Ethylene-propylene-diene rubber-based adhesive and method for producing the same, ethylene-propylene-diene rubber structure

Abstract

The application discloses a kind of ethylene propylene diene rubber-based adhesive and preparation method thereof, ethylene propylene diene rubber structural member, ethylene propylene diene rubber-based adhesive, including the following mass fraction of each component: ethylene propylene diene rubber raw rubber 100 parts, vulcanizing agent 3~6 parts, vulcanization accelerator 1~3 parts and tackifier;Wherein, the tackifier includes melamine formaldehyde resin 10~15 parts, phenolic resin 15~20 parts and amino cage type poly silesquioxane 5~15 parts;And the amino cage type poly silesquioxane includes cage type silicon oxygen cubic core structure, alkyl respectively connected with the 8 vertexes of the cage type silicon oxygen cubic core structure and end amino connected with the alkyl.The adhesive of the application can finally realize the two-way promotion of high-strength bonding and good mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of EPDM rubber structural components, and more specifically, to an EPDM rubber-based adhesive and its preparation method, and EPDM rubber structural components. Background Technology

[0002] Ethylene propylene diene monomer (EPDM) rubber is a type of ethylene propylene diene monomer and saturated rubber. Its molecular structure makes it less susceptible to chemical reactions, resulting in excellent weather resistance, aging resistance, chemical corrosion resistance, and shock absorption and damping properties.

[0003] Seismic damping bearings made of EPDM rubber are widely used in construction, transportation, and automotive industries. Rubber bearings are classified according to their structure, including: ordinary plate rubber bearings (simple structure, composed of multiple layers of rubber and steel plates stacked alternately, with strong load-bearing capacity, suitable for small and medium span bridges and building seismic isolation); pot bearings (composed of rubber blocks, steel pots, and sealing rings, capable of withstanding large vertical loads and horizontal displacements, suitable for large span bridges and heavy-duty structures); and lead-core rubber bearings (adding a lead core to ordinary rubber bearings to provide higher damping performance, effectively absorbing seismic energy, suitable for bridge and building seismic isolation in high-intensity earthquake zones), etc.

[0004] In the aforementioned prior art, EPDM rubber exhibits poor self-adhesion and mutual adhesion, resulting in poor bonding performance when bonded to metals such as steel plates. For instance, in ordinary plate rubber bearings, the rubber bearing has low shear strength and is prone to adhesion failure (separation of the steel plate from the rubber), leading to uneven bulging, deterioration, and exposed steel plates, thus affecting the service life of the rubber bearing. Adding a layer of rubber-specific adhesive between the rubber matrix and the metal is of great significance for improving the performance and service life of the rubber bearing.

[0005] Rubber-based adhesives are a class of polymeric adhesives formulated with rubber as the main material. Because rubber exhibits significant high elasticity over a wide temperature range, with a deformability that can increase several times over, adhesives formulated using this property possess good flexibility and excellent resistance to creep, flexural deformation, and impact vibration. They are suitable for bonding components or products with different coefficients of linear expansion and for use in dynamic conditions, such as rubber bearings.

[0006] However, existing rubber-based adhesives typically use unsaturated, highly polar rubbers (such as chloroprene rubber, nitrile rubber, and silicone rubber) as the base adhesive. This base adhesive exhibits poor compatibility with the EPDM rubber bearing matrix, which also affects the safe use and service life of the rubber bearing. Therefore, developing EPDM rubber-based adhesives that are compatible with the matrix is ​​one of the development directions for adhesives specifically designed for EPDM rubber bearings. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide a EPDM rubber-based adhesive and its preparation method, as well as EPDM rubber structural components. The adhesive is prepared using EPDM rubber as the base adhesive and is vulcanized together with the EPDM rubber substrate during use. This not only improves the shear strength of the adhesive but also enhances the compatibility between the adhesive and EPDM rubber, thereby improving the safety and lifespan of the adhesive.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: An EPDM rubber-based adhesive comprises the following components in parts by weight: 100 parts of EPDM raw rubber, 3-6 parts of vulcanizing agent, 1-3 parts of vulcanization accelerator and tackifier; The tackifier comprises 10-15 parts of melamine-formaldehyde resin, 15-20 parts of phenolic resin, and 5-15 parts of aminated cage-type polysilsesquioxane; and the aminated cage-type polysilsesquioxane comprises a cage-type silicon-oxygen cubic core structure, alkyl groups respectively connected to the eight vertices of the cage-type silicon-oxygen cubic core structure, and terminal amino groups connected to the alkyl groups.

[0009] This invention also discloses a method for preparing the above-mentioned EPDM rubber-based adhesive, comprising the following steps: The EPDM raw rubber, the vulcanizing agent, the vulcanization accelerator, and the tackifier are mixed to obtain the EPDM-based adhesive.

[0010] This invention also discloses a ternary propylene diene monomer (EPDM) rubber structural component, the preparation method of which includes the following process: The EPDM rubber-based adhesive is mixed to obtain an uncured rubber block of adhesive, wherein the EPDM rubber-based adhesive is as described above; The uncured adhesive compound block is placed between the uncured EPDM rubber substrate and the metal reinforcement structure to obtain a pre-cured laminated structure. The pre-vulcanized laminated structure is heated and vulcanized, so that the unvulcanized adhesive compound block and the unvulcanized EPDM rubber substrate are vulcanized together to obtain the EPDM rubber structural component.

[0011] Implementing the embodiments of the present invention will have the following beneficial effects: The adhesive of this invention uses EPDM raw rubber as the base rubber, which improves its compatibility with EPDM rubber. By adding a vulcanizing agent, a vulcanization accelerator, and phenolic resin (PF), melamine-formaldehyde resin (MF), and aminated cage-type polysilsesquioxane (aminoPOSS) as tackifiers, the adhesive achieves a bonding and cross-linking reaction during the heating and vulcanization process. During heating and vulcanization, the addition of PF, MF, and aminoPOSS synergistically enhances interfacial adhesion, improves the adhesive's cohesive cross-linking network, ensures uniform dispersion, and achieves complementary balance, resulting in a bonding effect far exceeding the sum of single components. The aminated cage-type polysilsesquioxane of this invention, with alkyl-terminated amino groups, primarily aims to provide flexible organic side chains.

[0012] Specifically, in terms of enhancing interfacial adhesion, PF, as a thermoplastic resin, exhibits decreasing viscosity during vulcanization and heating, making it easier to flow. This not only enhances the dispersion of each component but also allows it to flow to the interface, strengthening the adhesion effect. Simultaneously, PF's weak polarity allows for better compatibility with non-polar EPDM substrates, enhancing its adhesion to EPDM. MF contains a large number of strongly polar amino groups, which can form stable polar or coordination bonds with hydroxyl groups and oxides on metal surfaces, significantly improving adhesion to metals. Amino POSS acts as a crosslinking "intermediate bridge," its amino groups simultaneously undergoing condensation crosslinking reactions with the phenolic hydroxyl groups of PF and the hydroxyl groups of MF. Meanwhile, aminoPOSS can also covalently bond with EPDM through grafting under the action of vulcanizing agents, so that EPDM, PF, MF and aminoPOSS are covalently bonded through chemical cross-linking reaction. This not only provides a multifunctional surface bonding effect with different materials such as nonpolar molecules and metals, but also enhances the cross-linking density of the adhesive layer and provides sufficient cohesion. In addition, the cage-like silicon-oxygen cubic core structure of aminoPOSS belongs to nanoparticles, which can make the surface of the unvulcanized adhesive block rougher and more easily fill the micro gaps between the unvulcanized adhesive block and the surface of the EPDM substrate / metal structure, further enhancing the bonding effect through physical locking.

[0013] In terms of improving the cohesive cross-linking network of adhesives, not only do EPDM, PF, MF, and aminoPOSS form a three-dimensional cross-linking network through chemical cross-linking reactions, but the gaps inside the nanoparticle adhesive block with cage-type silicon-oxygen cubic core structure also reduce internal defects in the adhesive layer, further enhancing the cohesive strength.

[0014] Regarding ensuring uniform dispersion, MF is highly polar and easily aggregates in non-polar EPDM. Amino POSS is a nanoparticle that easily self-aggregates. Amino POSS can form bonds with MF and PF, reducing aggregation. PF is polarly compatible with EPDM and can assist in the dispersion of highly polar MF and POSS in EPDM. PF's fluidity increases after heating, which can assist in the dispersion of amino POSS and PF in EPDM and their diffusion to the surface.

[0015] In terms of performance balance, the synergy of the three components can offset the performance shortcomings of a single component. MF / PF will reduce the elasticity and elongation at break of EPDM; the nano-reinforcing effect of aminoPOSS and the spatial freedom of alkyl groups can improve the tensile / tear strength of EPDM, balancing "tackification" and "rubber flexibility". MF is too polar (easily delaminated with EPDM), and PF is too weak (insufficient adhesion to metals). The nonpolar core structure and polar organic side chains of aminoPOSS can connect the two, while ensuring metal adhesion and rubber compatibility.

[0016] Therefore, the adhesive of the present invention can ultimately achieve a dual improvement in both high-strength bonding and good mechanical properties. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] in: Figure 1 This is a schematic diagram of a ternary propylene diene monomer (EPDM) rubber structural component obtained according to a specific embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The purpose of this invention is to develop an EPDM-based adhesive that can be simultaneously vulcanized with EPDM rubber, mainly used for bonding EPDM rubber to metal, comprising the following components in parts by weight: The mixture comprises 100 parts of EPDM raw rubber, 3-6 parts of vulcanizing agent, 1-3 parts of vulcanization accelerator, and a tackifier. The tackifier includes 10-15 parts of melamine-formaldehyde resin, 15-20 parts of phenolic resin, and 5-15 parts of aminated cage-like polysilsesquioxane. The aminated cage-like polysilsesquioxane comprises a cage-like silica cubic core structure, alkyl groups connected to the eight vertices of the cage-like silica cubic core structure, and terminal amino groups connected to the alkyl groups.

[0021] This invention uses EPDM raw rubber as the base rubber, which improves its compatibility with EPDM. By adding vulcanizing agents, vulcanization accelerators, and phenolic resin (PF), melamine-formaldehyde resin (MF), and amino-coated cage-like polysilsesquioxane (aminoPOSS) as tackifiers, the adhesive achieves a bonding and cross-linking reaction during the heating and vulcanization process. During heating and vulcanization, the addition of PF, MF, and aminoPOSS synergistically enhances interfacial adhesion, improves the adhesive's cohesive cross-linking network, ensures uniform dispersion, and achieves complementary balance, resulting in a bonding effect far exceeding the sum of individual components. The amino-coated cage-like polysilsesquioxane of this invention, with alkyl-terminated amino groups, primarily aims to provide flexible organic side chains.

[0022] Specifically, in terms of enhancing interfacial adhesion, PF, as a thermoplastic resin, exhibits decreasing viscosity during vulcanization and heating, making it easier to flow. This not only enhances the dispersion of each component but also allows it to flow to the interface, strengthening the adhesion effect. Simultaneously, PF's weak polarity allows for better compatibility with non-polar EPDM substrates, enhancing its adhesion to EPDM. MF contains a large number of strongly polar amino groups, which can form stable polar or coordination bonds with hydroxyl groups and oxides on metal surfaces, significantly improving adhesion to metals. Amino POSS acts as a crosslinking "intermediate bridge," its amino groups simultaneously undergoing condensation crosslinking reactions with the phenolic hydroxyl groups of PF and the hydroxyl groups of MF. Meanwhile, aminoPOSS can also covalently bond with EPDM through grafting under the action of vulcanizing agents, so that EPDM, PF, MF and aminoPOSS are covalently bonded through chemical cross-linking reaction. This not only provides a multifunctional surface bonding effect with different materials such as nonpolar molecules and metals, but also enhances the cross-linking density of the adhesive layer and provides sufficient cohesion. In addition, the cage-like silicon-oxygen cubic core structure of aminoPOSS belongs to nanoparticles, which can make the surface of the unvulcanized adhesive block rougher and more easily fill the micro gaps between the unvulcanized adhesive block and the surface of the EPDM substrate / metal structure, further enhancing the bonding effect through physical locking.

[0023] In terms of improving the cohesive cross-linking network of adhesives, not only do EPDM, PF, MF, and aminoPOSS form a three-dimensional cross-linking network through chemical cross-linking reactions, but the gaps inside the nanoparticle adhesive block with cage-type silicon-oxygen cubic core structure also reduce internal defects in the adhesive layer, further enhancing the cohesive strength.

[0024] Regarding ensuring uniform dispersion, MF is highly polar and easily aggregates in non-polar EPDM. Amino POSS is a nanoparticle that easily self-aggregates. Amino POSS can form bonds with MF and PF, reducing aggregation. PF is polarly compatible with EPDM and can assist in the dispersion of highly polar MF and POSS in EPDM. PF's fluidity increases after heating, which can assist in the dispersion of amino POSS and PF in EPDM and their diffusion to the surface.

[0025] In terms of performance balance, the synergy of the three components can offset the performance shortcomings of a single component. MF / PF will reduce the elasticity and elongation at break of EPDM; the nano-reinforcing effect of aminoPOSS and the spatial freedom of alkyl groups can improve the tensile / tear strength of EPDM, balancing "tackification" and "rubber flexibility". MF is too polar (easily delaminated with EPDM), and PF is too weak (insufficient adhesion to metals). The nonpolar core structure and polar organic side chains of aminoPOSS can connect the two, while ensuring metal adhesion and rubber compatibility.

[0026] Therefore, the adhesive of the present invention can ultimately achieve a dual improvement in both high-strength bonding and good mechanical properties.

[0027] This invention employs a combination of a large amount of phenolic resin and a small amount of melamine-formaldehyde resin, achieving a synergistic tackifying effect. The small amount of phenolic resin weakens the bonding effect of the large amount of melamine-formaldehyde resin, failing to significantly improve the adhesion between the adhesive and non-polar rubber / resin materials, and significantly reducing the adhesion between the adhesive and metals. This is because the bonding ability of melamine-formaldehyde resin depends on the three-dimensional cross-linked structure formed by its own amino groups and formaldehyde. This dense structure enhances interfacial bonding with metals. The hydroxymethyl groups of the phenolic resin compete with the active amino groups of the melamine-formaldehyde resin for reaction sites, resulting in insufficient self-crosslinking of the melamine-formaldehyde resin, a loose cross-linked network, and an inability to form a strong bonding interface. However, a small amount of melamine-formaldehyde resin can assist in the vulcanization of phenolic resin, while simultaneously improving the adhesion between the adhesive and EPDM rubber and metal. This is because phenolic resin itself lacks self-crosslinking ability, while melamine-formaldehyde resin can act as a "crosslinking accelerator" for the vulcanization of phenolic resin. That is, the amino groups can activate the hydroxymethyl groups of phenolic resin, promoting the formation of methylene bridges between phenolic resin molecules. This not only helps phenolic resin transform from a linear structure to a three-dimensional crosslinked structure, making the adhesive system more stable, but the methylene bridges can also participate in the crosslinking of EPDM rubber, forming physical entanglement with the vulcanized structure of EPDM rubber, thus enhancing the adhesion to EPDM rubber.

[0028] Furthermore, based on MF and PF, the synergistic effect of amino POSS is added. Since the amino group of amino POSS can crosslink with MF, PF and EPDM respectively, while its alkyl group can provide greater flexibility and its silicon-oxygen cubic core can provide nanoparticles and compatibility with EPDM, amino POSS can not only act as a "multi-directional crosslinking bridge" but also as a "polarity-compatible bridge", which can achieve high-strength bonding and good mechanical properties.

[0029] Further preferred embodiments include aminopropyl isobutyl cage-type polysilsesquioxanes, etc.

[0030] In a preferred embodiment, the tackifier comprises 40 parts, wherein the tackifier includes 10-15 parts of melamine-formaldehyde resin, 15-20 parts of phenolic resin, and 5-15 parts of aminated cage-type polysilsesquioxane, and the sum of the parts of aminated cage-type polysilsesquioxane and melamine-formaldehyde resin is 20-25 parts. Subsequent specific embodiments and experimental data show that this composition ratio can achieve a dual improvement in both high-strength adhesion and good mechanical properties.

[0031] Preferably, the ethylene content in the EPDM raw rubber is 60% to 70% by mass. The vulcanizing agent may include peroxide vulcanizing agent and / or sulfur; the vulcanization accelerator may include accelerator CZ and / or accelerator TMTD.

[0032] In one specific embodiment, the EPDM rubber-based adhesive may further include one or more of other functional components such as activators, antioxidants, and reinforcing agents. The activators are used to enhance the activity of the vulcanization accelerators. Specifically, the activators may include stearic acid and / or zinc oxide, etc.; the reinforcing agents may include carbon black, etc.; and the antioxidants may include antioxidants such as RD, etc.

[0033] The present invention also provides a method for preparing the above-mentioned EPDM rubber-based adhesive, comprising the following steps: EPDM rubber raw rubber, vulcanizing agent, vulcanization accelerator and tackifier and other functional components are mixed to obtain EPDM rubber-based adhesive.

[0034] The above mixing process can be carried out in one go or in multiple stages. All components can be added at once or in batches.

[0035] The present invention also provides a ternary propylene diene monomer (EPDM) rubber structural component, the preparation method of which includes the following steps: S1: The above EPDM rubber-based adhesive is mixed to obtain an uncured mixed rubber block of adhesive; S2: Place the uncured adhesive compound block between the uncured EPDM rubber substrate and the metal reinforcement structure to obtain a pre-cured laminated structure. S3: The pre-vulcanized laminated structure is heated and vulcanized, so that the unvulcanized adhesive compound and the unvulcanized EPDM rubber substrate are vulcanized together to obtain EPDM rubber structural parts.

[0036] Preferably, the vulcanization temperature is 160℃~200℃ and the vulcanization time is 20min~30min.

[0037] The following are specific examples.

[0038] Examples 1-6 An EPDM rubber-based adhesive comprises the following components in parts by weight: The raw materials for the 100 parts of EPDM rubber are: antioxidant RD 1 part, stearic acid 0.5 parts, zinc oxide 5 parts, accelerator CZ 0.8 parts, carbon black N550 70 parts, coupling agent Si69 3 parts, paraffin oil 10 parts, accelerator TMTD 1.2 parts, dicumyl peroxide DCP 3 parts, and sulfur 0.5 parts. The tackifier raw materials include: phenolic resin (PF), melamine-formaldehyde resin (MF), and aminopropyl isobutyl cage polysilsesquioxane (aminoPOSS), and their parts are shown in Table 1.

[0039] Table 1: Formulations of the thickeners in various embodiments of the present invention

[0040] The preparation method of the above-mentioned EPDM rubber-based adhesive includes the following steps: Raw EPDM rubber is placed in a two-roll mill and broken down to the rolls. Antioxidant RD, stearic acid, zinc oxide, and accelerator CZ are mixed and added to the two-roll mill. The mixture is continuously pounded until fully incorporated, and rolled and triangularly wrapped 3-5 times each. Aminopropyl isobutyl cage-type polysilsesquioxane is added to the two-roll mill and continuously pounded until fully incorporated, and rolled and triangularly wrapped 5-7 times each. Carbon black, Si69, phenolic resin, and melamine-formaldehyde resin are mixed together and added to the two-roll mill. The mixture is continuously pounded until fully incorporated, and rolled and triangularly wrapped 5-7 times each. Paraffin oil is added and pounded until fully incorporated. Accelerator TMTD, dicumyl peroxide, and sulfur are mixed and added to the two-roll mill. The mixture is continuously pounded until fully incorporated, and rolled and triangularly wrapped 5-7 times each. The mixture is then sheeted to obtain an uncured compound of EPDM-based adhesive with a thickness of 4 mm.

[0041] An uncured EPDM rubber substrate is prepared, wherein the EPDM rubber substrate comprises the following components in parts by weight: 100 parts of EPDM raw rubber, 1 part of antioxidant RD, 0.5 parts of stearic acid, 5 parts of zinc oxide, 0.8 parts of accelerator CZ, 70 parts of carbon black N550, 3 parts of coupling agent Si69, 10 parts of paraffin oil, 1.2 parts of accelerator TMTD, 1.5 parts of dicumyl peroxide DCP, and 0.5 parts of sulfur.

[0042] The raw EPDM rubber is placed in a two-roll mill and broken down to the rolls. Antioxidant RD, stearic acid, zinc oxide, and accelerator CZ are mixed and added to the two-roll mill. The mixture is continuously pounded until fully incorporated, and rolled and formed into triangular shapes 3-5 times each. Carbon black and Si69 are mixed together and added to the two-roll mill. The mixture is continuously pounded until fully incorporated, and rolled and formed into triangular shapes 5-7 times each. Paraffin oil is added and pounded until fully incorporated. Accelerator TMTD, dicumyl peroxide, and sulfur are mixed and added to the two-roll mill. The mixture is continuously pounded until fully incorporated, and rolled and formed into triangular shapes 5-7 times each. The resulting sheet is a 4mm thick uncured EPDM rubber substrate.

[0043] The uncured compound of EPDM-based adhesive is placed between the uncured EPDM substrate and the metal reinforcement structure to obtain a pre-cured laminated structure. The pre-vulcanized laminated structure is heated and vulcanized together with the unvulcanized adhesive compound and the unvulcanized EPDM rubber compound. The vulcanization temperature is 160℃, the vulcanization pressure is 10MPa, and gas is released once every 2 minutes of hot pressing. The vulcanization time is set to 25 minutes to obtain the EPDM rubber structural component, the structure of which is shown in the attached figure. Figure 1 As shown.

[0044] The testing methods include vulcanization apparatus testing and mechanical property testing, as detailed below: Vulcanizer test Take about 3.5g of uncured compound rubber and test its curing performance on a rotorless vulcanizer. The test temperature is 160℃ and the test time is 45min. Obtain the vulcanization curve plotted by the vulcanizer. The horizontal axis of the vulcanization curve is the vulcanization time and the vertical axis is the torque. The torque is directly proportional to the shear modulus G.

[0045] The vulcanization curve includes the minimum torque value. M L and maximum torque value M H Minimum torque value M L Reflecting the flowability of uncured adhesive at a certain temperature, the adhesive needs to fill the tiny gaps between the EPDM adhesive block and the metal plate (such as scratches on the metal surface or gaps between adhesive blocks). A slightly lower [temperature value] is acceptable. M LThis value ensures better wettability during the initial stage of vulcanization (heating and softening stage), allowing it to adhere closely to the interface between the metal surface and the EPDM substrate, thus avoiding bubbles or voids caused by insufficient flowability. M L The value should not be too low (below the substrate). M L (70%), otherwise, during pressure vulcanization, excessive fluidity can cause it to be squeezed out from the interface, resulting in uneven adhesive layer thickness or localized missing adhesive, thus reducing adhesive strength. Maximum torque value M H Reflecting the maximum crosslinking degree of the vulcanized adhesive, similar crosslinking densities between the adhesive and the substrate can prevent internal stress caused by excessive modulus differences on both sides of the interface after vulcanization (e.g., if the substrate is soft and the adhesive is too hard, it can easily lead to interface delamination), thus ensuring the mechanical synergy of the overall structure. M H A slightly higher concentration (5%-10%) can increase the cohesive strength of the adhesive layer itself, preventing it from breaking first under external force; however, too high a concentration (more than 15%) will increase the brittleness of the adhesive layer, which will reduce its impact resistance and fatigue resistance. M H - M L The difference represents the magnitude of torque change during vulcanization. A value close to that of the substrate indicates that the crosslinking reaction from "unvulcanized" to "fully vulcanized" is synchronized, avoiding interfacial bonding defects caused by one side being fully crosslinked while the other is still reacting. Scorch time t s1 The time from the start of the experiment until the curve rises by 1 kg·cm from the lowest torque is the time required for the rubber to be safely processed and molded; initial vulcanization time. t 10 To achieve torque M L +10%* M H - M L The vulcanization time corresponding to the specified time is the point at which the rubber begins to vulcanize and crosslink; the adhesive's... t 10 Should be in relation to the substrate t 10 Approaching and synchronously initiating cross-linking, achieving "molecular-level bonding," if the adhesive... t 10 If initiated too early, a cross-linking network will form first, hindering the molecular chain entanglement with the substrate; if initiated too late, the substrate has already formed a preliminary cross-linking structure, making it difficult for adhesive molecules to penetrate into the substrate interface. Simultaneous initiation reduces localized stress concentration at the interface caused by the time difference in cross-linking initiation, lowering the risk of cracking after vulcanization. Positive vulcanization time. t 90 To achieve torque M L+90%* M H - M L The vulcanization time corresponding to the optimal performance of rubber is generally considered to be the vulcanization time for adhesives. t 90 Should be in relation to the substrate t 90 High consistency is achieved, the substrate achieves high strength, and the adhesive achieves a balance of "high cohesive strength + high interfacial adhesive strength", avoiding incomplete vulcanization (insufficient strength) or over-vulcanization (performance degradation) on one side.

[0046] Testing of mechanical performance indicators Dumbbell-shaped tensile and tear specimens and performance testing experiments: The pressure of the flat vulcanizing machine was set to 10MPa and the temperature to 160℃; a layer of high-temperature resistant, removable cellophane was laid on both the top and bottom of a 2mm thick mold cavity, and the adhesive was placed between the two layers of cellophane. t s1 and t 10 Based on the test results, it was determined that the gas should be released once every 2 minutes or so during hot pressing. t 90 Determine the vulcanization time to be between 20-35 minutes; remove the vulcanized rubber and cut it into dumbbell-shaped sheets and right-angle tear strips using a sheet punching machine.

[0047] Referring to the national standard GB / T 528-2009, measure the width and thickness at three different points in the middle of the dumbbell-shaped spline test section, record the data and take the median. Set the extensometer gauge length to 20 mm and the tensile speed to 500 mm / min. Stretch until fracture and record the data (tensile strength and elongation at break). Test at least 5 splines in each group.

[0048] Referring to the national standard GB / T 529-2008, the thickness of the right-angled portion was measured three times, and the median value was taken. The tensile speed was 500 mm / min until tensile fracture, and the tear strength was recorded.

[0049] Preparation and performance testing of hardness and resilience test specimens: The pressure of the flat vulcanizing machine was set to 10 MPa and the temperature to 160℃; a layer of high-temperature resistant, removable cellophane was laid on both the top and bottom of a 4 mm thick mold cavity, and the adhesive was placed between the two layers of cellophane. t s1 and t 10 Based on the test results, it was determined that the gas should be released once every 2 minutes of hot pressing. t 90Determine the vulcanization time to be between 20-35 minutes; remove the vulcanized rubber and cut it into 30*30mm pieces with scissors; referring to national standard GB / T 1681-2009, prepare 6 rubber blocks, stack three blocks on top of each other, test the rubber's resilience, and take the average of the two sets of data; referring to national standard GB / T 531.1-2008, prepare 10 rubber blocks, stack two rubber blocks on top of each other, and test the rubber hardness in the middle of the rubber blocks, and take the average of the 5 sets of samples.

[0050] Tensile strength test of polypropylene (PP) butt joint: A PP sample strip, 80 mm long, 10 mm wide, and 3.8 mm thick, is cut in half lengthwise and placed into a 4 mm thick mold cavity. The flat ends are aligned with the rubber block, and the other end is pressed firmly against the sides of the mold. The gap in the middle is filled with the mixed rubber block to ensure a good PP connection without adhesion to adjacent PP sections. A layer of high-temperature resistant cellophane is placed on both the top and bottom. The pressure is set at 3-5 MPa, and the temperature at 160℃. [Further details omitted] t s1 and t 10 Based on the test results, it was determined that the gas should be released once every 2 minutes of hot pressing. t 90 The vulcanization time was determined to be between 20 and 35 minutes (for each group of variables, the largest value was used). t 90 Take the integer value (e.g., when the melamine-formaldehyde resin is variable, the maximum value is 30.31 min, so the curing time is 31 min). After curing, remove the PP butt joint sample and remove the cellophane. Referring to the national standard GB / T 6329-1996, fix the sample symmetrically on the tensile testing machine holder, start the tensile testing machine, and stretch the sample in a constant displacement manner until the sample fails within 60±20 s. The test speed should be between 3-5 mm / min. The sample width should be 10 mm and the thickness should be 3.8 mm. At least 5 samples should be tested in each group, and the tensile strength should be recorded and the average value should be taken.

[0051] Tensile shear strength test of stainless steel sheets: Two identical rectangular stainless steel sheets (prepared by wire cutting, with a smooth surface, dimensions 25mm × 2mm × 100mm) are placed on a mold plate, overlapping each other with an overlap of approximately 12.5mm. A suitably sized compounded rubber sheet, approximately 1-3mm thick, is placed in the middle of the overlap. A layer of cellophane is placed on both the top and bottom. The mixture is then vulcanized on a 160℃ flat vulcanizing machine at a vulcanization pressure of 2-3MPa. t s1 and t 10 Based on the test results, it was determined that the gas should be released once every 2 minutes of hot pressing. t 90The vulcanization time was determined to be between 20 and 35 minutes (for each group of variables, the largest value was used). t 90 Take the integer value (e.g., when the melamine-formaldehyde resin is variable, the maximum value is 30.31 min, so the curing time is 31 min). After curing, remove the sample and remove the cellophane. Referring to the national standard GB / T 7124-2008, the length of the shear zone is 25 mm, and the width is measured with a ruler. The sample is symmetrically clamped on the gripper of the tensile testing machine, with the clamping point about 50 mm away from the nearest bonded end. The experiment is conducted at a constant test speed, so that the failure time is within 65 ± 20 s. The test speed is between 1 and 2 mm / min. At least 5 samples are tested in each group, and the tensile strength is recorded and the average value is taken.

[0052] Control Experiment 1 1) Without adding EPDM raw rubber, pure melamine-formaldehyde resin (MF resin), phenolic resin (PF resin), and aminopropyl isobutyl cage polysilsesquioxane (aminoPOSS) were used to directly bond PP and steel sheets, but none of them were successfully bonded. The test results are shown in Table 2.

[0053] 2) A 2mm EPDM rubber vulcanizate was added between the PP and the steel sheet. The vulcanizate was wrapped with MF resin, PF resin and amino POSS respectively. None of them were successfully bonded. The test results are shown in Table 2.

[0054] 3) A 2mm uncured EPDM rubber was added between the PP and the steel sheet. The uncured rubber was wrapped with MF resin, PF resin and amino POSS respectively. None of them were successfully bonded. The test results are shown in Table 2.

[0055] Table 2: Test results of control experiment 1

[0056] As can be seen from Table 2, pure MF resin, amino POSS or PF resin have weak self-crosslinking and the influence of polarity cannot achieve bonding.

[0057] Control Experiment 2 The difference between Control Experiment 2 and Example 1 is that the tackifier raw material in Control Experiment 2 only includes MF resin. The uncured compound was tested using a vulcanization apparatus, and the results are shown in Table 3.

[0058] Table 3: Test results of the vulcanizer in control experiment 2

[0059] Table 3 shows that 10-20 parts of MF resin significantly increased the crosslinking density (peak value reached 3.649); however, after exceeding 20 parts, the crosslinking density continuously decreased, and at 40 parts, it was lower than the unadded group, suggesting that excessive resin easily aggregated, hindering the crosslinking reaction of rubber molecules. Positive vulcanization time. t 90 The gradual increase in the amount of MF resin indicates that MF resin slows down the completion of vulcanization.

[0060] Table 3 also shows that adding only MF resin cannot synchronize the positive curing time of the adhesive with that of the EPDM substrate.

[0061] The mechanical properties of the uncured rubber compound were tested, and the results are shown in Table 4.

[0062] Table 4: Mechanical performance indicators of control experiment 2

[0063] Table 4 shows that the EPDM substrate without tackifier has higher tensile strength and elongation at break due to its uniform cross-linking network and the absence of rigid components interfering with the molecular chains; however, lacking tackifier components, its interfacial adhesion to PP / stainless steel is extremely weak. Adding 10-20 parts of MF resin... M H The increased crosslinking density enhances the cohesive strength of the rubber compound, but the MF (rigid component) dispersed between EPDM chains disrupts the flexible deformation ability of the molecular chains, thus reducing tensile strength and elongation at break. Simultaneously, the high crosslinking density of MF provides reinforcement and improves tear strength. Furthermore, the tackifying effect of MF significantly increases the interfacial adhesion between EPDM and PP / stainless steel. M H Increasing the proportion of rigid MF resin raises the hardness from 44 HA to 59 HA. When 30 parts of MF resin are added... M H The bonding strength with PP / stainless steel decreases slightly when the MF resin content is increased. The MF resin exhibits the best compatibility with the EPDM substrate, resulting in peak bonding strength. However, when 40 parts of MF resin are added, the excess MF hinders the cross-linking of rubber molecules, and the excessive MF tends to agglomerate, leading to uneven interfacial distribution.

[0064] Table 4 also shows that MF has strong adhesion to metals, but relatively weak adhesion to EPDM rubber.

[0065] Control Experiment 3 The difference between Control Experiment 3 and Example 1 is that the tackifier raw material in Control Experiment 3 only includes PF resin. The uncured compound was tested using a vulcanization apparatus, and the results are shown in Table 5.

[0066] Table 5: Test results of the vulcanizer in control experiment 3

[0067] As can be seen from Table 5, the maximum torque value increases with the increase of PF resin content. M H The continuous decrease indicates a continuous decrease in crosslinking density. This is because PF resin does not have the ability to self-crosslink, and PF resin is a thermoplastic resin. After heating, its fluidity increases, which inhibits the crosslinking reaction of rubber, and the density of the rubber network structure gradually weakens.

[0068] Table 5 also shows that adding only PF resin cannot synchronize the positive curing time of the adhesive with that of the EPDM substrate.

[0069] The mechanical properties of the uncured rubber compound were tested, and the results are shown in Table 6.

[0070] Table 6: Mechanical performance indicators of control experiment 3

[0071] As shown in Table 6, and in conjunction with Table 5, it is evident that with the increase of PF resin dosage, the crosslinking density continuously decreases. Furthermore, the PF resin fails to form an effective reinforcing network, thus failing to compensate for the decline in crosslinking density, resulting in a continuous decrease in tensile strength. Due to the inability to form an effective crosslinking network within the adhesive, the cohesive force is insufficient, leading to poor adhesion to both PP and stainless steel sheets.

[0072] Control Experiment 4 The difference between Control Experiment 4 and Example 1 is that the tackifier raw materials include MF resin and PF resin. The uncured compound was tested using a vulcanization apparatus, and the results are shown in Table 7.

[0073] Table 7: Test results of the vulcanizer in control experiment 4

[0074] Table 7 shows the maximum torque value when only MF resin and PF resin are added, respectively. M H and scorching time t s1 The difference is significant, and the positive vulcanization time t 90 The minimal difference suggests that MF and PF resins have complementary properties and may exhibit synergistic vulcanization. When MF and PF resins are added simultaneously, the positive vulcanization time... t 90 The decrease indicates a synergistic effect between MF and PF resins, which accelerates the crosslinking reaction rate of EPDM rubber. However, as shown in Table 7, the adhesive with added MF and PF resins... MH Generally lower than EPDM substrate, t 90 It also cannot be synchronized with EPDM substrates.

[0075] The mechanical properties of the uncured rubber compound were tested, and the results are shown in Table 8.

[0076] Table 8: Mechanical performance indicators of control experiment 4

[0077] As can be seen from Table 8, the butt tensile strength of PP in the compound group (20MF+20PF) (1.21MPa) is much higher than that of single 20MF (0.52MPa) and single 20PF (0.43MPa), and also significantly exceeds that of single 40MF (0.67MPa) and single 40PF (0.76MPa). This indicates that at this ratio, the tackifying groups of MF and PF have a synergistic effect, which greatly improves the interfacial adhesion between rubber and PP.

[0078] Table 8 also shows that the shear strength of the compound groups (such as 1.05 MPa for 20MF+20PF and 0.97 MPa for 10MF+30PF) is significantly higher than that of the single group with the same amount of PF (such as 0.50 MPa for single 20PF and 0.35 MPa for single 30PF), which reflects the synergistic reinforcement of PF on the performance of PF at the metal interface by MF.

[0079] However, the combination of MF and PF failed to improve the crosslinking density, and the MF and PF acted more as fillers, resulting in insufficient cohesion of the rubber block and reduced tensile strength.

[0080] Table 8 also shows that a small amount of phenolic resin weakens the bonding effect of a large amount of melamine-formaldehyde resin. It not only fails to significantly improve the bonding ability of the adhesive to non-polar rubber / resin materials, but also significantly reduces the bonding ability of the adhesive to metal. This is because the bonding ability of melamine-formaldehyde resin depends on the three-dimensional cross-linked structure formed by its own amino groups and formaldehyde. This dense structure can enhance the interfacial bonding with metal. The hydroxymethyl group of phenolic resin competes with the active amino group of melamine-formaldehyde resin for reaction sites, resulting in insufficient self-crosslinking of melamine-formaldehyde resin, loose cross-linking network, and inability to form a strong bonding interface.

[0081] However, a small amount of melamine-formaldehyde resin can assist in the vulcanization of phenolic resin, while simultaneously improving the adhesion between the adhesive and EPDM rubber and metal. This is because phenolic resin itself lacks self-crosslinking ability, while the amino groups of melamine-formaldehyde resin can act as "crosslinking promoters" for the vulcanization of phenolic resin. That is, the amino groups can activate the hydroxymethyl groups of phenolic resin, promoting the formation of methylene bridges between phenolic resin molecules. This not only helps phenolic resin transform from a linear structure to a three-dimensional crosslinked structure, making the adhesive system more stable, but the methylene bridges can also participate in the crosslinking of EPDM rubber, forming physical entanglement with the vulcanized structure of EPDM rubber, thus enhancing the adhesion to EPDM rubber.

[0082] Control Experiment 5 The difference between Control Experiment 5 and Example 1 is that the tackifier included aminopropyl isobutyl POSS (i.e., aminoPOSS in Table 9). The uncured compound was tested using a vulcanizer, and the results are shown in Table 9.

[0083] Table 9: Test results of the vulcanizer in control experiment 5

[0084] As can be seen from Table 9: M H (Crosslinking density) first increases and then decreases slightly. This is because a small amount of POSS grafted onto EPDM strengthens crosslinking, while a high amount is prone to aggregation, which slightly inhibits the crosslinking reaction. The amount of POSS should be less than 20 parts. t 90 The curing time is slightly extended because the dispersion of POSS slightly slows down the vulcanization process, but does not interfere with the core crosslinking reaction.

[0085] The mechanical properties of the uncured rubber compound were tested, and the results are shown in Table 10.

[0086] Table 10: Mechanical performance indicators of control experiment 5

[0087] As can be seen from Table 10, after adding POSS, the tensile strength, tear strength, PP butt joint strength, and stainless steel bond strength all first increased and then slightly decreased, reflecting the synergistic effect of POSS's nano-reinforcement and bridging crosslinking. The elongation at break and resilience continued to decrease, while the hardness continued to increase. This is because the rigid structure of POSS weakens the flexibility of the rubber molecular chain.

[0088] Control Experiment 6 The difference between Control Experiment 6 and Example 1 is that the tackifiers included aminopropyl isobutyl POSS and MF. The uncured compound was tested using a vulcanizer, and the results are shown in Table 11.

[0089] Table 11: Test results of the vulcanizer in control experiment 6

[0090] As can be seen from Table 11: Compound M H The cross-linking density is higher than that of EPDM alone, MF alone, or POSS alone, because POSS can undergo chemical cross-linking reactions with MF and EPDM respectively.

[0091] The mechanical properties of the uncured rubber compound were tested, and the results are shown in Table 12.

[0092] Table 12: Mechanical performance indicators of control experiment 6

[0093] As can be seen from Table 12, when MF and POSS are compounded, the tensile strength of PP butt joints is reduced. This is because both POSS and MF are relatively rigid. After compounding, the density and hardness of the cross-linking network are increased, making the adhesive layer too hard and the cohesion too large, which reduces the bonding performance with PP.

[0094] Control Experiment 7 The difference between Control Experiment 7 and Example 1 is that the tackifiers included aminopropyl isobutyl POSS and PF. The uncured compound was tested using a vulcanizer, and the results are shown in Table 13.

[0095] Table 13: Test results of the vulcanizer in control experiment 7

[0096] As can be seen from Table 13, after PF and aminoPOSS are combined, M H The density gradually increases because POSS can undergo chemical cross-linking reactions with both EPDM and PF simultaneously, thereby enhancing the cross-linking network density.

[0097] The mechanical properties of the uncured rubber compound were tested, and the results are shown in Table 14.

[0098] Table 14: Mechanical performance indicators of control experiment 7

[0099] As can be seen from Table 14, the combination of amino POSS and PF can enhance the bonding properties of PF, which should be the reason why crosslinking prevents PF from being lost during heating.

[0100] Table 15 shows the vulcanizing apparatus test results for Examples 1-6 of the present invention. As can be seen from Table 15, the present invention uses a three-component tackifier, which allows for adjustment of vulcanizing parameters. M L , M H as well ast 90 Similar to EPDM substrates, the uncured adhesive prepared by this invention can be simultaneously cured with uncured EPDM substrates and provides a slightly higher crosslinking density than EPDM substrates. Examples 3-6 are preferred embodiments, wherein the total amount of MF, PF, and aminoPOSS is preferably 40 parts, the amount of MF is preferably 10-15 parts, the amount of PF is preferably 15-20 parts, the amount of aminoPOSS is preferably 5-15 parts, and the total amount of MF and aminoPOSS is preferably 20-25 parts.

[0101] Table 15: Vulcanizer Test Results of Examples 1-6

[0102] Table 16 shows the test results of mechanical performance indicators of Examples 1-6 of the present invention. As can be seen from Table 16, the present invention uses a three-component tackifier, which can significantly improve the tensile strength of PP and the tensile shear strength of stainless steel sheets compared with any two or single components. At the same time, it also significantly improves the tensile strength, tear strength and hardness. This should be due to the uniform cross-linking network inside the adhesive.

[0103] Table 16: Mechanical performance indicators of Examples 1-6

[0104] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A EPDM rubber-based adhesive, characterized in that, The components include the following parts by mass: 100 parts of EPDM raw rubber, 3-6 parts of vulcanizing agent, 1-3 parts of vulcanization accelerator and tackifier; The tackifier comprises 10-15 parts of melamine-formaldehyde resin, 15-20 parts of phenolic resin, and 5-15 parts of aminated cage-type polysilsesquioxane; and the aminated cage-type polysilsesquioxane comprises a cage-type silicon-oxygen cubic core structure, alkyl groups respectively connected to the eight vertices of the cage-type silicon-oxygen cubic core structure, and terminal amino groups connected to the alkyl groups. The total number of parts of the aminated cage-type polysilsesquioxane and the melamine-formaldehyde resin is 20 to 25 parts, and the total number of parts of the aminated cage-type polysilsesquioxane, the melamine-formaldehyde resin and the phenolic resin is 40 parts.

2. The EPDM rubber-based adhesive according to claim 1, characterized in that, The aminated cage-type polysilsesquioxane includes aminopropyl isobutyl cage-type polysilsesquioxane.

3. The EPDM rubber-based adhesive according to claim 1, characterized in that, The ethylene content in the EPDM raw rubber is 60%~70% by mass. The vulcanizing agent includes peroxide vulcanizing agents and / or sulfur; The vulcanization accelerator includes accelerator CZ and / or accelerator TMTD.

4. The EPDM rubber-based adhesive according to any one of claims 1 to 3, characterized in that, It also includes one or more of the following: activators, anti-aging agents, and reinforcing agents.

5. The EPDM rubber-based adhesive according to claim 4, characterized in that, The activating agents include stearic acid and / or zinc oxide.

6. The EPDM rubber-based adhesive according to claim 4, characterized in that, The reinforcing agent includes carbon black.

7. The EPDM rubber-based adhesive according to claim 4, characterized in that, The antioxidant includes antioxidant RD.

8. A method for preparing a EPDM rubber-based adhesive as described in any one of claims 1 to 7, characterized in that, The process includes the following: The EPDM raw rubber, the vulcanizing agent, the vulcanization accelerator, and the tackifier are mixed to obtain the EPDM-based adhesive.

9. A ternary ethylene propylene diene monomer (EPDM) rubber structural component, characterized in that, Its preparation method The process includes the following: The EPDM rubber-based adhesive is mixed to obtain an uncured rubber block of adhesive, wherein the EPDM rubber-based adhesive is as described in any one of claims 1 to 7; The uncured adhesive compound block is placed between the uncured EPDM rubber substrate and the metal reinforcement structure to obtain a pre-cured laminated structure. The pre-vulcanized laminated structure is heated and vulcanized, so that the unvulcanized adhesive compound block and the unvulcanized EPDM rubber substrate are vulcanized together to obtain the EPDM rubber structural component.

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