FORM 2
HE PATENTS ACT, 1970
(39 of 1970) PATENTS RULES, 2003
COMPLETE SPECIFICATION
TITLE OF THE INVENTION
A RAPID CURING TWO-COMPONENT ADHESIVE SYSTEM FOR BONDING METALS WITH
LOW ENERGY SURFACES

APPLICANT Pvt
of W-27, MIDC, Industrial Area, Kalmeshwar, Nagpur-441 501, Maharashtra, India; India
following specification particularly describes the invention and the manner in which it is to be performed

A RAPID CURING TWO-COMPONENT ADHESIVE SYSTEM FOR BONDING METALS WITH LOW ENERGY SURFACES
FIELD OF THE INVENTION
5 [0001] The present disclosure relates to a rapid curing two-component adhesive system for bonding low-energy surface metals without the need for surface preparation and primer application.
BACKGROUND OF THE INVENTION
10 [0002] Metal sheets or metal articles may be subjected to galvanization, which makes the metal sheets or the metal articles rust proof. The galvanization process has become an integral and indispensable part of multiple industries. For example, galvanized metal sheets or metal articles are used in industries like appliance manufacturing industry, infrastructure industry, transportation industry, passenger vehicles industry, etc.
15
[0003] While manufacturing various appliances, devices, or apparatus, bonding of galvanized metal surfaces is inevitable. However, it is known in the art that bonding galvanized metal surfaces together without surface preparation is complex and tedious process. For example, it is inevitable for bonding two galvanized metal surfaces to prepare the surfaces thereof for
20 bonding and/or apply a primer. The bonding may be achieved using a suitable adhesive known in art.
[0004] Several conventional commercial adhesives are known in the art. However, the conventional adhesives exhibit several drawbacks listed herein below: 25
[0005] In order to use the conventional adhesives, it is required to prepare the surface by applying primer to the galvanized metal surface. This step of surface preparation is required to ensure proper bonding.
30 [0006] The conventional adhesives have inadequate shelf life, typically less than six months and have limited thermal stability.

[0007] The conventional adhesives have low lap shear strength, low handling strength, high fixture time, poor adhesion at elevated temperatures such as 120 °C, low impact strength at low temperatures such as - 40 °C, and low peel strength at - 40 °C.
5 [0008] Therefore, there is a need to provide an adhesive that simplifies the bonding of galvanized metal surfaces. Also, there is a need to provide an adhesive that eliminates the tedious processes of surface preparation and/or the primer application. Further, there is a need to provide an adhesive that enables high strength and rapid bonding of the galvanized metal surfaces or metals having low-energy surfaces. 10
OBJECTS OF THE INVENTION
[0009] Some of the objects of the present disclosure, of which at the minimum one
object is fulfilled by at least one embodiment disclosed herein, are as follows:
15 [00010] An object of the present disclosure is to provide an alternative that overcomes
at least one drawback encountered in the existing prior art.
[00011] Another object of the present disclosure is to provide an adhesive for bonding
galvanized metal surfaces. 20
[00012] Still another object of the present disclosure is to provide high-strength, rapid
curing adhesive to bond galvanized metal surfaces.
[00013] Yet another object of the present disclosure is to provide an adhesive that
25 enables the bonding of low-energy surface metals.
[00014] Another object of the present disclosure is to provide an adhesive that
eliminates the need for surface preparation and primer application.
30 [00015] Other objects and benefits of the present disclosure will be more apparent
from the following description, which is not intended to bind the scope of the present disclosure.

SUMMARY OF THE INVENTION
[00016] The present disclosure envisages a two-component adhesive system for bonding metals with low energy surfaces. The two-component adhesive system comprises an adhesive component and an activator component. The adhesive component comprises a
5 methacrylate monomer in an amount ranging from 60 wt.% to 75 wt.%; an antioxidant in an amount ranging from 0.5 wt.% to 2 wt.%; an inhibitor in an amount ranging from 0.02 wt.% to 0.1 wt.%; an adhesion promoter in an amount ranging from 4 wt.% to 10 wt.%; an etching agent in an amount ranging from 0.2 wt.% to 1 wt.%; a thermoplastic core-shell rubber in an amount ranging from 10 wt.% to 30 wt.%; an impact modifier in an amount ranging from 10
10 wt.% to 20 wt.%; an initiator in an amount ranging from 0 wt.% to 4 wt.%. The activator component comprises an inert plasticizer in an amount ranging from 30 wt.% to 70 wt.%; a catalyst pre-cursor in an amount ranging from 1 wt.% to 3 wt.%; an inorganic filler in an amount ranging from 30 wt.% to 60 wt.%; an accelerator in an amount ranging from 8 wt.% to 15 wt.%.
15
[00017] In one embodiment, the mix ratio of the adhesive component to the activator component is 10:1.
[00018] In one embodiment, the system exhibits a pot life of 4 to 5 minutes at 25°C. 20
[00019] In one embodiment, the system demonstrates a lap shear strength of greater than 12 MPa at 25°C on a substrate of electro galvanized steel.
[00020] In one embodiment, the system maintains lap shear strength of greater than 10 25 MPa at elevated temperatures up to 120oC and at low temperatures down to -40°C.
[00021] In one embodiment, the system exhibits an impact strength in the range of 15 to 30 kJ/M2 at -40°C.
30 [00022] In one embodiment, the system achieves a Shore A hardness in the range of 50 to 70.
[00023] In one embodiment, the system demonstrates stability with no significant change in viscosity or reactivity after exposure at 62°C for 5 days.
4

[00024] In one embodiment, the system exhibits salt spray resistance with no significant loss in lap shear strength after 8 weeks of exposure.
5 [00025] In one embodiment, the system is capable of bonding metals with low energy surfaces without the need for surface preparation or primer application.
[00026] In one embodiment, the system demonstrates cohesive failure mode rather than adhesive failure mode when subjected to lap shear testing at elevated temperatures. 10
[00027] In one embodiment, the adhesive component further comprises a chelating agent, corrosion inhibitor, pigments, chain transfer agents, and cross-linker.
[00028] In one embodiment, the activator component further comprises a thixotropic 15 agent and catalyst with plasticizer.
[00029] In one embodiment, the adhesive component comprises a thickener in an amount ranging from 2 wt.% to 8 wt.%
20 [00030] The present disclosure further envisages a method for bonding metals with low energy surfaces using the adhesive system, in accordance with an embodiment of the present invention. The method comprises the steps of mixing the adhesive component with the activator component in a ratio of 10:1 to form a mixed adhesive system; applying the mixed adhesive system to at least one metal surface with low energy; joining the metal
25 surfaces together; and allowing the mixed adhesive system to cure at room temperature to form a bonded assembly with a lap shear strength of greater than 12 MPa.
[00031] In one embodiment, the bonded assembly demonstrates no significant loss in lap shear strength after exposure to a salt spray test for 8 weeks. 30
[00032] In one embodiment, the bonded assembly maintains lap shear strength of greater than 10 MPa at elevated temperatures up to 120oC and at low temperatures down to -40°C.
5

[00033] In one embodiment, the bonded assembly exhibits an impact strength in the range of 15 to 30 kJ/M2 at -40°C.
[00034] In one embodiment, the bonded assembly achieves a Shore A hardness in the 5 range of 50 to 70.
[00035] In one embodiment, the bonded assembly demonstrates cohesive failure mode rather than adhesive failure mode when subjected to lap shear testing at elevated temperatures. 10
BRIEF DESCRIPTION OF THE DRAWINGS
[00036] For a more complete understanding of the features and advantages of the present disclosure, reference is now made to the detailed description along with the accompanying figures in which corresponding numerals in the different figures refer to 15 corresponding parts and in which:
[00037] FIG. 1 is a photographical representation illustrating the comparative lap shear strength (LSS) at high temperature (83oC) for various substrates bonded with the invented adhesive product versus competing products. 20
[00038] FIG. 2 is a graphical representation showing the lap shear strength (LSS) of different substrates when bonded with the invented adhesive product and competing products at low temperature (-40oC).
25 [00039] FIG. 3 is a graphical representation depicting the lap shear strength (LSS) of the invented product versus competition on Gal Metal Z-90 substrates at varied bond thicknesses (0.5 mm, 3.0 mm, 5.0 mm, and 10.0 mm).
DETAILED DESCRIPTION
30 [00040] All the terms and expressions, which may be technical, scientific, or otherwise, as used in the present disclosure have the same meaning as understood by a person having ordinary skill in the art to which the present disclosure belongs, unless and otherwise explicitly specified.
6

[00041] In the present specification, and the claims, the articles “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
[00042] The term “comprising” as used in the present specification and the claims will 5 be understood to mean that the list following is non-exhaustive and may or may not include any other extra suitable features or elements or steps or constituents as applicable.
[00043] Further, the terms “about” or “approximately” used in combination with ranges relating to sizes of parts, or any other physical properties or characteristics, are meant 10 to include small variations that may occur in the upper and/or lower limits of the ranges of the sizes.
[00044] The two-component adhesives system of the present disclosure exhibits optimal performance/properties due to synergy between core shell rubber polymers of 15 different classes, and additionally exhibits exceptional stability on ageing and high strength without hampering open time.
[00045] The two-component adhesives system of the present disclosure cures at room temperature and reaches high strength in a short period of time. More specifically, the 20 provision of the two-component adhesives system with adhesion promoter enables rapid curing at room temperature and further aids in achieving bonding strength of 10 MPa or greater in 120 minutes.
[00046] The two-component adhesives system of the present disclosure is observed to 25 bond exceptionally well to all galvanized processed metals and low energy surface metals without any pre-treatment and primer application prior to bonding.
[00047] The two-component adhesives system of the present disclosure exhibits the desired performance properties which are achieved by employing two component 30 methacrylate-based adhesive. More specifically the two-component adhesive system of the present disclosure includes an adhesive part which comprises a monomer component, a core shell rubber polymer of grafted polybutadiene by acrylonitrile and styrene, along with an adhesion promoter and an activator part which includes thixotropic agent and accelerator.
7

[00048] It is observed that the grafted core shell rubber polymer used provides higher bond strength and cohesive failure mode.
[00049] The two-component adhesives system of the present disclosure is formulated 5 to achieve desired properties without surface treatment by incorporation of adhesion promoter into methacrylate adhesive formulation. For this purpose, an adhesion promoter and an etching agent is included.
[00050] In accordance with the present invention, a two-component adhesive system is
10 disclosed. In accordance with one embodiment, the two-component adhesive system is specifically formulated for the bonding of metals with low energy surfaces. The two-component adhesive system, in accordance with an embodiment of the present invention, addresses the challenges commonly encountered with traditional adhesives and provides a novel solution that simplifies the bonding process.
15
[00051] In accordance with one embodiment of the present invention, the two-component adhesive system comprises an adhesive component and an activator component, each containing a specific blend of ingredients that synergistically work to achieve optimal bonding strength and performance.
20
[00052] In accordance with an embodiment of the present invention, the adhesive component of the system is a blend of several key ingredients. The adhesive component includes a methacrylate monomer, constituting between 60 wt.% and 75 wt.%. The monomer allows for ensuring the adhesive's bonding strength and overall durability. In accordance with
25 one embodiment of the present invention, to augment the properties of the methacrylate monomer, a thickener is added in a proportion ranging from 2 wt.% to 8 wt.%. The thickener aids in achieving the desired consistency and ease of application of the adhesive. Additionally, the adhesive component includes an antioxidant in the range of 0.5 wt.% to 2 wt.% and an inhibitor, ranging from 0.02 wt.% to 0.1 wt.%. In accordance with on
30 embodiment, the adhesive component includes an adhesion promotor in an amount in the range of 4 wt. % to 10 wt. %, an etching agent in an amount in the range of 0.2 wt. % to 1 wt. %, a thermoplastic core-shell rubber in an amount in the range of 10 wt. % to 30 wt. %, an impact modifier in an amount in the range of 10 wt. % to 20 wt. %, and an initiator in an amount in the range of 0 wt. % to 4 wt. %.
8

[00053] In accordance with one embodiment of the present disclosure, the adhesive system further includes a chelating agent, corrosion inhibitor, pigments, chain transfer agents, and cross-linker. 5 [00054] In accordance with one embodiment of the present disclosure, the thermoplastic core-shell rubber is core shell rubber polymer of grafted polybutadiene by acrylonitrile and styrene.
10 [00055] In accordance with an embodiment of the present invention, the activator component, which works in conjunction with the adhesive component, is composed of an inert plasticizer, constituting 30 wt.% to 70 wt.% of the mixture. The plasticizer is facilitates maintaining the flexibility and workability of the adhesive. The activator component further includes a catalyst pre-cursor in an amount ranging from 1 wt.% to 3 wt.%. The precursor
15 accelerates the curing process, ensuring rapid bonding upon application. Furthermore, the activator component includes an inorganic filler, which makes up 30 wt.% to 60 wt.% of the mixture, contributing to the adhesive's mechanical strength and volume. The activator component further includes an accelerator in a proportion of 8 wt.% to 15 wt.%, which further hastens the curing process and enhances the adhesive's bonding capabilities.
20
[00056] In accordance with one embodiment of the present disclosure, the activator component includes thixotropic agent and catalyst with plasticizer.
[00057] In accordance with one embodiment, the specified mix ratio of the adhesive 25 component to the activator component is maintained at 10:1. This ratio is critical for achieving the optimal balance between adhesive strength and curing time.
[00058] In accordance with one embodiment of the present invention, the system exhibits a pot life of 4 to 5 minutes at 25°C, allowing sufficient time for application before 30 the curing process begins.
[00059] In accordance with an embodiment of the present invention, the adhesive system is characterized by its high lap shear strength, which is greater than 12 MPa at 25°C
9

when applied to a substrate of electro-galvanized steel. This strength is maintained even under elevated temperatures up to 120oC and at low temperatures down to -40°C.
[00060] In accordance with an embodiment of the present invention, additionally, the
5 adhesive system demonstrates an impact strength in the range of 15 to 30 kJ/M2 at -40°C and achieves a Shore A hardness in the range of 50 to 70.
[00061] In accordance with an embodiment of the present invention, the stability of the
adhesive system is another advantageous aspect of the present invention. The adhesive
10 system, in accordance with one embodiment, shows no significant change in viscosity or reactivity after being exposed to a temperature of 62°C for 5 days. Moreover, it exhibits excellent salt spray resistance, with no significant loss in lap shear strength after 8 weeks of exposure. This aspect of the adhesive system, in accordance with an embodiment of the present invention, is particularly advantageous for applications where the bonded metals are
15 exposed to corrosive environments.
[00062] The present disclosure also describes a method for bonding metals with low
energy surfaces using this adhesive system. The method includes mixing the adhesive component with the activator component in the specified ratio to form a mixed adhesive
20 system. This mixture is then applied to at least one metal surface with low energy. Following the application, the metal surfaces are joined together and allowed to cure at room temperature. This results in a bonded assembly with a lap shear strength of greater than 12 MPa. The bonded assembly, prepared using this method, maintains its lap shear strength under extreme temperatures and shows excellent resistance to salt spray exposure.
25
[00063] In accordance with the embodiments of the present disclosure, the adhesive
system exhibits a pot life in the range of 4 minutes to 5 minutes at 25°C, lap shear strength of greater than 12 MPa at 25°C, lap shear strength of greater than 10 MPa at - 40 °C, Impact strength in the range of 15 to 30 KJ/M2 at - 40 °C, and a shore A hardness in the range of 50
30 to 70.

[00064] In accordance with one embodiment the two-component adhesive system of
the present disclosure with 10:1 ratio kept at 63° C +/-1°C for one week exhibited no change in viscosity thereof.
5 [00065] Further, the two-component adhesive system’s performance and lap shear
strength are found to be excellent even after ageing the sample at 63 °C for one week, indicating that the shelf life of the two-component adhesive system is more than a year.
[00066] Additionally, the 10:1 system with a secondary initiator when subjected to 80°
10 +/-1°C for two weeks exhibits no change in mechanical properties and cure profile.
[00067] Table 1 herein below provides a list of properties of the two-component
adhesives system of the present disclosure.
# Properties Method Values
1 Appearance, Part A f White
Part B - Yellow
2 Mix Ratio - 10:1
3 Pot Life at 25°C - 4- 5 min
4 Peak Exotherm,10 gm mass - 10-15 min
5 Lap Shear Strength at 25°C, MPa ASTM D1002 >10-12 MPa Substrate: Electro Galvanized steel, Z-90
6 Lap Shear Strength at 25°C, MPa ASTM D1002 >10-11 MPa Substrate: Hot dipped galvanized steel,
HDG- G90
7 Lap Shear Strength at 25°C, MPa ASTM D1002 >10-11 MPA Substrate: Cold Rolled Steel
8 Lap Shear Strength at 25°C, MPa ASTM D1002 >12-14 MPa Substrate: Greet Blasted Mild Steel
9 Lap Shear Strength at 25°C, MPa ASTM D1002 >10-12 MPa Substrate: Aluminum
11

10 Lap Shear Strength at 80°C, MPa ASTM D1002 >10-11 MPa
Substrate: Hot dipped Galvanized steel,
HDG- G90
11 Lap Shear Strength at 120°C, MPa ASTM D1002 >10 MPa
Substrate: Hot dipped galvanized steel,

12 Lap Shear Strength at -40°C ASTM D1002 >10 MPa
13 Impact Strength -40°C ASTM D 950 15-30 KJ/ M2
15 Shore Hardness Type A ASTM D2240 50-70
Examples
[00068] The following examples illustrate the performance of the invented two-5 component adhesive system in comparison with competitive products in various tests. These examples demonstrate the superior properties of the invented product in terms of stability, adhesive strength, and environmental resistance.
Example 1: Physical Properties Testing
10
[00069] The physical properties of the invented two-component adhesive system and competitive products were evaluated both fresh and after aging at 62°C for 5 days. The following table summarizes the results:
15 Table 1: Physical Properties: Fresh against aged sample at 62oC for 5 days

Test Parameters Invented Product Competition 1 Competition 2 Competition 3
Mix Ratio 10:1 10:1 10:2 10:1
Open time; minute RT 5 – 6 6.5 – 7.5 ~ 20 6 – 7
Open time; minute After exposure at 62°C/5 Days 5 - 6 DNC* DNC* DNC*
Viscosity, cps; RT Adhesive Activator 117K 76K 310K 170K 150K 70K 130K 101K

Viscosity, cps; 62°C/5 days Adhesive Activator 215K 123K Very High 200K 205K 156K 220K 126K
[00070] The table presents a comparative analysis of the physical properties of the invented two-component adhesive system against three competitive products. The parameters tested include mix ratio, open time at room temperature (rt), open time after aging at 62°C for
5 5 days, and viscosity measurements for both the adhesive and activator components at room temperature and after aging at 62°C for the same duration. After aging at 62°C for 5 days, the viscosity of the invented product's adhesive and activator increases to 215k cps and 123k cps, respectively, which is within a controllable range and does not hinder dispensability. In contrast, competition 1 experiences a substantial increase in viscosity, becoming very hard to
10 dispense from the cartridge, which could pose significant challenges in practical applications. The viscosity of competition 2 and competition 3 also increases but remains lower than that of competition 1.
Table 2: Lap Shear Strength in MPa at RT 7-day Cure
15

Substrates Invented Product Competition 1 Competition 2 Competition 3
Gal Metal Z 90 12 MPa 100% CF 4.28 MPa 100% AF 10 MPa 50%TCF 3.11 100%AF
Gal Metal Z 60 12 MPa 100% CF 3.27 MPa 100% AF 9.4 MPa 70%TCF 6.10 MPa 100%AF
Carbon Steel 12 MPa Substrate Pull 6.55 MPa Substrate Pull 3 MPa Substrate Pull 5.8 MPa; Substrate Pull
Hot Dip Galvanized 12 MPa 100% CF 5.62 MPa 60% CF 9.40 MPa 60%TCF 3 MPa 100%AF
Galvaneal 12 MPa 100% CF 9.10 MPa 50% CF 1924 Substrate Pull 12 MPa 50% AF
Aluminium 6061 12 MPa 100% CF 8.9 MPa 100% CF 11 MPa 100%TCF 13.57 100%CF
Stainless Steel 12 MPa 100% CF 8.4 MPa 70% CF 10.7 100%CF 12.9 MPa 100%AF
Carbon Reinforced Steel 12 MPa 100%CF 10.4 MPa 80% CF 10 MPa 100%CF 2251 80%CF
[00071] The invented product consistently shows a high LSS of 12 MPa across all substrates, indicating a strong and reliable bond. The failure mode for the invented product is predominantly cohesive (100% CF), which suggests that the adhesive bond is stronger than
13

the material itself, as the material fails before the bond does. The competitors show varying LSS values, with some instances of adhesive failure (AF), indicating that the bond is the weak point rather than the material.
Table 3: Lap Shear Strength in MPa at 830C

Substrates Invented Product Competition 1 Competition 2 Competition 3
Gal Metal Z-90 9 100% CF 0.5 100%AF 4.4 100%AF 0.6 100%AF
Gal Metal Z-60 9 100% CF 0.6 100%AF 4.25 100%AF 0.52 100%AF
Carbon Steel 11; SP 1.5 SP 1.6 SP 2.8; SP
Hot Dipped Galvanized 9 100% CF 0.3 100%AF 4.35 100%AF 0.8 100%AF
Galvaneal 11 100% CF 0.8 100%CF 4.7 100%AF 2.45 100%AF
Aluminum 6061 10 100%CF 1.1 100%CF 5.5 100%AF 2.75 50%CF
Stainless Steel 12 90%CF 1.0 TCF 7.06 100%CF 1.6 100%AF
Carbon Reinforced Steel 10 100%CF 1.1 90%CF 5.5 50%CF 2.0 100%AF
[00072] The cohesive failure mode in the invented product indicates that the adhesive bond is stronger than the substrate material itself, as the material fails before the adhesive 10 bond does. In contrast, as seen in FIG. 1, the adhesive failure in the competing products suggests that the bond is the weakest point, failing before the substrate material.
[00073] The percentage depletion in LSS at high temperature is significantly less for the invented product compared to the competition, demonstrating the superior thermal 15 stability and strength of the invented product under extreme conditions. This data could be crucial for applications where adhesives are exposed to high temperatures and require reliable performance.
Table 4: Lap Shear Strength in MPa at -400C
Substrates Invented Competition Competition Competition
Product 1 2 3

Gal Metal Z 90 8.6 80% TCF 5.94 100%AF 7.2 100%AF 2.08 100%AF
Gal Metal Z 60 5.61 80%TCF 4.81 100%AF 4.89 100%AF 2.20 100%AF
Carbon Steel 8.4 SP 6.8 SP 2,90 SP 6.77 SP
Hot Dipped Galvanized 8.7 100%AF 5.05 100%AF 7.48 100%AF 2.5 100%AF
Galvaneal 7.5 SP 10.5 70% TCF 12.7 80%SP 14.16 SP
Aluminum 6061 11.30 100%CF 9.38 100%AF 16.43 100%AF 16.24 100%AF
Stainless Steel 14.77 100%CF 9.67 100%AF 18.11 100%AF 16.30 100%AF
Carbon Reinforced Steel 14.60 80%TCF 11.15 100%AF 12.56 100%AF 11.52 100%AF
[00074] The failure mode for all substrates bonded with the invented product is either 100% AF or TCF (thin cohesive failure) or SP (substrate pull), which indicates that the adhesive bond is typically stronger than the substrate itself. This is in contrast to the 5 competitive products, which predominantly show 100% AF as seen in FIG. 2, suggesting that the bond created by these adhesives is the weakest point.
[00075] The superior performance of the invented product at low temperatures is attributed to the presence of butadiene in the formulation, which imparts better strength at 10 such conditions. The LSS of the invented product is found to be less depleted over the LSS values at room temperature demonstrating the product's exceptional cold-temperature performance and its suitability for applications that require robust bonding in cold environments.
15 Table 5: Lap Shear Strength MPa – Salt Spray Test - 8 Weeks Duration

Substrates Invented Product Competition 1 Competition 2 Competition 3
Gal Metal Z 90 7.20; 100% CF 3.60; 100%AF 9.0; 100%AF 3.60; 100%AF
Gal Metal Z 60 6.74 100% CF 3.67; 100%AF 9.3; 100%AF 5.52; 100%AF
Carbon Steel 2.56; SP 275; SP 254; SP 543; SP
Hot Dipped 7.01 5.12; 9.65; 5.05;

Galvanized 100% CF 100%AF 100%AF 100%AF
Galvaneal 6.4; SP 4.90; SP 7.98; SP 9.17; SP
Aluminum 6061 10.72; 100% CF 3.17; 100%AF 7.20; 100%AF 3.46; 100%AF
Stainless Steel 10.97; 100% CF 10.16; 100%AF 7.50; 50%CF 11.20; 100%AF
Carbon Reinforced Steel 6.80; 100% CF 4.35; 100%CF 10.60; 100%CF 7.39; 100%AF
[00076] The data shows that the invented product consistently exhibits cohesive failure rather than adhesive failure after exposure to salt spray, which suggests that the bond itself remains strong and the failure occurs within the substrate material. This is a desirable 5 property as it indicates that the integrity of the bond is not compromised by the corrosive environment.
[00077] In contrast, the competitive products often show adhesive failure, which indicates that the bond between the adhesive and the substrate is the weak point rather than 10 the substrate itself. This could lead to premature failure in real-world applications where corrosion resistance is important.
[00078] The results for the invented product on Gal Metal Z 90, Z 60, Aluminium etc are particularly noteworthy, as they maintain high LSS values with cohesive failure, which is 15 indicative of a robust and durable adhesive bond. The performance on carbon steel, with substrate peeling, suggests that the substrate itself is failing before the adhesive bond, which could be due to the nature of the substrate or the thickness of the galvanized coating.
Table 6: Comparative LSS at room temperature with varied thickness

Bond Thickness Invented Product Competition
LSS on Gal Metal Z-90 0.5 mm” 12 MPa 100%CF 8 MPa 70% CF
LSS on Gal Metal Z-90 3.0 mm 8 MPa 100%CF 6.3 MPa TCF
LSS on Gal Metal Z-90 5.0 mm 6 MPa 100%CF 4.5 MPa TCF
LSS on Gal Metal Z-90 10.0 mm 5 MPa 100%CF 3.4 MPa TCF
[00079] It is evident that the invented product consistently shows higher LSS values across all thicknesses compared to the competition. Additionally, as seen in FIG. 3, the invented product maintains 100% cohesive failure even as the bond thickness increases,
16

which suggests that the adhesive maintains its internal strength regardless of the layer thickness.
[00080] In contrast, as seen in FIG. 3, the competition's LSS values decrease with increasing bond thickness, and the failure mode shifts from 70% cohesive failure at 0.5 mm to thin cohesive failure at greater thicknesses. This could indicate that the competition's adhesive may not be as robust when used in thicker layers, potentially leading to weaker bonds under the same conditions.

Technical Advantages and Economical Significance of the Two-Component Adhesive System of the Present Disclosure
[00081] The two-component adhesive system of the present disclosure exhibits
excellent bonding to substrates including Electro galvanized, Hot dipped galvanized, CRS, 5 Aluminum, PVC, ABS, MS, vinyl and fiberglass without any surface preparation, treatment, and primer application.
[00082] The two-component adhesive system of the present disclosure exhibits
superior mechanical and bonding properties due to synergy between core shell rubber 10 polymers and other polymers of different classes.
[00083] The two-component adhesive system of the present disclosure:
a. demonstrates outstanding lap shear strength at temperature up to 120oC;
b. is fast curing and possesses excellent thermal stability over a wide temperature range;
15 c. has a better shelf life of more than a year at 25°C; and
d. is easy to use for end application.

We claim:
1. A two-component adhesive system for bonding metals with low energy surfaces,
comprising:
a. an adhesive component comprising:
5 i. a methacrylate monomer in an amount ranging from 60 wt.% to 75 wt.%;
ii. an antioxidant in an amount ranging from 0.5 wt.% to 2 wt.%;
iii. an inhibitor in an amount ranging from 0.02 wt.% to 0.1 wt.%;
iv. an adhesion promoter in an amount ranging from 4 wt.% to 10 wt.%;
v. an etching agent in an amount ranging from 0.2 wt.% to 1 wt.%; 10 vi. a thermoplastic core-shell rubber in an amount ranging from 10 wt.% to 30 wt.%;
vii. an impact modifier in an amount ranging from 10 wt.% to 20 wt.%;
viii. an initiator in an amount ranging from 0 wt.% to 4 wt.%;
b. an activator component comprising:
i. an inert plasticizer in an amount ranging from 30 wt.% to 70 wt.%; 15 ii. a catalyst pre-cursor in an amount ranging from 1 wt.% to 3 wt.%; iii. an inorganic filler in an amount ranging from 30 wt.% to 60 wt.%; iv. an accelerator in an amount ranging from 8 wt.% to 15 wt.%.
2. The adhesive system as claimed in claim 1, wherein the ratio of the adhesive component to
the activator component is 10:1.
20 3. The adhesive system as claimed in claim 1, wherein the adhesive component further comprises a chelating agent, corrosion inhibitor, pigments, chain transfer agents, and cross-linker.
4. The adhesive system as claimed in claim 1, wherein the activator component further comprises a thixotropic agent.
25 5. The adhesive system as claimed in claim 1, further comprising a thickener in an amount ranging from 2 wt.% to 8 wt.%
6. A method for bonding metals with low energy surfaces using the adhesive system as claimed in claim 1, comprising the steps of:

a. mixing the adhesive component with the activator component in a ratio of 10:1 to form a
mixed adhesive system;
b. applying the mixed adhesive system to at least one metal surface with low energy;
c. joining the metal surfaces together; and
5 d. allowing the mixed adhesive system to cure at room temperature to form a bonded assembly with a lap shear strength of greater than 12 MPa.