Compatibility Studies of Polyacrylamide/Nanoclay/Copper oxide Nanocomposites on the Fluidic Physical Properties for Improvement of Inkjet Printability

Water-borne ink, an industrially important ink based on the polyacrylates, in that polyacrylamides imparts specific properties to the inks. Some properties of inks such as glossy or hardness is also adjust by varying the polymers, so in the present studies, nanocomposites of Polyacrylamide /Nanoclay/copper oxide nanoparticles were synthesized. The Nanoclay and Nanoparticles were varied to 0.5, 1 and 2% with respect to monomer of acrylamide and the effect on physical properties of ink such as, density, viscosity, surface tension, drying and smudging were observed to see the performance of it on polymer nanocomposites mixed in ink. The final product were characterized by UV-Vis and FTIR spectroscopy to see the presence of individual component of nanocomposites. It was found that the solution with polymer nanocomposites shows, improved in the physical properties with variation of 2% with respect to ink solution. Finally the biological activities were performed to see the effect of it on the ink solution.


Introduction
Ink occupy an integral and versatile position in our daily life. On the basis of different types and uses, researchers defined ink in various ways but in simplest description, ink is a liquid or semi-liquid material used for writing, printing, or drawing. In the chemist's point of view, the ink is a colloidal system of fine pigments particles which are dispersed in a solvent [1]. There are mainly four elements of ink i.e. colorant, vehicle, solvent, and additives [2]. The first man made ink dates back to 4,500 years in Egypt, which consisted of a mixture of animal or vegetable charcoal (lampblack) and glue [3,4].
On the basis of colorant, the ink is basically divided in two parts i.e. dye based ink and pigment based ink. Some of the printing inks are; Quick-Set Ink, Heat-Set Ink, Moisture-Set Ink, Radiation-Curing Ink, High-Gloss Ink, Metallic Ink, Magnetic Ink, Fluorescents Ink, and Scuff-Resistant Ink [5].
In solvent-borne inks, the main polymers are based on nitrocellulose but in waterborne ink the main polymers are based on polyacrylates. Many of the homopolymers or copolymers of polyacrylates were widely used in water-borne inks such as polyurethanes, polyacrylamide and polyesters are useful in imparting specific properties of inks. Some properties of inks such as glossy or hardness is also adjust by polymers. The final properties of inks are depends on the reactivity of ink components with polymers. For e.g. the applicability and colour strength of ink is affected when polymer-surfactants interaction detract from fine properties such as dispersion stability [6][7][8].
Nanoclay is used to improve the ink properties such as avoiding pigment sedimentation, to provide good colour distribution, to obtained desired film thickness, reduction in misting, etc. [9]. The nanoparticles are Au, Ag, Cu, TiO2, Fe3O4 etc. which were used to improve various properties of inkjet ink. Gold, silver and Magnetic nanoparticles can be easily screen printed on to various type of paper with the nanoparticles being so small that they seep into the paper's pores [10,11].
So, in the present research work, an attempt were made to synthesis polymer nanocomposites of PAM/ Nanoclay/ CuO nanoparticles and were treated with Inkjet printer ink cyan, magenta and yellow to see the effect on density, viscosity, surface tension, drying, smudging and antibacterial activity.

MATERIALS USED
Acrylamide was purchased from Alfa Aesar, Germany. BPO, Ceric Ammonium Nitrate, HNO3, HCl and Glacial acetic acid were obtained from Merck India. Acetone and NaOH were obtained from Fisher Scientific, India. Ethanol was purchased from Changshu Yangyuan Chemical, China. Double distilled water was purchased from Veb Research Laboratory, India. Cupric acetate was obtained from S. D. Fine-Chem. Ltd. India. Nanoclay (alkyl quaternary ammonium bentonite) was requested from Esan Eczacıbaşı Endüstriyel Hammaddeler San. Ve Tic. A. Ş. Istanbul, Turkey. nkjet ink was obtained from Pro-Dot, Datalink Industrial Corporation, India. Desmat Glossy Paper was obtained from, Rational Business Corporation Pvt. Ltd., India. All chemicals and materials are used as they received and stored in a cool place.

Density
The density of ink was calculated at t 0 C by density bottle using the following expression [12],

Viscosity
The ink viscosity was measured by survismeter, which is patented instrument for viscosity, surface tension and interfacial tension measurements and invented by Prof. Man Singh [13], and calculated from the conventional formulaղ = ( ρt ρ r t r ) ղ r Where η and ηr are the viscosities, t and tr are the flow times, and ρ and ρr are the densities of the measured and reference liquids at the given temperature, respectively.

Surface Tension
The ink surface tension were also measured by the same Survismeter and surface tension coefficient is calculated using the standard formula.

= ( )
The test was performed on Desmat Glossy Paper at temperature 25 0 C. In this test, the pattern of prepared ink samples were marked on glossy paper with the help of drawing brush and the drying time was noted with the help of stopwatch.

Smudging
The test was performed on Desmat Glossy Paper at temperature 25 0 C. In this test, the pattern of prepared ink samples were marked on glossy paper with the help of drawing brush and smudged the ink with the help of hand thumb after interval of 3 sec.

UV-Vis Spectroscopy
UV-Vis. absorption spectra of polymer nanocomposite mixed ink samples were obtained using a LABINDIA 3000+ Double beam spectrophotometer. The scan range was from 300.00 to 1100.00 nm.

FTIR Spectroscopy
The FTIR spectra of ink samples were obtained by the instrument Bruker Alfa FT-IR/FT-IR (ATR Mode) with ZnSe crystal.

Antimicrobial Test
The antimicrobial activity of the polymer nanocomposites modified ink was tested against E. coli bacteria using by disc diffusion method. Nutrient agar plates were prepared, sterilized and solidified. After solidification, bacterial cultures were swabbed on the Petridish. The pure CuO nanoparticles, pure magenta, cyan, yellow ink and the sample code PNCM6, PNCC9 and PNCY9 were placed in the E. coli bacterial cultured nutrient agar plate and kept for incubation at 37 0 C for 24 hrs. to see the effect of polymer nanocomposites modified ink against bacteria.

Synthesis of CuO Nanoparticles
Nanoparticles of CuO were prepared by previously reported Sol-Gel method [14]. 0.2 M cupric acetate solution was taken in a cleaned round bottom flask. 1 ml of glacial acetic acid was added to above aqueous solution and heated at 100 0 C with constant stirring on magnetic stirrer. Solution of 8 M NaOH was added drop wise to above solution and heated till pH 7 is obtained and the colour of solution immediately changed from blue to black. The large amount of black precipitate of CuO nanoparticles were formed immediately which was collected. The precipitate was centrifuged and washed 3-4 times with deionized water and dried in air for 24 h.

Preparation of PAM/Nanoclay/CuO Nanocomposites
The solution of nanoclay was added drop wise in aqueous solution of acrylamide. Both initiator BPO and appropriate solution of ceric ammonium nitrate in 1N nitric acid (HNO3) were added and heated at 70 0 C with continuous stirring to complete polymerization. After 30 min, the sonicated CuO nanoparticles were carefully and slowly mixed in this polymerized solution. The prepared polymer nanocomposite was vigorously stirred for 4-5 hours to from viscous solution. The solution was taken in petridish and precipitated in access of acetone in acidic medium. This synthetic process was repeated for the variation studies of nanoclay and nanoparticles, which was provide in table 1.
The synthesized polymer nanocomposites were applied in ink and examined for various parameters of ink.

Preparation of Ink samples with Polymer Nanocomposites
The different sets of ink were prepared by mixing of polymer nanocomposites in three different main colour CMY ink. The ink samples were prepared by varying the different concentration of polymer nanocomposites in ink. Each polymer nanocomposites mixed with ink in variation of 0.5%, 1% and 2% in 30 ml of ink respectively. The detailed mixing for the formation of final polymer nanocomposites in inks is shown in table 2. The properties of prepared ink samples were studied on the basis of following physical parameters such as; Density, viscosity, surface tension, drying, smudging.

Effect of Polymer Nanocomposites on Density of Ink
Density has traditionally been used as the primary means to control the printing process. It has been widely held that it correlates well with the amount of colorant that is put on the paper over a limited range of ink film thicknesses [15]. After adding synthesized polymer nanocomposites in inks, the minor difference was observed in density of mixed polymer nanocomposites inks and pure inks, and it was observed that, the density was increased as comparison to the pure ink. The data of density was given in the table 3. After adding polymer nanocomposites in ink, the different graphs of density data were observed with different variations. Graphical representation of magenta ink in figure 1 shows that, the density of pure magenta ink was 1.053. After adding the polymer nanocomposites PNC52 and PNC54 in the variation of 0.5%, 1% and 2% with respect to the ink, it was observed that the density increases for each variation as compare to that of pure ink. It was observed that in all the samples, the density got increases at every steps. Graphical representation of cyan ink in figure 2 shows that, the density of pure cyan ink was 1.037. After adding the polymer nanocomposites PNC101, PNC102 and PNC104 in the variation of 0.5%, 1% and 2% with respect to the ink, it was observed that the density of all the samples increased at every step.

Fig. 2 Density Curves of Cyan Ink Samples
Graphical representation of yellow ink in figure 3 shows that, the density of pure yellow ink was 1.044. After adding the polymer nanocomposites PNC201 and PNC202 in the variation of 0.5%, 1% and 2% with respect to the ink, it was observed that the density got increases at every steps but after adding polymer nanocomposite PNC204 in the variation of 0.5%, 1% and 2%, the density decreased in first step and increased in last two steps.

Effect of Polymer Nanocomposites on Viscosity of Ink
The viscosity of ink strongly affects, how it behave on the press and is ultimately transferred to the sheet. The properties of the ink's viscosity can have several effects on ink absorption, colour strength and drying [16]. The experimental viscosity data of ink samples was calculated by using above standard formula and reported in the table 4. After adding polymer nanocomposites in ink, the following graphs of viscosity data were observed with different variations. Graphical representation of magenta ink in figure 4 shows that, the viscosity of pure magenta ink was 2.450. After adding polymer nanocomposite PNC52 in the variation of 0.5%, 1% and 2% with respect to the ink, it was observed that the viscosity got decreases in first step and got increases in remaining two steps but After adding the polymer nanocomposite PNC54 in the variation of 0.5%, 1% and 2%, it was observed that the viscosity got increases at every steps.

Fig. 4 Viscosity Curve of Magenta Ink Samples
Graphical representation of cyan ink in figure 5 shows that, the viscosity of pure cyan ink was 2.157. After adding the polymer nanocomposites PNC101 and PNC102 in the variation of 0.5%, 1% and 2% with respect to the ink, it was observed that the viscosity got increases at every steps but after adding the polymer nanocompositesPNC104 in the variation of 0.5%, 1% and 2%, it was observed that the viscosity decreases in variation of first step but in the last two steps, viscosity got increases as compare to that of pure ink.
Graphical representation of yellow ink in figure 6 shows that, the viscosity of pure yellow ink was 1.169. After adding the polymer nanocomposites PNC201 and PNC202 in the variation of 0.5%, 1% and 2% with respect to the ink, it was observed that the viscosity got increases at every step, but After adding the polymer nanocomposites PNC204 in the variation of 0.5%, 1% and 2%, it was observed that the viscosity decreases with variation in first step but got increases in the last two steps as compare to that of pure ink.

Fig. 6 Viscosity Curves of Yellow Ink Samples
In the all samples, it was observed that, the viscosity of most samples got increases. This may be beneficial in the ink properties i.e., dot sharpness increase, etc. This residues the efficiency of cells to carry ink and transfer to substrate. Controlling the ink viscosity is very important from both quality and economical point of view [17]. Surface tension is an important physical property of inks, which was determining ink meniscus recovery and drop formation from the print head nozzle. For example, a low surface tension can result in excessive nozzle faceplate wetting leading to poor ink ejection, thereby affecting jet reliability. On the other hand a high surface tension can lead to insufficient faceplate wetting, which may compromise droplet formation and ejection [18]. The experimental surface tension data of ink samples was calculate by using above standard formula and given in the table 5.

Effect of Polymer Nanocomposites on Ink Surface Tension
After adding polymer nanocomposites in ink, the following graphs of surface tension data were observed with different variations. Graphical representation of magenta ink in figure 7 shows that, the surface tension of pure magenta ink was 32.574. After adding the polymer nanocomposites PNC52 in the variation of 0.5%, 1% and 2% with respect to the ink, it was observed that the surface tension increased in case of 1% variation as compare to the pure ink and again decreased in 2% variation but after adding polymer nanocomposites PNC54 in the variation of 0.5%, 1% and 2%, it was observed that the surface tension decreased at every step.

Fig. 7 Surface tension Curve of Magenta Ink Samples
Graphical representation of cyan ink in figure 8 shows that, the surface tension of pure cyan ink was 30.295. After adding the polymer nanocomposites PNC101 and PNC102 in the variation of 0.5%, 1% and 2% with respect to ink, it was observed that the surface tension decreased at every step, but after adding polymer nanocomposites PNC104 in the variation of 0.5%, 1% and 2%, the surface tension increases in case of 0.5% variation and got decreases in remaining two steps.

Fig. 8 Surface tension Curves of Cyan Ink Samples
Graphical representation of yellow ink in figure 9 shows that, the surface tension of pure yellow ink was 37.859. After adding the polymer nanocomposites PNC201 in the variation of 0.5%, 1% and 2% with respect to ink, it was observed that the surface tension got decreases in case of 0.5% and 2% variations and got increases in case of 1% variation. but after adding polymer nanocomposites PNC202 in the variation of 0.5%, 1% and 2%, it was observed that the surface tension got decreases in case of 0.5% variation than increases in remain two steps but in all steps, the surface tension remains lower as compare to the pure yellow ink. but at last after adding polymer nanocomposite PNC204 in the variation of 0.5%, 1% and 2%, it was observed that the surface tension increased, but in case of 0.5% variation which was higher as compare to the pure ink, than decreased in 1% and 2% variations.

PNC201 PNC202 PNC204
Drying is one of the most important parameter of printing ink. In our study, the drying test was performed on the Desmat glossy paper which was shown in figure  10. In drying patterns, it was observed that, the pure magenta ink was dries on the paper in 3 min 6 sec. cyan ink was dries on the paper in 2 min 4 sec. and the pure yellow ink dries on the paper in 2 min 6 sec. The drying test shows that the maximum drying time was 10 min 1 sec for sample code PNC102 with variation of 2% and the minimum drying time was 1 min 5 sec for sample code PNC102 with variation of 1%. Drying time for each ink sample was given in table 6.

Fig. 11 Presentation of Smudging Test
Smudging is also most important factor of printing ink. The stability of ink on paper after printing is depends on that, how much ink is stable against smudging. In our present studies, the smudging test was performed on the Desmat glossy paper which was shown in figure 11.
From the smudging patterns, it was observed that, the pure magenta ink was smudge on the paper but pure cyan ink do not smudge on the paper similarly, the pure yellow ink smudge on the paper.
It was observed in all the samples, the smudging was maximum in 1% variation of PNC54 sample. The highest smudging may be attributed due to presence of polymer nanocomposite PNC54 in 2% variation which was found least in the less smudging samples.Smudging time for each ink sample was given in table 7.

UV-Vis Spectroscopy of Ink
Data of UV-visible spectroscopy of various ink samples is shown in table 8  It was observed from table 8 and UV spectrums ( figure 12) that, the highest absorption is seen in 0.5% variation of PNC104 in figure 13 and lowest in 1% variation of PNC201 in figure 14, which may be due to the contribution of polyacrylamide/nanoclay/CuO nanocomposite. The shift towards higher wavelength was seen in different variations of PNC101, PNC104 was due to the cyan ink, which absorb at higher wavelength. The spectra also shows that the UVvisible absorbance is due to the contributory effects of all the components not by the individual components.

FTIR Spectroscopy
In most of our samples studied, the following FTIR data is seen, which is shown in the table 9.

Table 9 FTIR Data of Prepared Ink Samples
Wavenumber (cm -1 ) Molecular motion C-C Aliphatic chain It was observed from FTIR data of prepared ink samples that, the absorption bands at 3277 and 1547 cm -1 were due to symmetrical stretching of NH2. Absorption bands at 2913 and 1461 cm -1 were observed due to symmetric stretching of CH2. Absorption bands at 2854, 1424 and 1326 cm -1 were observed due to stretching of CH. The presence of absorption band at 1743 cm -1 confirmed the C=O group in ink samples. Absorption bands at 1156 and 1102 cm -1 were observed due to C-C bending. The presence of these absorption bands in ink samples confirm the presence of polyacrylamide nanocomposites. The observed FTIR data of polyacrylamide was closely related to the observed data of Freddi [19].

Conclusion
In the present research work, nanocomposites of polyacrylamide, nanoclay and CuO nanoparticles have been prepared by solution mixing technique in different loadings of nanoclay and CuO nanoparticles. For the nanocomposites, CuO nanoparticles were synthesized from cupric acetate by using sol-gel method. The synthesized polymer nanocomposites were applied to enhance the properties of inkjet ink. Polymer nanocomposites were mixed in inkjet ink in different variations i.e. 0.5%, 1% and 2% with respect to ink and fluid physical properties of ink such as density, viscosity, surface tension, drying, smudging etc. were studied. In present study, after adding the polymer nanocomposites in ink it was observed in most of the samples that, the density of ink was slightly increased. Viscosity is also important parameter of ink. High viscosity of ink increases dot sharpness and sometimes causes the ink to dry inside the cell, resulting in cell clogging. Low viscous ink took more time in drying and flow on substrate while viscous ink got dried in less time, did not flow on substrate and gives better print quality.We observed in most of the samples that, viscosity of ink increased which might improve the print quality and also improve the flow properties of ink in printing. After adding the polymer nanocomposites in ink samples, it was observed in most of the samples that, the surface tension of ink was slightly decreased. Due this slightly decreased surface tension, the printing of ink may be smoother and the clotting of nozzles of print cartridge may be reduce. The low surface tension will also improve the flow properties of ink on substrate. During using of ink material, ink drying and smudging are also considered to be a very important function. After the ink has been applied to the surface to be printed, it must bind there to ensure it stays. After mixing the polymer nanocomposites in ink, it have seen that these properties were improved. The UV-Vis spectra result shows that polymer nanocomposites mixed with ink samples absorbed mostly in the visible region. The FTIR results of polymer nanocomposites mixed ink samples shows that, the polyacrylamide polymer nanocomposites were present in all ink samples. The results of in-vitro anti-bacterial screening of ink samples and CuO nanoparticles against bacteria E. coli exhibited that, the bacterial culture has least effect on the ink samples and CuO nanoparticles.