Calcium sulfate whisker-carbon black synergistically reinforced rubber composite based on whisker orientation regulation and preparation method thereof
By controlling the orientation of calcium sulfate whiskers in rubber to make them perpendicular to the main chain of rubber molecules, and combining this with multi-stage mixing and stretching processes, the problems of weak dispersion and interfacial bonding of calcium sulfate whiskers in rubber systems were solved, achieving efficient reinforcement and performance improvement.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BAOGANG GRP MINING RES INST (LLC)
- Filing Date
- 2026-03-05
- Publication Date
- 2026-06-12
AI Technical Summary
In the existing technology, calcium sulfate whiskers have poor dispersibility and weak interfacial bonding in rubber systems, resulting in poor reinforcement effect. Moreover, there is a contradiction between the amount added and the effect, making it difficult to achieve the ideal performance improvement.
By controlling the orientation of calcium sulfate whiskers to make them more perpendicular to the direction of the rubber molecular backbone, and combining them with carbon black, a calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material was prepared. A multi-stage mixing and stretching process was used to ensure that the whisker orientation was consistent.
This method achieves uniform dispersion and effective reinforcement of calcium sulfate whiskers in rubber, improves tensile strength, elongation at break and Shore hardness, resolves the contradiction between reinforcement effect and dosage, and optimizes material properties.
Smart Images
Figure CN122188294A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer composite materials technology, and in particular to a calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material based on whisker orientation regulation and its preparation method. Background Technology
[0002] Carbon black, an indispensable reinforcing filler in the rubber industry, significantly improves the strength and abrasion resistance of rubber. However, its high price and reliance on petroleum resources lead to increasing raw material cost pressures on rubber products. Meanwhile, my country produces a massive amount of desulfurized gypsum, a byproduct of industrial production. Its storage and disposal not only occupy land but also pose environmental risks. Calcium sulfate whiskers, prepared from desulfurized gypsum, are an inexpensive and environmentally friendly inorganic fiber material with advantages such as high strength and high-temperature resistance. If they can be used to partially replace carbon black in rubber, it can significantly reduce production costs and open up new avenues for the high-value and resource-based utilization of desulfurized gypsum, achieving both economic and environmental benefits.
[0003] However, the application of calcium sulfate whiskers to rubber systems still faces several technical bottlenecks: First, poor dispersibility—due to their high aspect ratio and high surface energy, whiskers are prone to agglomeration in non-polar rubber matrices, making it difficult to disperse evenly and form an effective reinforcing network; second, weak interfacial bonding—inorganic whiskers have poor compatibility with organic rubber, resulting in weak interfacial bonding and ineffective stress transfer; third, there is a contradiction between the reinforcing effect and the dosage. Exceeding the threshold, the more added, the worse the reinforcing effect becomes. Existing technologies lack clear guidance on the dosage, making it difficult to achieve the ideal reinforcing effect.
[0004] In view of this, the present invention is proposed. Summary of the Invention
[0005] The purpose of this invention is to provide a calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material based on whisker orientation control and its preparation method. Calcium sulfate whiskers are used as a reinforcing filler to partially replace carbon black. By actively controlling the orientation of calcium sulfate whiskers, targeted reinforcement of the weak areas of rubber performance can be achieved, thereby improving performance and optimizing costs.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material based on whisker orientation regulation, comprising the following components by mass parts: 80-120 parts rubber, 35-45 parts carbon black, 4.0-4.8 parts calcium sulfate whiskers, 3-7 parts zinc oxide, 0.5-1 part stearic acid, 0.5-1.5 parts antioxidant, 8-12 parts paraffin oil, 1-2 parts vulcanizing agent, and 1-2 parts accelerator; The mass percentage of calcium sulfate whiskers to the total mass of calcium sulfate whiskers and carbon black is 3-20%. In the composite material, the direction of the calcium sulfate whiskers tends to be perpendicular to the direction of the rubber molecular backbone.
[0007] Furthermore, based on the above technical solution, the mass of calcium sulfate whiskers accounts for 3-15% of the total mass of calcium sulfate whiskers and carbon black.
[0008] Furthermore, based on the above technical solution, the rubber is one of ethylene propylene diene monomer (EPDM) rubber, styrene-butadiene rubber (SBR) rubber, and nitrile rubber. And / or, the antioxidant is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer; And / or, the accelerator is EM33; And / or, the vulcanizing agent is sulfur.
[0009] Furthermore, based on the above technical solution, the calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material has an elongation at break of 450-475%, a tensile strength of 11.6-13.0 MPa, and a Shore hardness of 60-65.
[0010] This invention also provides a method for preparing a calcium sulfate whisker-carbon black synergistic reinforced rubber composite material based on whisker orientation regulation as described above, comprising the following steps: S1: Rubber, carbon black, zinc oxide, stearic acid, antioxidant and paraffin oil are first mixed, and the masterbatch is obtained after debinding; S2: After rolling the masterbatch rubber onto the rollers, add calcium sulfate whiskers and perform a second mixing to obtain the rubber compound; S3: Add vulcanizing agent and accelerator to rubber compound and perform third mixing to obtain compounded rubber; S4: Stretch the rubber compound, keep it in the stretched state and cool it to room temperature to set it, so that the calcium sulfate whiskers are oriented and fixed in the stretching direction. Finally, vulcanize it to obtain a calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material.
[0011] Furthermore, based on the above technical solution, in step S1, the first mixing is carried out in an internal mixer at a temperature of 120-150℃ and a rotation speed of 110-130rpm for 8-10 minutes.
[0012] Furthermore, based on the above technical solution, in step S2, the added calcium sulfate whiskers are calcium sulfate whiskers treated with surfactants. And / or, the aspect ratio of the calcium sulfate whiskers is 30-140, and the calcium sulfate whiskers are derived from industrial by-product desulfurized gypsum; And / or, in step S2, the roll gap of the wrapping roller is 1-5mm, the temperature is 33-37℃, and the rotation speed is 10-30rpm; And / or, in step S2, the second mixing is carried out in an open mill at a temperature of 33-37°C and a speed of 10-30 rpm for 20-40 minutes.
[0013] Furthermore, based on the above technical solution, the method for treating calcium sulfate whiskers with surfactants includes the following steps: Calcium sulfate whiskers were dispersed in anhydrous ethanol, and then a surfactant was added and stirred to obtain the treated calcium sulfate whiskers. The mass-to-volume ratio of calcium sulfate whiskers to anhydrous ethanol is 1g:90-110mL. The mass ratio of surfactant to calcium sulfate whiskers is 1:50-60; The stirring temperature is 75-85℃, the stirring speed is 150-250 rpm, and the stirring time is 30-40 min; And / or, the surfactant is γ-aminopropyltriethoxysilane.
[0014] Furthermore, based on the above technical solution, in step S3, the third mixing is carried out in an open mill at a temperature of 33-37℃ and a speed of 10-30 rpm for 2-8 minutes. And / or, in step S3, after the third mixing is completed, a thin sheet is then formed to obtain the mixed rubber.
[0015] Furthermore, based on the above technical solution, in step S4, the stretching includes: Clamp both ends of the rubber with clamps, place it in a stretching machine or stretching oven, stretch it perpendicular to the rubber discharge direction of the open mill at a temperature of 60-100℃, and stop stretching after stretching 5%-10%. And / or, the cooling and shaping includes: cooling the stretched and oriented rubber sheet while keeping it stretched, until it reaches room temperature, at which point the whisker orientation structure in the rubber has been fixed; And / or, in step S4, the vulcanization temperature is 165-175℃ and the vulcanization time is 8-12 min.
[0016] This invention provides a calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material based on whisker orientation regulation and its preparation method, the beneficial effects of which include at least the following: 1. The method for preparing calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material provided by the present invention disperses calcium sulfate whiskers during the open milling stage, which solves the problem of uneven dispersion of calcium sulfate whiskers in non-polar rubber matrix. 2. The calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material provided by the present invention, wherein the mass of calcium sulfate whisker accounts for 3-20% of the total mass of calcium sulfate whisker and carbon black, which effectively improves the tensile strength and elongation at break (i.e., elongation at break) of the rubber.
[0017] 3. This invention effectively improves the reinforcing effect of the composite material on rubber by limiting the mass of calcium sulfate whiskers in the calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material to 3-20% of the total mass of calcium sulfate whiskers and carbon black, thus solving the problem of the contradiction between the reinforcing effect and the dosage.
[0018] 4. The preparation method of calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material provided by the present invention introduces a pre-stretching and shaping process before vulcanization, so that the long axis of calcium sulfate whisker tends to be perpendicular to the orientation direction of the rubber molecular main chain, thereby directionally reinforcing the mechanically weak direction and realizing isotropic properties such as tensile strength and modulus. Attached Figure Description
[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0020] Figure 1 This is an EDS image of the rubber after stretching the compound in step S4 of Embodiment 1 of the present invention. Figure 2 The graph shows the effect of the percentage of calcium sulfate whiskers in the total mass of calcium sulfate whiskers and carbon black on the tensile strength of rubber. Figure 3 The graph shows the effect of the percentage of calcium sulfate whiskers in the total mass of calcium sulfate whiskers and carbon black on the elongation at break of rubber. Figure 4 The graph shows the effect of the percentage of calcium sulfate whiskers in the total mass of calcium sulfate whiskers and carbon black on the Shore A hardness of rubber. Figure 5 The graph shows the effect of adding calcium sulfate whiskers at different stages on the tensile strength of rubber. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.
[0022] The endpoints and any values of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.
[0023] According to a first aspect of the present invention, a calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material based on whisker orientation regulation is provided, comprising the following components by mass parts: 80-120 parts rubber, 35-45 parts carbon black, 4.0-4.8 parts calcium sulfate whiskers, 3-7 parts zinc oxide, 0.5-1 part stearic acid, 0.5-1.5 parts antioxidant, 8-12 parts paraffin oil, 1-2 parts vulcanizing agent, and 1-2 parts accelerator; The mass percentage of calcium sulfate whiskers to the total mass of calcium sulfate whiskers and carbon black is 3-20%, preferably 3-15%. In the composite material, the direction of the calcium sulfate whiskers tends to be perpendicular to the direction of the rubber molecular backbone.
[0024] Specifically, by limiting the mass of calcium sulfate whiskers (CSW) to the total mass of calcium sulfate whiskers and carbon black (the amount of carbon black replaced by CSW) to 3-20%, this invention not only allows calcium sulfate whiskers to effectively play a reinforcing role, but also improves the reinforcing performance of the composite material. However, if the mass exceeds this range (especially more than 20%), the performance will be significantly reduced due to problems such as poor interfacial bonding.
[0025] Furthermore, when the percentage is between 3% and 15%, calcium sulfate whiskers not only replace carbon black, but also improve the tensile strength and elongation at break of rubber, effectively enhancing interfacial bonding. A percentage of 20% represents the maximum amount of calcium sulfate whiskers that can replace carbon black without reducing rubber performance, and it also represents the lowest cost for rubber.
[0026] Furthermore, due to their high modulus and strength, whiskers, when aligned perpendicularly to the rubber molecular backbone, can more effectively intercept and hinder crack propagation along weak paths between molecular chains. Simultaneously, the perpendicularly oriented whiskers can transfer stress through interfaces, dispersing localized loads over a wider area and reducing stress concentration, thereby enhancing the material's load-bearing capacity and tear resistance in directions perpendicular to the rubber molecular backbone. This directional reinforcement not only inhibits crack growth but also improves the overall mechanical performance of rubber materials in structurally weak directions, achieving performance optimization and reinforcement design in specific directions.
[0027] In this invention, the orientation of the calcium sulfate whiskers being perpendicular to the direction of the rubber molecular backbone means that at least 80% (e.g., 81%, 85%, 90%, 95%, 98%, 100%) of the calcium sulfate whiskers have an angle greater than 45° and less than or equal to 90° with the direction of the rubber molecular backbone, preferably greater than 60° and less than or equal to 90°, and more preferably between 80° and 90°. In short, the closer the angle between the orientation of the calcium sulfate whiskers and the direction of the rubber molecular backbone is to 90°, the better the reinforcing effect.
[0028] As an optional embodiment of the present invention, the rubber is one of ethylene propylene diene monomer (EPDM), styrene-butadiene rubber (SBR), and nitrile rubber.
[0029] The antioxidant includes anti-thermal and oxidative aging agents, such as amine antioxidants or phenolic antioxidants. As an optional embodiment of the present invention, the antioxidant can be quinoline, p-phenylenediamine, diphenylamine, etc., preferably 2,2,4-trimethyl-1,2-dihydroquinoline polymer, manufactured by Shandong Shangshun Chemical Co., Ltd., and model number RD. Accelerators are one of the core components of a vulcanization system. They can significantly reduce vulcanization temperature, shorten vulcanization time, improve production efficiency, and enhance the performance of vulcanized rubber. The accelerator used in this invention can be a commonly used accelerator in the field. As an optional embodiment of this invention, the accelerator is EM33, manufactured by Kawaguchi Chemicals, Japan. Vulcanizing agents are key chemical substances in rubber production that can chemically react with rubber molecules to form stable cross-linking bonds (bridges), thereby transforming plastic rubber into vulcanized rubber with a highly elastic, high-strength three-dimensional network structure. Commonly used vulcanizing agents in this field can be selected, such as sulfur.
[0030] As an optional embodiment of the present invention, the calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material has an elongation at break of 450-475%, a tensile strength of 11.6-13.0 MPa, and a Shore hardness of 60-65.
[0031] Specifically, by controlling the percentage of calcium sulfate whiskers in the total mass of calcium sulfate whiskers and carbon black, not only will the Shore hardness of the composite material not be affected, but the compound can also achieve excellent tensile properties, thereby achieving the ideal reinforcing effect.
[0032] According to a second aspect of the present invention, a method for preparing the above-mentioned calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material based on whisker orientation regulation is provided, comprising the following steps; S1: Rubber, carbon black, zinc oxide, stearic acid, antioxidant and paraffin oil are first mixed, and the masterbatch is obtained after debinding; S2: After rolling the masterbatch rubber onto the rollers, add calcium sulfate whiskers and perform a second mixing to obtain the rubber compound; S3: Add vulcanizing agent and accelerator to rubber compound and perform third mixing to obtain compounded rubber; S4: Stretch the rubber compound, keep it in the stretched state and cool it to room temperature to set it, so that the calcium sulfate whiskers are oriented and fixed in the stretching direction. Finally, vulcanize it to obtain a calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material.
[0033] Specifically, the inventors discovered that during rubber processing (such as open milling, calendering, or extrusion), the main chain of rubber molecules will be oriented along the direction of material flow, that is, consistent with the direction of rubber extrusion. When the rubber is vulcanized and cooled, the direction of its main chain is fixed to the direction of material flow. Different orientations of the main chain of rubber molecules have a significant impact on the properties of rubber. Typically, the tensile strength, modulus, and other mechanical properties of rubber molecules with the main chain orientation parallel to the direction of rubber extrusion (such as the circumference of the roller) are usually better than those perpendicular to the direction of rubber extrusion. Although this asymmetry in properties is advantageous for products subjected to unidirectional forces (such as conveyor belts and sealing strips), it constitutes a technical bottleneck for products that require balanced properties in all directions (such as gaskets and shock absorbers).
[0034] The inventors further discovered that when the rubber matrix deforms under tensile loads, the arrangement direction of calcium sulfate whiskers in the rubber dynamically adjusts with the matrix deformation. For example, when the rubber is stretched along a direction perpendicular to the rubber extrusion direction, the direction of the calcium sulfate whiskers tends to align with the stretching direction. The reinforcing efficiency of the whiskers is directly related to the relative orientation of the whiskers and the rubber molecular backbone: when the long axis of the whiskers is perpendicular to the direction of the rubber molecular backbone, the whiskers' reinforcing effect of hindering crack propagation and transferring load can improve the mechanical properties in the weak direction. Therefore, this invention controls the arrangement direction of the whiskers so that their main orientation tends to be perpendicular to the direction of the rubber molecular backbone, thereby achieving targeted reinforcement of the weak direction and preparing a composite material with more balanced performance and directional designable properties.
[0035] As an optional embodiment of the present invention, in step S1, the first mixing is carried out in an internal mixer at a temperature of 120-150°C and a rotation speed of 110-130 rpm for 8-10 minutes.
[0036] As an optional embodiment of the present invention, in step S2, the added calcium sulfate whiskers are calcium sulfate whiskers treated with surfactants. The method for treating calcium sulfate whiskers with surfactants includes the following steps: Calcium sulfate whiskers were dispersed in anhydrous ethanol, and then a surfactant was added and stirred to obtain the treated calcium sulfate whiskers. The mass-to-volume ratio of calcium sulfate whiskers to anhydrous ethanol is 1g:90-110mL. The mass ratio of surfactant to calcium sulfate whiskers is 1:50-60; The stirring temperature is 75-85℃, the stirring speed is 150-250 rpm, and the stirring time is 30-40 min; The surfactant is KH-550 (γ-aminopropyltriethoxysilane).
[0037] As an optional embodiment of the present invention, the aspect ratio of the calcium sulfate whiskers is 30-140 (e.g., 40, 50, 60, 80, 100, 110, 120, 130, etc.), and the calcium sulfate whiskers are derived from industrial by-product desulfurized gypsum. Specifically, if the aspect ratio of calcium sulfate whiskers is too large, it will be significantly more difficult to change their orientation; if the aspect ratio is too small, it will be difficult to achieve an effective reinforcement effect.
[0038] As an optional embodiment of the present invention, in step S2, the rolling process involves applying the masterbatch in a two-roll mill to soften and viscoelasticize the masterbatch under mechanical shearing and friction, so that it is continuously, uniformly, and tightly wrapped around the faster-rotating front roller to form a smooth "rubber tube". The roller spacing of the wrapping roller is 1-5mm, the temperature is 33-37℃, and the rotation speed is 10-30rpm; In step S2, the second mixing is carried out in an open mill at a temperature of 33-37°C and a speed of 10-30 rpm for 20-40 minutes.
[0039] As an optional embodiment of the present invention, in step S3, the third mixing is carried out in a two-roll mill at a temperature of 33-37°C and a speed of 10-30 rpm for 2-8 minutes. Specifically, the present invention places the addition of calcium sulfate whiskers in the open milling stage after internal mixing, and adopts a two-step open milling process of "long-term mixing of whiskers followed by short-term addition of vulcanizing agent": adding whiskers in the open milling stage (step S2) can effectively avoid fiber breakage, and the long-term mixing of 20-40 minutes ensures that they are fully dispersed to form a reinforcing network; secondly, the vulcanizing agent is added in the later short-term mixing stage (step S3), which avoids the failure of the vulcanization system due to over-mixing.
[0040] In step S3, after the third mixing is completed, the mixture is sheeted out to obtain the compounded rubber. The thin-film unloading process includes the following steps: (1) After the third mixing is completed, adjust the roller gap to the minimum, cut the rubber material with a scraper, roll it up or fold it, and put it back into the roller from one end to let it pass through. Repeat this process 3-6 times. (2) After completing the final thin pass, quickly widen the roller gap to the target thickness; (3) Pass the entire rubber material through the widened roller gap to form a smooth and continuous thick sheet. Then, use a knife to cut a slit at one end of the sheet along the roller axis and peel or roll off the entire sheet to obtain the compounded rubber.
[0041] In an optional embodiment of the present invention, step S4, the stretching includes: Clamp the two ends of the rubber with clamps, place it in a stretching machine or stretching oven, stretch it in the direction perpendicular to the rubber discharge of the open mill, at a temperature of 60-100℃, stretch the sample in one direction at a constant speed, and stop stretching after stretching 5%-10%. Specifically, stretching at 60℃-100℃ softens the rubber, increasing its deformability without causing it to flow. The main purpose of stretching is to apply controlled and moderate deformation, causing the randomly distributed calcium sulfate whiskers inside the rubber to gradually align in an ordered manner along the stretching direction, thereby constructing a reinforcing micro-orientation structure.
[0042] Furthermore, if the stretching length is too long, the rubber molecular backbone may develop cracks or even break due to fatigue or overstretching under the combined action of heat and force; conversely, if the stretching length is insufficient, the whiskers will not have enough driving energy and time to complete the orientation adjustment, and will not be able to achieve an effective transformation from disorder to order, thereby weakening the expected orientation enhancement effect.
[0043] The cooling and shaping process includes: cooling the stretched and oriented rubber sheet while maintaining the stretch, and removing the clamps after cooling to room temperature. At this point, the whisker orientation structure in the rubber has been fixed.
[0044] Specifically, the present invention enables calcium sulfate whiskers to be oriented and shaped along the stretching direction during the stretching process by cooling and shaping, thereby avoiding the anisotropy problem of rubber caused by inconsistent orientation of calcium sulfate whiskers.
[0045] In step S4, the vulcanization temperature is 165-175℃ and the vulcanization time is 8-12 minutes.
[0046] The present invention will be further described in detail below with reference to specific embodiments and comparative examples. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available products.
[0047] Example 1 This embodiment provides a calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material based on whisker orientation control, comprising the following components by mass: 100 parts of EPDM rubber (Mounney viscosity 63, ethylene content 67.5 wt%, ENB content 5.4 wt%, volatile content 0.3 wt%), 40 parts of carbon black, 4.4 parts of calcium sulfate whiskers, 5 parts of zinc oxide, 1 part of stearic acid, 1 part of antioxidant RD, 10 parts of paraffin oil, 1.5 parts of sulfur, and 1.5 parts of accelerator; Of which, the mass of calcium sulfate whiskers accounts for 10% of the total mass of calcium sulfate whiskers and carbon black; In the composite material, the orientation of the calcium sulfate whiskers tends to be perpendicular to the orientation of the rubber molecular backbone: In this embodiment, the direction of the rubber molecular backbone is parallel to the extrusion direction of the roller.
[0048] This embodiment also provides a method for preparing the calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material as described above, including the following steps: S1: Place EPDM rubber, carbon black, zinc oxide, stearic acid, antioxidant and paraffin oil in a mixer and mix at 125 rpm for 8 minutes at a temperature of 130℃. After discharging the rubber along the direction parallel to the rollers, the masterbatch is obtained. S2: After wrapping the masterbatch with rollers on an open mill (roller gap of 2mm, temperature of 35℃, and speed of 15rpm), add calcium sulfate whiskers and mix for 30 minutes at 35℃ and 15rpm to obtain the rubber compound. Among them, the calcium sulfate whiskers are treated with KH-550, and the aspect ratio of the calcium sulfate whiskers is 30-80. The method for treating calcium sulfate whiskers with KH-550 includes the following steps: Calcium sulfate whiskers were dispersed in anhydrous ethanol, and then KH-550 was added. The mixture was stirred at 200 rpm for 30 min at 80℃ to obtain KH-550 treated calcium sulfate whiskers. The mass-to-volume ratio of calcium sulfate whiskers to anhydrous ethanol is 1g:100mL. The mass ratio of KH-550 to calcium sulfate whiskers is 1:50; S3: Add sulfur and accelerator EM33 to the rubber compound, and perform a third mixing at 35°C and 20 rpm for 5 minutes in a two-roll mill. After passing through the thin mill 6 times, the mixture is sheeted to obtain the compounded rubber. At this point, the direction of the rubber molecular chains in the compound is fixed, parallel to the open mixing direction of the roller, and the calcium sulfate whiskers in the compound are still in a disordered state.
[0049] S4: At 80℃, slowly stretch the compound along a direction perpendicular to the open mill, elongating it to 6% of its original length. Stop stretching and maintain the stretched state at 80℃ while cooling to room temperature for cooling and shaping. Figure 1 As shown, the orientation of calcium sulfate whiskers is roughly the same and tends to be perpendicular to the direction of the rubber produced by open mixing, that is, perpendicular to the direction of the rubber molecular backbone. Finally, the rubber is vulcanized at 160℃ for 10 minutes to obtain a calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material.
[0050] Example 2 The main difference between this embodiment and Embodiment 1 is that the amount of calcium sulfate whiskers added is 2.2 parts, and the amount of carbon black added is 42.2 parts, that is, the mass of calcium sulfate whiskers accounts for 5% of the total mass of calcium sulfate whiskers and carbon black. The remaining steps and technical parameters are the same as in Embodiment 1.
[0051] Example 3 The main difference between this embodiment and Embodiment 1 is that the amount of calcium sulfate whiskers added is 8.9 parts, and the amount of carbon black added is 35.5 parts, that is, the mass of calcium sulfate whiskers accounts for 20% of the total mass of calcium sulfate whiskers and carbon black. The remaining steps and technical parameters are the same as in Embodiment 1.
[0052] Example 4 The main difference between this embodiment and Embodiment 1 is that the amount of calcium sulfate whiskers added is 6.7 parts, and the amount of carbon black added is 37.7 parts, that is, the mass of calcium sulfate whiskers accounts for 15% of the total mass of calcium sulfate whiskers and carbon black. The remaining steps and technical parameters are the same as in Embodiment 1.
[0053] Comparative Example 1 The main difference between this comparative example and Example 1 is that calcium sulfate whiskers are not added, that is, the total amount of carbon black added is 44.4 parts. The remaining steps and technical parameters are the same as in Example 1.
[0054] Comparative Example 2 The main difference between this comparative example and Example 1 is that the amount of calcium sulfate whiskers added is 0.9 parts, and the amount of carbon black added is 43.5 parts, that is, the mass of calcium sulfate whiskers accounts for 2% of the total mass of calcium sulfate whiskers and carbon black. The remaining steps and technical parameters are the same as in Example 1.
[0055] Comparative Example 3 The main difference between this comparative example and Example 1 is that the amount of calcium sulfate whiskers added is 11.1 parts, and the amount of carbon black added is 33.3 parts, that is, the mass of calcium sulfate whiskers accounts for 25% of the total mass of calcium sulfate whiskers and carbon black. The remaining steps and technical parameters are the same as in Example 1.
[0056] Comparative Example 4 The main difference between this comparative example and Example 1 is that calcium sulfate whiskers are added in step S1 to obtain the masterbatch, and sulfur and accelerator are directly added after rolling for mixing. Specifically: S1: Place EPDM rubber, carbon black, zinc oxide, stearic acid, antioxidant, calcium sulfate whiskers and paraffin oil in a mixer and mix at 110-130 rpm for 8-10 minutes at a temperature of 130-150℃. After discharge, the masterbatch is obtained. S2: After wrapping the masterbatch rubber with rollers in a two-roll mill (roll gap of 2mm, temperature of 35℃, and speed of 15rpm), add sulfur and accelerator, mix in the two-roll mill for 5 minutes, and sheet out after passing through the thin mill 6 times to obtain the compound rubber. The raw material composition, remaining steps, and technical parameters are the same as in Example 1.
[0057] Comparative Example 5 The main difference between this comparative example and Example 1 is that the compound is not stretched in step S4, but vulcanized directly. The remaining steps and technical parameters are the same as in Example 1.
[0058] The mechanical properties of the rubber composites prepared in Comparative Example 5 and Example 1 along the direction parallel to and perpendicular to the extrusion direction of the open mill are shown in Table 1: Table 1 As shown in Table 1, it can be seen that without stretching the rubber compound in the direction perpendicular to the extrusion direction of the open mill, the direction of the calcium sulfate whiskers in the rubber is disordered. The rubber has better mechanical properties along the extrusion direction of the open mill, but poorer mechanical properties perpendicular to the extrusion direction of the open mill. However, in Example 1 of this invention, the rubber compound is stretched perpendicular to the extrusion direction of the open mill at the vulcanization front, so that the calcium sulfate whiskers in the rubber tend to be perpendicular to the direction of the rubber molecular backbone, thereby achieving targeted reinforcement of the weak performance direction and preparing a composite material with more balanced performance.
[0059] Comparative Example 6 The main difference between this comparative example and Example 1 is that the direction of stretching the compound in step S4 is opposite to that in Example 1. Instead, it is stretched slowly along the direction parallel to the rubber extrusion direction. The remaining steps and technical parameters are the same as in Example 1.
[0060] Table 2 According to Table 2, compared with Example 1, in Comparative Example 6, the stretching direction of the compound is consistent with the extrusion direction of the compound, which leads to the direction of calcium sulfate whiskers being the same as the extrusion direction. Although this further improves the tensile properties of the composite material in the extrusion direction, it does not form an effective reinforcing network structure in the vertical direction, resulting in extremely uneven performance of the composite material.
[0061] Comparative Example 7 The main difference between this comparative example and Example 1 is that the aspect ratio of the selected calcium sulfate whiskers is 150-200, while the other steps and technical parameters are the same as in Example 1.
[0062] Performance testing The testing standards for tensile strength, elongation at break and Shore hardness mainly follow the "Polymer Waterproof Materials Part 2: Waterstops" (GB / T 18173.2-2014).
[0063] Results data The mechanical properties of each embodiment and comparative example, measured along the rubber discharge direction parallel to the open mill, are shown in Table 3: Table 3 According to Table 3 and Figure 2-4 As shown, different amounts of calcium sulfate whiskers were added in Examples 1-4. Too much or too little calcium sulfate whisker content will affect tensile strength and elongation at break. Therefore, this invention limits the mass percentage of calcium sulfate whiskers (CSW) to the total mass of calcium sulfate whiskers and carbon black (the amount of carbon black replaced by CSW) to 3-20%. This not only allows calcium sulfate whiskers to effectively play a reinforcing role and effectively improve the reinforcing performance of the composite material, but also ensures that the Shore hardness of the composite material is between 60 and 65.
[0064] As shown in Table 3, compared with Example 1, Comparative Example 1 has poorer tensile properties because no calcium sulfate whiskers were added. This indicates that the calcium sulfate whiskers added in Example 1 formed an effective reinforcing network, thereby improving the tensile properties of the composite material.
[0065] As shown in Table 3, compared with Example 1, Comparative Example 2 has a lower content of calcium sulfate whiskers, which cannot effectively form a reinforcing network structure, resulting in a decrease in tensile properties.
[0066] As shown in Table 3, compared with Example 1, Comparative Example 3 had a significantly reduced tensile properties due to the excessive amount of calcium sulfate whiskers added, resulting in poor interfacial bonding between the calcium sulfate whiskers and rubber molecules.
[0067] According to Table 3 and Figure 5 As shown, compared with Example 1, Comparative Example 4 had calcium sulfate whiskers added in the internal mixer, which resulted in poor dispersion of the calcium sulfate whiskers and uneven formation of the reinforcing network structure, thus affecting the tensile properties.
[0068] According to Table 3, compared with Example 1, the calcium sulfate whiskers in Comparative Example 7 have a larger aspect ratio, which makes it difficult to turn during the stretching process in step S4. The direction of the calcium sulfate whiskers is not perpendicular to the direction of the open mill discharge, which affects the reinforcing effect of the calcium sulfate whiskers on the material in the vertical direction.
[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material based on whisker orientation regulation, characterized in that, By weight, it includes the following components: 80-120 parts rubber, 35-45 parts carbon black, 4.0-4.8 parts calcium sulfate whiskers, 3-7 parts zinc oxide, 0.5-1 part stearic acid, 0.5-1.5 parts antioxidant, 8-12 parts paraffin oil, 1-2 parts vulcanizing agent, and 1-2 parts accelerator. The mass percentage of calcium sulfate whiskers to the total mass of calcium sulfate whiskers and carbon black is 3-20%. In the composite material, the direction of the calcium sulfate whiskers tends to be perpendicular to the direction of the rubber molecular backbone.
2. The calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material based on whisker orientation regulation according to claim 1, characterized in that, The mass of calcium sulfate whiskers accounts for 3-15% of the total mass of calcium sulfate whiskers and carbon black.
3. The calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material based on whisker orientation regulation according to claim 1, characterized in that, The rubber is one of ethylene propylene diene monomer (EPDM), styrene-butadiene rubber (SBR), and nitrile rubber. And / or, the antioxidant is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer; And / or, the accelerator is EM33; And / or, the vulcanizing agent is sulfur.
4. The calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material based on whisker orientation regulation according to claim 1, characterized in that, The calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material has an elongation at break of 450-475%, a tensile strength of 11.6-13.0 MPa, and a Shore hardness of 60-65.
5. A method for preparing a calcium sulfate whisker-carbon black synergistically reinforced rubber composite material based on whisker orientation control as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: Rubber, carbon black, zinc oxide, stearic acid, antioxidant and paraffin oil are first mixed, and the masterbatch is obtained after debinding; S2: After rolling the masterbatch rubber onto the rollers, add calcium sulfate whiskers and perform a second mixing to obtain the rubber compound; S3: Add vulcanizing agent and accelerator to rubber compound and perform third mixing to obtain compounded rubber; S4: Stretch the rubber compound, keep it in the stretched state and cool it to room temperature to set it, so that the calcium sulfate whiskers are oriented and fixed in the stretching direction. Finally, vulcanize it to obtain a calcium sulfate whisker-carbon black synergistic reinforcing rubber composite material.
6. The preparation method of calcium sulfate whisker-carbon black synergistically reinforced rubber composite material based on whisker orientation control according to claim 5, characterized in that, In step S1, the first mixing is carried out in an internal mixer at a temperature of 120-150℃ and a speed of 110-130rpm for 8-10 minutes.
7. The preparation method of calcium sulfate whisker-carbon black synergistically reinforced rubber composite material based on whisker orientation control according to claim 5, characterized in that, In step S2, the added calcium sulfate whiskers are calcium sulfate whiskers that have been treated with a surfactant. And / or, the aspect ratio of the calcium sulfate whiskers is 30-140, and the calcium sulfate whiskers are derived from industrial by-product desulfurized gypsum; And / or, in step S2, the roll gap of the wrapping roller is 1-5mm, the temperature is 33-37℃, and the rotation speed is 10-30rpm; And / or, in step S2, the second mixing is carried out in an open mill at a temperature of 33-37°C and a speed of 10-30 rpm for 20-40 minutes.
8. The preparation method of calcium sulfate whisker-carbon black synergistically reinforced rubber composite material based on whisker orientation control according to claim 7, characterized in that, The method for treating calcium sulfate whiskers with surfactants includes the following steps: Calcium sulfate whiskers were dispersed in anhydrous ethanol, and then a surfactant was added and stirred to obtain the treated calcium sulfate whiskers. The mass-to-volume ratio of calcium sulfate whiskers to anhydrous ethanol is 1g:90-110mL. The mass ratio of surfactant to calcium sulfate whiskers is 1:50-60; The stirring temperature is 75-85℃, the stirring speed is 150-250 rpm, and the stirring time is 30-40 min; And / or, the surfactant is γ-aminopropyltriethoxysilane.
9. The preparation method of calcium sulfate whisker-carbon black synergistically reinforced rubber composite material based on whisker orientation regulation according to claim 5, characterized in that, In step S3, the third mixing is carried out in an open mill at a temperature of 33-37℃ and a speed of 10-30 rpm for 2-8 minutes. And / or, in step S3, after the third mixing is completed, a thin sheet is then formed to obtain the mixed rubber.
10. The preparation method of calcium sulfate whisker-carbon black synergistically reinforced rubber composite material based on whisker orientation control according to claim 5, characterized in that, In step S4, the stretching includes: Clamp both ends of the rubber with clamps, place it in a stretching machine or stretching oven, stretch it perpendicular to the rubber discharge direction of the open mill at a temperature of 60-100℃, and stop stretching after stretching 5%-10%. And / or, the cooling and shaping includes: cooling the stretched and oriented rubber sheet while keeping it stretched, until it reaches room temperature, at which point the whisker orientation structure in the rubber has been fixed; And / or, in step S4, the vulcanization temperature is 165-175℃ and the vulcanization time is 8-12 min.