Article pubs.acs.org/IECR
Synthesis of Nanoscale Binders through Mini Emulsion Polymerization for Textile Pigment Applications L. A. W. Abdou,† M. M. El-Molla,*,† O. A. Hakeim,† M. S. El-Gammal,† and Renzo Shamey‡ †
Textile Research Division, National Research Centre, Dokki, Box 12622, Cairo, Egypt College of Textile, North Carolina State University, 2401 Research Drive, Box 8301, Raleigh, North Carolina 27695, United States
‡
ABSTRACT: Different mini emulsion polymerizations were carried out with the combination of different concentration of anionic surfactant such as sodium dodecyl sulfate (SDS) or hydrophobic alkane such as (hexadecane), and/or different monomer ratios. The best comonomers composition that would lead to the best polymer latex properties to obtain nanoscale polymer latexes was studied. The polymer latexes in a size range between 156 and 65 nm by varying the SDS concentrations from 2 to 6 wt % were obtained, and also the particle size of the obtained polymer latexes decreases with the increases of hexadecane (HD) concentrations, and the best result was obtained with 4 wt % of a hexadecane. The best polymer latex properties in terms of particle size and binder softness were found in the best monomer ratio of BA:MMA:MAA (17.5:1.5:1.5) as the solid content was adapted to be 20%. Higher K/S values and improved crocking fastness are obtained with printing pastes containing prepared binder.
1. INTRODUCTION Nanotechnology is a ubiquitous technology that has thrived in research and industry. During the past decade, nanotechnology has gained prominent success in different areas such as material science, mechanics, electronics, optics, medicine, plastics, energy, and aerospace.1 Like other industries, nanotechnology generates many additional benefits for the textile industry. The purposes of using nanotechnology in textile and apparel applications are low chemical usage, low energy costs, and less change in physical and mechanical properties. The current applications of nanotechnology in the textile industry include fabric softness, durability, and breathability, water repellency, fire retardency, antimicrobial resistance, dyeing, coating, electronic textiles, fiber modification, and value added applications.2 Nanoscale materials can be obtained from confined nanometric structures, such as micelles, liquid crystals, and nanodroplets.3 The oil droplets of the mini emulsions can be used as nanoreactors for chemical reactions, such as polymerization, resulting in polymeric nanoparticles. For instance, nanoscale polymer latex particles could be obtained via radical polymerization of relatively stable oil droplets in a size range between 30 and 500 nm prepared by shearing system containing oil, water, a surfactant, and a so-called costabilizer. This concept is known as mini emulsion polymerization.4 One of the most important tricks in mini emulsions is the addition of an agent called costabilizer that dissolves in the dispersed phase but is insoluble in the continuous phase, which results in a considerable stability of the droplets against the diffusional degradation. Typically, these costabilizers are longchain alkanes or alcohols. Also, the surfactant is necessary to retard droplet coalescence. However, the utilization of a high shearing system such as ultrasonic processor or ultra high shear homogenizer is critical for the formation of stable mini emulsion droplets in a size range of 30−500 nm during the emulsification process.5−8 On the other hand, pigment coloration is one of the most important textile coloration methods. Advantages of this method © 2013 American Chemical Society
include simple procedures, applicability to all textile fabrics, and extensive color range with excellent fastness.9 Pigment fixation on textiles relies on a binding agent that requires a curing process to hold the pigments on a textile fabric. The binding agents are polymer or preferably copolymers of unsaturated monomers such as ethyl acrylate, butyl acrylate, styrene-acrylo-nitril, vinyl acetate, butadiene, etc. However, pigment coloration has some industrial and ecological problems such as relatively high temperature cure, stiff hand, poor crock fastness, formaldehyde emissions, and clogging the nozzles and screens in both textile inkjet and screenprinting processes. These disadvantages are related to the binding agent. Thus, to improve the quality of the textile pigmented colored goods, the overall properties of the binding agents should be improved.10−13 The aim of this work was to prepared nanoscale binders by mini emulsion polymerization to examine its viability for the textile pigment coloration.
2. EXPERIMENTAL SECTION 2.1. Materials. 2.1.1. Fabric. 100% polyester knitted fabric of 150 g/m2 was supplied by a private sector company. 100% scoured bleached cotton fabric of 140g/m2 was supplied by a private sector company. 2.1.2. Dyestuffs. C.I. Pigment orange 16 and C.I. Pigment blue 15 as a pigment were supplied by Daico Co., Switzerland. 2.1.3. Chemicals. Butyl acrylate (BA), methyl methacrylate (MMA), and methacrylic acid (MAA) were provided by Sigma Aldrich and were distilled under reduced pressure before the polymerization. Potassium per sulfate (KPS) was purified by recrystallization from water. Sodium dodecylsulfate (SDS) and hexadecane (HD) were provided by Sigma Aldrich. Received: Revised: Accepted: Published: 2195
June 27, 2012 September 23, 2012 January 16, 2013 January 16, 2013 dx.doi.org/10.1021/ie301705u | Ind. Eng. Chem. Res. 2013, 52, 2195−2200
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2.1.4. Thickeners. Alco print was used as thickening agents, supplied by Berssa, Turkey. 2.1.5. Binders. The synthesized binder that has the best polymer latex properties in terms of particle size and binder softness was found in the best monomer ratio of BA:MMA:MAA (17.5:1.5:1.5) as the solid content was adapted to 20%. Commercial Imperon binder MTB based on acrylate (∼1.1 μm) was supplied by Hoechst, Germany. 2.2. Methods. 2.2.1. Mini Emulsion Polymerization. A 20 g sample of butyl acrylate, methyl methacrylate, methacrylic acid, and 0.8 g of costabilizer (hexadecane) were mixed and added to a solution of SDS (4 wt %) and 10 mM sodium bicarbonate. After being stirred for 20 min by magnetic stirring, the mini emulsion was prepared by ultrasonicating the emulsion for 10 min, with an ultrasonic cell crusher of model JY92-II by Scientz Biotechnology Co, Ltd. To reduce any rise in temperature that may occur during the emulsification process, the beaker containing the mini emulsion mixture was immersed in an ice bath. For polymerization, the temperature was increased to 70 °C, and 180 mg of KPS was added. The time between mini emulsification and initiation was minimized to 5 min to reduce the droplet degradation (Ostwald ripening) period. The initial charge and monomer feeds were protected with nitrogen during the polymerization. The reaction is usually completed after 3 h. The theoretical solid content of the latex product is approximately 20%. 2.2.2. Preparation of Printing Pastes. The pigment printing pastes were prepared according to the following recipe: pigment bindera thickener distilled water a
3. RESULTS AND DISCUSSION 3.1. Effect of Surfactant on the Particle Size. To obtain nanoscale polymer latexes, different mini emulsion polymerizations were carried out with the combination of anionic surfactant, sodium dodecyl sulfate (SDS). Mini emulsions with different SDS concentrations were prepared (at 20% solid content, 4 wt % of hexadecane, and 10 min of ultrasonic). The effect of SDS concentrations on the particle sizes of the obtained nanoscale polymer latexes is represented by Table 1 and Figure 1. It is clear Table 1. Effect of Different Sodium Dodecyl Sulfate Concentrations on Particle Size of Mini Emulsions with Fixed 20% Solid content, 4 wt % of Hexadecane, and 10 min of Ultrasonic SDS concn (wt %)
particle size (nm) based on TEM
2 4 6 8
156a 75 74 65
a
Particle size of the samples was determined by accounting the mean of adjacent six particles.
from Table 1 that as SDS concentrations increase, the particle sizes of the polymerized particles decrease. The particle size decreases by increasing the SDS concentration; this may be due to the decreasing of the surface tension of the mini emulsion by increasing the SDS concentration, which leads to very tiny stable droplets. During polymerization, a copy of the stable droplets was converted to latex polymers in a size range between 156 and 65 nm by varying the SDS concentration from 2 to 6 wt %. 3.2. Effect of Hydrophobic (Hexadecane) Concentrations on the Latex Particle Size. Mini emulsions have been stabilized with long chain alkanes or alcohols. The inclusion of approximately 4 wt % of a hexadecane can significantly reduce the diffusional degradation of an emulsion. To examine the effect of hydrophobicity on the formation of stable mini emulsion droplets in a size range between 50 and 500 nm, different concentrations (2, 4, and 6 wt %) of hexadecane were added to the mini emulsions at a constant 20% monomer solid content, 4 wt % SDS, and 10 min ultrasonic time. The effects of HD concentrations on the particle sizes of the obtained nanoscale polymer latexes are represented by Table 2 and Figure 2. It is clear from Table 2 that the particle size of the obtained polymer latexes decreases with the increases of HD concentrations. Also, the best result was obtained with 4 wt % of a hexadecane; this may be due to the mini emulsions being stabilized with the increase in long chain hexadecane. 3.3. Effect of Monomer Ratios on the Particle Size Formation. Different mini emulsions were prepared with different monomer ratios to get the best comonomers composition, which would lead to the best polymer latex properties in terms of particle size and binder softness (Table 3). It was found that the best monomer ratio was BA:MMA:MAA (17.5:1.5:1.5) as the solid content was adapted to be 20%. 3.4. Infrared Spectroscopy. Figure 3 shows the FTIR of the polymer latex. The bands found in the infrared spectra are characteristic of the acrylic polymer. From Figure 3, it is noticed that the bands of moderate intensity related to methyl and methylene absorptions are observed in the spectra (at 2957 and 2874 cm−1). Bending of methyl groups is observed at 1481 cm−1 (CH3 and CH2 bending), 1448 cm−1 (asymmetric bending of
20 g X 25 g Y 1000 g
The binders’ concentrations were 2.5%, 5%, and 10%.
2.2.3. Printing Techniques. The printing pastes containing the ingredients were prepared. The homogenized printing pastes were applied to the fabrics using a flat screen technique. 2.2.4. Pigment Fixation. The samples printed were dry and thermo fixed at a temperature of 155 °C for a period of 4 min. 2.3. Measurements and Analysis. 2.3.1. Particle Size. The particle size of the dry film of latexes was determined with a transmission electron microscope (TEM) JEOL JEM-1200EX. 2.3.2. IR Spectroscopy. The final polymer latex was generally observed by FTIR spectroscopy using infrared spectrophotometer, Perkin-Elmer, system 2000FT-IR. 2.3.3. Differential Scanning Calorimeter. DSC curves were recorded on a Perkin-Elmer Pyris1 differential scanning calorimeter in N2 with the scanning rate of 20 °C/min, and the same sample was subjected to twice heating from 50 to 200 °C. 2.3.4. Color Strength Measurements. The relative color strength of the prints, expressed as K/S value14 of the colored samples, was determined by reflection measurements using data color international model SF 500, U.S. 2.3.5. Surface Roughness. The surface roughness of the binder film samples was measured by surface roughness measuring instrument SE 1770X, Kostaka Lab, Co. 2.3.6. Fastness Properties. Fastness to washing,15 rubbing,16 and perspiration17 was assessed according to the standard methods. 2196
dx.doi.org/10.1021/ie301705u | Ind. Eng. Chem. Res. 2013, 52, 2195−2200
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Figure 1. Transmission electron microscope images of the mini emulsions with different sodium dodecyl sulfate concentrations.
C−O bond. The presence of hydroxyl groups is very evident in the spectra at 3433 cm−1.18 3.5. Differential Scanning Calorimeter (DSC) Analyses. DSC curves of sample 3 (monomer ratio was BA:MMA:MAA (17.5:1.5:1.5) as the solid content) were shown in Figures 4 and 5. It is clear from Figure 4 that the curve had one endothermic slope and one sharp endothermic peak. The slope indicated that the glass transition temperature (Tg) of sample 3 (monomer ratio was BA:MMA:MAA (17.5:1.5:1.5) as the solid content) was at −15 °C. The onset point of endothermic peak showed that the cross-linking reaction happened at 48.13 °C as shown in Figure 5 providing the information that the printed fabrics should be subjected to heat treatment at 50 °C for strong pigment-fixing. The cross-link king reaction of latexes (BA:MMA:MAA (17.5:1.5:1.5)) may be suggested as follows: The propagation
Table 2. Effect of Different Hexadecane Concentrations on Particle Size of Mini Emulsions with Fixed 20% Solid Content, 4 wt % of SDS, and 10 min of Ultrasonic HD concn (wt %)
particle size (nm) based on TEM
0 2 4 6
560 170 75 75
CH3), and 1388 cm−1 (symmetric bending of CH3). The intense bands at 1735 and 1230 cm−1 are due to the absorption of the highly polar carboxyl groups present in the polymer, which presents axial deformation mode of CO at 1735 cm−1, while the band at 1230 cm−1 is attributed to the axial deformation of the 2197
dx.doi.org/10.1021/ie301705u | Ind. Eng. Chem. Res. 2013, 52, 2195−2200
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Figure 2. Transmission electron microscope images of the mini emulsions with different hexadecane concentrations.
16, and C.I. Pigment blue 15, respectively. The results show that both the color strength and the fastness properties of the printed samples depend on the type of binder used. Prepared binder gave printed samples with much higher color strength results as compared to those obtained upon using commercial binder at the same conditions. The rubbing fastness for printed samples using prepared binder is an improvement as compared to samples printed using commercial binder. The rubbing fastness ranged from good to very good in case of using the prepared binder and ranged from moderate to good in case of using commercial binder, and this is may be due to the prepared binder in nanosize, which leads to more fixation of the pigment onto the surface of the fabrics. Moreover, washing and perspiration fastness properties were in the range of very good to excellent for fabric printed using the prepared binders in the printed pastes. It was also shown that all of the samples printed using the nanoscale binder acquire a soft handle as it is clear in Tables 4 and 5. The particle size of the latex is the main reason for performance improvements of binder latex, and the soft polymer composition
Table 3. Effect of Monomers Ratio on the Particle Size Formation monomers ratio BA:MMA:MAA
solid content
particle size (nm)
handle
15:2.5:2.5 16:2:2 17:1.5:1.5 18:1:1
17.65% 17.43% 17.88% 18.22%
65 56 75 88
hard hard soft soft
of polymer chains is based on butyl acrylate monomer through the addition reaction on the vinyl group of BA, followed by crosslinking between the polymer chains through either MMA or MAA or both of them, and the termination reaction was carried out by adding the terminating agent, hydroquinone. 3.6. Textile Pigment Applications. Tables 4 and 5 show the color strength and overall fastness properties of screenprinted cotton and polyester fabrics that were thermally cured (at 155 °C for 4 min) with pigment printing pastes containing 2.5%, 5%, and 10% of binders, as well as 2% C.I. Pigment orange
Figure 3. FTIR spectroscopy of the polymer latex. 2198
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Figure 4. Differential scanning calorimeter (DSC) curve of the polymer latex.
Figure 5. Differential scanning calorimeter (DSC) curve of the polymer latex.
Table 4. Color Strength and Overall Fastness Properties of Screen-Printed Cotton and Polyester Fabrics with C.I. Pigment Orange 16a washing fastness K/S
crocking fastness polyester
cotton
polyester
handle
concentration of binder
cotton
polyester
Sc
Sw
Alt
Sc
Sw
Alt
dry
wet
dry
wet
cotton
polyester
2.5%
8.61 9.46 9.11 10.65 9.65 10.21
4.6 5.21 6.61 8.61 7.11 8.36
4−5 4−5 4−5 4−5 4−5 4−5
4−5 4−5 4−5 4−5 4−5 4−5
4−5 4−5 4−5 4−5 4−5 4−5
4−5 4−5 4−5 4−5 4−5 4−5
4−5 4−5 4−5 4−5 4−5 4−5
4−5 4−5 4−5 4−5 4−5 4−5
3 3−4 2−3 3−4 3 3−4
2 3 2−3 3 2 3
3 4 3 3−4 3 3−4
2−3 3 2 3 2 3
H S H S H S
H S H S H S
5% 10%
a
cotton
commercial binder nanobinder commercial binder nanobinder commercial binder nanobinder
Sc = staining on cotton, Sw = staining on wool, Alt = alteration of color. H = hash. S = soft. 2199
dx.doi.org/10.1021/ie301705u | Ind. Eng. Chem. Res. 2013, 52, 2195−2200
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Table 5. Color Strength and Overall Fastness Properties of Screen-Printed Cotton and Polyester Fabrics with C.I. Pigment Blue 15a washing fastness K/S
crocking fastness polyester
cotton
polyester
handle
concentration of binder
cotton
polyester
Sc
Sw
Alt
Sc
Sw
Alt
dry
wet
dry
wet
cotton
polyester
2.5%
11.67 15.67 14.49 17. 3 15.8 16.86
8.35 9.48 10.35 12.78 11.11 12.11
4−5 4−5 4−5 4−5 4−5 4−5
4−5 4−5 4−5 4−5 4−5 4−5
4−5 4−5 4−5 4−5 4−5 4−5
4−5 4−5 4−5 4−5 4−5 4−5
4−5 4−5 4−5 4−5 4−5 4−5
4−5 4−5 4−5 4−5 4−5 4−5
3 3−4 2−3 3−4 3 3
2 3 2−3 3 2 3
3 4 3 3−4 3 3−4
2−3 3−4 2 3 2 3
H S H S H S
H S H S H S
5% 10% a
cotton
commercial binder nanobinder commercial binder nanobinder commercial binder nanobinder
Sc = staining on cotton, Sw = staining on wool, Alt = alteration of color, H = hash, S = soft. (9) Eisenlobr, R.; Giesen, V. Pigment printing and ecology. Int. Dyer 1995, 180, 12−16. (10) Galgali, M. R. Environmental impact of textiles. Colourage 1998, 45, 20−22. (11) Jing, L. V.; Min, X.; Shuilin, C. Synthesis and characterization of nonformaldehyde releasing and low-temperature curable binder. AATCC Rev. 2003, 29−32. (12) Smith, H. G.; Gastonia, N. C. Method of screen printing on textile fabrics. U.S. Patent 6,196,126, 2001. (13) Pravinchandra, K. S.; Westlake, O. H. Formaldehyde free print binder. U.S. Patent 5,969,018, 1999. (14) Judd, B. D.; Wyszecki, G. Color in Business, Science and Industry, 3rd ed.; Wiley: New York, 1975. (15) AATCC Technical Manual, Method 8; 1989; Vol. 68, p 1993. (16) AATCC Technical Manual, Method 36; 1972; Vol. 68, p 1993. (17) AATCC Technical Manual, Method 15; 1989; Vol. 68, p 1993. (18) Stuart, B.; George, W.; McIntyre, P. S. Modern Infrared Spectroscopy; John Wiley & Sons: Chichester, 1996; p 106.
has been chosen to suit the textile printing application, which requires the soft handle for printed products.
4. CONCLUSIONS In view of the results presented, the following conclusions may be drawn. The particle size decreases by increasing the sodium dodecyl sulfate (SDS) concentration. During polymerization, a copy of the stable droplets was converted to latex polymers in a size range between 156 and 65 nm by varying the sodium dodecyl sulfate (SDS) concentrations 2−6 wt %. The particle size of the obtained polymer latexes decreases with the increase of hexadecane (HD) concentrations, and the best result was obtained with the 4 wt % of a hexadecane. The best polymer latex properties in terms of particle size and binder softness were found that the best monomer ratio was BA:MMA:MAA (17.5:1.5:1.5) as the solid content was adapted to be 20%. Higher K/S values and improved crocking fastness are obtained with printing pastes containing prepared binder. The washing and perspiration fastness are in the range of very good to excellent for all samples printed with pasts including the prepared binders as well as the commercial one irrespective of the type of fabric.
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AUTHOR INFORMATION
Corresponding Author
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[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
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