplets contact angles, namely: the lowest values of hygroscopicity correspond to the higher values of water droplets absorption times and respectively to the higher values of wetting contact angles (Table 1). 3.4.2. Air Permeability. The air permeability calculated as a mean of 10 determinations reveals the cotton fabric capacity to

The EDX detector was calibrated using two standards supports (Cu and Al). In the first stage the manual calibration was performed in order to bring the Cu and Al elements to the correct energy on the spectrum using offset control (to adjust the low-energy peak) and the gain control (to adjust the high-energy peak) followed in the second stage by autocalibration of the EDX spectrum to obtain accurate Quant results. Thus a spectrum was created as a standard. After calibration, hydrophobic fabric samples were fixed on Al support and then placed into the unit to be analyzed. The results of EDX elemental analyses corresponding to the previously shown SEM images are presented in Figure 3c,d. The EDX analysis for the untreated sample shows only the presence of C and O elements (Figure 5c). In the case of the treated sample (Figure 5d) one notices an increase in carbon content and a decrease in oxygen content. The change of C/O ratio in the favor of carbon is due to insertion of the hydrocarbonate radical from glycidyl stearate on the surface of the treated sample. 6274



Research Note

Table 2. Comfort Properties of Cotton Fabric treatment conditions GS (g/L)

NaOH (g/L)

cotton fabric properties

curing temperature (°C)

curing time (min)

hygroscopicity (%)

120 120 120 120 120 110 130 120 120

20 20 20 20 20 20 20 10 30

14.32 13.93 13.77 15.44 14.51 15.89 13.48 14.32 12.74 17.38

20 10 40 10 60 10 40 5 40 15 40 10 40 10 40 10 40 10 untreated sample

4. CONCLUSIONS A hydrophobization process by chemical fixation of glycidyl stearate on cotton fabric was accomplished. The presence of glycidyl stearate on treated cotton fabric was confirmed by SEM, EDX, and FTIR analysis. The effectiveness of hydrophobic treatment performed with glycidyl stearate is proven by high values of wetting angles and by a long period of time that the water droplet can stay on the treated fabric surface. The whiteness and the air permeability of treated samples do not change significantly compared to the untreated sample. The hygroscopicity and the tensile strength are lower for the treated samples, their values depending on treatment conditions (temperature, time, NaOH concentration). The durability of the hydrophobic treatment is proven by the absorption times of water droplets whose values do not change significantly after 10 washing cycles. AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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32.69 31.66 30.53 32.16 30.16 32.66 31.26 31.83 30.66 34.66

75.9 74.8 74.6 77.2 74.8 75.6 65.9 76.2 63.1 79

tensile strength (N) 184.9 184.4 184.3 191.6 172.4 188.2 159 192.6 165 195.2

(2) Nishi, K.; Jeong, D. S.; Tokuyama, T.; Itazu, T.; Miyaji, Y.; Wakida, T. Change of surface characteristic of cotton and polyester fabrics treated with silicone resin by washing and subsequent heat treatment. Sen-I Gakkaish. 2005, 61 (11), 309−312. (3) Periyasamy, S.; Khanna, A. Silicone multifunctional finishing. Melliand Int. 2008, 1, 54−55. (4) Thumm, S.; Sielemann, D.; Stainica, C.; Jiang, L. Technology and application of modern hybrid silicones. Melliand Int. 2008, 3, 180−182. (5) Cerne, L.; Siminic, B. Influence of repellent finishing on the surface free energy of cellulosic textile substrates. Text. Res. J. 2004, 74 (5), 426− 432. (6) Gadkari, R. G. Use of fluoropolymer emulsions in textile industry: Chemistry, classification and application. Colourage 2000, 47 (10), 15− 16. (7) Lammermann, D. Fluorocarbons in textile finishing. Melliand Textilber. 1991, 72 E 380, 949−954. (8) Grottenmüller, R. FluorocarbonsAn innovative auxiliary for the finish of textile surfaces. Melliand Textilber. 1998, 79 (10) E 195, 743− 746. (9) Otto, P. Novel fluoropolymers for textile finishing. Melliand Textilber. 1991, 72(5) E 155−156, 378−380 (10) Sato, Y.; Tomiji, T.; Tokino, S.; Niu, S.; Ueda, M.; Mizushima, H.; Takekoshi, S. Effect of crosslinking agents on water repellency of cotton fabrics treated with fluorocarbon resin. Text. Res. J. 1994, 64 (6), 316− 320. (11) Shao, H.; Sun, J. Y.; Meng, W. D.; Qing, F. L. Water and oil repellent and durable press finishes for cotton based on a perfluoroalkylcontaining multi-epoxy compound and citric acid. Text. Res J. 2004, 74 (10), 851−855. (12) Huang, P. Y.; Chao, Y. C.; Liao, Y. T. Enhancement of the water repellency durability of the fabrics treated by fluorinated nanocopolymer emulsions. J. Appl. Polym. Sci. 2007, 104 (4), 2451−2457. (13) Yeh, J. T.; Chen, C. L.; Huang, K. S. Preparation and application of fluorocarbon polymer/SiO2 hybrid materials, part 2: Water and oil repellent processing for cotton fabrics by sol−gel method. J. Appl. Polym. Sci. 2007, 103 (5), 3019−3024. (14) Castelvetro, V.; Francini, G.; Ciardelli, G.; Ceccato, M. Evaluating fluorinated acrylic latices as textile water and oil repellent finishes. Text. Res. J. 2001, 71 (5), 399−406. (15) Zhao, T.; Zheng, J.; Sun, G. Synthesis and applications of vegetable oil-based fluorocarbon water repellent agents on cotton fabrics. Carbohydrate Polym. 2012, 89 (1), 193−198. (16) Mahltig, B.; Bottcher, H. Modified silica sol coatings for water repellent textiles. J. Sol−Gel Sci. Technol. 2003, 27 (1), 43−52. (17) Mahltig, B.; Audenaert, F.; Böttcher, H. Functionalisation of textiles by inorganic sol gel coating. J. Mater. Chem. 2005, 15, 4385− 4398. (18) Fir, M.; Vince, J.; Šurca Vuk, A.; Vilcnik, A.; Jovanovski, V.; Mali, G.; Orel, B.; Simoncic, B. Functionalisation of cotton with hydrophobic urea/polydimethylsiloxane sol-gel hybrid. Acta Chim. Slov. 2007, 54, 144−148. (19) Quan, Z.; Qinwen, G.; Yuliang, G.; Charles, Q. Y.; Li, S. Modified silica sol coatings for highly hydrophobic cotton and polyester fabrics

permit the air to pass through it. By applying glycidyl stearate one notices a slight decrease of air permeability values compared to the values of the untreated sample due to reduction of the interstices from the fibers of fabric (Table 2). However, this decrease is not significant since by treating with glycidyl stearate a full coverage of the surface of cotton fabric does not occur. 3.4.3. Whiteness. The variation of NaOH and respectively glycidyl stearate concentration used in the treatments do not significantly change the whiteness values. A decrease of whiteness is noticed for high temperatures (130 °C) and long curing times (30 min). 3.4.4. Tensile Strength. The values of tensile strength on the warp direction (calculated as mean of 10 determinations) decrease for high NaOH concentrations, high temperatures, and long treatment times. For this reason, it can be concluded that an effective hydrophobization treatment with a minimum degradation of textile fabric can be carried out under the following conditions: 40−60 g/L GS, 10 g/L NaOH, temperature of 120 °C for 20 min.

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air permeability (m3/m2·min) whiteness (%)

REFERENCES

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using a one-step procedure. Ind. Eng. Chem. Res. 2011, 50 (10), 5881− 5888. (20) Pipatchanchai, T.; Srikulkit, K. Hydrophobicity modification of woven cotton fabrics by hydrophobic fumed silica coating. J. Sol−Gel Sci. Technol. 2007, 44, 119−123. (21) Lihui, X.; Wei, Z.; Xu, B.; Zaisheng, C. Fabrication of superhydrophobic cotton fabrics by silica hydrosol and hydrophobization. Appl. Surf. Sci. 2011, 257 (13), 5491−5498. (22) Senthelkumaar, S.; Thamiz Selvi, R. Functionalized nano finishing to cotton fabrics by sol-gel process. Melliand Int. 2008, 2, 110−112. (23) Dankovich, T. A.; Hsieh, Y. L. Surface modification of cellulose with plant triglycerides for hydrophobicity. Cellulose 2007, 14 (5), 469− 480. (24) Jay, R. Direct titration of epoxy compounds and azirides. Anal. Chem. 1964, 36, 667−668. (25) González, M. G.; Cabanelas, J. C.; Baselga J. Applications of FTIR on Epoxy ResinsIdentification, Monitoring the Curing Process, Phase Separation and Water Uptake. Infrared Spectroscopy−Materials Science, Engineering and Technology, (e-book);Theophile,T., Ed.; InTech: 2012; ISBN 978-953-51-0537-4; DOI 10.5772/36323.

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Durable Hydrophobic Treatment of Cotton Fabrics with Glycidyl

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