Polyurethane elastomer with adjustable viscosity and elastic modulus as well as preparation and application methods thereof

Abstract

The invention relates to the field of preparation of flexible intelligent materials, in particular to a polyurethane elastomer with adjustable viscosity and elastic modulus and a preparation and application method thereof, and the polyurethane elastomer is prepared by reaction of polyether polyol, alicyclic diisocyanate and tris (2-aminoethyl) amine; the elastomers have a lightly cross-linked network structure comprising cross-linking points consisting of tris (2-aminoethyl) amine, and each cross-linking point comprising on average at least one pendant unreacted primary amine group; the molar ratio of the alicyclic diisocyanate to the polyether polyol is (2-3): 1, and by adjusting the molar ratio, the elastic modulus of the elastomer is between 0.1 MPa and 1 MPa, and the adhesion strength is adjustable between 0 kPa and 200 kPa. The elastomer has excellent anti-aging performance, the adhesive force attenuation is less than 15% after 30 thousand cycles, and the elastomer is suitable for grabbing and desorption of ultrathin brittle targets (such as silicon wafers) and has universal substrate adaptability and anti-pollution capacity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flexible smart material preparation, and relates to a polyurethane elastomer with adjustable viscosity and elastic modulus and a preparation and application method thereof. BACKGROUND

[0002] In the application of flexible smart materials, the performance parameters of the adhesive material are crucial for ultra-thin fragile targets. If the adhesion strength is too high, the detachment process may be difficult and cause damage to the target or contamination of the residue; on the contrary, if the adhesion strength is too low, the target cannot be effectively grabbed. At the same time, the elastic modulus (which characterizes the stiffness of the material) also needs to be accurately controlled: if the modulus is too large (the material is too hard), it will crush the fragile surface when in contact, and if the modulus is too small (the material is too soft), it will prolong the detachment time and reduce the efficiency. In addition, the material is required to have long-term anti-aging performance and universality for various substrates (such as glass, metal, and polymer).

[0003] At present, common adhesive materials (such as acrylate or silicone-based adhesives) often have difficulty in balancing adhesion strength, elastic modulus, and durability at the same time. For example, some materials have a significant adhesion decay after being used repeatedly, or cannot adapt to different environmental conditions. The prior art lacks an elastomer material that can achieve adjustable adhesion performance and mechanical properties through simple chemical regulation, which limits its application in high-end manufacturing fields.

[0004] The information disclosed in this BACKGROUND section is only intended to enhance the understanding of the general background of the application and should not be taken as an acknowledgment or any form of suggestion that this information constitutes prior art. SUMMARY

[0005] The first object of the present application is to provide a hydroxyl-functionalized rigid cross-linked polyurethane elastomer with adjustable viscosity and elastic modulus, which has the characteristics of long service life, anti-aging, adjustable viscosity and elastic modulus according to needs, etc.

[0006] The above technical object of the present application is achieved by the following technical solution: A polyurethane elastomer with adjustable viscosity and elastic modulus is prepared by reacting a polyether polyol, an alicyclic diisocyanate, and tri(2-aminoethyl)amine; The elastomer has a lightly cross-linked network structure, which contains cross-linking points composed of tri(2-aminoethyl)amine, and each cross-linking point contains at least one pendant unreacted primary amine group on average; This invention involves initial curing / drying at room temperature or lower. At lower temperatures, molecular chain mobility is weaker, but soft segments are still more mobile than hard segments. During solvent evaporation, to achieve the lowest interfacial energy, compliant, polar polyether soft segments migrate more easily to the material-air interface. High-temperature curing avoids excessive chain segment movement, which can lead to hard segment aggregation and bubble formation within the film (sample).

[0007] Tris(2-aminoethyl)amine acts as a crosslinking agent. Its two primary amine groups react with the NCO groups at the ends of the two diisocyanate molecules to form rigid urea bonds, thereby connecting the long polymer chains to form a three-dimensional network. This mildly crosslinked network structure is achieved through a specific molar ratio (1:2~3:0.02), requiring a small amount of crosslinking agent and achieving a moderate network density. This stoichiometric approach ensures rapid reaction of the two primary amine groups on the crosslinking agent. The unreacted primary amine group, sterically hindered by the connected long chains, is suspended and fixed. This structure, by disrupting the regularity of the hard segments, inhibits excessive microphase separation, thereby forcing flexible segments to accumulate on the surface, achieving high adhesion.

[0008] The molar ratio of alicyclic diisocyanate to polyether polyol is 2-3:1. By adjusting this molar ratio, the elastic modulus of the elastomer can be adjusted between 0.1 and 1 MPa, and the adhesive strength between 0 and 200 kPa. Users can select the appropriate molar ratio according to application requirements to predictably obtain an ideal combination of modulus and adhesive strength within the ranges of 0.1-1 MPa and 0-200 kPa.

[0009] Preferably, the molar ratio of polyether polyol, alicyclic diisocyanate, and tris(2-aminoethyl)amine is 1:2 to 3:0.02. This ensures that when the crosslinking agent is added, there are a sufficient number and uniformly distributed NCO prepolymer chains in the system, allowing each crosslinking agent molecule to quickly find two reactive groups and be fixed, forming pendulous amine groups. The crosslinking agent ratio of 0.02 keeps the crosslinking density at a mild level, ensuring the overall elasticity of the material and the mobility of the soft segments, thus achieving adhesion. This avoids the unpredictability of performance caused by simultaneously changing two variables.

[0010] Preferably, the elastic modulus increases with the increase of the molar ratio of alicyclic diisocyanate to polyether polyol, while the adhesive strength decreases with the increase of the molar ratio of alicyclic diisocyanate to polyether polyol.

[0011] As the molar ratio increases, the proportion of rigid alicyclic diisocyanates in the system increases, leading to a higher density of rigid hard segments (urethane groups and urea bonds). This manifests macroscopically as an increase in elastic modulus and a harder material. At the same time, the relative proportion of flexible polyether soft segments that provide adhesion decreases, and their chain segment movement is more restricted, resulting in a decrease in adhesion strength.

[0012] A decrease in the molar ratio results in a relatively higher proportion of soft segments in the flexible polyether, making it easier for these segments to migrate to the surface and providing more hydrogen bond adhesion sites, thus enhancing adhesion strength. Simultaneously, a reduction in rigid components lowers the macroscopic elastic modulus, making the material softer.

[0013] Preferably, the alicyclic diisocyanate is at least one selected from isophorone diisocyanate, terephthalic diisocyanate, naphthalene diisocyanate, toluene-2,6-diisocyanate, and toluene-2,4-diisocyanate. These rigid diisocyanates have poor compatibility with the flexible polyether polyol segments, which drives microphase separation in the system, forming rigid microdomains rich in urethane / urea bonds dispersed in the flexible phase, giving the material elastomeric behavior and high strength.

[0014] Preferably, the alicyclic diisocyanate is isophorone diisocyanate (IPDI), and the molecular weight of the polyether polyol is 1000-6000. The alicyclic structure of IPDI provides inherent rigidity and reacts with tris(2-aminoethyl)amine to form rigid urea bonds, together constructing a robust cross-linked network framework. The long-chain polyether provides flexibility and viscosity, and the resulting polyurethane elastomer contains hydroxyl groups, urethane groups, and urea bonds in its molecular chain. The specific unit structure of the resulting polyurethane elastomer is as follows: This invention systematically studies the effect of the molar ratio of alicyclic diisocyanate to polyether polyol on the performance of the final product. The preferred range is 2-3; as the molar ratio increases, the elastic modulus (E) increases, but the adhesive strength (σ) decreases. For example: When the molar ratio is 2.0, E≈0.046MPa, σ≈170kPa; When the molar ratio is 2.25, E≈0.321MPa, σ≈107kPa; When the molar ratio is 2.66, E≈0.767MPa, σ<1kPa.

[0015] Alicyclic diisocyanates have alicyclic structures and high crosslinking density (achieved through tris(2-aminoethyl)amine), which enhances the rigidity of the molecular chain and improves the elastic modulus. Meanwhile, the hydroxyl functional groups of polyether polyols provide adhesion through hydrogen bonds and van der Waals forces. When the molar ratio decreases, the hydroxyl density increases relatively, thus improving the adhesion strength.

[0016] Preferably, the polyurethane elastomer also contains a catalyst and an antioxidant. The catalyst is dibutyltin dilaurate, and the antioxidant is at least one of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester (antioxidant 1076) or pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (antioxidant 1010). After undergoing 300,000 adhesion-desorption cycle tests, the elastomer exhibits an adhesion strength attenuation rate of less than 15%. This meets the stringent requirements of high-end manufacturing industries such as semiconductor chip sorting and micro-component assembly for extremely high uptime and stability of gripping tools, significantly reducing equipment maintenance costs and downtime risks.

[0017] The second objective of this invention is to provide a method for preparing a hydroxyl-functionalized rigid crosslinked polyurethane elastomer with adjustable viscosity and elastic modulus, which has the same technical effect.

[0018] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A method for preparing polyurethane elastomers with adjustable viscosity and elastic modulus specifically includes the following preparation steps: S1. Weigh each component according to the proportions; S2. Place the polyether polyol in a three-necked flask, add tetrahydrofuran solvent to dissolve it completely, then add alicyclic diisocyanate and tris(2-aminoethyl)amine sequentially. The tris(2-aminoethyl)amine is added slowly by titration to ensure that the local concentration of the crosslinking agent in the reaction system remains at an extremely low level. Due to the extremely high reactivity of its primary amine group, it reacts rapidly with the two NCO groups to form two rigid urea bonds. At this point, although the third primary amine group is still active, it is difficult to react due to the huge steric hindrance generated by the polymer chain. As the reaction proceeds, the viscosity of the system increases, molecular motion is hindered, and the unreacted third amine group forms a pendant unreacted primary amine group. Then, a catalyst is added, and the reaction is carried out at 55-65℃ for 3-5 hours. After adding an antioxidant, the reaction is carried out for another 0.5-1 hour to obtain a viscous elastomer solution. The reactants form a homogeneous system, ensuring sufficient contact between the cyanate groups and the hydroxyl and amino groups, avoiding uneven crosslinking or product performance defects caused by local aggregation. S3. Pour the solution obtained in S2 into a custom-made membrane container, vacuum defoam, and then place it in a fume hood to dry at room temperature for 30-45 hours. Next, place it in a forced-air drying oven at 55-65°C for 1-3 hours to obtain the polyurethane elastomer. Drying at room temperature is mainly to prevent the generation of bubbles during the reaction, which would lead to a decrease in the mechanical properties of the film. Finally, drying at 60°C ensures that the reaction is completely completed and the solvent is completely dried.

[0019] Preferably, in step S2, the reaction is carried out in an oil bath at 55~65°C under a nitrogen atmosphere, and a reflux condenser is provided. The reaction process isolates oxygen, protects the cyanate groups, and prevents them from oxidizing at high temperatures.

[0020] Preferably, in step S3, the solution obtained in S2 is poured into a customized membrane container, and the vacuum defoaming pressure is 10. 4 Pa, pump for 5-8 minutes at a time, while ensuring that the solution does not overflow from the membrane, repeat pumping 5-6 times until there are no visible bubbles in the solution.

[0021] Preferably, in step S2, the catalyst is dibutyltin dilaurate, and the catalyst content is 0.5wt%~1.5wt% of the mass of the polyether polyol. This ratio can precisely adapt to the requirements of the reaction system, taking into account reaction efficiency, product performance stability and process flexibility, and is a preferred range after targeted optimization.

[0022] Preferably, in step S2, the antioxidant content is 0.1wt% to 0.8wt% of the polyether polyol mass; the antioxidant is at least one of antioxidant 1076 and antioxidant 1010. This ratio balances the optimal range of anti-fading effect, system compatibility, and cost, and can suppress adhesion fading to the greatest extent. It is also suitable for both single-agent and compound-agent use in the reaction system.

[0023] A third objective of this invention is to provide a method for applying a hydroxyl-functionalized rigid crosslinked polyurethane elastomer with adjustable viscosity and elastic modulus, using the aforementioned polyurethane elastomer to grasp or transfer ultrathin and brittle materials, including semiconductor chips, ultrathin glass, or optical films.

[0024] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a hydroxyl-functionalized rigid crosslinked polyurethane elastomer with adjustable viscosity and elastic modulus, using polyether polyol and alicyclic diisocyanate as the molecular backbone and tri(2-aminoethyl)amine as the crosslinking agent. The hydrogen bonds and van der Waals forces between the polar functional groups (hydroxyl groups) of the polyether polyol and the substrate primarily enhance adhesion strength. The alicyclic structure of the diisocyanate and the rigid crosslinking network (urethane groups / urea bonds) of the tri(2-aminoethyl)amine together maintain the elastic modulus. That is, the molar ratio of the alicyclic structure of the diisocyanate to the polyether polyol can be used as a control parameter to balance the adhesion performance and elastic modulus of the polyurethane elastomer. This invention incorporates an antioxidant as a hydrogen donor to capture free radicals generated during oxidation, terminate the chain reaction, and delay the oxidative degradation of the polyurethane elastomer, achieving an adhesion strength attenuation of less than 15% after 300,000 cycles.

[0025] The core mechanism of polyurethane's adhesion retention in this invention lies in the synergistic effect of hydroxyl functionalization and mild crosslinking. The molecular chain retains a sufficient amount of hydroxyl groups, forming a "weakly polar adsorption layer" on the material surface. This achieves universal adhesion to multiple substrates such as glass, metal, and polymers, while avoiding the problem of "strong adhesion leading to desorption residue" in traditional adhesives. By using a low molar ratio of crosslinking agent and a controllable molar ratio, the elastic modulus is ensured to meet the gripping requirements, and the polar functional groups maintain adhesion, so that the material is neither hard and brittle nor sticky after curing, achieving "adhesion-desorption" cycle stability. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The molecular structure of this invention is shown in the embodiment. Figure 2 Infrared image of an embodiment of the present invention; Figure 3 The graphs show the relationship between elastic modulus and adhesion strength in Examples 1-5 of this invention. Figure 4 These are mechanical property diagrams for embodiments 1-5 of the present invention; Figure 5 This describes the anti-pollution capability of Embodiment 1 of the present invention; Figure 6 This illustrates the adaptation of Embodiment 1 of the present invention to different substrates; Figure 7 This is the cyclic aging condition of Embodiment 1 of the present invention. Detailed Implementation

[0028] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the specific implementation methods, features, and effects of a hydroxyl-functionalized rigid crosslinked polyurethane elastomer with adjustable viscosity and elastic modulus, its preparation and application methods, are described in detail below. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0029] In embodiments of the present invention, the specific sources of the various materials required are as follows: Elastomer polyether polyol (99%), molecular weight 2000, Shanghai Yuanye Biotechnology Co., Ltd. Tris(2-aminoethyl)amine (97%), Shanghai Maclean Biochemical Technology Co., Ltd. Isophorone diisocyanate (99%), Shanghai Maclean Biochemical Technology Co., Ltd. Tetrahydrofuran (analytical grade), Shanghai Aladdin Biochemical Technology Co., Ltd.; Catalyst (99%), dibutyltin dilaurate, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0030] Example 1, molar ratio 2.25: A polyurethane elastomer with adjustable viscosity and elastic modulus is prepared by reacting polyether polyol, isophorone diisocyanate and tris(2-aminoethyl)amine. The elastomer has a mildly cross-linked network structure containing cross-linking points composed of tris(2-aminoethyl)amine, and on average each cross-linking point contains at least one overhanging unreacted primary amine group; The molar ratio of polyether polyol, isophorone diisocyanate, and tris(2-aminoethyl)amine is 1:2.25:0.02. A catalyst and antioxidant are also added to the polyurethane elastomer; the catalyst is dibutyltin dilaurate, and the antioxidant is antioxidant 1076. After 300,000 adhesion-desorption cycle tests, the elastomer exhibits an adhesion strength attenuation rate of less than 15%.

[0031] A method for preparing a hydroxyl-functionalized rigid crosslinked polyurethane elastomer with adjustable viscosity and elastic modulus, specifically including the following preparation steps: S1. Weigh 7.2g (3.6mmol, molecular weight 2000) of elastomer polyether polyol and add it to a flask. Then add 5mL of tetrahydrofuran to the flask to make the elastomer polyether polyol miscible with the tetrahydrofuran. Weigh 1.798g (8.1mmol) of isophorone diisocyanate and add it to the flask. After stirring appropriately, weigh 0.0146g (0.1mmol) of crosslinking agent tris(2-aminoethyl)amine and add it to the flask. After the flask is installed in an oil bath, add 30uL of catalyst dibutyltin dilaurate, connect the condenser, and purge with nitrogen to continue the reaction for 4h. Then add 0.005g of antioxidant 1076 and react for another 0.5h to obtain a viscous elastomer solution. S2. Pour the solution obtained in S1 into a custom-shaped membrane container, and then evacuate (10). 4 (Pa) Defoaming treatment: Ensure that the solution does not overflow from the membrane. Draw for 5-8 minutes at a time, repeat 5-6 times, until there are no visible bubbles in the solution. Then place it in a fume hood to dry at room temperature for 40 hours, and then place it in a forced-air drying oven at 60°C for 2 hours to finally obtain a viscous hydroxyl-functionalized rigid crosslinked polyurethane elastomer.

[0032] Example 2, molar ratio 2: A polyurethane elastomer with adjustable viscosity and elastic modulus is prepared by reacting polyether polyol, isophorone diisocyanate and tris(2-aminoethyl)amine. The elastomer has a mildly cross-linked network structure containing cross-linking points composed of tris(2-aminoethyl)amine, and on average each cross-linking point contains at least one overhanging unreacted primary amine group; The molar ratio of polyether polyol, isophorone diisocyanate, and tris(2-aminoethyl)amine is 1:2:0.02. A catalyst and antioxidant are also added to the polyurethane elastomer; the catalyst is dibutyltin dilaurate, and the antioxidant is antioxidant 1076. After 300,000 adhesion-desorption cycle tests, the elastomer exhibits an adhesion strength attenuation rate of less than 15%.

[0033] A method for preparing a hydroxyl-functionalized rigid crosslinked polyurethane elastomer with adjustable viscosity and elastic modulus, specifically including the following preparation steps: S1. Weigh 7.2g (3.6mmol, molecular weight 2000) of elastomer polyether polyol and add it to a flask. Then add 5mL of tetrahydrofuran to the flask to make the elastomer polyether polyol miscible with the tetrahydrofuran. Weigh 1.592g (7.2mmol) of isophorone diisocyanate and add it to the flask. After stirring appropriately, weigh 0.0146g (0.1mmol) of crosslinking agent tris(2-aminoethyl)amine and add it to the flask. After assembling the flask in an oil bath, add 30uL of catalyst dibutyltin dilaurate, connect the condenser, and purge with nitrogen for 4h. Then add 0.005g of antioxidant 1076 and react for another 0.5h to obtain a viscous elastomer solution. S2. Pour the solution obtained in S1 into a custom-shaped membrane container, and then evacuate (10). 4 (Pa) Defoaming treatment: Ensure that the solution does not overflow from the membrane. Draw for 5-8 minutes at a time, repeat 5-6 times, until there are no visible bubbles in the solution. Then place it in a fume hood to dry at room temperature for 40 hours, and then place it in a forced-air drying oven at 60°C for 2 hours to finally obtain a viscous hydroxyl-functionalized rigid crosslinked polyurethane elastomer.

[0034] Example 3, molar ratio 2.167: A polyurethane elastomer with adjustable viscosity and elastic modulus is prepared by reacting polyether polyol, isophorone diisocyanate and tris(2-aminoethyl)amine. The elastomer has a mildly cross-linked network structure containing cross-linking points composed of tris(2-aminoethyl)amine, and on average each cross-linking point contains at least one overhanging unreacted primary amine group; The molar ratio of polyether polyol, isophorone diisocyanate, and tris(2-aminoethyl)amine is 1:2.167:0.02. A catalyst and antioxidant are also added to the polyurethane elastomer; the catalyst is dibutyltin dilaurate, and the antioxidant is antioxidant 1076. After 300,000 adhesion-desorption cycle tests, the elastomer exhibits an adhesion strength attenuation rate of less than 15%.

[0035] A method for preparing a hydroxyl-functionalized rigid crosslinked polyurethane elastomer with adjustable viscosity and elastic modulus, specifically including the following preparation steps: S1. Weigh 7.2 g (3.6 mmol, molecular weight 2000) of elastomer polyether polyol and add it to a flask. Then add 5 mL of tetrahydrofuran to the flask to make the elastomer polyether polyol miscible with the tetrahydrofuran. Weigh 1.7316 g (7.8 mmol) of isophorone diisocyanate and add it to the flask. After stirring appropriately, weigh 0.0146 g (0.1 mmol) of crosslinking agent tris(2-aminoethyl)amine and add it to the flask. After assembling the flask in an oil bath, add 30 μL of catalyst dibutyltin dilaurate, connect the condenser, and purge with nitrogen for 4 h. Then add 0.005 g of antioxidant 1076 and react for another 0.5 h to obtain a viscous elastomer solution. S2. Pour the solution obtained in S1 into a custom-shaped membrane container, and then evacuate (10). 4 (Pa) Defoaming treatment: Ensure that the solution does not overflow from the membrane. Draw for 5-8 minutes at a time, repeat 5-6 times, until there are no visible bubbles in the solution. Then place it in a fume hood to dry at room temperature for 40 hours, and then place it in a forced-air drying oven at 60°C for 2 hours to finally obtain a viscous hydroxyl-functionalized rigid crosslinked polyurethane elastomer.

[0036] Example 4, molar ratio 2.33: A polyurethane elastomer with adjustable viscosity and elastic modulus is prepared by reacting polyether polyol, isophorone diisocyanate and tris(2-aminoethyl)amine. The elastomer has a mildly cross-linked network structure containing cross-linking points composed of tris(2-aminoethyl)amine, and on average each cross-linking point contains at least one overhanging unreacted primary amine group; The molar ratio of polyether polyol, isophorone diisocyanate, and tris(2-aminoethyl)amine is 1:2.33:0.02. A catalyst and antioxidant are also added to the polyurethane elastomer; the catalyst is dibutyltin dilaurate, and the antioxidant is antioxidant 1076. After 300,000 adhesion-desorption cycle tests, the elastomer exhibits an adhesion strength attenuation rate of less than 15%.

[0037] A method for preparing a hydroxyl-functionalized rigid crosslinked polyurethane elastomer with adjustable viscosity and elastic modulus, specifically including the following preparation steps: S1. Weigh 7.2g (3.6mmol, molecular weight 2000) of elastomer polyether polyol and add it to a flask. Then add 5mL of tetrahydrofuran to the flask to make the elastomer polyether polyol miscible with the tetrahydrofuran. Weigh 1.862g (8.38mmol) of isophorone diisocyanate and add it to the flask. After stirring appropriately, weigh 0.0146g (0.1mmol) of crosslinking agent tris(2-aminoethyl)amine and add it to the flask. After assembling the flask in an oil bath, add 30uL of catalyst dibutyltin dilaurate, connect the condenser, and purge with nitrogen for 4h. Then add 0.005g of antioxidant 1076 and react for another 0.5h to obtain a viscous elastomer solution. S2. Pour the solution obtained in S1 into a custom-shaped membrane container, and then evacuate (10). 4 (Pa) Defoaming treatment: Ensure that the solution does not overflow from the membrane. Draw for 5-8 minutes at a time, repeat 5-6 times, until there are no visible bubbles in the solution. Then place it in a fume hood to dry at room temperature for 40 hours, and then place it in a forced-air drying oven at 60°C for 2 hours to finally obtain a viscous hydroxyl-functionalized rigid crosslinked polyurethane elastomer.

[0038] Example 5, molar ratio 2.66: A polyurethane elastomer with adjustable viscosity and elastic modulus is prepared by reacting polyether polyol, isophorone diisocyanate and tris(2-aminoethyl)amine. The elastomer has a mildly cross-linked network structure containing cross-linking points composed of tris(2-aminoethyl)amine, and on average each cross-linking point contains at least one overhanging unreacted primary amine group; The molar ratio of polyether polyol, isophorone diisocyanate, and tris(2-aminoethyl)amine is 1:2.66:0.02. A catalyst and antioxidant are also added to the polyurethane elastomer; the catalyst is dibutyltin dilaurate, and the antioxidant is antioxidant 1076. After 300,000 adhesion-desorption cycle tests, the elastomer exhibits an adhesion strength attenuation rate of less than 15%.

[0039] A method for preparing a hydroxyl-functionalized rigid crosslinked polyurethane elastomer with adjustable viscosity and elastic modulus, specifically including the following preparation steps: S1. Weigh 7.2 g (3.6 mmol, molecular weight 2000) of elastomer polyether polyol and add it to a flask. Then add 5 mL of tetrahydrofuran to the flask to make the elastomer polyether polyol miscible with the tetrahydrofuran. Weigh 2.126 g (9.576 mmol) of isophorone diisocyanate and add it to the flask. After stirring appropriately, weigh 0.0146 g (0.1 mmol) of crosslinking agent tris(2-aminoethyl)amine and add it to the flask. After assembling the flask in an oil bath, add 30 μL of catalyst dibutyltin dilaurate, connect the condenser, and purge with nitrogen for 4 h. Then add 0.005 g of antioxidant 1076 and react for another 0.5 h to obtain a viscous elastomer solution. S2. Pour the solution obtained in S1 into a custom-shaped membrane container, and then evacuate (10). 4 (Pa) Defoaming treatment: Ensure that the solution does not overflow from the membrane. Draw for 5-8 minutes at a time, repeat 5-6 times, until there are no visible bubbles in the solution. Then place it in a fume hood to dry at room temperature for 40 hours, and then place it in a forced-air drying oven at 60°C for 2 hours to finally obtain a viscous hydroxyl-functionalized rigid crosslinked polyurethane elastomer.

[0040] Performance testing: Figure 2 The infrared image shown in this embodiment of the invention is at 1700 cm. -1 A characteristic peak of the urethane group was observed at 3260 cm⁻¹. -1 The presence of a characteristic absorption peak for urea bonds confirms the successful synthesis of the target product.

[0041] Performance tests were conducted on Examples 1-5 respectively. Figure 3 The graphs show the relationship between elastic modulus and adhesion strength in Examples 1-5 of this invention. Figure 4 These are mechanical property diagrams for embodiments 1-5 of the present invention; The results showed that when the IPDI ratio decreased, the adhesion strength increased to 170 kPa, but the elastic modulus decreased to 0.046 MPa, and the tensile strength was only 0.352 MPa. At low IPDI ratios, the increased hydroxyl density enhanced interfacial adhesion, but insufficient crosslinking density led to interfacial residue and stringing during desorption. When the IPDI ratio increased to 2.66, the material's elastic modulus reached 0.767 MPa, and the tensile strength reached 4.197 MPa. However, due to the excessively low hydroxyl density, the adhesion strength dropped sharply to below 1 kPa, failing to meet basic adhesion requirements.

[0042] Figure 3 The intuitively displayed curves showing the relationship between molar ratio, elastic modulus, and adhesion strength demonstrate that the modulus increases linearly with the molar ratio, while the adhesion strength decreases non-linearly. This provides a precise design basis for specific applications (such as high-precision gripping requiring low modulus and high adhesion, and rapid desorption requiring high modulus and low adhesion).

[0043] The polyurethane formulation was adjusted based on the performance requirements of the target scenario: In high-adhesion scenarios, such as gripping rough substrates, the molar ratio is 2.0~2.2, the adhesion strength is 150~200kPa, and the modulus is <0.1MPa. Note that low modulus may be associated with the risk of stringing; therefore, the desorption rate must be controlled.

[0044] In high-modulus scenarios, such as rapid desorption from rigid substrates, the molar ratio is 2.5~2.7, and the modulus is >0.5MPa, but the adhesion strength drops to below 10kPa, making it suitable for non-adhesive supports.

[0045] The ultrathin and brittle target, with a molar ratio of 2.25 (Example 1), has an adhesion strength of 107 kPa, a modulus of 0.321 MPa, and a tensile strength of 2.47 MPa. It has the most suitable overall performance and can simultaneously meet the requirements of reliable gripping and rapid desorption.

[0046] Performance testing was continued on the polyurethane elastomer (Example 1) with a molar ratio of isophorone diisocyanate / polyether polyol of 2.25.

[0047] Figure 5 In the dust contamination resistance test of Example 1 of the present invention, dust contamination temporarily reduced the peel strength to 18%, but the recovery rate after washing reached 98%. This reversible characteristic is due to the hydrophilic surface of the polyurethane elastomer, whose physical adsorption-dominated contamination mechanism allows contaminants to be efficiently removed through physical cleaning, avoiding chemical residues.

[0048] Figure 6 As shown in Embodiment 1 of the present invention, it exhibits excellent adhesion performance on various substrates (including glass, acrylic, carbon fiber board and paper). The peel force on glass and acrylic is 1.310N, and on carbon fiber board and paper it is 0.841N.

[0049] Figure 7 For the cyclic aging test of Example 1 of the present invention, the long-term mechanical durability was demonstrated by performing 300,000 adhesion-desorption cycles in a Class 10,000 cleanroom (20°C, 20%RH), with the peel force decreasing by less than 5%. This excellent performance is attributed to the addition of antioxidants to the polyurethane elastomer material, the hemispherical contact design, the low adhesion and small elastic deformation required for lightweight and brittle targets, and the combined effect of constant temperature and humidity conditions.

[0050] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. An adjustable modulus polyurethane elastomer, characterized by, isocyanate and tri(2-aminoethyl)amine; The elastomer has a lightly cross-linked network structure, wherein cross-linking points composed of tri(2-aminoethyl)amine are contained, and each cross-linking point contains at least one overhanging unreacted primary amine group on average; The molar ratio of the cycloaliphatic diisocyanate to the polyether polyol is 2-3:1, and by adjusting the molar ratio, the elastic modulus of the elastomer can be adjusted to be between 0.1-1 MPa, and the adhesive strength can be adjusted to be between 0-200 kPa.

2. The polyurethane elastomer of adjustable viscosity and modulus of elasticity according to claim 1, characterized in that, The molar ratio of the polyether polyol, the cycloaliphatic diisocyanate and the tri(2-aminoethyl)amine is 1:2-3:0.

02.

3. The polyurethane elastomer of adjustable viscosity and modulus of elasticity according to claim 1, characterized in that, The elastic modulus increases with the increase of the molar ratio of the cycloaliphatic diisocyanate to the polyether polyol, and the adhesive strength decreases with the increase of the molar ratio of the cycloaliphatic diisocyanate to the polyether polyol.

4. The polyurethane elastomer of adjustable viscosity and modulus of elasticity according to claim 1, characterized in that, The cycloaliphatic diisocyanate is at least one of isophorone diisocyanate, p-phenylene diisocyanate, naphthalene diisocyanate, toluene 2,6-diisocyanate, and toluene-2,4-diisocyanate.

5. Process for the preparation of polyurethane elastomers with adjustable modulus of elasticity and viscosity according to any one of claims 1 to 4, characterized in that: Specifically comprising the following preparation steps: S1, weighing each component according to the proportion; S2, placing the polyether polyol in a three-necked flask, adding tetrahydrofuran solvent to completely dissolve it, then sequentially adding the cycloaliphatic diisocyanate and tri(2-aminoethyl)amine, titrating the tri(2-aminoethyl)amine, then adding a catalyst, reacting at 55-65°C for 3-5h, and then adding an antioxidant and reacting for 0.5-1h to obtain a viscous elastomer solution; S3, pouring the solution obtained in S2 into a customized film tool, vacuuming and defoaming, then placing it in a fume hood at room temperature for drying for 30-45h, and then placing it in a forced air drying oven at 55-65°C for drying for 1-3h to obtain the polyurethane elastomer.

6. The process for the preparation of an adjustable modulus of viscosity and elasticity polyurethane elastomer according to claim 5, characterized by the fact that: In step S2, the reaction at 55-65°C is oil bath heating, the reaction is completed under a nitrogen atmosphere, and a condensation reflux is provided, and the reaction process is isolated from oxygen.

7. The method of making an adjustable modulus of viscosity and elasticity polyurethane elastomer according to claim 5, characterized in that: In step S3, the solution obtained in S2 is poured into a customized film container, and the air pressure for vacuum defoaming is 10 4 Pa, 5-8 min per time, while ensuring that the solution does not overflow from the film container, and the process is repeated 5-6 times until there are no visible bubbles in the solution.

8. The method of making an adjustable modulus of viscosity and elasticity polyurethane elastomer according to claim 5, characterized in that: In step S2, the catalyst is dibutyltin dilaurate, and the content of the catalyst is 0.5wt%-1.5wt% of the mass of the polyether polyol.

9. The method of making an adjustable modulus of viscosity and elasticity polyurethane elastomer according to claim 5, characterized in that: In step S2, the content of the antioxidant is 0.1wt%-0.8wt% of the mass of the polyether polyol; and the antioxidant is at least one of antioxidant 1076 and antioxidant 1010.

10. An application method of a polyurethane elastomer with adjustable viscosity and elastic modulus, using the polyurethane elastomer of any one of claims 1-4 to realize the grasping or transferring of ultra-thin brittle materials, wherein the ultra-thin brittle materials include semiconductor chips, ultra-thin glass or optical thin films.

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