Liquid silicone rubber for robots and method for producing the same

Abstract

This application relates to the field of silicone rubber technology, specifically to a liquid silicone rubber for robots and its preparation method. The liquid silicone rubber comprises an A-type rubber and a B-type rubber. The A-type rubber consists of 400-450 parts of a base rubber, 30-38 parts of vinyl silicone oil, 120-170 parts of dimethyl silicone oil, and a platinum catalyst. The B-type rubber consists of 395-450 parts of a base rubber, 28-35 parts of vinyl silicone oil, 120-150 parts of dimethyl silicone oil, 4-6 parts of end-side hydrogen-containing silicone oil, and end-side hydrogen-containing silicone oil. 1.3-5 parts, 0.05-0.2 parts of ethynylcyclohexanol and 1-2.5 parts of vinyl-terminated hyperbranched polyester; base rubber: 100-135 parts of high-viscosity vinyl-terminated silicone oil, 100-140 parts of dimethyl silicone oil, 200-250 parts of silica, 30-40 parts of hexamethyldisilazane, distilled water and 240-265 parts of low-viscosity vinyl-terminated silicone oil; it has the advantage of improving the tensile strength of liquid silicone rubber while maintaining its toughness.

Description

Technical Field

[0001] This application relates to the technical field of silicone rubber, and in particular to a liquid silicone rubber for robots and a method for preparing the same. Background Technology

[0002] Addition-cure liquid silicone rubber has been widely used in electronic potting, medical, and mold manufacturing fields due to its excellent resistance to high and low temperatures, electrical insulation, physiological inertness, and ease of molding. With the rapid development of robotics and bionics, materials with high flexibility, biocompatibility, and skin-like feel have become a research hotspot, and liquid silicone rubber is one of the ideal candidate materials for robot skin. However, while conventional silicone rubber for robot skin meets the requirements of high elasticity and high realism, its mechanical strength, especially tensile strength, often fails to meet the demands of robot skin in resisting tearing and deformation during dynamic and complex movements. This limits its application in service robots and bionic prosthetics, which require high reliability and durability.

[0003] To improve the mechanical properties of silicone rubber, reinforcing materials such as fumed silica are often added to the formulation. However, due to factors such as insufficient interfacial compatibility between these reinforcing materials and the system, the toughness of the material can also be reduced. Summary of the Invention

[0004] In order to improve the tensile strength of liquid silicone rubber while maintaining its toughness, this application provides a liquid silicone rubber for robots and a method for preparing the same.

[0005] In a first aspect, this application provides a liquid silicone rubber for robots, employing the following technical solution: A liquid silicone rubber for robots comprises A and B in equal mass ratios. The A component comprises the following raw materials in parts by weight: 400-450 parts base rubber, 30-38 parts vinyl silicone oil, 120-170 parts dimethyl silicone oil, and a platinum catalyst; the amount of platinum catalyst added is 2500-5000 PPM. The B-type adhesive comprises the following raw materials in parts by weight: 395-450 parts base adhesive, 28-35 parts vinyl silicone oil, 120-150 parts dimethyl silicone oil, 4-6 parts end-side hydrogen-containing silicone oil, 1.3-5 parts end-side hydrogen-containing silicone oil, 0.05-0.2 parts ethynylcyclohexanol, and 1-2.5 parts end-vinyl hyperbranched polyester; The base adhesive comprises the following raw materials in parts by weight: 100-135 parts of high-viscosity vinyl-terminated silicone oil, 100-140 parts of dimethyl silicone oil, 200-250 parts of silica, 30-40 parts of hexamethyldisilazane, 8-12 parts of distilled water, and 240-265 parts of low-viscosity vinyl-terminated silicone oil. The viscosity of the vinyl silicone oil in adhesive A and adhesive B is 8000-12000 mPa·s; the viscosity of the dimethyl silicone oil is 40-60 mPa·s; the viscosity of the high-viscosity vinyl silicone oil is 15000-25000 mPa·s; and the viscosity of the low-viscosity vinyl silicone oil is 40-60 mPa·s.

[0006] By adopting the above technical solution, this application constructs a precisely controllable two-component liquid silicone rubber reaction system by limiting the formulation of A-type glue, B-type glue, and base glue, as well as the viscosity parameters of key raw materials. This provides a precise material basis for the subsequent formation of a composite multi-level crosslinked network. In particular, the specific viscosity of the end-side hydrogen-containing silicone oil ensures the formation of the main crosslinked network. The unique end-side hydrogen-containing silicone oil in B-type glue can reduce the local crosslinking density. The end-vinyl hyperbranched polyester can form point crosslinking centers with high crosslinking density, resulting in different distributions of crosslinking density within the same system. This different density distribution can buffer external forces, thereby overcoming the problem of reduced toughness caused by interfacial tension in traditional silica reinforcement systems. Ultimately, this significantly improves both the tensile strength and toughness of silicone rubber for robot skin.

[0007] Preferably, the end-vinyl hyperbranched polyester is prepared by reacting end-hydroxyl hyperbranched polyester with acryloyl chloride.

[0008] By adopting the above technical solution, using hydroxyl-terminated hyperbranched polyester and acryloyl chloride as reaction substrates, the reaction rate can be better controlled and the generation of by-products can be effectively reduced.

[0009] Preferably, the preparation method of the end-vinyl hyperbranched polyester is as follows: S1. Using tetrahydrofuran as a solvent, add hydroxyl-terminated hyperbranched polyester and polymerization inhibitor, stir until dissolved under nitrogen protection to obtain a reaction solution, and transfer it to an ice-water bath. S2. Dissolve excess triethylamine in tetrahydrofuran to obtain a triethylamine solution; dissolve excess acryloyl chloride in tetrahydrofuran to obtain an acryloyl chloride solution; S3. Simultaneously add triethylamine solution and acryloyl chloride solution to the reaction solution. After the addition is complete, continue stirring the reaction in an ice-water bath for 0.5-1.5 hours. Remove the ice-water bath and continue the reaction for 6-10 hours. Filter to obtain the filtrate. S4. Add the filtrate dropwise to a methanol / water mixture, filter, wash, and dry to obtain end-vinyl hyperbranched polyester.

[0010] By employing the above technical solution and limiting the reaction conditions, the synthesis reaction can be carried out under conditions of high selectivity and high conversion rate, effectively suppressing the occurrence of side reactions (such as acryloyl chloride hydrolysis and vinyl self-polymerization). This process ensures that the obtained end-vinyl hyperbranched polyester has high purity and high functionality, thereby avoiding interference from impurities on the subsequent silicone rubber curing system.

[0011] Preferably, the molar ratio of triethylamine to hydroxyl-terminated hyperbranched polyester is (1.2-3):1; and the molar ratio of acryloyl chloride to hydroxyl-terminated hyperbranched polyester is (1.01-1.3):1.

[0012] By adopting the above technical solution, the excess triethylamine ensures that the acid generated in the reaction is completely neutralized, driving the reaction equilibrium to the right; a slight excess of acryloyl chloride drives the terminal hydroxyl group to be nearly completely converted.

[0013] Preferably, the volume ratio of the methanol / water mixture to the filtrate is (8-11):1.

[0014] By adopting the above technical solution, this ratio ensures that the terminal vinyl hyperbranched polyester can be fully precipitated from the reaction solution, minimizing the dissolution loss of the product in the reaction solution, while effectively removing soluble salts and small molecule impurities, thereby improving the purity of the product.

[0015] Preferably, the average molecular weight of the terminal hydroxyl hyperbranched polyester is 2400-5200.

[0016] By adopting the above technical solution, hyperbranched polyesters with a molecular weight in the range of 2400-5200 have a moderate spatial configuration and a reasonable number of terminal functional groups. This ensures good solubility and dispersibility in the silicone oil matrix, avoiding phase separation or a sharp increase in system viscosity due to excessively large molecules. It also provides a sufficient number of vinyl end groups to form physical / chemical entanglements of ideal density and strength in the cured network, thereby dissipating stress and improving toughness with optimal efficiency.

[0017] Preferably, the end-vinyl hyperbranched polyester is added after being dissolved in tetrahydrofuran.

[0018] By adopting the above technical solution, the technical challenge of uniformly dispersing solid or high-viscosity polymers in silicone oil systems is solved. First, dissolving in a good solvent, THF, allows the hyperbranched polymer molecular chains to fully extend, achieving molecular-level pre-dispersion. After removing THF in the subsequent vacuum process, the polymer remains uniformly and stably within the silicone rubber matrix, ensuring its uniform distribution in the final cured three-dimensional network. This forms an effective global "point" reinforcement and toughening network, avoiding performance weaknesses caused by uneven dispersion.

[0019] Preferably, the hydrogen content of the end-side hydrogen-containing silicone oil is 0.4-0.55 wt%; the hydrogen content of the end-side hydrogen-containing silicone oil is 0.08-0.14 wt%.

[0020] By employing the above technical solution, the crosslinking density and distribution in the cured silicone rubber network are precisely controlled. The hydrogen content (0.4-0.55 wt%) of the end-side hydrogen-containing silicone oil determines the basic density and strength of the main crosslinking network. The special low hydrogen content (0.08-0.14 wt%) of the end-side hydrogen-containing silicone oil is used to introduce local, microscopic, highly interactive or reactive regions into the main network. The combination of these two, in synergy with "point" crosslinking, jointly constructs the composite network structure with gradient crosslinking density upon which this invention relies.

[0021] Secondly, this application provides a method for preparing liquid silicone rubber for robots, employing the following technical solution: A method for preparing liquid silicone rubber for robots, comprising the following steps: Preparation of S1 and A glue Add the base adhesive to the planetary mixing vessel, circulate cooling water, and then add vinyl silicone oil, dimethyl silicone oil and platinum catalyst in sequence. Mix at a speed of 200-400 r / min for 3-7 min, and then mix at a speed of 800-1200 r / min for 20-40 min. Stop the machine, raise the stirring paddle, scrape the material adhering to the stirring paddle into the vessel, and continue to stir and mix evenly to obtain adhesive A. Preparation of S2 and B adhesives Add the base adhesive to the planetary mixing vessel, circulate cooling water, and continue to add the remaining raw materials. Mix at a speed of 200-400 r / min for 3-7 min, then mix at a speed of 600-1000 r / min for 20-40 min. Stop the machine, raise the stirring paddle, scrape the material adhering to the stirring paddle into the vessel, and continue to stir and mix evenly to obtain adhesive B. S3, Colloidal Mixture Add A-type glue to a planetary mixing vessel, circulate cooling water, add B-type glue, and mix at 200-500 rpm for 3-8 minutes. Then mix at 800-1200 rpm for 20-50 minutes. Stop the machine, raise the stirring paddle, scrape the material adhering to the stirring paddle into the vessel, continue stirring until homogeneous, stop the machine, open the vacuum, and continue stirring for 20-40 minutes. Stop the machine, vent the vacuum, and transfer the material to a press for pressing and packaging to obtain liquid silicone rubber for robot skin.

[0022] By employing the above technical solution, and through a complete process method that defines the separate preparation and final mixing of adhesives A and B, particularly steps such as segmented rotational mixing, scraping and bonding agitator, and vacuum stirring, highly uniform and stable dispersion and mixing of all functional components (including silica in the base adhesive, catalyst in adhesive A, various crosslinking agents in adhesive B, and end-vinyl hyperbranched polyester) are ensured in the system. Segmented rotational mixing achieves a combination of gentle wetting and strong homogenization; scraping and bonding eliminates mixing dead zones; and vacuum stirring removes air bubbles. These steps together ensure that the pre-designed precision formulation can be perfectly realized in the final product, enabling the composite multi-level crosslinked network to be constructed as expected, thereby stably producing liquid silicone rubber for robotic skin with excellent and consistent mechanical properties.

[0023] Preferably, the preparation method of the base adhesive is as follows: Turn on the cooling water, add dimethyl silicone oil, low viscosity vinyl silicone oil, hexamethyldisilazane and distilled water into the kneader, mix at a speed of 40-60 r / min for 3-7 min, then add the silica powder in multiple batches, and after mixing the last batch, scrape the cylinder. Then maintain the temperature at 50-65℃, knead in the forward direction for 1.5-2.5 hours, turn off the cooling water, turn on the heating, raise the temperature to 140-155℃, start vacuuming, time for 3-5 hours, control the material temperature below 190℃, turn off the heating, scrape the wall, add high viscosity vinyl silicone oil in batches for vacuum dilution, discharge the material, grind, and obtain the base rubber.

[0024] By employing the above-mentioned technical solution and specifying the preparation method of the base adhesive, including fractional powder addition, heating and kneading, vacuum treatment, and batch-by-batch vacuum dilution, a high-performance base adhesive serving as the structural strength framework of the material was efficiently prepared. Fractional powder addition and kneading ensured sufficient wetting and primary dispersion of the silica filler; heating and vacuum treatment completed the silanization modification of the filler surface, significantly enhancing the interfacial bonding force between the filler and the silicone oil matrix, and improving the traditional reinforcing effect; batch-by-batch vacuum dilution was a key step, enabling the high-viscosity paste-like base adhesive to be steadily and uniformly diluted to a processable viscosity, while avoiding the introduction of air bubbles and secondary agglomeration of the filler. The resulting base adhesive is uniform, fine, and stable, providing an excellent foundation for the subsequent construction of a multi-level crosslinked network.

[0025] In summary, this application includes at least one of the following beneficial technical effects: 1. This application constructs a precisely controllable two-component liquid silicone rubber reaction system by limiting the formulation of A-component, B-component, and base rubber, as well as the viscosity parameters of key raw materials. This provides a precise material basis for the subsequent formation of a composite multi-level crosslinked network. In particular, the specific viscosity of the end-side hydrogen-containing silicone oil ensures the formation of the main crosslinked network. The unique end-side hydrogen-containing silicone oil in B-component can reduce the local crosslinking density. The end-vinyl hyperbranched polyester can form point crosslinking centers with high crosslinking density, resulting in different distributions of crosslinking density within the same system. This different density distribution can buffer external forces, thereby overcoming the problem of reduced toughness caused by interfacial tension in traditional silica reinforcement systems. Ultimately, this significantly improves both the tensile strength and toughness of silicone rubber for robot skin.

[0026] 2. The use of end-vinyl hyperbranched polyester solves the technical challenge of uniformly dispersing solid or high-viscosity polymers in silicone oil systems. Pre-dissolving in a good solvent, THF, allows the hyperbranched polymer molecular chains to fully extend, achieving molecular-level pre-dispersion. After THF removal in the subsequent vacuum process, the polymer remains uniformly and stably within the silicone rubber matrix, ensuring its uniform distribution in the final cured three-dimensional network. This forms an effective global "point" reinforcement and toughening network, avoiding performance weaknesses caused by uneven dispersion. Detailed Implementation

[0027] The following provides a more detailed description of this application in conjunction with specific details.

[0028] raw material All raw materials used in this application are commercially available products. Specifically, the viscosity of the vinyl silicone oil in adhesives A and B is 10000 mPa·s; the viscosity of the dimethyl silicone oil is 50 mPa·s; the viscosity of the high-viscosity vinyl silicone oil is 20000 mPa·s; and the viscosity of the low-viscosity vinyl silicone oil is 50 mPa·s. The platinum catalyst was purchased from Wacker Chemie, model Catalyst OL; and the precipitated silica was purchased from Fujian Yuanxiang New Materials Co., Ltd., model YS-5.

[0029] Preparation Example Preparation Example 1 A vinyl-terminated hyperbranched polyester is prepared by the following method: S1. Add 50g of hydroxyl-terminated hyperbranched polyester and hydroquinone to 300mL of tetrahydrofuran. The amount of hydroquinone added is 0.25% of the mass of the hydroxyl-terminated hyperbranched polyester. Stir under nitrogen protection until dissolved to obtain a reaction solution, and transfer it to an ice-water bath. The type of hydroxyl-terminated hyperbranched polyester is HyPer H103 (average molecular weight of 2400, hydroxyl value of 560mgKOH / g). S2. Dissolve 6 mL of triethylamine in 50 mL of tetrahydrofuran to obtain a triethylamine solution; dissolve acryloyl chloride in 50 mL of tetrahydrofuran to obtain an acryloyl chloride solution. The molar ratio of the added acryloyl chloride to the molar ratio of the hydroxyl-terminated hyperbranched polyester is 1.1:1. S3. Triethylamine solution and acryloyl chloride solution are added dropwise to the reaction solution at a time of 1 hour. After the addition is complete, the reaction is stirred in an ice-water bath for another 1 hour. The ice-water bath is then removed, and the reaction continues for another 8 hours. The triethylamine hydrochloride generated in the reaction is removed by filtration. The filter cake is washed with a small amount of tetrahydrofuran, and the filtrates are combined. S4. The filtrate was added dropwise to 8 times the volume of a 9:1 cold methanol / water mixture under stirring. A flocculent precipitate appeared. The precipitate was filtered and washed three times with cold methanol to thoroughly remove unreacted raw materials, polymerization inhibitors, and solvents. The precipitate was then vacuum-dried at 25°C to obtain a vinyl-terminated hyperbranched polyester. FT-IR analysis of the hydroxyl-terminated hyperbranched polyester and the product showed that the raw material was at -3470 cm⁻¹. -1 The strong, broad peak (-OH stretching vibration) at -1720 cm⁻¹ was significantly weakened; at -1720 cm⁻¹... -1 A strong peak appears at -1635 cm⁻¹ (C=O ester stretching vibration); at -1635 cm⁻¹ -1 (C=C stretching vibration), -1408 cm -1 and -810 cm -1 The presence of a characteristic absorption peak of the acrylate double bond at the (=CH out-of-plane bending vibration) indicates that the product is a terminal vinyl hyperbranched polyester.

[0030] Preparation Example 2 A vinyl-terminated hyperbranched polyester differs from Preparation Example 2 in that its hydroxyl-terminated hyperbranched polyester is of type HyPer H104 (average molecular weight of 5200, hydroxyl value of 520 mg KOH / g), while the remaining steps are the same as in Preparation Example 1. Example

[0031] Examples 1-3 A liquid silicone rubber for robots comprises A and B components in equal mass ratios. The raw materials for A and B are shown in Table 1, and the raw materials and amounts of the base rubbers used in A and B are shown in Table 2. The preparation method of the liquid silicone rubber is as follows: S1, Preparation of base adhesive Turn on the cooling water, put dimethyl silicone oil, low viscosity vinyl silicone oil, hexamethyldisilazane and distilled water into the kneader, mix at 45 r / min for 5 min, then divide the precipitated silica into 5 equal parts and add powder, mix and stir for 15 min after each addition, and scrape the tank after the last addition and mixing. Then maintain the temperature at 60℃, knead in the forward direction for 2 hours, turn off the cooling water, turn on the heating, raise the temperature to 150℃, start vacuuming, time for 4 hours, control the material temperature below 190℃, turn off the heating, scrape the wall, and dilute under vacuum: Add 5% of the high-viscosity vinyl silicone oil for the first time and knead under vacuum for 15 minutes; For the second dilution, add 10% of high-viscosity vinyl silicone oil, vacuum knead for 15 minutes, and scrape the wall. For the third dilution, add 20% of the high-viscosity vinyl silicone oil, vacuum knead for 15 minutes, and scrape the wall. For the fourth dilution, add 30% of the high-viscosity vinyl silicone oil, vacuum knead for 15 minutes, and scrape the walls. For the fifth dilution, add the remaining high-viscosity vinyl silicone oil, vacuum knead for 15 minutes, and scrape the walls. Continue vacuum stirring for 30 minutes, then discharge, grind, and obtain the base adhesive; Preparation of S2 and A glue Clean the planetary mixer rod and mixing vessel. Add the base adhesive to the planetary mixing vessel, circulate cooling water, and then add vinyl silicone oil, dimethyl silicone oil and platinum catalyst in sequence. Mix at 300 r / min for 5 min, then mix at 1050 r / min for 30 min. Stop the machine, raise the mixing paddle, scrape the material adhering to the mixing paddle into the vessel, continue mixing for 30 min, and then discharge the material to obtain adhesive A. Preparation of S3 and B adhesives Clean the planetary mixer rod and mixing vessel. Add the base adhesive to the planetary mixing vessel, turn on the cooling water, and continue to add the remaining raw materials. Mix at 300 r / min for 5 minutes, then mix at 800 r / min for 30 minutes. Stop the machine, raise the mixing paddle, scrape the material adhering to the mixing paddle into the vessel, continue mixing for 30 minutes, and discharge the material to obtain adhesive B. The vinyl-terminated hyperbranched polyester was prepared by the method of Preparation Example 1; S4, Colloidal Mixture Clean the planetary mixer rod and mixing vessel thoroughly. Add A-type glue to the planetary mixing vessel, circulate cooling water, add B-type glue, and mix at 300 rpm for 5 minutes. Then mix at 1000 rpm for 30 minutes. Stop the machine, raise the mixing paddle, scrape the material adhering to the mixing paddle, and pour it into the vessel. Continue mixing for 30 minutes. Stop the machine, slowly open the vacuum, and continue mixing for 30 minutes. Stop the machine, vent the vacuum, and transfer the material to a press for pressing and packaging to obtain liquid silicone rubber for robot skin.

[0032] Table 1. Raw materials and dosage (kg) for Examples 1-3

[0033] Table 2. Raw materials and dosage (kg) of the base adhesives in Examples 1-3

[0034] Example 4 A liquid silicone rubber for robots differs from Example 2 in that its end-vinyl hyperbranched polyester is added after being dissolved in tetrahydrofuran. The dissolution method is as follows: during stirring, tetrahydrofuran is added dropwise to the end-vinyl hyperbranched polyester until the end-vinyl hyperbranched polyester is completely dissolved. The remaining steps are the same as in Example 2.

[0035] Example 5 A liquid silicone rubber for robots differs from Example 4 in that its end-vinyl hyperbranched polyester is prepared by the preparation method of Example 2, while the remaining steps are the same as in Example 4.

[0036] Example 6 A liquid silicone rubber for robots differs from Example 5 in that the amount of end-vinyl hyperbranched polyester added is 1.5 kg, while the remaining steps are the same as in Example 5.

[0037] Example 7 A liquid silicone rubber for robots differs from Example 5 in that the amount of end-vinyl hyperbranched polyester added is 2 kg, while the remaining steps are the same as in Example 5.

[0038] Example 8 A liquid silicone rubber for robots differs from Example 5 in that the amount of end-vinyl hyperbranched polyester added is 2.5 kg, while the remaining steps are the same as in Example 5.

[0039] Comparative Example Comparative Example 1 A liquid silicone rubber for robots differs from Example 2 in that the end-vinyl hyperbranched polyester is replaced with an equal mass of vinyl silicone oil, while the remaining steps are the same as in Example 2.

[0040] Comparative Example 2 A liquid silicone rubber for robots differs from Example 2 in that the terminal vinyl hyperbranched polyester is replaced with an equal mass of terminal hydroxyl hyperbranched polyester, while the remaining steps are the same as in Example 2.

[0041] Comparative Example 3 A liquid silicone rubber for robots differs from Example 2 in that the 0.1 end hydrogen-containing silicone oil is replaced with an equal mass of 0.45 end hydrogen-containing silicone oil, while the remaining steps are the same as in Example 2.

[0042] Comparative Example 4 A liquid silicone rubber for robots differs from Example 2 in that the end-vinyl hyperbranched polyester used in its preparation is of the type HyPer H102, while the remaining steps are the same as in Example 2.

[0043] Performance testing Detection methods / test methods Liquid silicone rubber for robots was prepared according to the preparation methods of Examples 1-8 and Comparative Examples 1-4, and then tested according to the following testing methods. The test results are shown in Table 3.

[0044] The prepared liquid silicone rubber sample was poured into the corresponding mold and cured at room temperature (25℃) for 6 hours. Alternatively, curing can be performed by increasing the temperature to 130℃ for 4-10 minutes to improve production efficiency. The test data are based on room temperature curing.

[0045] Table 3. Detection results of Examples 1-8 and Comparative Examples 1-4

[0046] As can be seen from Examples 1-8, Comparative Examples 1-4, and the test data in Table 3, the liquid silicone rubber prepared in this application has extremely low hardness and tensile strength that can reach above 2.4 MPa, with a maximum of 3.9 MPa. At the same time, its tensile strength can reach 597-626%, and its tear strength can reach 9.3-10.6 kN / m. This indicates that the liquid silicone rubber prepared in this application can simultaneously possess ultra-low hardness, mechanical strength, and toughness, which can fully meet the requirements for manufacturing robot skin.

[0047] Combining Examples 2 and 4, dissolving the end-vinyl hyperbranched polyester in tetrahydrofuran before adding it allows the hyperbranched polymer molecular chains to fully extend, achieving molecular-level pre-dispersion. After removing THF in the subsequent vacuum process, the polymer remains uniformly and stably within the silicone rubber matrix, ensuring its uniform distribution in the final cured three-dimensional network. This forms an effective global "point" reinforcement and toughening network, avoiding weak performance areas caused by uneven dispersion and further improving the performance of the silicone rubber.

[0048] In conjunction with Examples 4-5 and Comparative Example 4, hyperbranched polyesters with molecular weights in the range of 2400-5200 exhibit moderate spatial configurations and a reasonable number of terminal functional groups. This ensures good solubility and dispersibility in the silicone oil matrix, preventing phase separation or a dramatic increase in system viscosity due to excessively large molecules. Simultaneously, it provides a sufficient number of vinyl end groups to form ideal density and strength of physical / chemical entanglements in the cured network, thereby dissipating stress and improving toughness with optimal efficiency. When the molecular weight of the hydroxyl-terminated hyperbranched polyester is low, the analysis suggests that its small molecular weight and low viscosity, coupled with a significant difference in polarity compared to the system, make it prone to precipitation from the system, resulting in a less pronounced effect.

[0049] In conjunction with Examples 5-8, as the amount of end-vinyl hyperbranched polyester added increases, the tensile strength and tear strength of the silicone rubber gradually increase, but its hardness increases while its toughness decreases. Therefore, its addition amount should not exceed 2.5 kg.

[0050] Combined with Example 2 and Comparative Examples 1-3, the advantages of adding the end-vinyl hyperbranched polyester prepared in this application can be demonstrated.

[0051] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A liquid silicone rubber for robots, characterized in that: It comprises A glue and B glue in equal mass ratio. The A glue comprises the following raw materials in parts by weight: 400-450 parts base glue, 30-38 parts vinyl silicone oil, 120-170 parts dimethyl silicone oil, and platinum catalyst; the amount of platinum catalyst added is 2500-5000 PPM. The B-type adhesive comprises the following raw materials in parts by weight: 395-450 parts base adhesive, 28-35 parts vinyl silicone oil, 120-150 parts dimethyl silicone oil, 4-6 parts end-side hydrogen-containing silicone oil, 1.3-5 parts end-side hydrogen-containing silicone oil, 0.05-0.2 parts ethynylcyclohexanol, and 1-2.5 parts end-vinyl hyperbranched polyester; The base adhesive comprises the following raw materials in parts by weight: 100-135 parts of high-viscosity vinyl-terminated silicone oil, 100-140 parts of dimethyl silicone oil, 200-250 parts of silica, 30-40 parts of hexamethyldisilazane, 8-12 parts of distilled water, and 240-265 parts of low-viscosity vinyl-terminated silicone oil. The viscosity of the vinyl silicone oil in adhesive A and adhesive B is 8000-12000 mPa·s; the viscosity of the dimethyl silicone oil is 40-60 mPa·s; the viscosity of the high-viscosity vinyl silicone oil is 15000-25000 mPa·s; and the viscosity of the low-viscosity vinyl silicone oil is 40-60 mPa·s.

2. The liquid silicone rubber for robots according to claim 1, characterized in that: The terminal vinyl hyperbranched polyester is prepared by reacting terminal hydroxyl hyperbranched polyester with acryloyl chloride.

3. The liquid silicone rubber for robots according to claim 2, characterized in that: The preparation method of the end-vinyl hyperbranched polyester is as follows: S1. Using tetrahydrofuran as a solvent, add hydroxyl-terminated hyperbranched polyester and polymerization inhibitor, stir until dissolved under nitrogen protection to obtain a reaction solution, and transfer it to an ice-water bath. S2. Dissolve excess triethylamine in tetrahydrofuran to obtain a triethylamine solution; dissolve excess acryloyl chloride in tetrahydrofuran to obtain an acryloyl chloride solution; S3. Simultaneously add triethylamine solution and acryloyl chloride solution to the reaction solution. After the addition is complete, continue stirring the reaction in an ice-water bath for 0.5-1.5 hours. Remove the ice-water bath and continue the reaction for 6-10 hours. Filter to obtain the filtrate. S4. Add the filtrate dropwise to a methanol / water mixture, filter, wash, and dry to obtain end-vinyl hyperbranched polyester.

4. The liquid silicone rubber for robots according to claim 3, characterized in that: The molar ratio of triethylamine to hydroxyl-terminated hyperbranched polyester is (1.2-3):1; the molar ratio of acryloyl chloride to hydroxyl-terminated hyperbranched polyester is (1.01-1.3):

1.

5. The liquid silicone rubber for robots according to claim 4, characterized in that: The volume ratio of the methanol / water mixture to the filtrate is (8-11):

1.

6. The liquid silicone rubber for robots according to claim 2, characterized in that: The average molecular weight of the hydroxyl-terminated hyperbranched polyester is 2400-5200.

7. The liquid silicone rubber for robots according to claim 1, characterized in that: The end-vinyl hyperbranched polyester is added after being dissolved in tetrahydrofuran.

8. The liquid silicone rubber for robots according to claim 1, characterized in that: The hydrogen content of the end-side hydrogen-containing silicone oil is 0.4-0.55 wt%; the hydrogen content of the end-side hydrogen-containing silicone oil is 0.08-0.14 wt%.

9. A method for preparing liquid silicone rubber for robots according to any one of claims 1-8, characterized in that: It includes the following steps: Preparation of S1 and A glue Add the base adhesive to the planetary mixing vessel, circulate cooling water, and then add vinyl silicone oil, dimethyl silicone oil and platinum catalyst in sequence. Mix at a speed of 200-400 r / min for 3-7 min, and then mix at a speed of 800-1200 r / min for 20-40 min. Stop the machine, raise the stirring paddle, scrape the material adhering to the stirring paddle into the vessel, and continue to stir and mix evenly to obtain adhesive A. Preparation of S2 and B adhesives Add the base adhesive to the planetary mixing vessel, circulate cooling water, and continue to add the remaining raw materials. Mix at a speed of 200-400 r / min for 3-7 min, then mix at a speed of 600-1000 r / min for 20-40 min. Stop the machine, raise the stirring paddle, scrape the material adhering to the stirring paddle into the vessel, and continue to stir and mix evenly to obtain adhesive B. S3, Colloidal Mixture Add A-type glue to a planetary mixing vessel, circulate cooling water, add B-type glue, and mix at 200-500 rpm for 3-8 minutes. Then mix at 800-1200 rpm for 20-50 minutes. Stop the machine, raise the stirring paddle, scrape the material adhering to the stirring paddle into the vessel, continue stirring until homogeneous, stop the machine, open the vacuum, and continue stirring for 20-40 minutes. Stop the machine, vent the vacuum, and transfer the material to a press for pressing and packaging to obtain liquid silicone rubber for robot skin.

10. The method for preparing liquid silicone rubber for robots according to claim 9, characterized in that: The preparation method of the base adhesive is as follows: Turn on the cooling water, add dimethyl silicone oil, low viscosity vinyl silicone oil, hexamethyldisilazane and distilled water into the kneader, mix at a speed of 40-60 r / min for 3-7 min, then add the silica powder in multiple batches, and after mixing the last batch, scrape the cylinder. Then maintain the temperature at 50-65℃, knead in the forward direction for 1.5-2.5 hours, turn off the cooling water, turn on the heating, raise the temperature to 140-155℃, start vacuuming, time for 3-5 hours, control the material temperature below 190℃, turn off the heating, scrape the wall, add high viscosity vinyl silicone oil in batches for vacuum dilution, discharge the material, grind, and obtain the base rubber.

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