An explosion-proof and impact-resistant polymer coating material for aircraft shells

Abstract

The present invention relates to the technical field of polymer composite materials, specifically, to an explosion-proof and impact-resistant polymer coating material for aircraft shells. The coating comprises an aliphatic polyurethane acrylate, a cycloaliphatic epoxy resin, nanosilica, polyethylene glycol, polyurea microcapsules, dicyclopentadiene resin, Grubbs catalyst, graphene oxide, and polysulfide rubber, with the remainder being auxiliary materials. In this invention, the aliphatic polyurethane acrylate serves as a flexible matrix to mitigate the risk of hydrolysis of aromatic isocyanates. Dicyclopentadiene resin undergoes in-situ ring-opening polymerization under Grubbs catalyst, synergistically with hydrophobic nanosilica to provide water resistance. Polyurea microcapsules rupture upon impact, releasing silicone oil that instantly fills cracks and reduces friction. Mica flakes extend the permeation path for water molecules. The epoxy-polyurethane network achieves self-healing of microcracks through dynamic ester exchange, ensuring the coating's explosion-proof and impact-resistant properties and the structural stability of the aircraft shell in extreme environments.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer composite materials, in particular to an explosion-proof and impact-resistant polymer coating material for aircraft shells. Background Art

[0002] Polymer composite coating materials are coatings with specific functions formed by combining polymer materials with other substances. They have the advantages of light weight, high strength, high temperature resistance, and corrosion resistance. These properties are crucial for reducing aircraft weight, improving fuel efficiency, and enhancing structural stability. Therefore, polymer composite coating materials are widely used in the aerospace field.

[0003] High-resolution composite coatings are typically applied to aircraft hulls to absorb explosive impact energy through material deformation, preventing structural rupture of the hull. Furthermore, stress dispersion mechanisms are utilized to reduce the risk of fragmentation and ensure flight safety. For example, CN112980301B discloses a super-strong explosion-proof and impact-resistant composite coating and its preparation method. The composite coating comprises a flexible coating material and a rigid coating material. The two coating materials are designed with different isocyanate indices to promote the reaction of their respective excess groups at the interface. A delayed reaction chain extender is used to regulate the gel curing time of the two coating materials, enabling a wet-on-wet lamination spray process to achieve chemical crosslinking between the layers and achieve inter-layer fusion.

[0004] The problem is that when the aircraft takes off, the surface of the outer shell absorbs moisture in the low-altitude and high-humidity environment, and suddenly cools down during climbing to form a condensation water film. Moisture continues to invade the interior of the coating, especially accumulating in the hydrophilic chain segments of the rigid layer polyester polyol, accelerating the hydrolysis of the aromatic isocyanate in the above-mentioned composite coating, that is, the carbamate bond of the aromatic isocyanate undergoes a chain breaking reaction when it comes into contact with water. This reaction expands microcracks due to thermal stress during the temperature change cycle, forming a vicious cycle of "water infiltration-hydrolysis-embrittlement-crack expansion", and eventually losing the explosion-proof and impact-resistant functions. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that the explosion-proof and impact-resistant functions of the existing polymer composite coating fail due to the hydrolysis of the key component, namely aromatic isocyanate.

[0006] The purpose of the present invention is to provide an explosion-proof and impact-resistant polymer coating material for aircraft shells. By improving the composition of the polymer coating material and eliminating the aromatic isocyanate component, the hydrolysis weakness of carbamate is eliminated, and the water molecule penetration path is extended, thereby avoiding the loss of the explosion-proof and impact-resistant functions of the coating.

[0007] To achieve the above object, the present invention provides an explosion-proof and impact-resistant polymer coating material for aircraft shells, comprising the following raw materials in the following mass proportions:

[0008] Aliphatic polyurethane acrylate 18-28%, cycloaliphatic epoxy resin 15-22%, nano-silica 2-4%, polyethylene glycol 4-9%, polyurea microcapsule 2-7%, dicyclopentadiene resin 5-11%, Grubbs catalyst 0.3-0.8%, graphene oxide 1-2% and polysulfide rubber 10-15%, and the balance are auxiliary materials.

[0009] As a further improvement of the present technical solution, the mass proportion of the aliphatic polyurethane acrylate in the explosion-proof and impact-resistant polymer coating material is one of 22% or 25%, and the mass proportion of the cycloaliphatic epoxy resin in the explosion-proof and impact-resistant polymer coating material is one of 18%, 20% or 21%.

[0010] As a further improvement of the present technical solution, the polyethylene glycol is polyethylene glycol with an average molecular weight of 1500-2000.

[0011] As a further improvement of the present technical solution, the mass proportion of the polyethylene glycol in the explosion-proof and impact-resistant polymer coating material is one of 5%, 7% or 8%.

[0012] As a further improvement of the present technical solution, the wall material of the polyurea microcapsule is polyaspartic acid ester, and the core material is silicone oil.

[0013] As a further improvement of the present technical solution, the mass proportion of the polyurea microcapsules in the explosion-proof and impact-resistant polymer coating material is one of 3%, 4% or 5%.

[0014] As a further improvement of the present technical solution, the mass proportion of the dicyclopentadiene resin in the explosion-proof and impact-resistant polymer coating material is one of 7%, 8% or 9%.

[0015] As a further improvement of the present technical solution, the Grubbs catalyst is a second-generation Grubbs catalyst, and the mass proportion of the Grubbs catalyst in the explosion-proof and impact-resistant polymer coating material is one of 0.5% and 0.6%.

[0016] As a further improvement of the present technical solution, the graphene oxide is a modified graphene oxide with long-chain alkylsilane grafted on the surface.

[0017] As a further improvement of the present technical solution, the auxiliary materials include mica powder, a photoinitiator and a curing agent containing an amide bond, and the mass ratio of the mica powder, the photoinitiator and the curing agent containing an amide bond is 3:2:6.

[0018] In the present invention, the raw materials include aliphatic polyurethane acrylate, cycloaliphatic epoxy resin, nano-silica, polyethylene glycol, polyurea microcapsules, dicyclopentadiene resin, Grubbs catalyst, graphene oxide, polysulfide rubber and auxiliary materials; wherein:

[0019] The aliphatic polyurethane acrylate serves as the main film-forming resin to provide flexibility. Its aliphatic structure avoids the hydrolysis weakness of aromatic isocyanate and improves water resistance. The cycloaliphatic epoxy resin serves as a rigid skeleton to improve tensile strength. Its epoxy bond is resistant to hydrolysis and forms a dense cross-linked network by reacting with an amide bond-containing curing agent.

[0020] The nano-silica is treated with hydrophobic surface treatment and dispersed in the matrix to block the diffusion path of water molecules. The polyethylene glycol acts as a plasticizer to improve low-temperature toughness, and its high molecular weight and low crystallinity reduce the exposure of hydrophilic end groups. The polyurea microcapsules use hydrolysis-resistant polyaspartic acid ester as the wall material to encapsulate the hydrophobic silicone oil core material. When impacted, they rupture and release fluid to achieve triggered energy absorption.

[0021] The dicyclopentadiene resin acts as a toughening agent to reduce low-temperature brittleness. Its hydrophobic ring structure synergistically blocks water molecule penetration, and in-situ ring-opening polymerization under the action of Grubbs' catalyst strengthens the network. The graphene oxide is grafted with long-chain alkylsilane to achieve both dispersibility and hydrophobicity, thereby improving the tear strength of the matrix. The polysulfide rubber absorbs energy through its hydrolysis-resistant sulfide bond structure, significantly improving elongation at break.

[0022] The auxiliary materials include mica powder, a photoinitiator and an amide bond-containing curing agent, wherein the mica powder extends the water penetration path through a layered structure, the photoinitiator triggers the curing of the coating, and the amide bond-containing curing agent reacts with the cycloaliphatic epoxy resin to form a flexible cross-linked network.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This explosion-proof and impact-resistant polymer coating material for aircraft shells first uses an aliphatic polyurethane acrylate as a flexible film-forming matrix. Its fatty chain structure avoids the risk of hydrolysis of aromatic isocyanates, and simultaneously forms a primary network through free radical polymerization triggered by a photoinitiator. A cycloaliphatic epoxy resin is then introduced as a rigid reinforcement skeleton. Under the catalysis of an amide bond-containing curing agent, it undergoes ring-opening crosslinking and interpenetrates with the polyurethane network to form a dense, hydrolysis-resistant barrier. Simultaneously, modified graphene oxide grafted with long-chain alkylsilane is directionally arranged during high-speed dispersion. Its lamellar structure induces crack deflection and bridges the polysulfide rubber phase through sulfide bonds to construct energy dissipation channels. Secondly, dicyclopentadiene resin undergoes in-situ ring-opening polymerization under the action of Grubbs' catalyst, synergistically forming physical water-blocking nodes in the matrix with nano-silica.

[0025] Under impact load conditions, the polyurea microcapsules rupture under stress and release the silicone oil core material, transiently filling the cracks and reducing the friction coefficient; the polyethylene glycol plasticizer phase inhibits the glass transition at low temperatures and maintains the ultra-high elongation of the polysulfide rubber phase; more importantly, the mica powder is horizontally oriented in the coating through the polytetrafluoroethylene coating, and its flaky stacking extends the permeation path of water molecules; finally, in a thermal-mechanical coupling environment, the epoxy-polyurethane interpenetrating network achieves self-repair of microcracks through dynamic ester bond exchange, thereby avoiding affecting the explosion-proof and impact-resistant functions of the coating, and being able to protect and maintain the structural stability of the aircraft shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the strength retention rate of the coating after wet heat aging when the mass proportions of aliphatic polyurethane acrylate and cycloaliphatic epoxy resin are different;

[0027] Figure 2 Schematic diagram of the critical height of the coating ball drop when the mass proportion of dicyclopentadiene resin is different;

[0028] Figure 3 Schematic diagram of the strength retention rate of the coating after wet heat aging when the mass proportion of polyethylene glycol is different;

[0029] Figure 4 Schematic diagram of the strength retention rate of the coating after wet-heat aging when the mass proportion of polyurea microcapsules is different;

[0030] Figure 5 Schematic diagram of the strength retention rate of the coating after wet-heat aging when the mass proportion of Grubbs catalyst is different. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] The present invention aims to provide an explosion-proof and impact-resistant polymer coating material for an aircraft shell, comprising the following raw materials in the following mass proportions:

[0033] Aliphatic polyurethane acrylate 18-28%, cycloaliphatic epoxy resin 15-22%, nano-silica 2-4%, polyethylene glycol 4-9%, polyurea microcapsule 2-7%, dicyclopentadiene resin 5-11%, Grubbs catalyst 0.3-0.8%, graphene oxide 1-2% and polysulfide rubber 10-15%, and the balance are auxiliary materials.

[0034] In the above coating material formula, aliphatic polyurethane acrylate serves as the main film-forming resin, providing flexibility. Its aliphatic structure has higher hydrolysis resistance than aromatic isocyanate. Cycloaliphatic epoxy resin serves as a rigid skeleton, improving tensile strength. Its epoxy bond is resistant to hydrolysis and can form a dense cross-linked network with a curing agent containing an amide bond.

[0035] Nano-silica is treated with hydrophobic surface treatment to block the diffusion path of water molecules; polyethylene glycol is used as a plasticizer to improve low-temperature toughness and reduce the exposure of hydrophilic end groups; polyurea microcapsules are used for triggered energy absorption, releasing damping fluid when impacted;

[0036] Dicyclopentadiene resin is used as a toughening agent to reduce low-temperature brittleness, and its hydrophobic ring structure can block the penetration of water molecules; Grubbs catalyst is used to catalyze the ring-opening polymerization of dicyclopentadiene resin; graphene oxide is used to improve tear strength; polysulfide rubber is used as an energy absorption layer to increase elongation at break, and the sulfide bond (—C—S—C—) of polysulfide rubber is resistant to hydrolysis.

[0037] Wherein, the polyethylene glycol is polyethylene glycol with an average molecular weight of 1500-2000. When the molecular weight is greater than 1500, the crystallinity is low, which can further reduce the exposure of the hydrophilic end group.

[0038] The wall material of polyurea microcapsules is polyaspartic acid ester (hydrolysis resistant) and the core material is silicone oil (hydrophobic);

[0039] Grubbs' catalyst is a ruthenium carbene complex catalyst discovered by Robert Grubbs, winner of the 2005 Nobel Prize in Chemistry. The Grubbs' catalyst in the embodiments of the present invention is a second-generation Grubbs' catalyst. This second-generation Grubbs' catalyst is an improvement over the first-generation product. Its optimized structure enhances catalytic efficiency and has a higher tolerance for functional groups, making it suitable for complex organic synthesis.

[0040] Graphene oxide is a modified graphene oxide with long-chain alkylsilane (KH-570) grafted on the surface, which has both dispersibility and hydrophobicity;

[0041] Auxiliary materials include mica powder, photoinitiator and curing agent containing amide bonds, and the mass ratio of mica powder, photoinitiator and curing agent containing amide bonds is 3:2:6. The layered barrier of mica powder can extend the water penetration path. The photoinitiator is used to trigger curing, while the curing agent containing amide bonds is combined with epoxy resin to form a flexible cross-linked network.

[0042] The aforementioned aliphatic polyurethane acrylate, cycloaliphatic epoxy resin, polyethylene glycol, and polysulfide rubber are mixed in a suitable ratio to form a base resin. Nanosilica, graphene oxide, dicyclopentadiene resin, and a system containing a Grubbs catalyst are then added, followed by ultrasonic dispersion for 20-40 minutes. Polyurea microcapsules and auxiliary materials are then incorporated, and the mixture is milled at high speed until a viscosity of 2000-3000 mPa·s is achieved. Finally, the protective coating is formed by spraying and UV curing.

[0043] The explosion-proof and impact-resistant polymer coating material for an aircraft shell provided by the present invention is further described through the following specific embodiments.

[0044] Example 1

[0045] This embodiment provides an explosion-proof and impact-resistant polymer coating material for an aircraft shell, comprising the following raw materials in the following mass proportions:

[0046] Aliphatic polyurethane acrylate 18%, cycloaliphatic epoxy resin 22%, nano-silica 2%, polyethylene glycol 9%, polyurea microcapsule 2%, dicyclopentadiene resin 11%, Grubbs catalyst 0.3%, graphene oxide 2% and polysulfide rubber 10%, and the rest are auxiliary materials.

[0047] Wherein, polyethylene glycol is polyethylene glycol with an average molecular weight of 2000;

[0048] The wall material of polyurea microcapsules is polyaspartic acid ester, and the core material is silicone oil;

[0049] Grubbs catalyst is the second generation of Grubbs catalyst;

[0050] The graphene oxide is a modified graphene oxide with long-chain alkylsilane grafted on the surface;

[0051] The auxiliary materials include mica powder, a photoinitiator and a curing agent containing an amide bond, and the mass ratio of the mica powder, the photoinitiator and the curing agent containing an amide bond is 3:2:6.

[0052] The aforementioned aliphatic polyurethane acrylate, cycloaliphatic epoxy resin, polyethylene glycol, and polysulfide rubber are mixed in a suitable ratio to form a base resin. Nanosilica, graphene oxide, dicyclopentadiene resin, and a system containing a Grubbs catalyst are then added, followed by ultrasonic dispersion for 20-40 minutes. Polyurea microcapsules and auxiliary materials are then incorporated, and the mixture is milled at high speed until a viscosity of 2000-3000 mPa·s is achieved. Finally, the protective coating is formed by spraying and UV curing.

[0053] Example 2

[0054] This embodiment provides an explosion-proof and impact-resistant polymer coating material for an aircraft shell, comprising the following raw materials in the following mass proportions:

[0055] Aliphatic polyurethane acrylate 25%, cycloaliphatic epoxy resin 20%, nano silicon dioxide 3%, polyethylene glycol 7%, polyurea microcapsule 5%, dicyclopentadiene resin 8%, Grubbs catalyst 0.5%, graphene oxide 1% and polysulfide rubber 12%, and the rest are auxiliary materials.

[0056] Wherein, polyethylene glycol is polyethylene glycol with an average molecular weight of 1800;

[0057] The wall material of polyurea microcapsules is polyaspartic acid ester, and the core material is silicone oil;

[0058] Grubbs catalyst is the second generation of Grubbs catalyst;

[0059] The graphene oxide is a modified graphene oxide with long-chain alkylsilane grafted on the surface;

[0060] The auxiliary materials include mica powder, a photoinitiator and a curing agent containing an amide bond, and the mass ratio of the mica powder, the photoinitiator and the curing agent containing an amide bond is 3:2:6.

[0061] The aforementioned aliphatic polyurethane acrylate, cycloaliphatic epoxy resin, polyethylene glycol, and polysulfide rubber are mixed in a suitable ratio to form a base resin. Nanosilica, graphene oxide, dicyclopentadiene resin, and a system containing a Grubbs catalyst are then added, followed by ultrasonic dispersion for 20-40 minutes. Polyurea microcapsules and auxiliary materials are then incorporated, and the mixture is milled at high speed until a viscosity of 2000-3000 mPa·s is achieved. Finally, the protective coating is formed by spraying and UV curing.

[0062] Example 3

[0063] This embodiment provides an explosion-proof and impact-resistant polymer coating material for an aircraft shell, comprising the following raw materials in the following mass proportions:

[0064] Aliphatic polyurethane acrylate 28%, cycloaliphatic epoxy resin 15%, nano-silica 4%, polyethylene glycol 4%, polyurea microcapsule 7%, dicyclopentadiene resin 5%, Grubbs catalyst 0.8%, graphene oxide 1% and polysulfide rubber 15%, and the rest are auxiliary materials.

[0065] Wherein, polyethylene glycol is polyethylene glycol with an average molecular weight of 1500;

[0066] The wall material of polyurea microcapsules is polyaspartic acid ester, and the core material is silicone oil;

[0067] Grubbs catalyst is the second generation of Grubbs catalyst;

[0068] The graphene oxide is a modified graphene oxide with long-chain alkylsilane grafted on the surface;

[0069] The auxiliary materials include mica powder, a photoinitiator and a curing agent containing an amide bond, and the mass ratio of the mica powder, the photoinitiator and the curing agent containing an amide bond is 3:2:6.

[0070] The aforementioned aliphatic polyurethane acrylate, cycloaliphatic epoxy resin, polyethylene glycol, and polysulfide rubber are mixed in a suitable ratio to form a base resin. Nanosilica, graphene oxide, dicyclopentadiene resin, and a system containing a Grubbs catalyst are then added, followed by ultrasonic dispersion for 20-40 minutes. Polyurea microcapsules and auxiliary materials are then incorporated, and the mixture is milled at high speed until a viscosity of 2000-3000 mPa·s is achieved. Finally, the protective coating is formed by spraying and UV curing.

[0071] The protective coatings prepared in Examples 1-3 were tested for their explosion-proof, impact-resistant and hydrolysis-resistant properties.

[0072] Explosion-proof performance testing was conducted in accordance with "GJB 5891.24-2006 Test Methods for Explosion-Proof Materials." A TNT equivalent loading device (50-200g gradient) was used to subject coating-aviation aluminum alloy composite test panels (200×200×3mm) to explosive impact. A 3D laser scanner monitored the central deflection, and a DH5960 ultra-dynamic strain gauge recorded the peak overpressure behind the target. The specific impulse (N·s / cm²) was calculated. The test was terminated when deflection >2mm / 100g TNT or coating delamination occurred. The minimum specific impulse value was recorded in Table 1.

[0073] Impact resistance testing was performed using a modified version of ASTM D7136-15, Composite Materials - Drop Weight Impact Test Method, using an environmentally simulated ball drop tester. After preconditioning the specimen at -60°C / 80°C / 95% RH, a 0.9-pound steel ball was dropped from a height of 0.6-2 meters. The critical height (m) at which no cracks were observed was recorded.

[0074] Hydrolysis resistance was tested according to ISO 6270-2:2017 humidity-heat cycling, with 30 cycles (72 hours of humidity-heat and 24 hours of -40°C) at 85°C / 85% RH. Adhesion was then tested using the pull-off method according to GB / T 5210-2006. Tensile strength retention was calculated (after humidity-heat aging / initial value × 100%) and reported in Table 1.

[0075] Table 1 Specific impulse, critical ball drop height and strength retention after wet heat aging of the protective coatings of Examples 1-3

[0076] Example 1 Example 2 Example 3 Specific impulse (N·s / cm²) 47 50 49 Critical height of falling ball (m) 1.2 1.5 1.3 Strength retention after wet heat aging (%) 82 85 84

[0077] As shown in Table 1, the specific impulse of the protective coatings prepared in Examples 1-3 is higher than 47 N·s / cm², the critical ball drop height is not less than 1.2 m, and the strength retention rate after wet heat aging is higher than 82%. This shows that the explosion-proof and impact-resistant polymer coating material for aircraft shells provided by the present invention has good explosion-proof performance, impact resistance, and anti-hydrolysis performance.

[0078] In the present invention, aliphatic polyurethane acrylate is first used as a flexible film-forming matrix. Its fatty chain structure avoids the risk of hydrolysis of aromatic isocyanates, and a primary network is simultaneously formed by free radical polymerization triggered by a photoinitiator. A cycloaliphatic epoxy resin is then introduced as a rigid reinforcing skeleton. Ring-opening crosslinking is catalyzed by an amide-containing curing agent, and the resin interpenetrates with the polyurethane network to form a dense, hydrolysis-resistant barrier. Simultaneously, modified graphene oxide grafted with long-chain alkylsilane is directionally arranged during high-speed dispersion. Its lamellar structure induces crack deflection and bridges the polysulfide rubber phase through sulfide bonds to construct energy dissipation channels. Secondly, dicyclopentadiene resin is in situ ring-opening polymerized under the action of Grubbs' catalyst, synergistically forming physical water-blocking nodes in the matrix with nano-silica.

[0079] Under impact load conditions, the polyurea microcapsules rupture under stress and release the silicone oil core material, transiently filling the cracks and reducing the friction coefficient; the polyethylene glycol plasticizer phase inhibits the glass transition at low temperatures and maintains the ultra-high elongation of the polysulfide rubber phase; more importantly, the mica powder is horizontally oriented in the coating through the polytetrafluoroethylene coating, and its flaky stacking extends the permeation path of water molecules; finally, in a thermal-mechanical coupling environment, the epoxy-polyurethane interpenetrating network achieves self-repair of microcracks through dynamic ester bond exchange, thereby avoiding affecting the explosion-proof and impact-resistant functions of the coating, and being able to protect and maintain the structural stability of the aircraft shell.

[0080] Example 4

[0081] Aliphatic urethane acrylate is a light-curable resin synthesized by the reaction of aliphatic isocyanate, polyol, and hydroxyethyl acrylate. In this invention, UV-triggered aliphatic urethane acrylate undergoes ring-opening polymerization to form urethane bonds and acrylic double bonds. The flexible long chains (aliphatic hydrocarbon segments) of the aliphatic urethane acrylate are interspersed between the rigid rings of the epoxy resin, forming a topological interlocking structure. The cationic polymerization of the epoxy groups and the free radical polymerization of the acrylate occur without side reactions, achieving simultaneous curing.

[0082] In addition, the ether bond (-COC-) of the epoxy resin wraps the urethane bond (-NHCOO-) to form a steric shield; the hydroxyl group (-OH) in the epoxy network forms a hydrogen bond with the side chain carbonyl group (C=O) of the aliphatic polyurethane acrylate, reducing the electron cloud density of the urethane bond and reducing the hydrolysis rate.

[0083] In order to prove that in the explosion-proof and impact-resistant polymer coating material, the mass proportion of 18-28% of aliphatic polyurethane acrylate and 15-22% of cycloaliphatic epoxy resin is one of the important factors for the explosion-proof and impact-resistant polymer coating material provided by the present invention to have good hydrolysis resistance. This embodiment is based on the above-mentioned Example 2, and only changes the mass proportion of aliphatic polyurethane acrylate and cycloaliphatic epoxy resin. The mass proportion of aliphatic polyurethane acrylate is set to 15%, 18%, 22%, 25%, 28% or 32%, and the mass proportion of cycloaliphatic epoxy resin is set to 10%, 15%, 18%, 20%, 21%, 22% or 25%. Then, a protective coating is prepared and tested according to the strength retention rate test method after wet heat aging provided in the above embodiment. The measured results are as follows: Figure 1 shown.

[0084] according to Figure 1 It can be seen that when the mass proportion of the aliphatic polyurethane acrylate is 15% or 32%, that is, not 18-28%, the strength retention rate of the protective coating after wet heat aging is significantly lower, and when the mass proportion of the cycloaliphatic epoxy resin is 10% or 25%, that is, not 15-22%, the strength retention rate of the protective coating after wet heat aging is significantly lower. This shows that the mass proportions of 18-28% of the aliphatic polyurethane acrylate and 15-22% of the cycloaliphatic epoxy resin are both important factors for the explosion-proof and impact-resistant polymer coating material provided by the present invention to have good anti-hydrolysis properties;

[0085] In addition, according to Figure 1 It can be seen that when the mass proportion of aliphatic polyurethane acrylate is 22% or 25%, and the mass proportion of cycloaliphatic epoxy resin is 18%, 20% or 21%, the strength retention rate of the protective coating after wet heat aging is at a high level.

[0086] Example 5

[0087] Dicyclopentadiene resin is a cycloolefin monomer containing a rigid norbornene backbone. In this invention, ring-opening metathesis polymerization, triggered by a Grubbs catalyst, produces a polynorbornene network containing flexible ester side chains. The cyclopentane units in the polynorbornene rotate freely at low temperatures (-60°C), absorbing impact energy through conformational changes, thereby increasing elongation at break. Furthermore, upon stretching, the ester groups align to form crystalline regions, further enhancing impact strength.

[0088] In addition, the condensed ring structure of dicyclopentadiene resin (contact angle 105°) can wrap the urethane bond, reducing the hydrolysis rate of the urethane bond after wet-heat aging. That is, dicyclopentadiene resin constructs a dynamic toughening network and condensed ring hydrophobic shield through ring-opening polymerization, collaboratively overcoming the technical bottlenecks of low-temperature brittle cracking, wet-heat aging and thermal shock of aviation coatings at the molecular scale. Its aromatization characteristics further give it active protection capabilities under extreme working conditions.

[0089] In order to prove that the mass proportion of 5-11% of dicyclopentadiene resin in the explosion-proof and impact-resistant polymer coating material is one of the important factors for the explosion-proof and impact-resistant polymer coating material provided by the present invention to have good impact resistance. Based on the above Example 2, this Example only changes the mass proportion of dicyclopentadiene resin, and sets the mass proportion of dicyclopentadiene resin to 3%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or 15%, and then prepares a protective coating, and tests it according to the impact resistance test method provided in the above Example, and the measured results are as follows Figure 2 shown.

[0090] according to Figure 2 It can be seen that when the mass proportion of the dicyclopentadiene resin is 3%, 12% or 15%, that is, not 5-11%, the critical height of the ball drop of the protective coating is significantly lower than the critical height of the ball drop when the mass proportion of the dicyclopentadiene resin is 5%, 6%, 7%, 8%, 9%, 10% or 11%. This shows that the 5-11% mass proportion of the dicyclopentadiene resin is one of the important factors for the explosion-proof and impact-resistant polymer coating material provided by the present invention to have good impact resistance;

[0091] In addition, according to Figure 2 It can be seen that when the mass proportion of dicyclopentadiene resin is 7%, 8% or 9%, the critical height of the falling ball of the protective coating is at a higher level.

[0092] Example 6

[0093] Polyethylene glycol is a linear polymer containing repetitive ether bonds. In the present invention, its molecular segments form a dynamic hydrogen bond network through the ether oxygen atoms and the thioether bonds of the polysulfide rubber. When impacted, the hydrogen bonds break, dissipating energy, and then reassemble and repair after unloading, thereby improving the elongation at break of the coating material. Furthermore, the hydrophilic end hydroxyl groups of the polyethylene glycol are encapsulated by the hydrophobic fused rings of the dicyclopentadiene resin, reducing the exposure of the hydrophilic end and thus lowering the water absorption of the coating material.

[0094] Polyethylene glycol effectively reduces the water absorption rate of the coating material through the low-temperature mobility of the ether bond and the dynamic hydrogen bond network, thereby improving the strength retention rate of the coating material after wet heat aging. In order to verify that the 4-9% mass proportion of polyethylene glycol in the explosion-proof and impact-resistant polymer coating material is one of the important factors for the explosion-proof and impact-resistant polymer coating material provided by the present invention to have good hydrolysis resistance. Based on the above embodiment 1, this embodiment only changes the mass proportion of polyethylene glycol, and sets the mass proportion of polyethylene glycol to 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or 11%, and then prepares a protective coating, and tests it according to the strength retention rate test method after wet heat aging provided in the above embodiment, and the measured results are as follows Figure 3 shown.

[0095] according to Figure 3 It can be seen that when the mass proportion of polyethylene glycol is 2%, 3%, 10% or 11%, that is, not 4-9%, the strength retention rate of the protective coating after wet heat aging is significantly lower than the strength retention rate of the protective coating after wet heat aging when the mass proportion of polyethylene glycol is 4%, 5%, 6%, 7%, 8% or 9%. This shows that the 4-9% mass proportion of polyethylene glycol in the explosion-proof and impact-resistant polymer coating material is also one of the important factors for the explosion-proof and impact-resistant polymer coating material provided by the present invention to have good anti-hydrolysis performance;

[0096] In addition, according to Figure 3 It can be seen that when the mass proportion of polyethylene glycol is 5%, 7% or 8%, the strength retention rate of the protective coating after wet heat aging is at a high level.

[0097] Example 7

[0098] Polyurea microcapsules are functional units that encapsulate a hydrophobic silicone oil core material with a hydrolysis-resistant polyaspartic acid ester wall material. In this invention, when the coating is subjected to excessive impact stress (e.g., exceeding 15 MPa), the polyurea wall material undergoes controlled rupture, releasing the silicone oil core material. The terminal hydroxyl groups of the polyurea react in situ with the thioether bonds of the polysulfide rubber to form sulfur-siloxane bonds, dynamically filling the cracks and forming a super-hydrophobic repair layer with a contact angle greater than 150°.

[0099] At the same time, the released silicone oil migrates to the gaps between the graphene oxide sheets, extending the water molecule penetration path through physical barriers, and synergizing the electron delocalization stabilization effect of the urea bond in the polyurea wall material, so that the coating has good strength retention after wet-heat aging.

[0100] The process of in-situ reaction of the terminal hydroxyl groups of the silicone oil core material with the sulfide bonds of the polysulfide rubber to form sulfur-siloxane bonds is as follows:

[0101]

[0102]

[0103] Where, is the sulfur atom of the thioether, is hydrogen ion, is a sulfonium salt cation, It is the terminal hydroxyl group of the silicone oil core material. is sulfur-siloxane, is thiol;

[0104] In an acidic environment, the sulfur atom of the thioether is protonated to form a sulfonium salt cation, which enhances its electrophilicity. Then the oxygen atom of the terminal hydroxyl group acts as a nucleophile to attack the protonated thioether, resulting in a substitution reaction to obtain a sulfur-siloxane bond (thioether carbon) and release thiol.

[0105] In order to prove that the 2-7% mass proportion of polyurea microcapsules in the explosion-proof and impact-resistant polymer coating material is one of the important factors for the explosion-proof and impact-resistant polymer coating material provided by the present invention to have good anti-hydrolysis performance, this embodiment is based on the above embodiment 3, only the mass proportion of polyurea microcapsules is changed, and the mass proportion of polyurea microcapsules is set to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, and then a protective coating is prepared. The strength retention rate after wet heat aging provided in the above embodiment is tested, and the measured results are as follows: Figure 4 shown.

[0106] according to Figure 4 It can be seen that when the mass proportion of polyurea microcapsules is 1%, 8%, 9% or 10%, that is, not 2-7%, the strength retention rate of the protective coating after wet heat aging is significantly lower than the strength retention rate of the protective coating after wet heat aging when the mass proportion of polyurea microcapsules is 2%, 3%, 4%, 5%, 6%, or 7%. This shows that the 2-7% mass proportion of polyurea microcapsules is also one of the important factors for the explosion-proof and impact-resistant polymer coating material provided by the present invention to have good anti-hydrolysis properties;

[0107] In addition, according to Figure 4 It can be seen that when the mass proportion of polyurea microcapsules is 3%, 4% or 5%, the strength retention rate of the protective coating after wet-heat aging is at a high level.

[0108] Example 8

[0109] Grubbs' catalyst (structural formula: Ru(=CHPh)Cl2(PCy3)2) is a ruthenium metal carbene complex. In the present invention, it activates the strained bonds of the norbornene rings of the dicyclopentadiene resin, triggering a ring-opening metathesis polymerization reaction to form a polynorbornene network containing flexible ester side chains. The cyclopentane units in this network absorb impact energy through conformational rotation at low temperatures, improving the coating's elongation at break. Simultaneously, the heat of polymerization promotes the interlocking of the dicyclopentadiene fused rings with the polyurethane urethane bonds, synergistically reducing the hydrolysis rate during wet-heat aging.

[0110] In order to prove that the 0.3-0.8% by weight proportion of the Grubbs catalyst in the explosion-proof and impact-resistant polymer coating material is one of the important factors for the explosion-proof and impact-resistant polymer coating material provided by the present invention to have good hydrolysis resistance, this example is based on the above Example 3, and only the weight proportion of the Grubbs catalyst is changed, and the weight proportion of the Grubbs catalyst is set to 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1.0%, and then a protective coating is prepared and tested according to the strength retention rate test method after wet heat aging provided in the above example. The measured results are as follows: Figure 5 shown.

[0111] according to Figure 4 It can be seen that when the mass proportion of the Grubbs catalyst is 0.1%, 0.2%, 0.9% or 1.0%, that is, not 0.3-0.8%, the strength retention rate of the protective coating after wet heat aging is significantly lower than the strength retention rate of the protective coating after wet heat aging when the mass proportion of the Grubbs catalyst is 0.3%, 0.4%, 0.5%, 0.6%, 0.7% or 0.8. This shows that the 0.3-0.8% mass proportion of the Grubbs catalyst is also one of the important factors for the explosion-proof and impact-resistant polymer coating material provided by the present invention to have good anti-hydrolysis performance;

[0112] In addition, according to Figure 5 It can be seen that when the mass proportion of Grubbs catalyst is 0.5% or 0.6%, the strength retention rate of the protective coating after wet-heat aging is at a high level.

[0113] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. An explosion-proof and impact-resistant polymer coating material for aircraft shell, characterized in that: Including the following raw materials by mass: Aliphatic polyurethane acrylate 18-28%, cycloaliphatic epoxy resin 15-22%, nano-silica 2-4%, polyethylene glycol 4-9%, polyurea microcapsule 2-7%, dicyclopentadiene resin 5-11%, Grubbs catalyst 0.3-0.8%, graphene oxide 1-2% and polysulfide rubber 10-15%, and the balance are auxiliary materials.

2. The explosion-proof and impact-resistant polymer coating material for aircraft shell according to claim 1, characterized in that: The mass proportion of the aliphatic polyurethane acrylate in the explosion-proof and impact-resistant polymer coating material is 22% or 25%, and the mass proportion of the cycloaliphatic epoxy resin in the explosion-proof and impact-resistant polymer coating material is 18%, 20% or 21%.

3. The explosion-proof and impact-resistant polymer coating material for aircraft shell according to claim 1, characterized in that: The polyethylene glycol has an average molecular weight of 1500-2000.

4. The explosion-proof and impact-resistant polymer coating material for aircraft shell according to claim 1, characterized in that: The mass proportion of the polyethylene glycol in the explosion-proof and impact-resistant polymer coating material is 5%, 7% or 8%.

5. The explosion-proof and impact-resistant polymer coating material for aircraft shell according to claim 1, characterized in that: The wall material of the polyurea microcapsule is polyaspartic acid ester, and the core material is silicone oil.

6. The explosion-proof and impact-resistant polymer coating material for aircraft shell according to claim 1, characterized in that: The mass proportion of the polyurea microcapsules in the explosion-proof and impact-resistant polymer coating material is one of 3%, 4% and 5%.

7. The explosion-proof and impact-resistant polymer coating material for aircraft shell according to claim 1, characterized in that: The mass proportion of the dicyclopentadiene resin in the explosion-proof and impact-resistant polymer coating material is one of 7%, 8% and 9%.

8. The explosion-proof and impact-resistant polymer coating material for aircraft shell according to claim 1, characterized in that: The Grubbs catalyst is a second-generation Grubbs catalyst, and the mass proportion of the Grubbs catalyst in the explosion-proof and impact-resistant polymer coating material is one of 0.5% and 0.6%.

9. The explosion-proof and impact-resistant polymer coating material for aircraft shell according to claim 1, characterized in that: The graphene oxide is modified graphene oxide with long-chain alkylsilane grafted on the surface.

10. The explosion-proof and impact-resistant polymer coating material for aircraft shell according to claim 1, characterized in that: The auxiliary materials include mica powder, a photoinitiator and a curing agent containing an amide bond, and the mass ratio of the mica powder, the photoinitiator and the curing agent containing an amide bond is 3:2:6.

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