Ultra-light and ultra-wear-resistant rubber and preparation method thereof

Abstract

The invention discloses ultra-light and ultra-wear-resistant rubber and a preparation method thereof, and relates to the technical field of rubber materials, the ultra-light and ultra-wear-resistant rubber comprises 60-98% of a rubber matrix, 0.3-10% of a foaming system, 0.1-8% of a permanent covalent cross-linking system, and 0.1-12% of a dynamic reversible cross-linking system; according to the dynamic reversible crosslinking system, in the foaming forming process, dynamic crosslinking points are enriched in a surface layer and a foam wall area, and the ratio of the effective crosslinking density of the surface layer and the foam wall area to the effective crosslinking density of a core layer is 1.5-6.0. By forming a cross-linking density gradient structure relative to the core layer, an abrasion bearing area has reversible fracture and recombination energy dissipation capacity in the stress and abrasion process, so that microcrack propagation of a cell wall is inhibited on the premise that the overall density is not improved, low density, abrasion resistance and rebound stability are considered, and the wear resistance and the rebound stability are improved. And light weight and wear resistance are synergistically improved.

Description

Technical Field

[0001] This invention relates to the field of rubber materials technology, and in particular to an ultralight and ultra-wear-resistant rubber and its preparation method. Background Technology

[0002] Existing foamed rubbers typically achieve lightweighting by forming a cell structure within the rubber matrix and rely on permanent covalent crosslinking methods such as sulfur or peroxides to stabilize the cell morphology. While dynamic crosslinking strategies based on reversible B–O bonds in borate esters can provide energy dissipation and structural rearrangement capabilities, the dynamic crosslinking points in foamed rubber are often uniformly distributed. Improving wear resistance still mainly depends on increasing the overall crosslinking density or filler content, which can easily lead to increased density, decreased resilience, or cell wall embrittlement. It is difficult to simultaneously achieve both lightweighting and wear resistance. Therefore, there is an urgent need for an ultra-lightweight and ultra-wear-resistant rubber material that can maintain high wear resistance while reducing density. Summary of the Invention

[0003] In view of this, this application provides an ultralight and ultra-wear-resistant rubber and a method for preparing the same.

[0004] According to one aspect of this disclosure, an ultralight and ultra-wear-resistant rubber is provided, comprising: a rubber matrix of 60–98%, a foaming system of 0.3–10%, a permanent covalent crosslinking system of 0.1–8%, and a dynamic reversible crosslinking system of 0.1–12%; the rubber matrix includes at least one vinyl elastomer, which, after functionalization modification, can form reversible B–O bond reaction sites with boric acid groups on its molecular chain; the permanent covalent crosslinking system refers to the covalent crosslinking bonds formed between the molecular chains of the rubber matrix through covalent chemical reactions during foaming and curing; the dynamic reversible crosslinking system refers to the crosslinking structure in the rubber matrix formed by reversible B–O bonds between boron-source crosslinking components and glycol-source crosslinking components, resulting in reversible breakage and recombination; during the foaming process, the dynamic reversible crosslinking system enriches the dynamic crosslinking points in the surface layer and cell wall region, and the ratio of the effective crosslinking density in the surface layer and cell wall region to the effective crosslinking density in the core layer is 1.5–6.0.

[0005] According to another aspect of this disclosure, an ultralight and ultra-wear-resistant rubber is provided, comprising: Step 1, functionalizing at least one vinyl elastomer to form reversible B–O bond reaction sites with boric acid groups on the molecular chain of the vinyl elastomer, thereby obtaining a functionalized vinyl elastomer; Step 2, uniformly mixing the functionalized vinyl elastomer with the diol-based crosslinking component to obtain a diol-based dispersion masterbatch; Step 3, adding the boron-based crosslinking component to the diol-based dispersion masterbatch and mixing to obtain a dynamically reversible crosslinking premix, wherein the ratio of boric acid group equivalent to o-diol equivalent is controlled at 0.8–1.5; Step 4, adding the foaming system and the permanently covalently crosslinked system to the dynamically reversible crosslinking premix and mixing to obtain a foamed molding compound; Step 5, performing foaming molding and post-curing on the foamed molding compound to obtain a foamed vulcanized rubber product, wherein during the foaming molding process, dynamic crosslinking points are enriched in the surface layer and cell wall region.

[0006] The beneficial effects of this invention are as follows: by simultaneously constructing a permanent covalent crosslinking network and a dynamic reversible crosslinking network based on reversible B–O bonds in foamed vulcanized rubber, and selectively enriching the dynamic crosslinking points in the surface layer and cell wall region during the foaming process, a crosslinking density gradient structure relative to the core layer is formed. This enables the wear-bearing area to have the energy dissipation capacity of reversible fracture and recombination during stress and wear, thereby suppressing the propagation of microcracks in the cell wall without increasing the overall density, and taking into account low density, wear resistance and resilience stability, thus achieving a synergistic improvement in lightweight and wear resistance performance. Attached Figure Description

[0007] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. 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.

[0008] Figure 1 A schematic diagram of the structure of cross-linked density gradient foamed rubber.

[0009] Figure 2 SEM images showing the overall structure of the bubble (a) and a magnified view of a local area of ​​the bubble wall region (b).

[0010] Figure 3 A schematic diagram of the process for forming a crosslinking density gradient.

[0011] Figure 4 This is a schematic diagram of bubble formation and gas diffusion during the first heating stage. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0013] This invention aims to construct an ultralight and ultra-wear-resistant rubber. In the embodiments of this application, the ultralight and ultra-wear-resistant rubber comprises: a rubber matrix of 60–98%, a foaming system of 0.3–10%, a permanently covalently crosslinked system of 0.1–8%, and a dynamically reversible crosslinked system of 0.1–12%. The rubber matrix includes at least one vinyl elastomer, which, after functionalization modification, can form reversible B–O bond reaction sites with boric acid groups on its molecular chain. The permanently covalently crosslinked system refers to the covalent crosslinking bonds formed between the molecular chains of the rubber matrix through covalent chemical reactions during foaming and curing. The dynamically reversible crosslinking system refers to the formation of reversible B–O bonds between boron-source crosslinking components and glycol-source crosslinking components, resulting in a reversible breakage and recombination crosslinking structure in the rubber matrix. During the foaming process, the dynamically reversible crosslinking system enriches the dynamic crosslinking points in the surface layer and cell wall region, and the ratio of the effective crosslinking density in the surface layer and cell wall region to the effective crosslinking density in the core layer is 1.5–6.0.

[0014] In some embodiments of this application, the vinyl elastomer is selected from one or more of styrene-butadiene rubber, cis-butadiene rubber, and isoprene rubber; The reversible B–O bond reaction site of the vinyl elastomer is one or more of the following: vicinal diol group, catechol group, or dihydroxyphenyl group.

[0015] In some embodiments of this application, the ratio of the borate equivalent provided by the boron source crosslinking component to the vicinal diol equivalent provided by the diol source crosslinking component is 0.8–1.5.

[0016] In some embodiments of this application, the boron source crosslinking component is selected from one or more of aromatic boric acid, difunctional borate esters, and polyfunctional borate esters; The diol source crosslinking component is selected from one or more of diol-terminated oligomers, polyols, or diolized plasticized segments.

[0017] In some embodiments of this application, the rubber matrix further contains 1–25% reinforcing filler by mass percentage; The reinforcing filler is selected from one or more of precipitated silica and layered nanoclay.

[0018] In some embodiments of this application, the rubber matrix further includes 0.05–3% by weight of an interface anchoring agent; The interface anchoring agent is selected from one or more of epoxy-containing silane coupling agents, amino-containing silane coupling agents, and boric acid-containing organosilanes. The interface anchoring agent and the reinforcing filler are co-located and distributed in the cell wall region.

[0019] In some embodiments of this application, the foaming system refers to a component system that can decompose and release gas under heating conditions and form a cell structure in a rubber matrix, including chemical foaming agents and foaming aids; The chemical foaming agent is selected from one or more of azodicarbonamide and p-toluenesulfonyl hydrazine; The foaming agent is selected from one or more of urea-based agents and zinc salt agents.

[0020] In some embodiments of this application, the permanent covalent crosslinking system includes one of a sulfur crosslinking component or a peroxide crosslinking component; When the permanent covalent crosslinking system includes a sulfur crosslinking component, the permanent covalent crosslinking system also includes one or more of thiazole accelerators or sulfenamide accelerators.

[0021] This application also provides a method for preparing ultralight and ultra-wear-resistant rubber, including, Step 1: At least one vinyl elastomer is functionalized to form reaction sites on the molecular chain of the vinyl elastomer that can form reversible B–O bonds with borate groups, thereby obtaining a functionalized vinyl elastomer. Step 2: Mix the functionalized vinyl elastomer and the diol source crosslinking component evenly to obtain a diol source dispersion masterbatch; Step 3: Add the boron source crosslinking component to the diol source dispersion masterbatch and mix to obtain a dynamically reversible crosslinking premix, wherein the ratio of boric acid equivalent to vicinal diol equivalent is controlled to be 0.8–1.5. Step 4: Add the foaming system and the permanent covalent crosslinking system to the dynamic reversible crosslinking premix and mix them to obtain the foamed molding compound; Step 5: Perform foaming and post-curing on the foamed molding compound to obtain a foamed vulcanized rubber product, and during the foaming process, the dynamic crosslinking points are enriched in the surface and cell wall areas.

[0022] Preferably, the foaming and post-curing process includes a first heating stage, a second heating stage, and a post-curing stage in sequence. The first heating stage forms a permanent covalent cross-linked network and brings the adhesive to the vicinity of the gel point; The second heating stage completes the foaming and pore formation, and the dynamic cross-linking points are enriched as the pore walls are formed; The post-curing stage stabilizes the ratio of the effective crosslinking density of the surface layer and cell wall region to the effective crosslinking density of the core layer at 1.5–6.0.

[0023] Example 1: The components were formulated by weight percentage as follows: rubber matrix 82.0%, foaming system 3.0%, permanent covalent crosslinking system 2.0%, and dynamic reversible crosslinking system 13.0%. The rubber matrix consisted of 70.0% functionalized vinyl elastomer (styrene-butadiene rubber / cis-butadiene rubber mass ratio 60 / 40, functionalized reaction sites being vicinal diol groups), 11.0% reinforcing filler (precipitated silica), and 1.0% interface anchoring agent (containing epoxy silane coupling agent); the foaming system consisted of 2.5% azodicarbonamide and 0.5% foaming aid; the permanent covalent crosslinking system consisted of 0.6% sulfur, 0.9% sulfenamide accelerator, and 0.5% activator; the dynamic reversible crosslinking system consisted of 10.0% diol-terminated oligomer and 3.0% borate ester crosslinking agent, with the ratio of borate equivalent provided by the boron-source crosslinking component to vicinal diol equivalent provided by the diol-source crosslinking component being 1.0. Functionalized vinyl elastomers, reinforcing fillers, and interface anchoring agents are added to an internal mixer and mixed at 90–105°C for 6–8 min; glycol-terminated oligomers are added and mixed for 2–3 min; after cooling to 80–90°C, borate ester crosslinking agents are added and mixed for 2 min; the mixture is then transferred to an open mill and the permanent covalent crosslinking system and foaming system are added and passed through 8–10 times to obtain a foamed molding compound; the foamed molding compound is placed in a flat vulcanizing machine for segmented heating and molding: the first heating stage is 145°C × 4 min, the second heating stage is 165°C × 6 min, and the post-curing stage is 130°C × 25 min to obtain foamed vulcanized rubber products.

[0024] After segmented heating and foaming molding, a gradient structure is formed in the foamed vulcanized rubber, where the crosslinking density of the surface layer and cell wall region is higher than that of the core layer. Its overall structural characteristics are as follows: Figure 1 As shown.

[0025] Scanning electron microscopy (SEM) observation of the obtained foamed vulcanized rubber revealed significant morphological differences between the overall cell structure and the cell wall region. The SEM images of the overall cell structure (a) and a magnified portion of the cell wall region (b) are shown below. Figure 2 As shown.

[0026] Example 2, the components were proportioned as follows by mass percentage: rubber matrix 84.0%, foaming system 4.0%, permanent covalent crosslinking system 1.6%, and dynamic reversible crosslinking system 10.4%. The rubber matrix consisted of 72.0% functionalized vinyl elastomer (styrene-butadiene rubber / cis-butadiene rubber mass ratio 50 / 50, functionalized reaction sites being vicinal diol groups), 11.0% reinforcing filler (precipitated silica), and 1.0% interface anchoring agent (containing epoxy silane coupling agent); the dynamic reversible crosslinking system consisted of 8.2% diol-terminated oligomer and 2.2% aromatic boric acid, with a boric acid equivalent / vicinal diol equivalent of 1.0. Prepared using the same mixing and staged heating process as in Example 1, the resulting product had a lower density and finer pores, while maintaining wear resistance within the usable range at a low density level.

[0027] Example 3: The components were proportioned as follows by mass percentage: 80.0% rubber matrix, 3.0% foaming system, 2.2% permanent covalent crosslinking system, and 14.8% dynamic reversible crosslinking system. The rubber matrix consisted of 67.5% functionalized vinyl elastomer (butadiene rubber / isoprene rubber mass ratio 70 / 30, functionalized reaction sites being catechol groups), 11.5% reinforcing filler (precipitated silica), and 1.0% interface anchoring agent (boronic acid-containing organosilane). The dynamic reversible crosslinking system consisted of 11.5% glycol-terminated oligomer and 3.3% polyfunctional borate ester, with a borate equivalent / vicinal glycol equivalent of 1.2. The product was molded using the same preparation steps as in Example 1, resulting in a further reduction in wear volume at a similar density level, and a more pronounced effective crosslinking density gradient between the surface and cell wall regions.

[0028] Example 4: The components were proportioned as follows by mass percentage: 81.5% rubber matrix, 2.5% foaming system, 2.0% permanent covalent crosslinking system, and 14.0% dynamic reversible crosslinking system. The rubber matrix consisted of 69.0% functionalized vinyl elastomer (styrene-butadiene rubber, with vicinal diol functionalization sites), 11.5% reinforcing filler (layered nanoclay), and 1.0% interface anchoring agent (containing aminosilane coupling agent). The dynamic reversible crosslinking system consisted of 12.0% diol-terminated oligomer and 2.0% aromatic boric acid, with a boric acid equivalent / vicinal diol equivalent ratio of 0.8. Prepared using the same process as in Example 1, the resulting product exhibited a dynamic crosslinking point enrichment at the lower limit of the gradient formation range, resulting in a smaller increase in wear resistance compared to Examples 1 and 3.

[0029] Example 5, the components were proportioned as follows by mass percentage: rubber matrix 82.0%, foaming system 3.5%, permanent covalent crosslinking system 1.8%, and dynamic reversible crosslinking system 12.7%. The rubber matrix consisted of 69.8% functionalized vinyl elastomer (styrene-butadiene rubber / cis-butadiene rubber mass ratio 60 / 40, functionalized reaction sites being dihydroxyphenyl groups), 11.2% reinforcing filler (precipitated silica), and 1.0% interface anchoring agent (containing epoxy silane coupling agent); the dynamic reversible crosslinking system consisted of 9.2% glycol-terminated oligomer and 3.5% polyfunctional borate ester, with a borate equivalent / vicinal glycol equivalent of 1.5. Prepared using the same process as in Example 1, the resulting product had lower wear volume and maintained its rebound within a usable range, with a higher crosslinking density gradient than in Example 1.

[0030] Example 6: The components were formulated as follows by mass percentage: rubber matrix 78.5%, foaming system 3.0%, permanent covalent crosslinking system 2.6%, and dynamic reversible crosslinking system 15.9%. The rubber matrix consisted of 66.0% functionalized vinyl elastomer (butadiene rubber / isoprene rubber mass ratio 60 / 40, functionalized reaction sites being catechol groups), 11.5% reinforcing filler (precipitated silica), and 1.0% interface anchoring agent (boronic acid-containing organosilane). The dynamic reversible crosslinking system consisted of 12.5% ​​glycol-terminated oligomer and 3.4% polyfunctional borate ester, with a borate equivalent / vicinal glycol equivalent of 1.0. Prepared using the same process as in Example 1, the resulting product exhibited one of the best abrasion resistance performances, while its density was slightly higher than the low-foaming formulation but still within the range of lightweight foaming.

[0031] Example 7: The components were proportioned as follows by mass percentage: rubber matrix 86.0%, foaming system 3.0%, permanent covalent crosslinking system 1.2%, and dynamic reversible crosslinking system 9.8%. The rubber matrix consisted of 74.0% functionalized vinyl elastomer (styrene-butadiene rubber, with vicinal diol functionalization sites), 11.0% reinforcing filler (precipitated silica), and 1.0% interfacial anchoring agent (containing epoxy silane coupling agent). The dynamic reversible crosslinking system consisted of 7.6% diol-terminated oligomer and 2.2% aromatic boric acid, with a boric acid equivalent / vicinal diol equivalent of 1.0. Prepared using the same process as in Example 1, the resulting product had the lowest density but a relatively limited improvement in wear resistance, and the corresponding crosslinking density gradient was close to the lower limit of the claims.

[0032] Example 8: The components were proportioned as follows by mass percentage: rubber matrix 83.0%, foaming system 3.0%, permanent covalent crosslinking system 2.0%, and dynamic reversible crosslinking system 12.0%. The rubber matrix consisted of 70.5% functionalized vinyl elastomer (styrene-butadiene rubber / cis-butadiene rubber mass ratio 60 / 40, functionalized reaction sites being vicinal diol groups), 11.5% reinforcing filler (precipitated silica), and 1.0% interface anchoring agent (containing epoxy silane coupling agent). The dynamic reversible crosslinking system consisted of 9.6% diol-terminated oligomer and 2.4% difunctional borate ester, with a borate equivalent / vicinal diol equivalent of 1.0. During preparation, a holding condition of 165℃ for 7 minutes was used in the second heating stage, and the remaining steps were the same as in Example 1. The resulting product formed a more stable crosslinking density gradient between the surface layer and the cell wall, resulting in a better overall balance between wear resistance and resilience. Comparative Example 1 had the following formulation by mass percentage: 86.0% rubber matrix, 3.0% foaming system, 11.0% permanent covalent crosslinking system, and 0% dynamic reversible crosslinking system. The rubber matrix consisted of 74.0% unfunctionalized styrene-butadiene rubber, 11.0% precipitated silica, and 1.0% epoxy-containing silane coupling agent; the permanent covalent crosslinking system used a combination of sulfur / accelerator / activator. The preparation process was the same as in Example 1. The resulting product exhibited significantly higher wear volume at low density levels, and the crosslinking density ratio between the surface and core layers was nearly uniform.

[0033] Comparative Example 2 used the same formulation as Product Example 1, but the molding process was changed to a single-stage heating at 165℃ for 8 minutes, followed by direct post-curing at 130℃ for 25 minutes. The first and second heating stages were not distinguished. The resulting product showed a more uniform distribution of dynamic crosslinking points in the bulk phase, with a crosslinking density ratio between the surface and core layers close to 1.2. The improvement in wear resistance was significantly less than that under the segmented heating condition.

[0034] Comparative Example 3, the formulation by mass percentage is: rubber matrix 76.0%, foaming system 3.0%, permanent covalent crosslinking system 21.0%, and dynamic reversible crosslinking system 0%. The rubber matrix consists of unfunctionalized vinyl elastomer 60.0%, precipitated silica 15.0%, and epoxy-containing silane coupling agent 1.0%; the permanent covalent crosslinking system increases the amount of sulfur and accelerator and increases the level of activator. The preparation process is the same as in Example 1. The resulting product can reduce the wear volume to a lower level, but the density increases and the resilience decreases, making it difficult to simultaneously meet the synergistic goals of lightweighting and wear resistance.

[0035] Under the sequential action of the first heating stage, the second heating stage, and the post-curing stage, the permanent covalent cross-linked network and the dynamically reversible cross-linking points undergo a synergistic evolution in spatial distribution, thereby forming a cross-linking density gradient. The formation mechanism is illustrated in the diagram below. Figure 3 As shown.

[0036] In the first heating stage, the foaming system begins to decompose and release gas, which diffuses within the compound. Simultaneously, a permanent covalent cross-linked network gradually forms and restricts gas migration. The cell formation and gas diffusion process is illustrated in the diagram below. Figure 4 As shown.

[0037] Apparent density test, DIN abrasion test, rebound test, compression set test and crosslinking density gradient test were performed on the products of Examples 1 to 8 and the samples of Comparative Examples 1 to 3.

[0038] Apparent density test: After molding, each sample was placed in a room temperature environment to allow the internal structure to stabilize. Then, regularly shaped test blocks were cut along the foaming direction, the edges of the test blocks were trimmed, and the mass of the test blocks was weighed. The volume corresponding to the test block was determined using a liquid displacement method, and the apparent density of the sample was calculated accordingly. The apparent density test is used to characterize the degree to which different embodiments achieve lightweighting under foam molding conditions and is used for comparative analysis with abrasion resistance results.

[0039] Abrasion resistance test: Uniformly thick test pieces are cut from each sample along the foaming direction and processed into standard specimens that meet the abrasion resistance test requirements. After being conditioned in a constant temperature and humidity environment, the specimens are placed in an abrasion testing device, and their surfaces are continuously rubbed under specified loads and abrasion conditions. The abrasion volume is calculated by comparing the mass change of the specimens before and after abrasion to evaluate the sample's ability to resist abrasion under low-density conditions. The abrasion resistance test directly reflects the abrasion resistance level of foamed rubber under repeated friction in actual use.

[0040] Rebound performance test: Each sample is processed into a specimen with flat upper and lower surfaces and fully conditioned at room temperature. An impactor is applied perpendicularly to the specimen surface using a free impact method, and the relationship between the rebound height and the initial drop height is recorded to obtain the sample's rebound performance index. The rebound performance test is used to evaluate whether the material's elasticity can still be maintained within a reasonable range while improving wear resistance, thus verifying that the invention does not significantly sacrifice overall rebound performance due to enhanced local cross-linking.

[0041] Compression set test: Regularly sized compression specimens are cut from each sample, and the initial thickness is measured. The specimens are placed in a compression fixture, subjected to a specified compression, and held in a heated environment for a certain period of time to simulate long-term stress and thermal conditions. The compression is then released, and the specimens are allowed to fully recover at room temperature. The thickness change after recovery is then measured. The compression set test is used to evaluate the material's ability to retain deformation under long-term compression and reflects the contribution of the permanently covalently cross-linked network to structural stability.

[0042] Crosslinking density gradient test: To verify the selective enrichment effect of dynamically reversible crosslinking points in the surface and cell wall regions, samples from the surface and cell wall regions and the core region of each sample were taken for comparative testing. The surface and cell wall region samples were cut from the outer surface of the product and included cell wall structural features, while the core layer samples were taken from the central region of the product. After drying and achieving mass stability, each sample was placed in an organic solvent for full swelling, allowing the crosslinking network to limit the degree of swelling. After swelling, the samples were weighed and dried, and the effective crosslinking degree in different regions was obtained by comparing the mass changes before and after swelling. Furthermore, the ratio of the crosslinking degree in the surface and cell wall regions to the crosslinking degree in the core layer was compared to characterize the difference in crosslinking density distribution along the thickness direction of the product, serving as an important basis for determining whether a crosslinking structural gradient has formed.

[0043] Table 1 Comparison of main performance test results of each embodiment and comparative example.

[0044] As can be seen from Table 1, the apparent density of the embodiments of the present invention is between 0.38 and 0.46 g / cm³. 3 Within the lightweight range, a significantly lower wear volume than the comparative example can still be obtained. Examples 3, 5, 6, and 8 have an apparent density of approximately 0.43–0.46 g / cm³. 3 Under these conditions, the DIN wear volume is 118mm. 3 121mm 3 114mm 3 and 119mm 3 Both were significantly lower than the 215 mm of Comparative Example 1 under similar apparent density conditions. 3 And the 176mm of Comparative Example 2 3 This indicates that the wear resistance has been substantially improved without increasing the overall apparent density.

[0045] Further analysis of the crosslinking density gradient data reveals that in Examples 3, 5, 6, and 8, the crosslinking density ratios of the surface layer and cell wall region relative to the core layer reached 2.9, 3.1, 2.7, and 2.6, respectively, significantly higher than the 1.1 in Comparative Example 1, 1.2 in Comparative Example 2, and 1.0 in Comparative Example 3. This data indicates that the dynamically reversible crosslinking structure selectively accumulates in the surface layer and cell wall region during the foaming process, resulting in a higher effective crosslinking density in the wear-bearing region compared to the core layer. This is a key reason for the significant reduction in DIN wear volume.

[0046] As can be seen from the comparison of low-density samples, Example 7 reduced the apparent density to 0.38 g / cm³. 3At that time, the DIN wear volume increased to 168mm. 3 The corresponding crosslinking density ratio is 1.6, which is close to the lower limit range defined in the claims. Related results indicate that, under conditions of insufficient dynamic crosslinking enrichment, simply reducing the apparent density weakens wear resistance retention, thus demonstrating that the present invention does not rely on reducing apparent density or increasing crosslinking amount, but rather on the optimization of the spatial distribution of the crosslinking structure.

[0047] Regarding resilience and compression set, the embodiments of the present invention achieve improved wear resistance while maintaining usable elasticity and deformation stability. For example, the resilience rates of Examples 3, 5, and 6 are 46%, 45%, and 44%, respectively, and the compression set is maintained at 20%–21%. In contrast, Comparative Example 3, although the DIN wear volume is reduced to 123 mm... 3 However, the apparent density increased to 0.52 g / cm³. 3 The resilience rate decreased to 38%, and the compression set increased to 29%, indicating that improving wear resistance by simply increasing the degree of permanent covalent crosslinking would come at the cost of sacrificing lightweight and elastic properties.

[0048] The above description is only a specific embodiment of this disclosure, but the protection scope of this disclosure is not limited thereto. The protection scope of this disclosure should be determined by the protection scope of the claims.

Claims

1. An ultralight and ultra-wear-resistant rubber, characterized in that: It includes 60–98% rubber matrix, 0.3–10% foaming system, 0.1–8% permanent covalent crosslinking system, and 0.1–12% dynamic reversible crosslinking system; The rubber matrix includes at least one vinyl elastomer, which, after functionalization modification, can form reversible B–O bond reaction sites with borate groups on its molecular chain. The permanent covalent crosslinking system refers to the covalent crosslinking bonds formed between the molecular chains of the rubber matrix through covalent chemical reactions during the foaming and curing process; The dynamic reversible crosslinking system refers to the crosslinking structure in the rubber matrix that can be reversibly broken and recombined by forming reversible B–O bonds between the boron-source crosslinking component and the diol-source crosslinking component. During the foaming process, the dynamic reversible crosslinking system enriches the dynamic crosslinking points in the surface layer and cell wall region, and the ratio of the effective crosslinking density in the surface layer and cell wall region to the effective crosslinking density in the core layer is 1.5–6.

0.

2. The ultralight and ultra-wear-resistant rubber as described in claim 1, characterized in that: The vinyl elastomer is selected from one or more of styrene-butadiene rubber, cis-butadiene rubber, and isoprene rubber; The reversible B–O bond reaction site of the vinyl elastomer is one or more of the following: vicinal diol group, catechol group, or dihydroxyphenyl group.

3. The ultralight and ultra-wear-resistant rubber as described in claim 1, characterized in that: The ratio of the borate equivalent provided by the boron source crosslinking component to the vicinal diol equivalent provided by the diol source crosslinking component is 0.8–1.

5.

4. The ultralight and ultra-wear-resistant rubber as described in claim 3, characterized in that: The boron source crosslinking component is selected from one or more of aromatic boric acid, difunctional borate esters, and polyfunctional borate esters; The diol source crosslinking component is selected from one or more of diol-terminated oligomers, polyols, or diolized plasticized segments.

5. The ultralight and ultra-wear-resistant rubber as described in any one of claims 1 to 4, characterized in that: The rubber matrix also contains 1–25% reinforcing filler by mass percentage; The reinforcing filler is selected from one or more of precipitated silica and layered nanoclay.

6. The ultralight and ultra-wear-resistant rubber as described in claim 5, characterized in that: The rubber matrix also includes 0.05–3% by weight of an interface anchoring agent; The interface anchoring agent is selected from one or more of epoxy-containing silane coupling agents, amino-containing silane coupling agents, and boric acid-containing organosilanes. The interface anchoring agent and the reinforcing filler are co-located and distributed in the cell wall region.

7. The ultralight and ultra-wear-resistant rubber as described in claim 6, characterized in that: The foaming system refers to a component system that can decompose and release gas under heating conditions and form a cell structure in a rubber matrix, including chemical foaming agents and foaming aids; The chemical foaming agent is selected from one or more of azodicarbonamide and p-toluenesulfonyl hydrazine; The foaming agent is selected from one or more of urea-based agents and zinc salt agents.

8. The ultralight and ultra-wear-resistant rubber as described in claim 6, characterized in that: The permanent covalent crosslinking system includes one of sulfur crosslinking components or peroxide crosslinking components; When the permanent covalent crosslinking system includes a sulfur crosslinking component, the permanent covalent crosslinking system also includes one or more of thiazole accelerators or sulfenamide accelerators.

9. The method for preparing ultralight and ultrawear-resistant rubber according to any one of claims 1-8, characterized in that: include, Step 1: At least one vinyl elastomer is functionalized to form reaction sites on the molecular chain of the vinyl elastomer that can form reversible B–O bonds with borate groups, thereby obtaining a functionalized vinyl elastomer. Step 2: Mix the functionalized vinyl elastomer and the diol source crosslinking component evenly to obtain a diol source dispersion masterbatch; Step 3: Add the boron source crosslinking component to the diol source dispersion masterbatch and mix to obtain a dynamically reversible crosslinking premix, wherein the ratio of boric acid equivalent to vicinal diol equivalent is controlled to be 0.8–1.5; Step 4: Add the foaming system and the permanent covalent crosslinking system to the dynamic reversible crosslinking premix and mix them to obtain the foamed molding compound; Step 5: Perform foaming and post-curing on the foamed molding compound to obtain a foamed vulcanized rubber product, and during the foaming process, the dynamic crosslinking points are enriched in the surface and cell wall areas.

10. The preparation method according to claim 9, characterized in that: The foaming and post-curing process includes, in sequence, a first heating stage, a second heating stage, and a post-curing stage; The first heating stage forms a permanent covalent cross-linked network and brings the adhesive to the vicinity of the gel point; The second heating stage completes the foaming and pore formation, and the dynamic cross-linking points are enriched as the pore walls are formed; The post-curing stage stabilizes the ratio of the effective crosslinking density of the surface layer and cell wall region to the effective crosslinking density of the core layer at 1.5–6.0.

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