Claims:1) A hybrid organic-inorganic composite comprising a phosphonic silane based inorganic matrix, and polymer capped nanoparticles.
2) The hybrid organic-inorganic composite as claimed in claim 1, comprising a polyacrylate based organic component and a polyethylene-based additive.
3) The hybrid organic-inorganic composite as claimed in claim 2, wherein the polyacrylate based organic component is in form of a polyacrylate emulsion, and wherein the polyethylene based additive is a high-density polyethylene.
4) The hybrid organic-inorganic composite as claimed in claim 1, wherein the composite is a nanocomposite and comprises nanoparticles selected from polymer capped silver nanoparticles or polymer capped copper nanoparticles.
5) The hybrid organic-inorganic composite as claimed in claim 4, wherein the polymer capped silver or copper nanoparticles are dispersed within the phosphonic silane based inorganic matrix.
6) The hybrid organic-inorganic composite as claimed in claim 4, wherein the polymer employed for capping of the nanoparticles is selected from a group comprising polyacrylic acid, trisodium citrate, ethylenediaminetetraacetic acid and 2-mercaptobenzothiazole or any combination thereof.
7) The hybrid organic-inorganic composite as claimed in claim 1, wherein the phosphonic silane based inorganic matrix is formed by reacting silane compound selected from a group comprising 3-glycidoxypropyltrimethoxy silane (GPTMS), vinyltrimethoxysilane (VTMS) and tetraethoxysilane (TEOS) with a phosphonic acid selected from a group comprising ethylenediaminetetra(methylenephosphonic) acid (EDTPO), phenyl phosphonic acid (PPA), aminotris(methylenephosphonic) acid (ATMP), and hydroxy ethylidene diphosphonic acid (HEDPA).
8) The hybrid organic-inorganic composite as claimed in claim 3, wherein the polyacrylate emulsion comprises an acid stable nonionic or cationic emulsifier.
9) The hybrid organic-inorganic composite as claimed in claim 1, wherein the phosphonic silane based inorganic matrix is in form of a sol, and is at a concentration ranging from about 30% to about 40% with respect to the composite.
10) The hybrid organic-inorganic composite as claimed in claim 3, wherein the polyacrylate emulsion is at a concentration ranging from about 10% to about 30% with respect to the composite, and wherein the polyethylene based additive is at a concentration ranging from about 1% to about 5% with respect to the composite.
11) The hybrid organic-inorganic composite as claimed in claim 1, wherein the polymer capped nanoparticles are at a concentration ranging from about 100 ppm to about 10000 ppm, have an average particle size ranging from about 17 nm to about 96 nm, and have a D50 size distribution ranging from about 35 nm to about 85 nm.
12) The hybrid organic-inorganic composite as claimed in any of claim 10 or 11, wherein the polyacrylate emulsion is at a concentration of about 35% with respect to the composite, wherein the polyethylene based additive is at a concentration of about 2% with respect to the composite, and wherein the polymer capped nanoparticles are at a concentration ranging from about 200 ppm to about 5000 ppm.
13) The hybrid organic-inorganic composite as claimed in claim 1, wherein the composite is applied on a metallic substrate in form of a coating and wherein the composite coating imparts corrosion resistance, lubricity, conductivity and spot weldability to the substrate.
14) The hybrid organic-inorganic composite as claimed in claim 13, wherein the composite is applied on the metallic substrate as a single layer coating, and wherein the metallic substrate is galvannealed steel.
15) The hybrid organic-inorganic composite as claimed in claim 13, wherein the composite coating reduces onset of the corrosion on the metallic surface by at least about 2 folds to about 4 folds when compared to a metallic surface devoid of the composite coating.
16) The hybrid organic-inorganic composite as claimed in claim 13, wherein the composite coating increases total resistance of the metallic surface to the corrosion by at least about 1000 ohms-cm2 to about 40000 ohms-cm2 when compared to a metallic surface devoid of the composite coating.
17) The hybrid organic-inorganic composite as claimed in claim 13, wherein the composite coating enhances the spot weldability of the metallic surface and increases nugget diameter by at least about 19% to about 42% when compared to a metallic surface devoid of the composite coating.
18) The hybrid organic-inorganic composite as claimed in claim 1, wherein the polymer capped nanoparticles enhance electrical conductivity of the composite by at least about 2 folds to about 4.5 folds when compared to a composite devoid of the polymer capped nanoparticles.
19) A process for preparing a hybrid organic-inorganic composite comprising a phosphonic silane based inorganic matrix, and polymer capped nanoparticles, said process comprising:
• preparing a dispersion of polymer capped nanoparticles;
• preparing a phosphonic silane sol based inorganic matrix by reacting a silane compound with a phosphonic acid; and
• mixing the phosphonic silane sol with the dispersion of polymer capped nanoparticles, followed by adding a polyacrylate based organic component and a polyethylene-based additive, to prepare the said hybrid organic-inorganic composite.
20) The process as claimed in claim 19, wherein the nanoparticles are selected from polymer capped silver nanoparticles or polymer capped copper nanoparticles, and wherein the polymer employed for capping of the nanoparticles is selected from a group comprising polyacrylic acid, trisodium citrate, ethylenediaminetetraacetic acid and 2-mercaptobenzothiazole or any combination thereof.
21) The process as claimed in claim 19, wherein the silane compound is selected from a group comprising 3-glycidoxypropyltrimethoxy silane (GPTMS), vinyltrimethoxysilane (VTMS), and tetraethoxysilane (TEOS), wherein the phosphonic acid is selected from a group comprising ethylenediaminetetra(methylenephosphonic) acid (EDTPO), phenyl phosphonic acid (PPA), aminotris(methylenephosphonic) acid (ATMP), and hydroxy ethylidene diphosphonic acid (HEDPA), wherein the polyacrylate based organic component is in form of a polyacrylate emulsion, and wherein the polyethylene based additive is a high-density polyethylene.
22) The process as claimed in claim 19, wherein the phosphonic silane based inorganic matrix is at a concentration ranging from about 30% to about 40% with respect to the composite, wherein the polyacrylate based organic component is at a concentration ranging from about 10% to about 30% with respect to the composite, wherein the polyethylene based additive is at a concentration ranging from about 1% to about 5% with respect to the composite, and wherein the polymer capped nanoparticles are at a concentration ranging from about 100 ppm to about 10000 ppm.
23) The process as claimed in claim 19, wherein the preparation of the dispersion of polymer capped nanoparticles comprises:
• preparing silver or copper precursor solution;
• preparing capping solution by mixing the polymer selected from a group comprising polyacrylic acid, trisodium citrate, ethylenediaminetetraacetic acid and 2-mercaptobenzothiazole or any combination thereof, with water; and
• mixing the precursor solution and the capping solution, followed by adding hydrazine to obtain the dispersion of polymer capped nanoparticles.
24) The process as claimed in claim 23, wherein the precursor solution is prepared by dissolving silver precursor selected from a group comprising silver nitrate, silver acetate and silver oxide, or any combination thereof, or copper precursor selected from a group comprising copper acetate, copper chloride, cupric oxide and copper sulphate pentahydrate, or any combination thereof, in water to form a solution having molar concentration ranging from about 0.01M to about 0.05M.
25) The process as claimed in claim 23, wherein for preparing of the capping solution, concentration of the polymer in water ranges from about 1% to about 4%, and wherein upon mixing the polymer with the water, the solution is stirred at about 500 rpm at a temperature of about 75?C.
26) The process as claimed in claim 23, wherein the mixing of the precursor solution and the capping solution is carried out by slowly adding the precursor solution to the capping solution, followed by addition of about 0.1M NaOH and hydrazine.
27) The process as claimed in claim 26, wherein the precursor solution and the capping solution are mixed in a ratio of about 1:2, wherein the NaOH is added in a ratio of about 1:1200 with respect to the dispersion, and wherein the hydrazine is added in a ratio of about 1:400 with respect to the dispersion.
28) The process as claimed in claim 19, wherein the preparation of the phosphonic silane sol based inorganic matrix comprises:
• mixing a phosphonic acid selected from a group comprising Ethylenediaminetetra(methylenephosphonic) acid (EDTPO), phenyl phosphonic acid (PPA), aminotris(methylenephosphonic) acid (ATMP), and hydroxy ethylidene diphosphonic acid (HEDPA), with water to prepare a phosphonic acid solution;
• mixing a silane compound selected from a group comprising 3-glycidoxypropyltrimethoxy silane (GPTMS), vinyltrimethoxysilane (VTMS), and tetraethoxysilane (TEOS), with water to prepare a silane solution; and
• adding the silane solution in a dropwise manner to the phosphonic acid solution to obtain the said phosphonic silane sol based inorganic matrix.
29) The process as claimed in claim 28, wherein the phosphonic acid or the EDTPO is mixed with water in a ratio ranging from about 2:1 to about 3:1; and wherein concentration of the silane compound or GPTMS in the water is at about 5%.
30) The process as claimed in claim 28, wherein post adding of the phosphonic acid or EDTPO solution to the silane or GPTMS solution, the mixture is stirred at a speed ranging from about 400 rpm to about 500 rpm, for about 2 hours to about 3 hours.
31) The process as claimed in claim 19, wherein the phosphonic silane sol is mixed with the dispersion of polymer capped nanoparticles, at a ratio of about 3:1, and allowed to mix for about 1 hour to about 2 hours.
32) The process as claimed in claim 19, wherein the polyacrylate based organic component is added in form of a polyacrylate emulsion at a concentration ranging from about 10% to about 30% with respect to the composite.
33) The process as claimed in claim 32, wherein the polyethylene-based additive is added, post the addition of the polyacrylate emulsion, at a concentration ranging from about 1% to about 5%, and allowed to blend in, to prepare the said hybrid organic-inorganic composite.
34) A method of imparting corrosion resistance and spot weldability to a metallic substrate, said method comprising coating the metallic substrate with the hybrid organic-inorganic composite of claim 1.
35) The method as claimed in claim 34, wherein the composite is applied on the metallic substrate as a single layer coating, and wherein the metallic substrate is galvannealed steel.
36) The method as claimed in claim 34, wherein the composite coating reduces onset of the corrosion on the metallic surface by at least about 2 folds to about 4 folds, increases total resistance of the metallic surface to the corrosion by at least about 1000 ohms-cm2 to about 40000 ohms-cm2, enhances the spot weldability of the metallic surface and increases nugget diameter by at least about 19% to about 42% when compared to a metallic surface devoid of the composite coating.
37) Use of the hybrid organic-inorganic composite of claim 1, for imparting corrosion resistance and spot weldability to a metallic substrate.
38) A metallic substrate coated with the hybrid organic-inorganic composite of claim 1.
Dated this 16th day of March 2021
Signature:
Name: Durgesh Mukharya
To: Of K&S Partners, Bangalore
The Controller of Patents Agent for the Applicant
The Patent Office, at Kolkata IN/PA No. 1541
, Description:TECHNICAL FIELD
The present disclosure generally relates to the field of coating compositions for substrates including but not limited to steel. In particular, the present disclosure provides an organic-inorganic composite coating system for application on metallic substrates, to protect them from corrosion. The coating system is a hybrid coating system comprising of a phosphonic silane based inorganic component, a polyacrylate based organic component, a polyethylene based additive and polymer capped nanoparticles. The composite so provided is employed as a simple single layer coating on metallic substrates for corrosion resistance along with enhanced lubricity and spot weldability. Also provided herein are corresponding processes to prepare the said hybrid composite and the applications of the same.
BACKGROUND AND PRIOR ART
Galvannealed (GA) steel is a result of galvanization followed by annealing of sheet steel, and is preferred form of steel over galvanized steel, as the coating is harder, and more brittle. However, GA steel is required to be further treated with rust preventive oils and/or chromate-based conversion coatings as a surface treatment to provide temporary corrosion protection during transportation from steel manufacturing units to end customers. The end customers then carry out degreasing, washing and rinsing operations on these RP oil coated GA sheet for further operations like forming, welding, phosphating and painting process as per the different requirements.
Chromate-based conversion coatings and thin-organic coatings have been quite popular for achieving the corrosion protection, but these organic based coatings are neither weldable nor can they withstand forming operations without delaminating. This has triggered the search for a coating which is not only corrosion resistive but can also impart additional functional properties to the GA steel, such as weldability, formability and post-paintability.
Cold rolled steel sheet is generally coated or treated with different coating system to make it corrosion resistive as well as weldable to enable fabrication processes for making automobile panels, etc. at downstream units. Zn-alloy based (e.g. Zn-Ni, Zn-Fe) coating systems on steel have been found to provide significantly higher corrosion resistance even with lower coating thickness. Miura et.al1 have developed Zn-Ni alloy and Zn-Fe alloy electroplated steel sheet along with organic composite coating on steel sheets for automobile body panels. Although these materials were found to provide some beneficial properties, these coatings are made of costly element (Ni) which also produces toxic fumes during welding and consists of multilayers which makes the coating development process tenuous.
Patents such as US5,330,850 discuss about synthesis of multilayer organic-inorganic composite coating system on steel sheet for automobile panels application which have good formability, weldability and corrosion resistivity. However, the coating has two layers of zinc-alloy system which is followed by a third layer of chromating and final layer of organic coating. US4,910,097 also provides a similar zinc-alloy plated steel sheet which is chromated and comprises an organic coating on top. On the other hand, US5,397,638 discusses about development of resin coated steel sheet which is weldable and electrocoatable, but the resin was modified with colloidal silica or silane coupling agent, phosphates of different elements and conducting fine powders. However, this resin coating had chromated zinc alloy layer beneath the resin film.
As is apparent, most of the work discussed provide multilayer coatings with chromate treatment. However, hexavalent chrome treatment is extremely harmful and facing bans due to its carcinogenic effect, thereby making use of chrome laden steel undesirable. Also, the multilayer coating deposition makes the process much more difficult, time consuming and expensive.
While subsequent work has hence been carried out by different research groups to develop chromium-free coating systems to address chrome related deficiencies/side effects, most of these efforts have still led to two layer coating systems, with sometimes a need for pre-treatment.
Thus, there exists a multi-pronged need of a simple single layer coating that is devoid of chromium, is eco-friendly to use and not only provides temporary corrosion protection, but also provides the coated steel characteristics of weldability and formability. Such a coating should also be able to replace the use of RP oil and the subsequent need of degreasing, washing and rinsing operations associated with surface treated steel. The present disclosure aims to address these needs.
SUMMARY OF THE DISCLOSURE
The present disclosure relates to a hybrid organic-inorganic composite comprising a phosphonic silane based inorganic matrix, and polymer capped nanoparticles.
In some embodiments, the present disclosure relates to a hybrid organic-inorganic composite comprising a phosphonic silane based inorganic matrix, and polymer capped nanoparticles, further comprising a polyacrylate based organic component and a polyethylene-based additive.
In some embodiments, the polymer capped silver or copper nanoparticles are dispersed within the phosphonic silane based inorganic matrix to form the hybrid organic-inorganic composite of the present disclosure.
In some embodiments, the hybrid organic-inorganic composite is applied on a metallic substrate, such as galvannealed steel, in form of a single layer coating and wherein the composite coating imparts corrosion resistance, lubricity, conductivity and spot weldability to the substrate.
In some embodiments, the hybrid organic-inorganic composite reduces onset of corrosion of the metallic substrate, increases total resistance of the metallic substrate to the corrosion, enhances the spot weldability of the metallic substrate, increases nugget diameter of the metallic substrate, and enhances electrical conductivity of the metallic substrate, when compared to a metallic substrate devoid of the composite coating.
The present disclosure also relates to a process for preparing the hybrid organic-inorganic composite of the present disclosure, said process comprising:
• preparing a dispersion of polymer capped metal nanoparticles;
• preparing a phosphonic silane sol based inorganic matrix by reacting a silane compound with a phosphonic acid; and
• mixing the phosphonic silane sol with the dispersion of polymer capped metal nanoparticles, followed by adding a polyacrylate based organic component and a polyethylene-based additive, to prepare the said hybrid organic-inorganic composite.
The present disclosure also provides a method of imparting corrosion resistance and spot weldability to a metallic substrate, such as a GA steel, said method comprising coating the metallic substrate with the hybrid organic-inorganic composite of the present disclosure.
The present disclosure also relates to the use of the hybrid organic-inorganic composite of claim for imparting corrosion resistance and spot weldability to a metallic substrate, such as GA steel; and also to the metallic substrate itself, which is coated with such a composite.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where:
Figure 1: (a) Colloidal stability of Ag NP and (b) Colloidal stability of Cu NP, dispersions in water indicating better stability of TSC-capped and PAA-capped Ag and Cu over a wider range of pH.
Figure 2: UV-Vis Spectra for PAA & TSC-capped (a) Ag and (b) Cu NPs, respectively, showing characteristic surface plasmon resonance peaks.
Figure 3: SEM images of polymer-capped nanoparticles indicating spherical morphologies of particles - (a) Ag PAA-capped, (b) Ag TSC-capped, (c) Cu PAA-capped, and (d) Cu TSC-capped.
Figure 4: (a) TEM images showing a shell of TSC on Ag nanoparticles with size of Ag NPs around 20 -35 nm and that of the TSC capped NP in the range of 55-85 nm; (b) HRTEM images of TSC-capped Ag NPs; and (c) SAED patterns indicating crystalline phases of Ag NPs within an amorphous presence of the polymers.
Figure 5: (a) TEM images showing a sheath of PAA polymer on Ag nanoparticles with size of Ag NPs around 5 -20 nm and that of the PAA capped NP in the range of 30-75 nm; (b) HRTEM images of PAA-capped Ag NPs; and (c) SAED patterns indicating crystalline phases of Ag NPs within an amorphous presence of the polymers.
Figure 6: (a) Cross-section of the GPE-5C coating indicating a uniform coating thickness of around 2-3 µm; (b) Uniform coating with dispersed nanoparticles visible from the top section of the coating; (c) & (d) indicating EDS analysis showing a good dispersion of silver nanoparticles across the cross-section of the coating.
Figure 7: (a) TEM images showing dispersion of fine sized nanoparticles across the cross-section of the GPE-5C coating; (b) & (c) EDS analysis on selected area indicating the presence of Ag nanoparticles; and (d) Diffraction pattern on the selected area indicated the presence of crystalline silver within an amorphous polymer matrix.
Figure 8 : IR spectra for the coating liquid and the coated film on steel.
Figure 9: Polarisation plots of coated and uncoated samples.
Figure 10: Bode Impedance Plot of the coated and uncoated galvannealed steel samples.
Figure 11: Electrical equivalent circuits used to fit the Bode impedance plot of (a) bare GA and (b) coated samples.
Figure 12: Dome-formed sections till fracture and to a punch height of 36mm for (a) GPE -5 to 5D coated systems (b) GPE-5E coated system.
Figure 13: SEM images of (a) GPE-5 and (b) GPE-5E coated sample after dome-forming.
DETAILED DESCRIPTION
In view of the limitations discussed above, and to remedy the need in the art for simple single layer coating that provides corrosion protection, weldability and formability to a coated steel, the present disclosure provides a hybrid organic-inorganic composite comprising an inorganic matrix, and organic component, along with nanoparticles and additive.
More particularly, the present disclosure provides a hybrid organic-inorganic composite comprising a phosphonic silane based inorganic matrix, a polyacrylate based organic component, a polyethylene-based additive, along with and polymer capped nanoparticles.
However, before describing the invention in detail, provided below are definitions of some terms used throughout the present disclosure.
Throughout the present disclosure, the term ‘organic-inorganic composite’ is intended to convey the ordinary conventional meaning of the term known to a person skilled in the art and intends to cover a material which is produced from two or more constituent materials, wherein at least one constituting material is an organic material, and at least one other constituting material is an inorganic material. Throughout the present disclosure, this term has also been associated with the term ‘hybrid’ which itself is a type of composite having at least two constituents at the nanometer or molecular level. While a person skilled in the art understands that the term ‘hybrid’ by itself generally refers to a composite of organic and inorganic constituents, the present disclosure cumulatively uses the term ‘hybrid organic-inorganic composite’ to provide more clarity on the material that is being referred to within the present disclosure. In other words, the ‘hybrid organic-inorganic composite’ or simply ‘hybrid composite’ of the present disclosure refers to a material that is formed by combination of at least one organic material, and at least one inorganic material at nanometer or molecular level. Generally, these hybrid composite materials are prepared through a sol-gel or sol-emulsion process, as is also the case in the present disclosure.
As will be clear from the subsequent portions of this disclosure, the ‘hybrid organic-inorganic composite’ of the present disclosure can also be a ‘nanocomposite’. The term ‘nanocomposite’ is therefore again intended to convey the ordinary conventional meaning of the term known to a person skilled in the art and intends to cover a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm) or structures having nano-scale repeat distances between the different phases that make up the material. Particularly in the context of the present disclosure, ‘nanocomposite’ refers to combination of organic and inorganic structural constituents that yield a material with composite properties.
Further, terms that remain specifically undefined in this disclosure, such as ‘galvannealed steel’ and ‘nanoparticles’ are again intended to convey the ordinary conventional meaning of the term known to a person skilled in the art and intends to cover all forms of such substrate/material known till date. If the teachings of this disclosure are found to be applicable to new substrates or materials that are unknown hitherto, but are discovered or prepared post publication of this disclosure, then such substrates or materials are also intended to be within the purview of the present disclosure. Further, the present disclosure also uses the phrase ‘polymer capped nanoparticles’, ‘polymer capped metal nanoparticles’, ‘polymer capped silver nanoparticles’ and ‘polymer capped copper nanoparticles’ interchangeably, and intends to cover nanoparticles that have been capped with a polymer of the present disclosure. The said nanoparticles are achieved when a metal precursor solution, such as a silver or copper precursor solution is reduced by a reducing agent such as hydrazine, to form corresponding metal particles whose size is restricted to nanoparticle range by capping agents.
Accordingly, to reiterate, the present disclosure relates to a hybrid organic-inorganic composite comprising a phosphonic silane based inorganic matrix, and polymer capped nanoparticles.
More particularly, the present disclosure relates to a hybrid organic-inorganic composite comprising a phosphonic silane based inorganic matrix, and polymer capped nanoparticles, along with a polyacrylate based organic component and a polyethylene-based additive. Thus, it is due to the presence of these organic and inorganic based constituents, that the composite of the present disclosure is a hybrid organic-inorganic composite.
In some embodiments, the polyacrylate based organic component that forms part of the hybrid organic-inorganic composite of the present disclosure is in form of a polyacrylate emulsion. In some embodiments, the polyacrylate emulsion optionally comprises an acid stable nonionic or cationic emulsifier.
In some embodiments, the acid stable non-ionic or cationic emulsifier is selected from a group comprising Alberdingk AC 2420 VP, Alberdingk AC 2486, Alberdingk AC 2403, Pidicryl QC 100 and Pidicryl GH500, or any combination thereof.
In some embodiments, the polyethylene based additive that forms part of the hybrid organic-inorganic composite of the present disclosure is a high-density polyethylene.
While the organic and inorganic constituents come together in the form of a hybrid organic-inorganic composite, in some embodiments this composite is a nanocomposite.
Thus, in some embodiments, the present disclosure relates to a hybrid organic-inorganic nanocomposite comprising a phosphonic silane based inorganic matrix, and polymer capped nanoparticles, along with a polyacrylate based organic component and a polyethylene-based additive.
As mentioned above, the nanoparticles employed in the present disclosure are capped nanoparticles and include but are not limited to capped silver nanoparticles or capped copper nanoparticles. These nanoparticles play an important role in enhancing the electrical conductivity of the composite, when it is applied as a coating on to a substrate.
Thus, in some embodiments, the present disclosure relates to a hybrid organic-inorganic composite comprising a phosphonic silane based inorganic matrix, and polymer capped silver nanoparticles, along with a polyacrylate based organic component and a polyethylene-based additive. Similarly, in some embodiments, the present disclosure relates to a hybrid organic-inorganic composite comprising a phosphonic silane based inorganic matrix, and capped copper nanoparticles, along with a polyacrylate based organic component and a polyethylene-based additive.
As the nanoparticles employed in the present disclosure are capped nanoparticles, the capping is facilitated by polymers, to provide polymer capped nanoparticles. The polymer employed for capping of the nanoparticles is selected from a group comprising polyacrylic acid, trisodium citrate, ethylenediaminetetraacetic acid and 2-mercaptobenzothiazole or any combination thereof.
Accordingly, in some embodiments, the hybrid organic-inorganic composite of the present disclosure comprise polymer capped silver nanoparticles, or polymer capped copper nanoparticles, wherein the polymer is polyacrylic acid.
In some embodiments, the hybrid organic-inorganic composite of the present disclosure comprise polymer capped silver nanoparticles, or polymer capped copper nanoparticles, wherein the polymer is trisodium citrate.
In some embodiments, the hybrid organic-inorganic composite of the present disclosure comprise polymer capped silver nanoparticles, or polymer capped copper nanoparticles, wherein the polymer is ethylenediaminetetraacetic acid.
In some embodiments, the hybrid organic-inorganic composite of the present disclosure comprise polymer capped silver nanoparticles, or polymer capped copper nanoparticles, wherein the polymer is 2-mercaptobenzothiazole.
Further, these polymer capped silver or copper nanoparticles are dispersed within the phosphonic silane based inorganic matrix of the present disclosure. This phosphonic silane based inorganic matrix is formed by reacting silane compound selected from a group comprising 3-glycidoxypropyltrimethoxy silane (GPTMS), vinyltrimethoxysilane (VTMS), and tetraethoxysilane (TEOS) with a phosphonic acid selected from a group comprising ethylenediaminetetra(methylenephosphonic) acid (EDTPO), phenyl phosphonic acid (PPA), aminotris(methylenephosphonic) acid (ATMP), and hydroxy ethylidene diphosphonic acid (HEDPA).
In some embodiments, the present disclosure provides the phosphonic silane based inorganic matrix formed by reacting the silane compound and the phosphonic acid through the combinations indicated in Table 1. In Table 1, X represents presence of the corresponding silane compound and phosphonic acid encompassed in each row and column, respectively. Accordingly, every single combination provided in Table 1 represents a separate embodiment of the present disclosure. However, the present disclosure also envisages a merger or mixture of these embodiments to provide for further possible combinations. Thus, for the purposes of the present disclosure, each of the combinations that are derivable from Table 1 below are envisaged to exist individually, all together or in different combinations within the ambit of the present disclosure.

EDTPO PPA ATMP HEDPA
GPTMS X
VTMS X
TEOS X
GPTMS X
VTMS X
TEOS X
GPTMS X
VTMS X
TEOS X
GPTMS X
VTMS X
TEOS X
Table 1
Once formed, in some embodiments, the phosphonic silane based inorganic matrix is present in the hybrid composite of the present disclosure in form of a sol. The concentration of this phosphonic silane based inorganic matrix ranges from about 30% to about 40% with respect to the composite.
Accordingly, in some embodiments, the phosphonic silane based inorganic matrix is present in the hybrid composite of the present disclosure at a concentration of about 30%, about 31%, about 32%, about 33%, about 34%, about 35%, about 36%, about 37%, about 38%, about 39%, or about 40%.
On the other hand, the organic component, i.e., the polyacrylate emulsion, is present in the hybrid composite of the present disclosure at a concentration ranging from about 10% to about 30% with respect to the composite.
Accordingly, in some embodiments, the polyacrylate emulsion is present in the hybrid composite of the present disclosure at a concentration of about 10%, about 11%, about 12%, about 13%, about 14%, about 15%, about 16%, about 17%, about 18%, about 19%, about 20%, about 21%, about 22%, about 23%, about 24%, about 25%, about 26%, about 27%, about 28%, about 29%, or about 30%.
Further, the polyethylene based additive is present in the hybrid composite of the present disclosure at a concentration ranging from about 1% to about 5% with respect to the composite.
Accordingly, in some embodiments, the polyethylene based additive is present in the hybrid composite of the present disclosure at a concentration of about 1%, about 2%, about 3%, about 4%, or about 5%.
Furthermore, the polymer capped nanoparticles are present in the hybrid composite of the present disclosure at a concentration ranging from about 100 ppm to about 10000 ppm.
Accordingly, in some embodiments, the polymer capped nanoparticles, which are polymer capped silver or polymer capped copper nanoparticles, and wherein the polymer is selected from a group comprising polyacrylic acid, trisodium citrate, ethylenediaminetetraacetic acid and 2-mercaptobenzothiazole or any combination thereof, is present in the hybrid composite of the present disclosure at a concentration of about 100 ppm, about 200 ppm, about 300 ppm, about 400 ppm, about 500 ppm, about 600 ppm, about 700 ppm, about 800 ppm, about 900 ppm, about 1000 ppm, about 2000 ppm, about 3000 ppm, about 4000 ppm, about 5000 ppm, about 6000 ppm, about 7000 ppm, about 8000 ppm, about 9000 ppm, or about 10000 ppm.
In some embodiments, the nanoparticles that form part of the hybrid composite have an average particle size ranging from about 17 nm to about 96 nm.
In some embodiments, the nanoparticles that form part of the hybrid composite have a D50 size distribution ranging from about 35 nm to about 85 nm.
In exemplary embodiments, the polyacrylate emulsion is present in the hybrid organic-inorganic composite at a concentration of about 35% with respect to the composite, the polyethylene based additive is present in the hybrid organic-inorganic composite at a concentration of about 2% with respect to the composite, and the polymer capped nanoparticles are present in the hybrid organic-inorganic composite at a concentration ranging from about 200 ppm to about 5000 ppm.
Since the objective of the hybrid composite of the present disclosure is to impart beneficial properties and/or characteristics to a substrate on which it is applied, in some embodiments, the hybrid composite of the present disclosure is applied on the metallic substrate as a single layer coating, and wherein the metallic substrate is galvannealed steel.
In some embodiments, the hybrid composite of the present disclosure is applied on a metallic substrate in form of a coating that imparts corrosion resistance to the substrate.
In some embodiments, the hybrid composite coating reduces onset of the corrosion on the surface of the metallic substrate by at least about 2 folds to about 4 folds when compared to a metallic surface devoid of the composite coating.
In some embodiments, the hybrid composite coating increases total resistance of the surface of the metallic surface to the corrosion by at least about 1000 ohms-cm2 to about 40000 ohms-cm2 when compared to a metallic surface devoid of the composite coating.
In some embodiments, the hybrid composite of the present disclosure is applied on a metallic substrate in form of a coating that imparts lubricity to the substrate.
In some embodiments, the hybrid composite of the present disclosure is applied on a metallic substrate in form of a coating that imparts conductivity to the substrate.
In some embodiments, the polymer capped nanoparticles of the hybrid composite coating enhance electrical conductivity of the composite by at least about 2 folds to about 4.5 folds when compared to a composite devoid of the polymer capped nanoparticles.
In some embodiments, the hybrid composite of the present disclosure is applied on a metallic substrate in form of a coating that imparts spot weldability to the substrate.
In some embodiments, the hybrid composite coating enhances the spot weldability of the surface of the metallic substrate and increases nugget diameter by at least about 19% to about 42% when compared to a metallic surface devoid of the composite coating.
In some embodiments, the hybrid composite of the present disclosure is applied on a metallic substrate in form of a coating that imparts corrosion resistance, lubricity, conductivity and spot weldability to the substrate.
While the hybrid organic-inorganic composite as such forms an important aspect of the present disclosure, equally important is the manner in which the primary constituents, i.e., the phosphonic silane based inorganic matrix, the polyacrylate based organic component, the polymer capped nanoparticles and the polyethylene-based additive, come together to form the said composite.
Accordingly, the present disclosure also relates to a process for preparing the hybrid organic-inorganic composite of the present disclosure, said process comprising:
• preparing a dispersion of polymer capped nanoparticles;
• preparing a phosphonic silane sol based inorganic matrix by reacting a silane compound with a phosphonic acid; and
• mixing the phosphonic silane sol with the dispersion of polymer capped metal nanoparticles, followed by adding a polyacrylate based organic component and a polyethylene-based additive, to prepare the said hybrid organic-inorganic composite.
Embodiments provided above with respect to each of the constituents that go into the process for preparing the hybrid organic-inorganic composite of the present disclosure are equally applicable for the process described herein, and are not repeated merely for the sake of brevity. The focus of the following embodiments will therefore be on the actual steps that define the process and bring these constituents together to prepare the hybrid composite of the present disclosure.
First up, is the preparation of the dispersion of polymer capped metal nanoparticles.
In some embodiments, preparation of the dispersion of polymer capped nanoparticles comprises:
• preparing precursor solution;
• preparing capping solution by mixing a polymer, with water; and
• mixing the precursor solution and the capping solution, followed by adding hydrazine to obtain the dispersion of polymer capped metal nanoparticles.
The said nanoparticles are achieved when the precursor solution is reduced by the reducing agent such as hydrazine, to form metal particles whose size is restricted to nanoparticle range by capping agents.
As mentioned above, since the polymer capped nanoparticles are selected from a group comprising polymer capper silver nanoparticles or polymer capped copper nanoparticles, the precursors employed to prepare the nanoparticle precursor solution is accordingly selected. A person skilled in the art understands the precursors that can be employed that would lead to silver or copper nanoparticles.
In some embodiments, the precursor employed for preparing the silver precursor solution is selected from a group comprising silver nitrate, silver acetate and silver oxide, or any combination thereof. On the other hand, the precursor employed for preparing the copper precursor solution is selected from a group comprising copper acetate, copper chloride, cupric oxide and copper sulphate pentahydrate, or any combination thereof.
In some embodiments, the precursor employed for preparing the precursor solution is selected from a group comprising silver nitrate or copper acetate.
In some embodiments, the precursor solution is prepared by dissolving silver nitrate or copper acetate in water to form a solution having molar concentration ranging from about 0.01M to about 0.05M.
In some embodiments, the precursor solution is prepared by dissolving silver nitrate or copper acetate in water to form a solution having molar concentration of about 0.01M, about 0.02M, about 0.03M, about 0.04M, or about 0.05M.
Accordingly, in some embodiments, preparation of the dispersion of polymer capped metal nanoparticles comprises:
• preparing silver or copper precursor solution;
• preparing capping solution by mixing a polymer, with water; and
• mixing the precursor solution and the capping solution, followed by adding hydrazine to obtain the dispersion of polymer capped metal nanoparticles.
In some embodiments, the precursor employed for preparing the silver precursor solution is selected from a group comprising silver nitrate, silver acetate and silver oxide, or any combination thereof, preferably silver nitrate; whereas the precursor employed for preparing the copper precursor solution is selected from a group comprising copper acetate, copper chloride, cupric oxide and copper sulphate pentahydrate, or any combination thereof, preferably copper acetate.
In some embodiments, the precursor employed for preparing the precursor solution is selected from a group comprising silver nitrate or copper acetate.
With respect to the capping solution, as again described previously, the polymer employed for capping of the nanoparticles is selected from a group comprising polyacrylic acid, trisodium citrate, ethylenediaminetetraacetic acid and 2-mercaptobenzothiazole or any combination thereof.
Accordingly, in some embodiments, the polymer polyacrylic acid is mixed with water to prepare the capping solution employed to cap the silver or copper nanoparticles.
Similarly, in some embodiments, the polymer trisodium citrate is mixed with water to prepare the capping solution employed to cap the silver or copper nanoparticles.
Similarly, in some embodiments, the polymer ethylenediaminetetraacetic acid is mixed with water to prepare the capping solution employed to cap the silver or copper nanoparticles.
Similarly, in some embodiments, the polymer 2-mercaptobenzothiazole is mixed with water to prepare the capping solution employed to cap the silver or copper nanoparticles.
In some embodiments, for preparing of the capping solution, concentration of the polymer in water ranges from about 1% to about 4%, and wherein upon mixing the polymer with the water, the solution is stirred at about 500 rpm at a temperature of about 75?C.
In some embodiments, for preparing of the capping solution, concentration of the polymer in water is at about 1%, about 2%, about 3% or about 4%, and wherein upon mixing the polymer with the water, the solution is stirred at about 500 rpm at a temperature of about 75?C.
Accordingly, in some embodiments, preparation of the dispersion of polymer capped metal nanoparticles comprises:
• preparing silver nitrate or copper acetate precursor solution;
• preparing capping solution by mixing the polymer selected from a group comprising polyacrylic acid, trisodium citrate, ethylenediaminetetraacetic acid and 2-mercaptobenzothiazole or any combination thereof, with water; and
• mixing the precursor solution and the capping solution, followed by adding hydrazine to obtain the dispersion of polymer capped metal nanoparticles.
In some embodiments, the mixing of the precursor solution and the capping solution is carried out by slowly adding the precursor solution to the capping solution, followed by addition of about 0.1M NaOH and hydrazine.
In some embodiments, the precursor solution and the capping solution are mixed in a ratio of about 1:2, wherein the NaOH is added in a ratio of about 1:1200 with respect to the dispersion, and wherein the hydrazine is added in a ratio of about 1:400 with respect to the dispersion.
Once the dispersion of polymer capped nanoparticles is prepared, as mentioned above, it is mixed with the phosphonic silane sol based inorganic matrix.
Thus, next up, is the preparation of the phosphonic silane sol based inorganic matrix.
In some embodiments, preparation of the phosphonic silane sol based inorganic matrix comprises:
• mixing a phosphonic acid with water to prepare a phosphonic acid solution;
• mixing a silane compound with water to prepare a silane solution; and
• adding the silane solution in a dropwise manner to the phosphonic acid solution to obtain the said phosphonic silane sol based inorganic matrix.
As mentioned above, the phosphonic acid is selected from a group comprising ethylenediaminetetra(methylenephosphonic) acid (EDTPO), phenyl phosphonic acid (PPA), aminotris(methylenephosphonic) acid (ATMP), and hydroxy ethylidene diphosphonic acid (HEDPA).
Thus, in some embodiments, preparation of the phosphonic silane sol based inorganic matrix comprises:
• mixing a phosphonic acid selected from a group comprising ethylenediaminetetra(methylenephosphonic) acid (EDTPO), phenyl phosphonic acid (PPA), aminotris(methylenephosphonic) acid (ATMP), and hydroxy ethylidene diphosphonic acid (HEDPA)with water to prepare a phosphonic acid solution;
• mixing a silane compound with water to prepare a silane solution; and
• adding the silane solution in a dropwise manner to the phosphonic acid solution to obtain the said phosphonic silane sol based inorganic matrix.
In some embodiments, the phosphonic acid such as the EDTPO is mixed with water in a ratio ranging from about 2:1 to about 3:1.
As also mentioned above, the silane compound is selected from a group comprising 3-glycidoxypropyltrimethoxy silane (GPTMS), vinyltrimethoxysilane (VTMS), and tetraethoxysilane (TEOS).
Thus, in some embodiments, preparation of the phosphonic silane sol based inorganic matrix comprises:
• mixing a phosphonic acid selected from a group comprising ethylenediaminetetra(methylenephosphonic) acid (EDTPO), phenyl phosphonic acid (PPA), aminotris(methylenephosphonic) acid (ATMP), and hydroxy ethylidene diphosphonic acid (HEDPA)with water to prepare a phosphonic acid solution;
• mixing a silane compound selected from a group comprising 3-glycidoxypropyltrimethoxy silane (GPTMS), vinyltrimethoxysilane (VTMS), and tetraethoxysilane (TEOS) with water to prepare a silane solution; and
• adding the silane solution in a dropwise manner to the phosphonic acid solution to obtain the said phosphonic silane sol based inorganic matrix.
In some embodiments, concentration of the silane compound such as the GPTMS in the water is at about 5%.
As mentioned with respect to Table 1 above, all combinations of the phosphonic acid and silane compound are envisaged explicitly, as separate embodiments within the purview of the present disclosure.
Once the silane solution such as GPTMS solution is added to the phosphonic acid solution such as the EDTPO solution, the mixture is stirred at a speed ranging from about 400 rpm to about 500 rpm, for about 2 hours to about 3 hours, to prepare the phosphonic silane sol based inorganic matrix.
Now that both, the dispersion of polymer capped metal nanoparticles, and the phosphonic silane based inorganic matrix are prepared, they are mixed together. Once mixed, the polyacrylate based organic component and the polyethylene-based additive are added, to prepare the said hybrid organic-inorganic composite of the present disclosure.
In some embodiments, the phosphonic silane based inorganic matrix is mixed with the dispersion of polymer capped nanoparticles, at a ratio of about 3:1, and allowed to mix for about 1 hour to about 2 hours.
Accordingly, the process for preparing the hybrid organic-inorganic composite of the present disclosure, comprises:
• preparing a dispersion of polymer capped metal nanoparticles;
• preparing a phosphonic silane sol based inorganic matrix by reacting a silane compound with a phosphonic acid; and
• mixing the phosphonic silane sol with the dispersion of polymer capped metal nanoparticles at a ratio of about 3:1, followed by adding a polyacrylate based organic component and a polyethylene-based additive, to prepare the said hybrid organic-inorganic composite.
Upon mixing of the phosphonic silane sol with the dispersion of polymer capped nanoparticles, the polyacrylate based organic component is added.
In some embodiments, the polyacrylate emulsion is at a concentration ranging from about 10% to about 30% with respect to the composite.
In some embodiments, the polyacrylate emulsion optionally comprises an acid stable nonionic or cationic emulsifier.
In some embodiments, the acid stable non-ionic or cationic emulsifier is selected from a group comprising Alberdingk AC 2420 VP, Alberdingk AC 2486, Alberdingk AC 2403, Pidicryl QC 100 and Pidicryl GH500, or any combination thereof.
Thereafter, post the addition of the polyacrylate emulsion, the polyethylene-based additive is added, and allowed to blend in for about 1 hour.
In some embodiments, the polyethylene-based additive is at a concentration ranging from about 1% to about 5%, and allowed to blend in, to prepare the said hybrid organic-inorganic composite.
Since there are multiple possibilities for each of phosphonic acid, silane compound and type of nanoparticles, all permutations & combinations of such possibilities are explicitly envisaged in the present disclosure. While Table 1 above described all combinations of the phosphonic acid and the silane compound, each of those possibilities are further envisaged individually with polymer capped silver nanoparticles and polymer capped copper nanoparticles. Similarly, within the nanoparticles, as there are possibilities of various polymers to be used as capping agents, each of those possibilities are once again explicitly envisaged by the present disclosure.
In other words, any possible combination of phosphonic acid and silane compound mentioned in Table 1 employed to prepare the phosphonic silane based inorganic matrix of the present disclosure, can be combined with polymer capped silver nanoparticles, wherein the polymer is selected from a group comprising polyacrylic acid, trisodium citrate, ethylenediaminetetraacetic acid and 2-mercaptobenzothiazole or any combination thereof.
Similarly, any possible combination of phosphonic acid and silane compound mentioned in Table 1 employed to prepare the phosphonic silane based inorganic matrix of the present disclosure, can be combined with polymer capped copper nanoparticles, wherein the polymer is selected from a group comprising polyacrylic acid, trisodium citrate, ethylenediaminetetraacetic acid and 2-mercaptobenzothiazole or any combination thereof.
Accordingly, to sum up, in some embodiments, the hybrid composite of the present disclosure is prepared by a process comprising:
• preparing silver nitrate or copper acetate precursor solution;
• preparing capping solution by mixing the polymer selected from a group comprising polyacrylic acid, trisodium citrate, ethylenediaminetetraacetic acid and 2-mercaptobenzothiazole or any combination thereof, with water;
• mixing the precursor solution and the capping solution, followed by adding hydrazine to obtain the dispersion of polymer capped metal nanoparticles;
• separately, mixing a phosphonic acid selected from a group comprising ethylenediaminetetra(methylenephosphonic) acid (EDTPO), phenyl phosphonic acid (PPA), aminotris(methylenephosphonic) acid (ATMP), and hydroxy ethylidene diphosphonic acid (HEDPA)with water to prepare a phosphonic acid solution;
• mixing a silane compound selected from a group comprising 3-glycidoxypropyltrimethoxy silane (GPTMS), vinyltrimethoxysilane (VTMS), and tetraethoxysilane (TEOS) with water to prepare a silane solution; and
• adding the silane solution in a dropwise manner to the phosphonic acid solution to obtain the said phosphonic silane sol based inorganic matrix; and
• mixing the phosphonic silane sol based inorganic matrix with the dispersion of polymer capped metal nanoparticles at a ratio of about 3:1, followed by adding a polyacrylate based organic component and a polyethylene-based additive, to prepare the said hybrid organic-inorganic composite of the present disclosure.
The present further relates to a method of imparting corrosion resistance and spot weldability to a metallic substrate, said method comprising coating the metallic substrate with the hybrid organic-inorganic composite as described above.
In some embodiments, the composite is applied on the metallic substrate or its surface as a single layer coating, and wherein the metallic substrate is galvannealed steel.
In some embodiments, the composite coating reduces onset of the corrosion on the surface of the metallic substrate by at least about 2 folds to about 4 folds, increases total resistance of the surface to the corrosion by at least about 1000 ohms-cm2 to about 40000 ohms-cm2, enhances the spot weldability of the surface and increases nugget diameter by at least about 19% to about 42% when compared to a metallic substrate devoid of the composite coating.
In some embodiments, the metallic substrates, such as galvannealed steel coated with the hybrid composite of the present disclosure find extensive applications in automobile industry.
The present disclosure also provides a use of the hybrid organic-inorganic composite as described above, for imparting corrosion resistance and spot weldability to a metallic substrate.
The metallic substrate so coated with the hybrid organic-inorganic composite as described above is also envisaged by the present disclosure.
EXAMPLES
The present disclosure is further described with reference to the following examples, which are only illustrative in nature and should not be construed to limit the scope of the present disclosure in any manner.
Materials
Silver(I) nitrate (AgNO3), copper acetate (Cu(CH3COO)2) and hydrazine were purchased to synthesize the conducting nanoparticles. (3-Glycidyloxypropyl) trimethoxysilane (GPTMS) and Ethylenediaminetetra(methylenephosphonic) acid (EDTPO) were purchased from Sigma Aldrich and TCI, respectively, and were used to build the phosphonic silane matrix of the coating film. polyacrylic acid (MW-100000, 35wt% in H2O), trisodium citrate (TSC), ethylenediaminetetraacetic acid (EDTA) and 2-mercaptobenzothiazole (MBT) were also purchased from Sigma Aldrich and were mainly used to cap the copper or silver nanoparticles preventing them from oxidation or agglomeration. The organic component was a polyacrylate-based emulsion purchased from Alberdingk Inc. and stabilized with either acid stable nonionic or cationic emulsifier. The polyacrylate compound had a molecular weight of 100000. A lubricating additive with high-density polyethylene (HDPE) chemistry was purchased from Keim Additec and was added into the base formulation for ease of forming and abrasion resistance of the coated system.
Example 1: Synthesis of polymer capped conducting nanoparticles
Polymer capped copper and silver nanoparticles were synthesized by the reduction of copper and silver precursors, copper acetate(Cu(CH3COO)2) and silver nitrate(AgNO3), respectively, with hydrazine in aqueous solution. The capping or stabilizing solution was prepared by slowly adding 1 ml of PAA, TSC, EDTA or 2-Mercaptobenzothiazole (MBT) (1 wt%) in 98.5 ml of water. The solution was stirred continuously at 500 rpm maintaining a temperature of 75oC. The precursor solutions were prepared with varying concentrations of Cu(CH3COO)2 and AgNO3, i.e., 0.01M, 0.02M and 0.05M. After 20 minutes, 50 ml of the precursor solutions were slowly added to the capping solution. Following the addition, 125 ?L of 0.1M NaOH was added to adjust the pH of the solution. Finally, 375 ?L of hydrazine was added slowly to reduce the precursor into the metal nanoparticles. The different combinations of polymer capped metal nanoparticle dispersions and their concentrations are listed in Tables 2 (silver nanoparticles) and 3 (copper nanoparticles) below.
Precursor solution- molarity Precursor volume (ml) Capping chemical-concentration (wt %) Water (ml) 0.1M NaOH (?L) Hydrazine (?L)
0.01 M AgNO3
50 TSC – 1 98.5
125
375

PAA-1
EDTA-1
MBT-1
0.02 M AgNO3
50 TSC – 1 98.5
125
375

PAA-1
EDTA-1
MBT-1
0.05 M AgNO3
50 TSC – 1 98.5
125
375

PAA-1
EDTA-1
MBT-1
Table 2

Precursor solution- molarity Precursor volume (ml) Capping chemical-concentration (wt %) Water (ml) 0.1M NaOH (?L) Hydrazine (?L)
0.01 M Cu(CH3COO)2
50 TSC – 1 98.5
125
375

PAA-1
EDTA-1
MBT-1
0.02 M Cu(CH3COO)2
50 TSC – 1 98.5
125
375

PAA-1
EDTA-1
MBT-1
0.05 M Cu(CH3COO)2
50 TSC – 1 98.5
125
375

PAA-1
EDTA-1
MBT-1
Table 3
Example 2: Synthesis of hybrid organic-inorganic composite
In a separate beaker from the one used to hold the nanoparticle dispersion prepared in example 1, 0.08g of EDTPO was mixed in 35 ml of water to prepare the phosphonic acid solution. Further, a 5wt % GPTMS solution (silane solution) was prepared and was added in a dropwise manner to the EDTPO solution, to obtain the silane sol mixture (phosphonic silane inorganic matrix). This silane sol mixture is allowed to stir at a speed of 400-500 rpm for 2-3 hours This solution was then added in 3:1 ratio to the nanoparticle dispersion and allowed to mix for 1-2 hours. Following that, the polyacrylate emulsion was added in varying amounts starting from 10 wt% to 30 wt% in increments of 5 ml to prepare different formulations. Thereafter, 2 ml of HDPE lubricating additive was added to each formulation at the end and allowed to blend into the formulation for 1 hour. Different combinations of the hybrid composite of the present disclosure were prepared from different concentrations of polyacrylate emulsion, and polymer capped nanoparticles dispersion as listed in Table 4 below.
Sample-ID Concentration of Polymer capped nanoparticles dispersion (ppm) Silane sol mixture (ml) Polyacrylate emulsion (ml) Lubricating Additive
(ml) Water
(ml)
GPE-1 0 35 10 2 50
GPE-2 0 35 15 2 50
GPE-3 0 35 20 2 50
GPE-4 0 35 25 2 50
GPE-5 0 35 30 2 50
GPE-5A 200 ppm Ag 35 30 2 50
GPE-5B 500 ppm Ag 35 30 2 50
GPE-5C 1000 ppm Ag 35 30 2 50
GPE-5D 2000 ppm Ag 35 30 2 50
GPE-5E 5000 ppm Ag 35 30 2 50
GPE-5(ii) 200 ppm Cu 35 30 2 50
GPE-5(iii) 500 ppm Cu 35 30 2 50
GPE-5(iv) 1000 ppm Cu 35 30 2 50
GPE-5(v) 2000 ppm Cu 35 30 2 50
GPE-5(vi) 5000 ppm Cu 35 30 2 50
Table 4
Example 3: Characterization of the polymer capped nanoparticles - zeta potential measurement
Zeta potential is a measure of the “effective” electric charge on the nanoparticle surface and quantifies the charge stability of colloidal nanoparticles. The dispersion stability of the nanoparticles in water was measured through zeta potential technique using a zeta-sizer instrument (Malvern NanoSizer). 50ml of freshly prepared polymer capped nanoparticle dispersions with same concentration but different polymer capping agents (PAA,TSC, EDTA & MBT) were taken and were continuously stirred at between 200-300 rpm. The pH of the solution was adjusted using HCl and NaOH solution. After 30 mins, 10µl solution was taken and injected into zeta-sizer cuvette. The zeta potentials were measured from pH 3 to 10 at increments of 1. The zeta potential values were noted for both the polymer capped Ag and Cu nanoparticles at different pH values to know the stability of the dispersions.
Zeta potential values of greater than +30mV or lesser than -30mV indicates a good dispersion stability. Figures 1(a) and (b) show the zeta potential values of the polymer capper silver and copper nanoparticles respectively as a function of pH.
Example 4: Characterization of the polymer capped nanoparticles - UV-visible Spectroscopy
UV-visible spectra of the synthesized nanoparticles were recorded at room temperature using UV-3600i Plus UV-Vis-NIR Spectrophotometer (Shimadzu), using a 1 cm path length quartz cuvette, and a fixed slit width of 5 nm. The spectra of the nanoparticles under different polymer capping were recorded at a data interval of 1 nm and the final spectra was analyzed to identify the peaks.
The formation of the Ag NPs with both PAA and TSC-capping agent was confirmed through the UV-Vis absorption spectrum [Figure 2(a)]. Both the colloidal solutions showed characteristic surface plasmon resonance (SPR) peak at around 400 nm. Similarly, the formation of colloidal copper nanoparticles with PAA capping agent was confirmed by the presence of a characteristic peak at around 600 nm. A similar characteristic peak was also found with TSC-capped Cu colloidal solution along with the presence of a smaller peak at around 400 nm which was indicative of copper oxide nanoparticles [Figure 2(b)].
Example 5: Characterization of the polymer capped nanoparticles – particle size analysis
The average particle sizes and size distributions of the synthesized nanoparticles were determined by dynamic light scattering (DLS) using Litesizer 500 (Anton-Paar). The samples were diluted in distilled water (Type 1) at ambient temperature (23°C) to obtain a dilution factor that allow a reliable reading. Three measurements were made, each with 30 s of balance and 10 runs of 10 s of duration.
DLS analysis was carried out on PAA-capped and TSC-capped Ag and Cu nanoparticles, respectively, to find out the particle sizes and distribution of the synthesized nanoparticles. The average particle sizes and the distribution are shown in Table 5.

Nanoparticle Dispersion Number average particle size (nm) Size Distribution (nm)
D10 D50 D90
PAA-capped Ag 21.39 ± 2.84 7.54 36.70 45.03
TSC-capped Ag 80.73 ± 13.87 65.44 84.58 136.42
PAA-capped Cu 70.7 ± 3.36 7.60 53.91 101.40
TSC-capped Cu 68.42 ± 8.90 7.51 52.58 98.08
Table 5
Example 6: Characterization of the polymer capped nanoparticles – Scanning Electron Microscopy (FEG-SEM)
SEM analysis was carried out on a field emission gun scanning electron microscope APREO S to understand the size and morphology of the polymer capped copper nanoparticles and also used to understand the distribution of the nanoparticles across the coating. The EDAX analysis of coating helped to understand the distribution of different phases across the coating surface. The nanoparticle samples for SEM characterization were prepared by drop-casting the dispersions on copper stubs followed by gold coating to prevent charging of particles.
Figures 3(a)-(d) show the SEM micrographs for the PAA-capped and TSC-capped Ag and Cu nanoparticles, respectively. The particles were found to be spherical in nature and were found to have a particle size less than 100 nm.
Example 7: Characterization of the polymer capped nanoparticles and the hybrid composite of the present disclosure – Transmission Electron Microscopy
HRTEM images of the polymer capped nanoparticles and the cross-section of the coatings were obtained in a FEL TALOS F200X microscope operating at 200kV. Furthermore, selected area electron diffraction (SAED) patterns and energy dispersive spectroscopic (EDS) analysis was carried out to confirm the chemistry and crystallinity of the nanoparticles. The nanoparticle samples for TEM analysis were prepared by drop-casting the nanoparticle dispersions on carbon film coated copper grid of 300 mesh size. For preparation of the cross-sections for the coated sample, two pieces of the coated steel with dimensions 1.5×0.5mm are cut with the help of slow speed saw using the 0.15 thick diamond wheel and are glued together by a transparent thermoplastic glue on a glass plate. Following that, the sample was polished to form a cylinder which was then inserted into the slot of a brass tube (2mm inner diameter). Thin discs were then sectioned from the tube, polished and thinned down to below 100µm. These discs were then polished by dimple grinder to form a depression at the center of the disc followed by ion beam milling PIPS II to form an electron transparent hole.
TEM analysis was further done on capped silver nanoparticles to understand the exact size of the metal nanoparticles and the extent of the polymer capping on each particle. HRTEM images and SAED pattern also gave an indication of the crystallinity and chemistry of the particles. Figure 4 shows the TEM analysis done on the TSC-capped silver nanoparticles. Further, Figure 5 shows the similar kind of TEM studies conducted on PAA-capped Ag nanoparticles.
Microstructural study was then conducted on the polymer nanocomposite films formed from the composite of the present disclosure to check for dispersion of the conducting nanoparticles within the coating matrix as well as to check the uniformity and thickness of the coatings. Figure 6 shows the top and cross-section of the coating GPE-5C along with energy-dispersive spectroscopic (EDS) analysis indicating the presence of different elements within the coating.
TEM analysis was further done on the cross-section of the coated sample to study the dispersion of the conducting nanoparticles within the coating matrix. EDS analysis on definite areas across the cross-section of the coating indicated presence of ppm levels of Ag nanoparticles. Furthermore, SAED pattern indicated the presence of crystalline phases of Ag within amorphous phases (seen as diffused rings in the diffraction pattern).
Example 8: Characterization of the chemical formulation – Fourier Transformed Infrared Spectroscopy (FTIR)
FTIR spectroscopic studies were performed in Vertex 80 FTIR System, Bruker, Germany to understand the formation of chemical bonds during chemical formulation as well as after curing of coating. The scan wave numbers range for each test was from 450 to 4000 cm-1.
FTIR spectra was obtained for the nanocomposite coating formulation (GPE-5C) and the coating film (applied and subsequently cured) on the galvannealed substrate and is shown in Figure 8.
The characteristic peaks in the coating liquid and the coated film are presented in Table 6 below. The carboxylic group peaks (1727 cm-1) was indicative of the polyacrylate resin used in the formulation. This was also present in the coated film which indicated that despite the cross-linking reaction happening there are free carboxylic group also available. The presence of phosphonic groups in the coating formulation and their absence in the film indicate further cross-linking of the inorganic moiety. Broad peaks at 1100 cm-1 in the coated film is for Si-O-Si8 indicates cross-linking of the phosphonic and silane moieties to form the inorganic coupling. The peak at 900cm-1 is indicative of the Si-O-M bonding conferring good adhesion of the coating system to the steel substrate.

Peak in cm -1 Liquid Coating Remarks
3320 Hydroxyl group - Free hydroxyl groups is present in the formulation but absent in coating film
2871,2931 C-H stretching C-H stretching C-H groups present in the coating matrix backbone
1727 Carboxylic group - Carboxylic group present in the polyacrylate moiety of coating
1200 P=O group - Cross-linking reaction of the phosphonic group.
1100 Si-O-Si Silane peak
1034 P-O-C stretch - Phosphonic moiety
900 Si-O-C Si-O-M Cross-linking reaction of silane
Table 6
Example 9: Corrosion measurement – Salt Spray Testing
The corrosion resistance of the coating was evaluated by means of an accelerated test in a simulated high-saline environment. The test involves placing the coated material in a salt spray (fog) apparatus and the white rust generation is observed visually over a definite time interval, in accordance with ASTM B117 standard. Generation of greater than 5% white rust across the exposed area of the coating surface was considered to be the maximum corrosion resistance offered.
Neutral salt spray testing (NSST) of the coated samples viz. GPE-5 to GPE-5E, were done on polymer nanocomposite coatings and the samples were monitored till 5% white rust appeared on them. The NSST hours of each samples (ASTM B117) have been shown in Table 7.
Sample Code NSST hours (before 5% white rust)
Bare GA 72 hours
GPE- 5 264 hours
GPE - 5A 240 hours
GPE-5B 216 hours
GPE-5C 192 hours
GPE-5D 192 hours
GPE-5E 168 hours
Table 7
Example 10: Electrochemical testing
A three-electrode flat cell system was used to perform all the electrochemical experiments where coated samples were used as the working electrode (WE), platinum mesh as counter electrode (CE) and saturated calomel electrode (SCE) as reference electrode (RE). A 3.5wt% aqueous sodium chloride (NaCl) solution was used as electrolyte for all the electrochemical tests. The exposed area for the working electrode was kept fixed at 1cm2 for all the electrochemical experiments. The sample was kept immersed in the electrolyte solution for 30 mins to reach a steady Open Circuit Potential (OCP) before commencing potentiodynamic polarization and Electrochemical Impedance spectroscopy tests. All the electrochemical tests were carried out at room temperature (25oC) in freely aerated conditions. The scan range for all the potentiodynamic polarization tests was ±500mV with respect to the OCP and the scan rate was 0.5mV/s. Electrochemical impedance spectroscopy (EIS) studies was carried out to understand the barrier properties of the silane-coating on the galvanized steel and the mechanisms of corrosion. The impedance data was obtained by applying sinusoidal perturbation of ±10 mV at OCP in the frequency range of 100 kHz to 10 mHz. The obtained spectra were fitted with relevant equivalent electric circuits to calculate the values of electrochemical parameters.
Electrochemical tests viz. potentiodynamic polarization and electrochemical impedance spectroscopic studies was also carried out to determine the corrosion resistance of the coating samples. Potentiodynamic polarization curves for the uncoated and the coated samples were generated and shown in Figure 9. The polarization curves of the coated samples were found to be on the left side compared to the bare GA samples indicating a decrease in the corrosion current density, and hence, an increase in the corrosion resistance.
Bode impedance plot, shown in Figure 10, further reveals that the uncoated as well as the coated samples have resistive behavior at higher frequency (103 to105 Hz) and lower (100 to 10-2 Hz) frequency region. The intermediate frequency region (100 to103 Hz) shows the evidence of a capacitive behavior. From the graph, it can be inferred that the coated samples have the higher impedance at lower frequency which is a clear indication of improved barrier to corrosion by the coated samples as compared to the bare.
The electrochemical values were obtained by fitting the impedance spectra using an equivalent electric circuit to emulate the phenomena occurring at the different interfaces (electrolyte/coating & coating/steel) [Figures 11(a) &(b)]. The Bode impedance data of bare GA was fitted with a Randles circuit where the solution resistance (Rs) is in series with the parallel combination of constant phase element (CPEdl) and charge transfer resistance (Rct) [Figure 11(a)]. All the coated samples were fitted with an equivalent circuit with twotime constants – one to explain the corrosion processes of the base substrate consisting of resistance Rcoat in parallel with constant-phase element CPEc and another to explain the contribution of the coating in electrochemical reactions consisting of a constant-phase element (CPEdl) and charge transfer resistance (Rct) in parallel. Rcoat represents the resistance offered by the coating to the penetration of electrolyte and corrosive ions whereas the CPEc represents the dielectric impedance offered by the coating layer.
From the fitted parameters, the total resistance to corrosion offered by the coating was calculated as the summation of the charge-transfer (Rct) and the coating resistance (Rcoat).
The electrochemical parameters obtained by fitting impedance spectra of the coated and uncoated samples are summarized in Table 8 below.
Samples Rs (? cm2) Rct (? cm2) Rcoat (? cm2) CPEdl n CPEc (S*s^m) m Rt= (Rct+Rcoat) (? cm2) Goodness of fit
(S*s^n)
Bare GA 19.2 6.17E+03 - 4.93E-05 0.76 - - 349 7.80E-03
GPE-5 23.7 2.48E+04 1.54E+04 6.60E-05 0.39 2.02E-05 0.88 40200 9.77E-04

GPE-5A 19.7 8.18E+03 6.08E+03 8.74E-05 0.71 2.37E+05 0.87 14260 1.86E-03

GPE-5B 20.8 2.46E+03 8.81E+03 4.77E-05 0.96 1.98E-05 0.89 11270 1.48E-02

GPE-5C 16.73 1.76E+03 5.73E+03 1.23E-03 0.72 3.94E-05 0.85 7490 5.61E-03

GPE-5D 24.4 8.00E+02 1.05E+03 8.02E-04 0.72 9.77E-05 0.82 1850 1.10E-03

GPE-5E 24.25 4.98E+02 9.96E+02 1.02E-02 1 6.84E-04 0.7 1494 1.01E-02

Table 8
Example 11: Spot weldability test
The spot weldability test was done to check the weldability of coating. According to standard AWS D8.9, a coated system is called spot weldable only when the experimental nugget diameter is more than or equal to the theoretical nugget diameter. The theoretical nugget diameter of a coated steel sample is represented by the following formula-
Theoretical nugget dia.= 4vt (where t=thickness of steel substrate)
The spot-welding tests were carried out at 6.5 kA with constant weld time of 250 milliseconds, constant force of 2 kN, constant squeeze time of 450 milliseconds. After that the nugget diameter of the spot-welded samples were measured and compared with the theoretical nugget diameter to identify the spot weldability of coating. Further, the initial contact resistance between the electrode and the coated/uncoated sample was measured at 2 kA with a constant weld time of 150ms, constant load of 2.2kN and a dwell time of 83 milliseconds. The steel substrate thickness for the weldability tests was 0.7 mm.
Spot weldability tests were carried out at a weld time of 250 milliseconds on the coated samples. Table 9 summarizes all the spot-welding parameters and gives a comparison of the theoretical and experimentally obtained nugget diameters post spot-welding of the different coating systems. It was observed that the coating system GPE-5 without any addition of silver nanoparticles was not spot-weldable at 5kA and was only weldable at higher currents as 6.5kA. All the polymer-capped silver nanoparticle incorporated coatings (GPE-5A to 5E & GPE-5(ii) to 5(vi)) showed proper spot weldability when the applied current is more than or equal to 5kA indicating that the conducting nanoparticles and its uniform distribution throughout the coating matrix has allowed for proper passage of weld current through the dielectric coating.
Sample Current (kA) Weld time (ms) Force (kN) Squeeze time (ms) Experimental Nugget dia. (mm) Theoretical nugget dia. (mm)
GPE-5 5 250 2 450 2.96 3.35
5.5 250 2 450 3.0 3.35
6 250 2 450 3.15 3.35
6.5 250 2 450 3.4 3.35
GPE-5A 5 250 2 450 3.55 3.35
GPE-5B 5 250 2 450 3.85 3.35
GPE-5C 5 250 2 450 3.95 3.35
GPE-5D 5 250 2 450 4.05 3.35
GPE-5E 5 250 2 450 5 3.35
GPE-5(ii) 5 250 2 450 3.91 3.35
GPE-5(iii) 5 250 2 450 3.9 3.35
GPE-5(iv) 5 250 2 450 3.98 3.35
GPE-5(v) 5 250 2 450 4.2 3.35
GPE-5(vi) 5 250 2 450 4.21 3.35
Table 9
Example 12: Forming test
The lubrication behavior of the coating was studied through limiting dome height test where the aim was to find the extent of delamination (if any) of the coating post dome formation. The tests were performed on a typical punch-die assembly with a 130T servo-hydraulic forming press. The punch height was maintained at 36mm for the coated sheet with a punch force of 50kN. The punch diameter was set at 102mm and the drawing speed of punch was kept constant at 1 mm/s.
Limiting dome height test was done on the coated samples to check for its adhesion to the substrate and to check for any possible delamination post dome forming process. Two samples for each coating system was taken – one which was formed till fracture and another which was formed till a punch height of 36 mm. Figure 12 below shows the visual appearance of the dome-formed coated samples. It can be observed that from visual investigation there is no delamination that is observed.
SEM micrographs (Figure 13) were taken on these dome samples to check for microcrack formation and no such evidence was found. Thus, it could be concluded that the coating has enough lubricity to withstand severe forming operations without getting delaminated from the base metal.
In view of the experiments conducted above, and the results obtain, provided below in Table 10 is a summary of the major characteristics that were observed for different composites prepared in the present disclosure.
Sample-ID Nanoparticle dispersion (ppm) Particle Size (nm) Zeta Potential (mV) Solution Conductivity (mS/cm) Corrosion Resistance (SST) Spot Weldability Formability
GPE-1 0 - - 0.722 72 hours - -
GPE-2 0 - - 0.718 96 hours - -
GPE-3 0 - - 0.723 120 hours - -
GPE-4 0 - - 0.719 168 hours - -
GPE-5 0 - - 0.721 264 hours - Y
GPE-5A 200 ppm Ag 7.54 -35.6 1.62 240 hours Y Y
GPE-5B 500 ppm Ag 12.67 -38.2 2.12 216 hours Y Y
GPE-5C 1000 ppm Ag 16.52 -35.1 2.31 192 hours Y Y
GPE-5D 2000 ppm Ag 21.39 -40.9 2.60 192 hours Y Y
GPE-5E 5000 ppm Ag 24.35 -35.1 2.99 168 hours Y Y
GPE-5(ii) 200 ppm Cu 52.58 -48.5 1.91 96 hours Y Y
GPE-5(iii) 500 ppm Cu 53.71 -49.1 2.779 96 hours Y Y
GPE-5(iv) 1000 ppm Cu 60.4 -50.4 2.831 72 hours Y Y
GPE-5(v) 2000 ppm Cu 65.43 -51.2 2.99 48 hours Y Y
GPE-5(vi) 5000 ppm Cu 70.72 -49.2 3.28 48 hours Y Y
Table 10
Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.
The foregoing description of the specific embodiments fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising” wherever used, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. The term "about" is used herein to mean approximately, in the region of, roughly, or around. When the term "about" is used in conjunction with a numerical value/range, it modifies that value/range by extending the boundaries above and below the numerical value(s) set forth. In general, the term "about" is used herein to modify a numerical value(s) above and below the stated value(s) by a variance of 20%.
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.
As regards the embodiments characterized in this specification, it is intended that each embodiment be read independently as well as in combination with another embodiment. For example, in case of an embodiment 1 reciting 3 alternatives A, B and C, an embodiment 2 reciting 3 alternatives D, E and F and an embodiment 3 reciting 3 alternatives G, H and I, it is to be understood that the specification unambiguously discloses embodiments corresponding to combinations A, D, G; A, D, H; A, D, I; A, E, G; A, E, H; A, E, I; A, F, G; A, F, H; A, F, I; B, D, G; B, D, H; B, D, I; B, E, G; B, E, H; B, E, I; B, F, G; B, F, H; B, F, I; C, D, G; C, D, H; C, D, I; C, E, G; C, E, H; C, E, I; C, F, G; C, F, H; C, F, I, unless specifically mentioned otherwise.
Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
All references, articles, publications, general disclosures etc. cited herein are incorporated by reference in their entireties for all purposes. However, mention of any reference, article, publication etc. cited herein is not, and should not be taken as, an acknowledgment or any form of suggestion that they constitute valid prior art or form part of the common general knowledge in any country in the world.