Claims:WE CLAIM:
1. A synergistic composition comprising nanoparticles of Iron titanate and Carbon nanotubes, wherein the Iron titanate and the carbon nanotubes are in ratio 1: x, where x≥1-8; for coating on a material to shield electromagnetic interference and block UV light.
2. The synergistic composition as claimed in claim 1,wherein the nanoparticle size of Iron titanate ranges from 2 to 5micron and the nanoparticle size of Carbon nanotubes range from and 5 to 15 nm in diameter.
3. The synergistic composition as claimed in claim 1, wherein the nanoparticles of Iron titanate and Carbon nanotubes are present as a mixture or as a single entity formed by chemically coupling of iron titanate and carbon nanotubes.
4. The synergistic composition as claimed in claim 1, wherein the composition is in a form selected from a group comprising dispersion, powder and the like.
5. The synergistic composition as claimed in claim 4, wherein the dispersion is in a polymer selected from a group comprising but not limited to polyurethanes, polysiloxanes, polyacrylics, polyvinylaceates, synthetic rubbers and the like.
6. The synergistic composition as claimed in claim 1, wherein the material is selected from a group comprising fabric and pre-coated fabric.
7. The synergistic composition as claimed in claim 1, wherein the fabric is selected from a group comprising but not limited to cotton, silk nylon, rayon, polyester, polyacrylic and pre-coated fabric is cotton fabric coated with Polyaniline.
8. The synergistic composition as claimed in claim 1, wherein the shielding from electromagnetic interference range from -8db to -20db and blocking of UV light is ranging from 99.94% to 99.99%.
9. A method of preparation of dispersion of synergistic composition comprising nanoparticles of Iron titanate and Carbon nanotubes, wherein the Iron titanate and the carbon nanotubes are in ratio 1:x, where x≥1-8; for electromagnetic interference shielding and UV light blocking; said method comprising acts of
a) mixing nanoparticles of Iron titanate and Carbon nanotubes in a solvent to obtain the dispersion of synergistic composition comprising nanoparticles of Iron titanate and Carbon nanotubes;

or
b)(i) mixing chemically coupled functionalized nanoparticles of Iron titanate and functionalized nanoparticles of Carbon nanotubes, with a solvent to obtain a mixture;
(ii) sonicating and heating the mixture in presence of a catalyst and activator;
(iii)centrifuging, washing the heated mixture; and
(iv) drying to obtain the dispersion of synergistic composition comprising nanoparticles of Iron titanate and Carbon nanotubes.
10. The method as claimed in claim 9, wherein the solvent is selected froma group comprising but not limited to Dimethyl sulphoxide, Toluene, Dimethyl formamide, and Carbon Tetrachloride.
11. A fabric coated with dispersion comprising synergistic composition of nanoparticles of Iron titanate and Carbon nanotubes, wherein the Iron titanate and the carbon nanotubes are in ratio 1: x, where x≥1-8; to shield electromagnetic interference and block UV light.
12. The fabric as claimed in claim 11, wherein the fabric is selected from a group comprising cotton, silk nylon, rayon, polyester, polyacrylic and pre-coated fabric is cotton fabric coated with Aniline.
13. The fabric as claimed in claim 12, wherein the fabric comprise composition ranging from 80mg to100 mg per square centimeter of the fabric.
, Description:TECHNICAL FIELD

The present invention is in relation to composite materials. In particular to a composition that can shield electromagnetic waves. The invention also relates to adoption of the composition as coating on fabrics. More particularly, the invention is in relation to a synergistic composition comprising Iron titanate and Carbon nanotubes, its method of preparation and suitable adoption for shielding electromagnetic interferences and ultra violet light.

BACKGROUND

The advent of electronic gadgets, wireless devices has exposed us to various Electromagnetic radiations. The stupendous rise in the usage of devices like cell phones, Wi-Fi, blue tooth, near filed communications cause Electromagnetic interference (EMI); whose impact on environment and living beings are to be considered seriously and mitigated. Also, the electromagnetic interferences can cause malfunctioning of electronic and electrical devices which may have potential impact on various aspects in the society.
Efforts have been dedicated for the development of EMI shielding materials. EMI shielding can be achieved by prevention of Electromagnetic (EM) waves passing through an electric system either by reflection or by absorption of the incident radiation power.
An ideal EMI shield should have a good performance at low thickness. The current industrial scenario is occupied with composite materials based on high loadings of stainless-steel fibres and carbon fibres whose shielding effectiveness is measured with samples of thicker cross sections. The problem with such composites is that they are stiff and involve challenges in processing due to the high filler contents involved. This would not only restrict the range of applications where these composites can be used, but also increase their cost.

Patent document WO 2015191003 describes about a composition for EMI shielding; however the composition can be adopted only on rigid materials. Another document US20160009934 discuss about a composition comprising metal nanowires and carbon nanoparticles, in particular the invention provides a highly conductive material, prepared by mixing a conductive carbon nanomaterial having a higher-order structure based on multiple hydrogen bonding and a metal nanomaterial to give a composite material, the conductive carbon nanomaterial being grafted with a functional group capable of forming multiple hydrogen bonds. The preparation of the composition is cumbersome and renders the product very expensive.
Recent research focuses on the development of flexible EMI shielding materials with mechanical flexibility also, said materials would be crucial especially in areas of aerospace, automobile, and next-generation flexible electronics. Textile-based EMI shields have emerged as promising candidates for efficient EMI shielding in view of their lightweight, good flexibility and conformability. In this regard, attempts have been made to incorporate nanoparticles into fabrics, which may be readily achieved by various coating techniques. But a good performing shield requires significantly large amounts of fillers which does not leach out from the fabric with time. Textiles have a great potential to be used as flexible casings having the ability to encapsulate something inside. This can also find a place in packaging applications where it can used as multi-layered pack to shield a particular circuit or object. This is of significant importance, as shielding a device from EM radiation would also prevent remote access or hacking the device.
The present invention aims to provide a composition that can be adopted on a fabric in a facile manner for electromagnetic wave shielding and absorption.
SUMMARY OF INVENTION

Accordingly, the present invention provides a synergistic composition, its preparation and a fabric coated with composition that can effectively shield UV and EMI; wherein,
the synergistic composition is comprising of nanoparticles of Iron titanate and Carbon nanotubes, wherein the Iron titanate and the carbon nanotubes are in ratio 1: x, where x≥1-8; for coating on a material to shield electromagnetic interference and block UV light.
A method of preparation of dispersion of synergistic composition comprising nanoparticles of Iron titanate and Carbon nanotubes, wherein the Iron titanate and the carbon nanotubesare in ratio 1:x, where x≥1-8; for electromagnetic interference shielding and UV light blocking; said method comprising acts of
a) mixing nanoparticles of Iron titanate and Carbon nanotubes in a suitable resin to obtain the dispersion of synergistic composition comprising nanoparticles of Iron titanate and Carbon nanotubes;

or
b)(i) mixing chemically coupled functionalized nanoparticles of Iron titanate and functionalized nanoparticles of Carbon nanotubes, with a solvent to obtain a mixture;
(ii) sonicating and heating the mixture in presence of a catalyst and activator;
(iii)centrifuging, washing the heated mixture; and
(iv) drying to obtain the dispersion of synergistic composition comprising nanoparticles of Iron titanate and Carbon nanotubes.
A fabric coated with dispersion comprising synergistic composition of nanoparticles of Iron titanate and Carbon nanotubes in a suitable resin, wherein the Iron titanate and the carbon nanotubes are in ratio 1: x, where x≥1-8; to shield electromagnetic interference and block UV light.
BRIEF DESCRIPTION OF FIGURES
The features of the present invention can be understood in detail with the aid of appended figures. It is to be noted however, that the appended figures illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope for the invention.
Figure 1: shows EMI shielding effectiveness of neat and polyaniline treated cotton fabric.
Figure 2: shows comparative analysis of effectiveness of shielding of fabric coated with FT-CNT and fabric coated with CNT only.
Figure 3: shows effectiveness of EMI shielding with fabric coated with FT only.
Figure 4: shows the Limiting Oxygen Index of different coated cotton fabric and neat cotton fabric.
Figure 5: shows the TGA thermograms of the different fabrics.
Figure 6: shows the water contact angle of the different samples of fabrics.
DETAILED DESCRIPTION OF INVENTION

The foregoing description of the embodiments of the invention has been presented for the purpose of illustration. It is not intended to be exhaustive or to limit the invention to the precise form disclosed as many variations are possible in light of this disclosure for a person skilled in the art in view of the figures and description. It may further be noted that as used herein, the singular “a” “an” and “the” include plural reference unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by a person skilled in the art.
Abbreviations:
CF:Cotton fabric
PAni-CF: Polyaniline treated cotton fabric
WPU: Water borne polyurethane
Ac: Acrylic resin
Sil: Silicone resin
CNT: Carbon nanotubes
FT: Iron titanate
EMI: Electromagnetic interference
APTES: (3-Aminopropyl)triethoxysilane
In an embodiment the present invention provides a multifunctional composite material based on a composition comprising nanoparticles of Iron titanate(FT) and Carbon nanotubes (CNT);which can be coated on a fabric to render it effective for mitigating a) Electromagnetic interference shielding and b) blocking UV light.
In another embodiment, the composition of present invention comprises nanoparticles of Iron titanate (FT) and Carbon nanotubes(CNT), wherein the nanoparticle size of Iron titanate ranges from about200 to 700 nm and the nanoparticle size of Carbon nanotubes range from about 1 micron to 5 micron in diameter and 5 to 15 nm in diameter.
In another embodiment, the Iron titanate and Carbon nanotubes in the composition are in a ratio1:x, where x≥ 1and x can vary between 1 to 8.
In another embodiment, the carbon nanotubes is multiwalled nano tube, wherein the number of layers vary from 5 to 10; and the length of the carbon nano tubes vary from 1micron to 5 micron.
In another embodiment, the Iron titanate is obtained from naturally available Ilmenite sand as mentioned below and CNT (the grade NC 7000) adopted in the invention is commercially procured from Nanocyl, Belgium.
In another embodiment, the composition is dispersed as per requirement in a compound selected from a group comprising but not limited to polymers- polyurethanes (water borne and solvent borne), acrylics, silicones (polysiloxanes), polyvinylaceate and synthetic rubbers, and coated on to a fabric to render itwith multifunctional properties like electromagnetic waves absorption and blocking. The solvent is selected from a group comprising but not limited to Dimethylsulphoxide, Toluene, Dimethyl formamide, and Carbon Tetrachloride.
In another embodiment, the fabric is selected from natural and synthetic sources, both treated and untreated with polyaniline. The source of fabric can be cotton, silk, jute, wool, polyester, nylon, acrylic, cotton treated with polyaniline and the like.
In another embodiment, Polyaniline treatment is carried out to facilitate charge transfer which is beneficial in EMI shielding. Apart from coating polyaniline, any treatment which facilitates charge transfer like use of intrinsically conducting polymers, electroless plating may be adopted for the same effect.
In still another embodiment, the fabric is coated by a method selected from a group comprising exhaust drying, padding, polymerization and the like, which can coat a given mass of coating on to a given area of the fabric.
In another embodiment, the optimization of the ratio of composition comprising Iron titanate and Carbon nanotube for its EMI shielding properties on neat and polyaniline treated cotton fabrics is carried out by taking different ratios of Iron titanate and Carbon nanotubes (FT:CNT of 1:x , where x≥1). The results of the study is tabulated in table 1 and graphically depicted in figure 1.The shielding effectiveness of -20 dB is achieved for a ratio of 1:8 of FT:CNT for the neat cotton fabric which is further enhanced by the pre-treatment with polyaniline. A typical shielding effectiveness of -20 dB indicates a shielding of 99 % of the incoming EM radiation.
In another embodiment, it is found that the composition containing FT and CNT nanoparticles in the ratio 2:1 shows less shielding effectiveness than the one containing nanoparticles in the ratio 1:1. The figures 2a and 2b illustrate the shielding effectiveness of the above-mentioned samples along with samples containing only CNT as a control. Also, the compositions are tested are of 4 layers of fabric, which confirms the that for optimum performance, the amount of CNT added should be greater than that of FT.
Table 1: The EMI shielding effectiveness of the fabrics coated with coatings containing different ratios
Sample EMI SE (dB)
CF/WPU/FT-CNT (1:2) -10 dB
CF/WPU/FT-CNT (1:4) -15 dB
PAni-CF/WPU/FT-CNT (1:2) -15 dB
PAni-CF/Ac/FT-CNT (1:8) -8 dB
PAni-CF/Sil/FT-CNT (1:8) -20 dB

In another embodiment the compositions are also analysed for UV blocking properties, the results of which are tabulated in table 2.

Table 2: UV blocking properties of different ratios of FT-CNT
Sample %UV blocking
CF/WPU/FT 97.42
CF/WPU/CNT 99.12
CF/WPU/FT-CNT (1:2) 99.998
CF/WPU/FT-CNT (1:4) 99.943
CF/WPU/FT-CNT (1:8) 99.982
PAni-CF/WPU/FT-CNT (1:2) 99.962
PAni-CF/WPU/FT-CNT (1:8) 99.998
PAni-CF/Ac/FT-CNT (1:8) 99.942
PAni-CF/Sil/FT-CNT (1:8) 99.974
PAni-CF/WPU/m[FT-CNT] (1:8) 99.998

All the coated fabrics exhibited about above 99% UV blocking. The coated samples block 99% of both UV- A and UV-B radiation. This is attributed to the synergistic effect of iron titanate and carbon nanotubes which act based on an absorption-based mechanism for UV shielding. The availability of π electrons and exceptional strength of C-C bonds make CNTs an ideal complement to FT in shielding UV.

Other properties of the coated fabric:
The coated fabrics (post curing)tend to be resistant towards washing-laundering cycles where the coating is strongly adherent to the fabric and does not come out in flakes or leach out nanoparticles.
The coated fabrics (post curing) tend to exhibit an enhanced limiting oxygen index values(% oxygen required to catch fire) in comparison to the neat cotton fabrics attributed to the high thermal stability of the nanoparticles ( figure 4). The test is done by igniting the samples with a flame in a closed chamber provided with a controlled supply of oxygen and nitrogen that can be varied. Limiting oxygen index is noted as that percentage of oxygen in the nitrogen-oxygen mixture that ignites the sample to burn.
The coated fabrics (post-curing) are thermally stable and maintain their integrity up to 120 °C( figure 5).This is characterized using thermogravimetric analysis wherein the weight loss of a given sample is monitored with increase in temperature. It is noted that there is very negligible weight loss in the coated samples upto 120 °C.
The coated fabrics (post curing) tend to show a reduced wettability towards water which is attributed to the non-polar functional groups conferred onto the surface by the resin( figure 6) as measured by static contact angle studies. The coating containing functionalized nanoparticles (m[FT-CNT]) tend to show increased wettability which is induced by the hydrophilic functional groups.

Experimental:
A. Synthesis of FT Nanoparticles.

Raw Ilmenite is used as the starting material for the synthesis. Said ore is subjected to digestion with concentrated H2SO4 (about 98% GR) at 300 °C for 3 h in a muffle furnace. The resulting dry cake of the mixture is allowed to cool to about 27°C. After digestion, it is leached using deionized (DI) water to yield a water-soluble iron titanium sulfate solution.
The precursor solution prepared above is used as a base material to synthesizeFeTiO3 nanoparticles. The obtained iron titanium sulfate precursor solution (500 mL) is taken in a1000 mL beaker and stirred vigorously at 700 rpm. Then, the reducing agent (25 mL of ammonia) is added dropwise into the precursor solution and maintained at pH 7. Later, the obtained solution is centrifuged at 10 000 rpm and the particles are collected. The collected particles are kept in ahot air oven at 80 °C for 12 h, followed by annealing at 450°Cfor 3h. Finally, reddish brown FT nanoparticles are obtainedand used for further investigations.
B. Characterization of FT Nanoparticles.
The crystalline phase of FT nanoparticles is characterized by X-ray powder diffraction. The measurement is obtained using a X’Pert PRO X-ray diffractometer with Cu Kα (λ = 1.54 Å) radiation. The morphology and purity of the FT nanoparticles are characterized using a scanning electron microscope equipped with an energy-dispersive spectrometer (SEM-EDS, Ultra 55). Thermal analysis is carried out using a thermogravimetric analyzer from TA Instruments.
Magnetic responses of the FT nanoparticles are measured at 27°Cusing a Lakeshsore vibrating sample magnetometer (JDM-13) with an applied force of −8000 to8000 Oe. The optical properties (absorption spectra) are recorded using a UV−Vis−NIR spectrometer (Shimadzu MPC3600) in thin film holder measuring transmittance from 200-400 nm.
C. Pre-treatment of fabric with Aniline
Deposition of polyaniline on the fabric is accomplished by in situ polymerization. The fabric to be coated is stirred in anilinium hydrochloride solution (prepared by dissolving 1 M solution of aniline in 1 M HCl) for 3 hours at 0-5 °C to allow diffusion of aniline to the fabric. After treatment, drops of saturated ammonium persulphate solution(oxidant), cooled to 0 – 5 °C, is added to the reaction bath. The reaction is allowed to proceed for 1 hour after the addition of oxidant where the bath turns green indicating the polymerization of aniline. Later, the fabric is removed from the bath and washed with distilled water to remove any excess polyaniline on the surface and dried for 3 hours at 90 °C.
D. Preparation and testing of compositions
Two typical compositions comprising 1:1 ratio and 2: 1 ratio of FT and CNT, with the specific content of a) CNT being 250 mg and 250 mg of FT and b) CNT being125 mg and 75mg FT, respectively are prepared and dispersed in WPU 20g. The dispersions are used as coatings for EMI shielding efficiency. The results are compared with coatings comprising 250mg and 125 mg of CNT alone (without FT) in WPU 20g on the EMI shielding efficiency. It is very clear from the below graphs ( figure 2a, 2b and figure 3) that the combination of FT and CNT is better that CNT alone. For instance, 1:1 composition showed better results than only CNT.
E. Preparation of modified FT and CNT[m-(FTCNT)]
The coatings are also prepared with modified (FT-CNT) nano particles. Preparation of m(FT-CNT) involve modification done to neat FT and CNT, via chemically coupling by functionalizing them with appropriate functional groups, to enhance both the EMI and UV shielding properties. This contributes to enhanced microwave absorption due to increased dielectric losses instead of magnetic losses.
To prepare modified [m(FT-CNT)] particles, FT particles are functionalized with NH2 groups and CNT is functionalized with COOH groups. m(FT-CNT) particles are prepared by DCC/NHS coupling of weighted proportions of FT and CNT to covalently couple both the nanoparticles. The synthesis of m(FT-CNT) is provided below:
Step-1: Preparation of -OH functionalized FeTiO3(FT) Nanoparticles
To hydroxylate the FT, 1 g of FT nanoparticles is dispersed in a 400 mL aqueous solution of H2O2 by bath sonication for 15 min. After bath sonication, the suspended solution is refluxed at 106 °C for 4 h, followed by washing with deionized water in sequence several times. The H2O2-treated FT is then dried in an oven at 80 °C for 24 h and stored in desiccators.
Step-2: Preparation of -NH2 functionalized FeTiO3(FT) Nanoparticles
The as-prepared hydroxylated FT nanoparticles are refluxed again in the presence of APTES at 80 °C for 24 h. Centrifugation of the obtained mixture followed by washing with toluene for several times to remove the excess APTES to beget FT-NH2, which is denoted as f-FT. Finally, the solvent is evaporated under vacuum.
Step-3: Preparation of -COOH functionalized CNTs
MWNTs are modified with 1-pyrenebutyric acid by adopting the following method. In a 250 ml beaker, 100 mg MWNTs and 220 mg of 1-pyrenebutyric acid are dispersed in 100 ml of DMF and bath sonicated for 2 h. The mixture is vigorously stirred at room temperature for 12 h and kept overnight for ageing. After 12 h, the unbound PBA is removed by centrifugation in DMF at least four times until the solution turned colourless and finally dried under vacuum at 80 °C.
Step-4:Synthesis of modified- [m(FT-CNT)]
The method involves grafting of amine-functionalized FT nanoparticles chemically onto carboxyl-functionalized CNTs.
The nanoparticles, (125 mg FT and 1000 mg CNT) are taken in a round-bottomed flask and dispersed in DMF, followed by bath sonication for 45 min. The obtained nanoparticle mixture is then refluxed at 80 °C for 24 h in the presence of a catalyst-Dicyclohexylcarbodiimide (DCC)and activator N-Hydroxysuccinimide(NHS).The mixture is then centrifuged and washed several times with DMF and toluene to remove excess DCC and NHS and finally dried at 80 °C under vacuum.
F. Preparation of coated fabricmaterials:
The template samples are prepared by laboratory-based techniques like dip coating and film applicator (doctor blade technique). This can be upscaled to similar large-scale processes either using a coating knife or rollers and transfer coating techniques. To get effective shielding, it is observed that there should be a minimum of 100 mg of coating material per sq. cm of the fabric.

Example 1
The nanoparticle composition with ratio 1:1 FT-CNTwith 250mg of FT and 250 mg of CNT prepared as described above is dispersed in 20 g of WPU. Uniform dispersion of the nanoparticles is achieved by probe sonication for 20 minutes followed by 15 minutes of bath sonication, which reduces the agglomeration. The coating resin is stirred intermittently during sonication to ensure there are no lumps formed in the process. The resin is then coated on to the pre-coated Cotton fabric with Aniline, washed in 0.1 M NaOH and dried before coating using a film applicator to obtain a desirable coating thickness of about 300 microns, which can be modified as per the application.
Example 2
The nanoparticle composition with ratio 1:8m[FT-CNT] is first prepared by the above mentioned protocol with 125 mg of amine functionalized FT and 1000 mg of carboxyl functionalized CNT. The prepared m[FT-CNT] is dispersed in 20 g of WPU. Uniform dispersion of the nanoparticles is achieved by probe sonication for 20 minutes followed by 15 minutes of bath sonication, which reduces the agglomeration. The coating resin is stirred intermittently during sonication to ensure there are no lumps formed in the process. The resin is then coated on to the pre-coated Cotton fabric with Aniline (washed in 0.1 M NaOH and dried before coating) using a film applicator to obtain a desirable coating thickness of about 300 microns, which can be modified as per the application.

Thus, the present invention provides a composition that can be dispersed in coating base material and coated onto a neat fabric or pretreated fabric to give it radio wave and UV light blocking properties. The material would prove useful as a packaging material for electronics, flexible housing for circuitry used in critical care units to avoid crosstalk and a part of personal protective equipment for personnel who are prone to exposure of radio waves and microwaves at work.