Synthesis and Characterization of Nano-TiO 2 / SiO 2-Acrylic Composite Resin

Waterborne acrylic resin is widely used as a binder of waterborne printing ink because of its excellent comprehensive properties. However, its further developments and applications are hindered by its poor UV resistance and water resistance. )erefore, an approach to prepare acrylic resin with excellent UV resistance and water resistance is described in this present study. )e nano-TiO2/SiO2 composite particles were first modified with a silane coupling agent (KH-570) and a titanate coupling agent (NDZ-101) and then embedded into acrylic resin via a blending method. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and thermogravimetry analysis (TGA) were applied to investigate the structure and morphology of the modified nano-TiO2/SiO2 composite particles. )e effects of the modified nano-TiO2/SiO2 composite particles on the UV and water resistance of the acrylic resin were investigated by UV spectroscopy and water resistance analysis. )e weight loss of modified nano-TiO2/SiO2 was about 20% when heated to 600°C, which indicated that the nano-TiO2/SiO2 composite particles were modified by the coupling agents successfully. )e UV-Vis spectra of acrylic resin showed that the UV resistance was improved upon the addition of nano-TiO2/SiO2. )e water absorption of the nano-TiO2/SiO2-acrylic resin was less than 5%, indicating that the water resistance of the material was improved.


Introduction
Acrylic resin as a binder of waterborne printing ink has the advantages of printing adaptability and ink stability.It has been widely used in the printing industry due to its excellent properties such as good hardness, luster, acid and alkali resistance, weather and pollution resistance, and nontoxicity [1].e relatively poor ultraviolet (UV) and water resistance of acrylic resin due to the introduction of hydrophilic carboxyl groups, however, restrain it from further developments and applications [2][3][4][5].To achieve good UV and water resistance for acrylic resin, it is necessary and significant to prepare a modified waterborne acrylic resin [6].
ere are four main popular methods that are widely applied to modify acrylic resin: monomer modification, compound modification, process modification, and nanomodification [7,8], to be widely applied to modify acrylic resin.Since titanium dioxide (TiO 2 ) nanoparticles are widely used because of their good UV absorbance and photocatalytic activity, low cost, and nontoxicity as inorganic materials, the nanomodification was adopted as a more effective method to improve the UV and water resistance of the acrylic resin.e composite particles formed by coating silica (SiO 2 ) nanoparticles on the surface of nano-TiO 2 particles may obtain excellent UV absorption properties.In addition, the photocatalytic activity of the nano-TiO 2 particles can be reduced, allowing the wide use of nanoparticles.
e nano-TiO 2 /SiO 2 composite particles, combined with low surface energy materials, may be incorporated into the acrylic resin to enhance UV resistance and hydrophobic properties, simultaneously.us, nano-TiO 2 particles have been widely introduced into polymers to improve the heat resistance, UV resistance, and photocatalytic performance of polymer materials in the past several years [9][10][11].Duan et al. [12] presented a novel approach to synthesize acrylic resin used as a binder of waterborne printing ink on plastic film with excellent adhesion and water resistance.Liu et al. [13] suggested a two-step esterification process to prepare epoxy-acrylic-graft-copolymer waterborne resins used in anticorrosion coatings on metal substrates.Zhang et al. [14] studied the properties of acrylic emulsion with 2-acrylamido-2-methylpropane sulfonic acid (AMPS) as a reactive comonomer and methyl methacrylate (MMA), nbutyl acrylate (BA), and 2-hydroxyethyl acrylate (HEA) as a copolymerization system.Viornery et al. [15] used phosphoric acid to modify the surface of nano-TiO 2 .Cheng et al. [16] synthesized acrylic resin with high gloss and strong water resistance by introducing nonionic groups.
In this study, a new, low cost, and easily industrialized technique was used to modify the UV and water resistance of acrylic resin.e nano-TiO 2 /SiO 2 composite particles were first modified by c-methacryloxypropyltrimethoxysilane (KH-570) and isopropyl dioleic acyloxy (dioctylphosphate) titanate (NDZ-101) [17,18].Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were applied to study the morphology of the modified nano-TiO 2 /SiO 2 composite particles.In fact, the method of using these two coupling agents to reduce the problem of easy agglomeration of nanomaterials in resins and improve their UV and water resistance has rarely been reported.A waterborne acrylic resin with excellent UV and water resistance was prepared by introducing modified nano-TiO 2 /SiO 2 composite particles.We further investigated the effects of the modified nano-TiO 2 /SiO 2 composite particles on the UV and water resistance of the acrylic resin.e experimental data in this paper show that the UV and water resistance of the acrylic resin were all improved with this method.In this way, the ink coating can simultaneously obtain anti-ultraviolet and superhydrophobic properties and can be applied not only to areas such as umbrellas, sun protection clothes, waterproof packaging bags, food and medicine packaging materials, but also to aviation, the aerospace industry, medical treatment, and military fields.is work has the potential to expand the application fields of resin nanomaterials and has broad application prospects.
e nano-TiO 2 /SiO 2 powder was dissolved in 95% ethanol via an ultrasonic process for 20 min.
e above KH-570 and NDZ-101 were added to this solution in a constant temperature water bath at 65 °C.e reaction was carried out under ultrasonic dispersion for 1 h.After the reaction, the samples were washed by centrifugation, dried, and ground to obtain the modified nano-TiO 2 /SiO 2 composite particles.

Synthesis of Acrylic Resin.
e acrylic resin was prepared by solution polymerization of MMA (99%), BA (99%), and AA (98%, 12.5 wt.%) as monomers and BPO (98%) as initiator.e ratios of the soft monomer to hard monomer and the solvent to monomers were all 1 : 1.A half of butanol (99.5%), a third of monomers, and a quarter of initiator were added to a dropping funnel (250 ml) equipped with a stirrer and a thermometer.e mixture was stirred at 100 °C for 30 min.en, the mixture of remaining monomers, initiator, and butanol was added dropwise into the dropping funnel within 2 h.e polymerization was carried out for another 3 h.Subsequently, the dropping funnel was naturally cooled down to 35 °C, and ammonia (25%) was added under stirring to adjust the pH value to 8-9.After 0.5 h, the obtained product was waterborne acrylic resin.

Preparation of Nano-TiO 2 /SiO 2 -Acrylic Composite Resin.
e basic preparation procedure is shown in Scheme 3. e nano-TiO 2 /SiO 2 -acrylic composite resin was prepared via a blending method.e modified nano-TiO 2 /SiO 2 composite particles at mass ratios of 1%, 5%, and 10% were added into the acrylic resin solution.e reaction was carried out under ultrasonic dispersion for 30 min.Finally, the product was placed on a glass dish and dried at room temperature for several hours.

Characterization.
e surface morphologies of the modified nano-TiO 2 /SiO 2 composite particles were observed by SEM (SU-8010, Hitachi, Japan).FT-IR was used to characterize various functional groups of the composite particles using KBr tablets for samples.TGA (Q600SDT, TA Instruments, USA) was performed on the nano-TiO 2 /SiO 2 composite particles before and after modification under nitrogen gas with a heating rate of 10 °C/min to determine their thermal stability.In the TGA experiment, the scanned temperature ranged from ambient temperature to 600 °C.e acrylic resins with nano-TiO 2 /SiO 2 composite particles before and after modification at mass ratios of 1%, 5%, and 10% were cut into 2 cm × 2 cm × 2 mm dimensions after being allowed to 2 Advances in Materials Science and Engineering stand for 7 days.Absorbance was obtained by a UV spectrophotometer at 200-800 nm. e absorbance of acrylic resin both with and without nano-TiO 2 /SiO 2 composite particles at 200-800 nm was measured and compared.e cut lms were washed by distilled water and placed on a glass dish.After being dried in an oven under 50 °C for 1 h, the lms were cooled down to room temperature and weighed (M W1 ).
en, the coating lms were soaked in distilled water for 24 h.e weights of both applied lms and adsorbed water (M W2 ) were used to calculate the water absorption by the following formula: water absorption(%) where M W1 is the weight of the applied lms cooled to room temperature and M W2 is the weight of the coating lms soaked in distilled water for 24 h.

Results and Discussion
3.1.Morphological Analysis.As seen in Figures 1(b), 1(d), and 1(f ), the nano-TiO 2 /SiO 2 composites without modication were completely precipitated in acetone [20,21] In comparison, the modi ed nano-TiO 2 /SiO 2 composite particles were preferably dispersed in acetone as shown in Figures 1(a), 1(c), and 1(e), which exhibit good lipophilicity.As can be seen from the gures of modi ed nano-TiO 2 /SiO 2 composite particles, the dispersion e ect of Sample 3 was inferior to that of Samples 1 and 2.

SEM Analysis.
e surface morphologies of the modied nano-TiO 2 /SiO 2 composite particles were observed by SEM.As a reference, the SEM images of nano-TiO 2 /SiO 2 composite particles without the modi cation of coupling agents are marked as "none" in Figures 2(a) and 2(e).It can be seen that the agglomeration of nano-TiO 2 particles is of considerable amounts.
ere were many free nano-SiO 2 particles that could not be formed and coated well on the surface of the nano-TiO 2 particles.

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As shown in Figures 2(b)-2(d), the surface of the nano-TiO 2 /SiO 2 particles is covered with a rounded organic layer.It can be seen clearly in Figures 2(f )-2(h) that the organic coating is dense, while the coating effect is quiet clear under a magnification of 130,000.ere is still a little agglomeration in the modified nano-TiO 2 /SiO 2 composite particles, which may be due to the insufficient grinding of the composite particles or the poor dispersion effect of the powder in the preliminary experiment [22,23].e SEM images of modified nano-TiO 2 /SiO 2 particles combined with the figures of nano-TiO 2 /SiO 2 composite particles before and after modification in acetone indicate that the coating effect of Sample 1 and Sample 2 is better than that of Sample 3.

FT-IR Analysis.
e FT-IR spectra of the nano-TiO 2 / SiO 2 composite particles before and after modification are shown in Figure 3.
e peak at 3500 cm −1 in Figures 3(a)-3(c) is the bending vibration peak of -OH in the absorbed water of nano-TiO 2 particles, while abroad absorption band at 3460 cm −1 in Figures 3(d)-3(f ) may be attributed to an -OH group of absorbed water in the nano-TiO 2 /SiO 2 particles.e stretching vibration of C�O in KH-570 is also observed at 1650 cm −1 , while the absorption peak at 1880 cm −1 can be attributed to C�O groups in NDZ-101 [24,25].e asymmetric stretching vibration of Si-O-Si near 1080 cm −1 can be attributed to a change in the chemical state, which is ascribed to the chemical reaction of KH-570 with nano-SiO 2 particles.At the same time, the spectrum clearly illustrates the absorption peak of Si-O-Ti at 975 cm −1 due to the chemical reaction of NDZ-101 with nano-SiO 2 particles on the nano-TiO 2 [22].ese results indicate the presence of KH-570 and NDZ-201 on the surface of the nanoparticles, and the coupling agents are grafted onto the surface of the nanoparticles through chemical changes rather than a simple physical coating.

TG Analysis.
Figure 4 shows the TGA curves of nano-TiO 2 /SiO 2 composite particles both before and after modification with the coupling agents (KH-570 and NDZ-101).All the samples were dried in a vacuum oven for 24 h before  4 Advances in Materials Science and Engineering being tested.e small mass loss observed for nano-TiO 2 / SiO 2 composite particles between 0 °C and 200 °C is probably due to the evaporation of water vapor adsorbed on the surface of the samples at high temperatures.e temperature at which 20% mass loss occurs is about 600 °C for modi ed nano-TiO 2 /SiO 2 composite particles.e appearance of the Tg indicates that nano-TiO 2 /SiO 2 composite particles have been modi ed by coupling agents successfully.A sharp transition occurs at about 450 °C corresponding to the thermal decomposition of the coupling agents, while the weight loss in the temperature range of 500 °C-600 °C is due to the thermal decomposition of grafted coupling agents at high temperatures [26].

UV Resistance Properties Analysis.
e UV resistance characteristic of nano-TiO 2 /SiO 2 -acrylic composite resin was investigated by UV-Vis absorption spectra shown in Figure 5.
e UV resistance characteristic is only discussed in the UVA band (320-400 nm) and the UVB band (280-320 nm) [27].Figure 5 shows the UV-Vis spectra of acrylic resin before and after adding modied nano-TiO 2 /SiO 2 composite particles.e absorbance of acrylic resin without nano-TiO 2 /SiO 2 composite particles is always lower than 2 in the wavelength range of 200-800 nm, while the absorbance of nano-TiO 2 /SiO 2acrylic composite resin reaches about 4 in the wavelength range of 200-320 nm.
ere is a high absorption at 280-320 nm, that is, a low transmittance.
e same phenomenon occurs at 320-400 nm. e enhancement of UV resistance can be ascribed to the production of electron-hole pairs caused by the nano-TiO 2 particles being irradiated by the light whose energy greater than the forbidden bandwidth [28,29].
e e ects of the content of modi ed nano-TiO 2 /SiO 2 composite particles on the UV resistance of modi ed acrylic resin are shown Figure 6.It can be seen that the UV absorbance improves as the content of nano-TiO 2 /SiO 2 composite particles increases.As the content of nano-TiO 2 /SiO 2 composite particles increases from 1% to 10%, the UV wavelengths were completely shielded by the composite acrylic coating when the range was from 310 nm to 350 nm, while the transparency was still maintained above 90%.e UV transmittance of the composite particles is below 30% when the mass ratio of nano-TiO 2 /SiO 2 composite particles is 10%.e result indicates that the UV resistance and transparency of modi ed acrylic resin are all improved and the e ect of nano-TiO 2 /SiO 2 -acrylic composite resin with 10% nano-TiO 2 /SiO 2 composite particles is better than the others.Advances in Materials Science and Engineering capacity to absorb water.It is a property that mainly depends on the ratio of hydrophilic/hydrophobic functional groups and on the nature of these groups as well [30].As waterborne acrylic resin contains a lot of hydrophilic carboxyl groups, they generally have an ability to absorb considerable amounts of water.us, water-resistant modi cations must be applied to the surface of the nanoparticles.e e ects of altering the modi ed nanocomposite particles ratio (1%, 5%, and 10%) on water resistance of acrylic resin were investigated.As a reference, a pure acrylic resin was prepared.e test values of water absorption are listed in Table 1.It was determined that the water absorption decreases when the mass ratio changes from 1% to 5%.e result may be due to the formation of micro-and nanoconvex structures on the surface of the acrylic resin coating caused by the addition of nano-TiO 2 /SiO 2 composite particles and the hydrophobic treatment by coupling agents.However, the water absorption increases when the ratio changes from 5% to 10%.e reason is the agglomeration of excess SiO 2 molecules due to interactions between hydroxyl hydrogen bonds, which results in a reduction in the length of the movable segment unit and a weakening of the bonding force between the material and the substrate so that the water resistance is reduced.As shown in Table 1, the water absorption of the acrylic resin with modi ed nano-TiO 2 /SiO 2 particles is less than 5% for all three contents, indicating that the water resistance of composite acrylic resins is improved compared with pure acrylic resin [31].

Conclusions
A novel preparation method was developed to prepare nano-TiO 2 /SiO 2 -acrylic composite resin with excellent UV and water resistance.e main purpose of this study is to investigate the methodology of improving the properties of acrylic resin as a binder of waterborne printing ink.rough TGA curves, it can be shown that the nano-TiO 2 /SiO 2 composite particles were modi ed by the coupling agents successfully.FT-IR con rms that KH-570 and NDZ-101 were grafted on the surface of nanocomposite particles in a bonding form.According to UV-Vis absorption spectra, it was observed that, after introducing modi ed nano-TiO 2 / SiO 2 composite particles into acrylic resin, the UV resistance and transparency of modi ed acrylic resin were all improved.e water absorption of the nano-TiO 2 /SiO 2 -acrylic resin, which was less than 5%, indicates that the water resistance of these materials is enhanced by the modi ed nano-TiO 2 /SiO 2 composite particles.In summary, the results show that the UV and water resistance of acrylic resin modi ed with nano-TiO 2 /SiO 2 composite particles by a blending method are improved.e experiment data indicate that the nano-TiO 2 /SiO 2 -acrylic composite resin synthesized in this study can be hopeful candidates for environmentally waterborne printing ink to be used in printing and related industries.

Table 1 :
E ects of di erent ratios of nanocomposite particles on water resistance.Figure 6: UV-Vis absorption spectrum of composite resin with di erent nano-TiO 2 /SiO 2 contents.
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