Use of the Novel Synthesized Aqueous Binders for Pigment Printing Cotton Fabrics Using Three Modes of Fixation

Use of the synthesized aqueous polyurethane acrylate (no volatile organic compound emission) binders 1-7, in pigment printing of cotton fabrics using silk screen technique. FT-IR spectra of binders via UV curing show the disappearance of ast C=C and δ: =C-H absorption bands from the spectra chart of cured, which proofed the occurrence of cross linking reaction via terminal free acry late double bond. Color strength of printed fabrics depends on binders' type and concentration as well as the fixat ion temperature. The K/S values at lower fixat ion temperatures on using the prepared binders in the printing paste are better than the K/S of fabric printed with paste including the commercial binder at the same condition ( saving energy& money). The fastness properties of the printed samples depend on the type of binder used. The washing and perspiration ranged from good to excellent for all printed samples. Slightly enhancement in K/S values of printed cotton fabric with increase the concentration of aliphatic polyurethane acrylate binders was noticed. The presence of 1% concentration of polyurethane acrylate binders (1-7) in the cotton pigment printing paste, and either UV curing or microwave cured for 3 min. could be considered as optimum conditions. Improved rubbing fastness results for all the printed samples using the synthesized polyurethane acrylate binders in printed paste and UV cured are noticed as compared to those obtained by the traditional thermal curing technique. The results show that these binders can be used safely in preparing printing paste for printing cotton fabrics using pigment dyes.


Introduction
The difference bet ween dyeing processes and pigmentati on is that pigment colored text iles require a curing procedure. Since pig ments do not have an affinity to textiles. Pig ment fixation on text iles relies on binders that require a curing process to hold the pigments on a textile. Conventional curing is a thermal process where pig ment co lored text iles must be dried and then cured with heat to convert the soft organic base (monomer and/or oligo mers) to a tough polymer [1].
Currently, p ig ment print ing is perhaps the most commonly and extensively used technique for printing text iles, due to its obvious advantages [2,3], such as versatility; ease of near final print at the printing stage itself, applicable to almost every kind of fiber or mixture, and the ability to avoid any wash in g p ro cesses after fixat ion [4]. Ho wever p ig ment printing has a few prob lems -relat ively h igh temperatu re cure, stiff hand and poor crock fastness of printed goods.
These disadvantages are related to binder used. Thus, to improve the quality of pig ment goods, the overall properties of the binders need to be improved. Methods to lower the curing temperature have received the most attention because the high temperature cure process not only wastes energy but also runs the risk of destroying substrates that can't endure high temperature processes.
Radiat ion curing technologies(as UV and microwave) are used in much industrial application as well as in the text ile area [5], because of low energy consumption, short start-up period, fast and reliable curing, low environ mental pollution, fixation at roo m temperature, space saving, etc.
Microwave irradiat ion is a well-known method for heating and drying materials and is utilized in many private households and industrial applications. It offers a nu mber of advantages over conventional heating, such as noncontact heating (circu mventing the decomposition of molecules close to the walls of the reaction vessel), instantaneous and rapid heating (resulting in a uniform heating of the reaction liquor), and h ighly specific heating (with the material selectivity emerging fro m the wavelength of microwave irradiation that intrinsically excites dipolar oscillation and induces ionic conduction) [6]. The aim of this work is a imed to investigate the use of the aqueous polyurethane acrylate, Fabrics Using Three M odes of Fixation synthesized in part 1 as binders which having zero vo latile organic emissions (aqueous binders) based on polyethylene glycol with different molecular weight and Polyol mixture, in pig ment printing of cotton fabrics using silk screen technique, and pigment fixation through the polymerization process of the binder by using the thermo fixat ion mode, and the newly adopted UV and microwave techniques.

Curing of Prepared Binders Using UV Rays
Prepared binders of 0.1 g were well mixed with 0 .1% Esacure DP 250, photo in itiator and subjected to UV rays at wave length 254 n m. The resulting cross linking films was investigated by FTIR spectroscopy.

Preparation of Printing Pastes
The pigment printing pastes were prepared according to the following recipe:

Printing Techniques
Two printing pastes containing, the thermal init iator or UV curing photo initiator, in addition to the other ingredients were prepared. The homogenized printing pastes were applied to the fabrics using a flat screen technique.

Pig ment Fixation
The samples printed with the thermal paste (i.e. including the thermal in itiator). were thermo fixed at different temperatures (80,100,120 and160℃) for period of 4 min, while the samples printed with the pastes including the photo initiator , were either fixed using UV rays at wave length 254 nm, for (3,5, and 10 min.), or using micro wave oven at 500 watt for (3,4,5 min ) .

Co lor St rength Measurements
The relative colour strength of the prints, expressed as K/S value [8] of the coloured samples, was determined by reflection measurements using data colour international model SF 500, USA.

Results and Discussion
The aim o f this paper is to investigate the possibility of using the prepared polyurethane acrylate poly mers based on PEG with different molecular weight and polyol mixtu re (part 1) as b inders for p ig ment printing of cotton fabrics, using silk screen techniques. The results were always compared with those obtained when a co mmercial b inder was used in every case under similar conditions. Fixat ions of the prints were achieved v ia thermo fixation (conventional method) as well as via UV and micro wave techniques.

Scheme 1. Mechanism of radical generation via thermal initiation
In thermo fixation technique the corsslinking reaction was initiated by thermal decomposition of the persulphate groups to produce sulphate ion radicals alone with their radical species. The radical formed in this way were used as initiators for the cross linking reaction. The mechanism of free rad ical generation reaction is shown by following scheme 1 [12].

Scheme 2. Formulation of photocurabel system
Thus, the acrylate terminal double bond polymerizat ion can be initiated by either the SO4 -. or by . OH radicals. In the presence of polyurethane acrylate, these free radicals can attack polyurethane at terminal ends (double bond), thereby give rise to form macro radicals capable of initiation the crosslinking reaction (crosslinking poly merization of the polyurethane). Radiat ion curing is an alternative to the thermal process. Radiation curing resin formu lat ions contain mono mers, and photo initiators. These components can be polymerized (hardened) by the free rad ical mechanis m as shown in scheme 2 [13].
The free rad ical generated by mean of high energy radiation [14][15][16] is shown in the following scheme 3. Use of a photo initiator triggers a nearly instantaneous curing reaction upon exposure to UV light.

Scheme 3. Generation of free radical via photoinatiation
Thus UV curing produces a completely poly merized network in seconds which is faster than thermal curing [17]. After free rad ical has been generated the polymerization reaction was occurred as follo wing: The curing process creates a tightly crosslinked poly mer network [13], which is represented schematically in Scheme 5, The ment ioned mechanisms and chemical change occurring upon UV exposure of prepared PUA (i.e., the disappearance of reactive groups) can be monitored by using FTIR spectra.
for cured PUA poly mers, shows the disappearance of ast C= C and δ: =C-H absorption bands at almost 1986 cm -1 and 958 cm -1 respectively. Fro m the spectra chart of cured, wh ich proofed the occurrence of crosslinking reaction via terminal free acrylate double bond, it is clear fro m the previous results that the prepared PUA could be used as self crosslinking binders in pig ment printing.
One of the d istinct advantages of waterborne UV-cured PUA is that they combine hardness and flexib ility [18].

Effect of Fi xation Temperature, Type of Binders and Their Concentrati on on the Col or Strength of Printed Samples
In the first stage of the investigation, the prepared pigment pastes, containing 5% Bercolin Red B3E, and different concentrations (1, 2, 3, and 4 %) of the synthesized polyurethane acrylate (binders 1-7), as well as the commercial binder (thermal type), were printed on cotton fabrics by the flat silk screen technique, dried then thermally polymerized with hot air at different fixation temperatures (80,100,120 and 160°C) for 4min. The co lor strength results of the pig ment printed cotton fabrics are represented by Figure 8.
The collective diagrams show the effect of the aforementioned binders on the color strength of the printed cotton fabrics thermally cured under the above conditions. It is clear fro m the results that the color strength of printed cotton fabric depends on binders' type and concentration as well as the fixat ion temperature. It can be seen that for almost type of binders color strength of printed cotton fabric is higher at low concentration and this is true irrespective of the fixation temperature. Th is may be due to the probability of self poly merization at higher concentration. It is also clear that K/S of the fabric printed using pastes including the synthesized binders are higher than the color strength of fabric p rinted with pastes including the commercial binder, this hold is true at only low temperatures.
Fro m figure 8 it is clear that, the synthesized binders give acceptable results for color strength values at low fixation temperature. This may be attributed to the presence of functional groups (double bond, hydroxyl groups) which are able to increase the crosslinking density.
We can conclude that binders 1, 3 and 6 have the best results for color strength at low fixation temperature and low binder concentration.

Effect of UV Fixati on Ti me, Type of Binders and Their Concentrati on on Col or Strength of Printed Samples
Pig ment printing cured via irrad iation (UV, microwave) eliminates the drying step and greatly reduces the energy required for curing. High curing speed, high cross-linking densities and the absence of organic solvents have made radiation curing a well established technology for all kinds of coating and ink applicat ions [19].
Today numerous UV-curable mono mers and like polyether, polyester, epoxy, polyacrylate and urethane acrylates are available on the market. By the choice of raw materials, namely as binders and accompanying mono mers, and photo initiators, the film properties such as hardness, flexib ility, resistance and adhesion can be controlled in a very flexib le way [20][21][22]. Acrylic mono mers do not absorb UV-light in a very efficient way and will not in itiate radical polymerization fast enough. As such, a photo polymerisable film forming formu lation essentially consists of a polymerisable vehicle and a light sensitive co mpound that is able to convert the absorbed light energy into a more useful form capable of causing the binder to polymerize into a hard solid mass.
Such a light sensitive co mpound is known as photo initiator/ sensitizer. Thus a photo initiator is added to produce initiator free radicals direct ly by the frag mentation of the photo-excited state; these free radicals are capable of initiat ing the polymerizat ion reaction [23].
Photo initiator is of paramount importance in radiation curable systems. A photo initiator is selective in terms of light of specific wavelengths. During formu lation, the absorbency characteristics of the photo initiator are matched to the radiation characteristics of the lamp output. Indeed, the choice of photo init iator is of prime impotence in the light induced polymerizat ion since it directly governs the cure rate [24].
As mentioned before, the prepared pigment pastes containing Bercolin Red B3E p ig ment, and different concentrations (1, 4%) of the prepared polyurethane acrylate (binders 1-7), as well as the selected suitable UV curing commercial binder Ebecry l 2001 and the photo initiator Esacure DP 250 were printed on cotton fabrics by the flat screen technique, dried and then subjected to UV curing for different intervals of time 3, 5, and 10 minutes.
The results are expressed in Figure 9. Binders (1-7) with different structures containing some unsaturated groups, which under the effect of UV rays can undergo a polymerization reaction which leads ultimately to pigment fixation on the cotton fabrics. As regarding to the b inder concentration, slightly enhancement in K/S values of printed cotton fabric with increasing the concentration of b inders 1,2,3,4 (aliphatic po lyurethane acrylate) this may be attributed to the increase of the unsaturated double bonds, so when they are subjected to UV curing results in h igher degree of polymerizat ion crosslinking.
The highest K/S value is obtained on using binder4 at high concentration this may be due to percents HPMA. The ability of HPMA to expand the backbone increases corsslinking ability of that binder.
Also it can be seen that, binder concentration of 1% produces cotton printed samples with color strength values higher than those obtained by binder concentration of 4% under similar fixation conditions in case of binders 5, 6 and 7. This may be due to the presence of benzene rings along the structures (aromatic urethane acrylate) the aro matic ring dissipates radiation energy due to the high conjugation double bond system [25].
Binder 6 shows highest K/S values at lower binder concentration that may be due to its structure (based on PEG 20000 and HPMA) which elongates its backbone. With regards to the type of binder used it can be noticed that, in general, the h ighest color strength values were obtained in case of using binder 4 and 6in the UV curab le print ing pastes while lower values were obtained upon using the commercial binder (Ebecry l 2001) and moderate values, in case of using binders 1, 2, 3, 5 and 7. This is true irrespective of either the binder concentration or the UV-curing t ime. Th is could be attributed to the difference in structure of the binders used as well as the difference in their contents of the unsaturated groups, which are responsible for the pig ment fixation, and also to the influence of UV rays on these different structures.
It is also clear fro m Figure 9 that, increasing the UV-curing fixat ion time fro m 3 to 5 and up to 10 min. did not result in any significance increase in the color strength values of the cotton printed samp les irrespective of the type and concentration of the binders used in these experiments. This may be due to the rap id curing process, on using UV rays on fixat ion process. A curing time of 3 min. could be recommended under such circumstances to save energy and time.
Generally it could be concluded that, the presence of 1% concentration of polyurethane acrylate binders (1-7) in the cotton pigment printing paste, and UV curing for 3 min. could be considered as optimu m conditions.

Effect of Microwave Fi xation Ti me, Type of Binders and Their Concentration on the Color Strength of Printed Samples
Microwave irradiation is one of powerful techniques of noncontact heating, because the dielectric substances with large dielectric loss constant vigorously fever by vibration and rotation of permanent dipole in microwave field. Microwave has been used for reacting, drying, curing, fin ishing of cellu losic-based textile [26]. Microwave heating has been proved more rabid, uniform, and efficient. It penetrated easily into particles, wh ich can be heated simu ltaneously, thus reduction heat transfer problems. So me studies have been investigated the possibility of using micro wave heating in dyeing and printing of d ifferent fabrics as well as the effect of microwave irradiat ion on their fabric structure [26]. Fabrics Using Three M odes of Fixation The prepared pigment pastes containing Bercolin Red B3E pig ment, and different concentrations (1, and 4%) of the prepared polyurethane acrylate binders (1-7), as well as the selected suitable commercial b inder Ebecryl 2001 and the photoinitiator Esacure DP 250 were printed on cotton fabrics by the flat screen technique, then introduced into microwave oven as it is wet without drying, to be cured for different interval of times (2, 3, 4 min) at operating power at 500 watt. The results are shown in Figure 10. Regarding the type of binder derivatives, it can be noticed that it has no significant influence on the color strength values of the printed fabric at low b inder concentration irrespective of the fixat ion time. While at higher concentration there is some d ifference in color strength of some binder derivatives, this may be attributed to the role of electro magnetic waves and their influence on different binder derivatives (difference in their structure, their content of unsaturated groups, and difference in backbone). Colo r strength values observed for cotton fabric printed using pastes including the prepared binders are higher than those obtained using the commercial one; this hold is true irrespective of fixation t ime and b inder concentration, due to the nature of micro wave dielectric heating [27] and the use of unmodified domestic house hold oven accurate temperature measurement using conventional means of temperature determination during the irradiation process were not possible.
Therefore the reason for the observed rate-enhancement were in many cases not fully understood and led a lot of speculation and fierce debate of existing of so-called non-thermal or specific micro wave effect.
The results in the collective diagram 10 show that, the concentration of the prepared binders of polyurethane acrylate binder derivatives (1-7) in the printing paste has slightly effect on the color strength values of the screen printed cotton fabrics. So on using lower concentration of these binders 1% and subsequently microwave cured for different interval of t imes (2, 3, and 4 min ), K/S values are more or less comparable with those printed using higher concentration of these binders 4% under the same conditions. This may be due to the self polymerizat ion of high binder concentration when the prints are exposure to microwave irradiation.
It is also clear fro m Figure10 that, increasing the micro wave curing fixation time fro m 2 and up to 4 min gives results with slightly increase in the color strength values of the cotton printed samples irrespective of the type and concentration of the binders used. This may be attributed to the fast drying of prints during their espousing to microwave irradiation. Material including water, are described as loss and may be heated by the use of microwaves, hence due to the fact that the molecular chains in their structure have resonant frequencies similar to the frequency of microwave energy, so that strong interaction occurs, the molecules vibrating violently and causing heat to be generated [28] .
It could be concluded that the presence of 1% concentration of polyurethane acrylate binders (1-7) in the cotton pigment printing paste, and microwave curried fo r 3 min. could be considered as optimu m conditions.

Effect of the Mode of Fixati on on the Col or Strength of the Printed Samples
The color strength results obtained by thermal, UV and micro wave fixat ion techniques for screen printed cotton fabrics with p ig ment past containing 4% Bercolin red B3E pigment and 1% binder concentration (binder 1-7) and to those obtained by commercial b inders are represented by Figure11. The highest K/S is obtained with binder 1, 6 in case of thermo fixed printed cotton samples. It clear that the K/ S of printed samples with pastes containing the synthesized binders and cured by using UV and microwave techniques are higher than the printed samples using commercial b inder in its pasts and fixed by same mentioned techniques.
Generally spoken, the highest K/S values observed within radiation curing (UV and micro wave) in case of binder 6, 7.

Fastness Properties
Since pig ment printing using thermal, UV curing and micro waves curing is a surface application, the major concern is the abrasion resistance of the p rinted fabrics either towards washing or rubbing. In thermal curing process, the cross linking is essential for the adhesion of the binder to the text ile surface and to give the pig ment prints optimu m fastness properties [29]. Apply ing high curing temperature to fix the p ig ment colors, as much as needed is an unfavorable printing aspect. It does not only waste energy but also runs the risk of the thermo degradation of substrates. In UV curing, these risks are minimized [30].
Tables 1 show the color strength and overall fastness properties of screen printed and thermally cured ( at 160℃ for 3min. ) cotton fabrics with pig ment printing pastes containing 1% polyurethane acrylate binders (1-7), as well as 5% Bercolin Red B3E pig ment, and of those obtained upon using the commercial binder (Bercolin metal CM) 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 binders gave printed samples with much higher color strength results as compared 5 Fabrics Using Three M odes of Fixation to those obtained upon using commercial b inder at the same conditions. The rubbing fastness results were acceptable for thermally cured cotton printed samples, but improvement is noticed with binders 1, 2, 4, 5 and 6 as co mpared to those for binder 3, 7 and the co mmercial b inder. The rubbing fastness ranging fro m good to very good in case of using the binders 1, 2, 4, 5, 6 and co mmercial b inder and ranging fro m moderate to good in case of using binder3, 7. 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. Table 2 shows the roughness properties of screen printed cotton using printing pastes containing 4% Bercolin Red B3E, 1% of the synthesized polyurethane acrylate binders(1-7), as well as the commercial binder Bercolin meta l CM and thermally cured at 160 ℃ for 4min. The results show that the roughness for both printed fabrics depends on the type of binder used. The commercial b inder gave high roughness results to those obtained by synthesized binders. Tables 3 represent the color strength and overall fastness properties of screen printed and UV cured (for 3 min. ) cotton fabrics using pig ment printing pastes containing 1% polyurethane acrylate binders (1-7), as well as 5% Bercolin Red B3E pig ment, as well as the commercial binder Ebecryl 2001 respectively. The results show that, the fastness properties of the printed samples depend slightly on the type of binder used as well as the type of the selected fab ric. Binders 3, 4, 6 and 7 gave printed samples with much higher color strength results as compared to those obtained by binder 1, 2, 5 and the commercial binder. Table 4 shows the roughness properties of screen printed cotton fabrics, using printing pastes containing (4% Bercolin Red B3E, 1% of the synthesized polyurethane acrylate binders (1-7), as well as the commercial b inder Ebecryl 2001) and UV cured for 5min. at wave length 254n m. The results show that the roughness of printed fabrics depends on the type of binder used. Binders 3, 6 and7 gave high roughness results compared to commercial binder used.  Table 5 represent the color strength and overall fastness properties of screen printed cotton fabrics using pigment printing pastes containing 1% polyurethane acrylate b inders (1-7), as well as 5% Bercolin Red B3E p ig ment, and those obtained upon using the commercial binder Ebecryl 2001 and microwave cured (for 3 min. ). The results show that, the washing and perspiration fastness properties of the printed samples are in depended on binder or fabric type. While in case of rubbing fastness properties it depends on the type of binder used as well as the selected fabric. It could be also noticed that the rubbing fastness results for printed samples, upon using all the aforementioned synthesized polyurethane acrylate binders through the use of microwave curing technique as compared to those obtained by the traditional thermal curing technique, some imp rovement is noticed with binders 2, 4, 5, 6 and 7 as co mpared to those for b inder 1, 3 and the commercial b inder especially in case of using these binders for printed polyester fabric, the rubbing fastness ranging fro m good to very good in case of using the binders 2, 4, 5, 6, 7 and co mmercial b inder and ranging fro m moderate to good in case of using binder 1,3. The washing and perspiration fastness ranged from very good to excellent for all binders. As mentioned before radiation in energy controlled by the electron vibrat ing in the molecules at the surface of a body. The amount of energy is that can be transformed depends on the absolute temperature of body and radiation properties of the surface.
However to date, microwave curing has only been studied by experimental methods.  Table 6 shows the roughness properties of screen printed cotton fabrics, using printing pastes containing (4% Bercolin Red B3E, 1% of the synthesized polyurethane acrylate binders (1-7), as well as the commercial b inder Ebecryl 2001) and microwave cured for 5min. at 500 watt.
The data show that the roughness for all these printed fabrics depends on the type of binder used. Binders 1, 2, 3, 4, 6 and7 gave higher roughness results compared to commercial b inder used.

Conclusions
FT-IR spectra of binders via UV curing show the disappearance of ast C=C and δ: =C-H absorption bands fro m the spectra chart of cured, which proofed the occurrence of cross linking reaction via terminal free acrylate double bond. Color strength of printed fabrics depends on binders' type and concentration as well as the fixation temperature. The K/S values at lower fixation temperatures on using the prepared binders in the printing paste are better than the K/S o f fabric printed with paste including the commercial b inder at the same condition ( saving energy). The fastness properties of the printed samples depend on the type of binder used. The washing and perspiration ranged fro m good to excellent for all printed samples. Slightly enhancement in K/S values of printed cotton fabric with increase the concentration of aliphatic polyurethane acrylate binders was noticed. Binder concentration of 1% produces cotton printed samples with higher color strength values within aro matic urethane acrylate binders than 4% of the same g roup. Increasing the UV-curing fixat ion time fro m 3 to 5 and up to 10 min. did not result in any significance increase in the color strength values of printed cotton fabric. The presence of 1% concentration of polyurethane acrylate binders (1-7) in the cotton pigment printing pastes, and either UV curried or micro wave curing for 3 min . could be considered as optimu m conditions. Improved rubbing fastness results for all the printed samples using the synthesized polyurethane acrylate binders in printed paste and UV cured are noticed as compared to those obtained by the traditional thermal curing technique. The washing and perspiration fastness results are comparab le for the printed samples produced by the two techniques. Improved rubbing fastness results for all the printed samples using the synthesized polyurethane acrylate binders and micro wave curing are noticed as compared to those obtained by the traditional thermal curing technique. Rubbing fastness are in range fro m good to very good in case of using the binders 2, 4, 5, 6, 7 and commercial binder while it in rang fro m moderate to good in case of using binder 1, 3. The washing and perspiration fastness are in rang of very good to excellent for all samp les printed with pasts including the prepared binders as well as the commercial one.