Self-healing polyurethane as well as preparation method and application thereof

Abstract

The invention relates to self-healing polyurethane as well as a preparation method and application thereof, and belongs to the technical field of preparation of environment-friendly flexible high polymer materials, and the prepared self-healing polyurethane elastomer has rapid self-healing property, high mechanical strength and recyclable processability of materials.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and specifically relates to a self-healing polyoxime urethane, its preparation method, and its application. Background Technology

[0002] Traditional polyurethanes, polymerized from petroleum-based polyols and isocyanates, are widely used in aerospace and medical devices. However, the contradiction between the application demands of polyurethanes and the scarcity of fossil fuels as raw materials is becoming increasingly severe. Furthermore, the rapid development of flexible electronics, wearable devices, and smart sensing technologies places higher demands on the environmental adaptability, durability, and functional repairability of polyurethanes. Against this backdrop, the preparation of self-healing polyurethanes using bio-based or recycled raw materials has become a research hotspot in the field of green chemistry. Polyester polyols obtained from the alcoholysis of waste PET, as an environmentally friendly raw material, can not only replace traditional petroleum-based polyols but also introduce reversible π-π interactions through the stacking of benzene rings in the molecular chain to construct green self-healing polyurethanes. However, the dynamic nature of these π-π interactions in the self-healing polyurethane requires activation by external stimuli, making room-temperature self-healing impossible.

[0003] However, there are few reports on the preparation of green room temperature self-healing polyurethane by combining alcoholysis polyester polyols with oxime-carbamate bonds in the existing technology. Furthermore, how to achieve dynamic synergy between the soft segments of alcoholysis polyester polyols and oxime-carbamate bonds through molecular design, while taking into account the rapid self-healing properties, high mechanical strength and recyclability of the material, is a key problem that urgently needs to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a self-healing polyoxime urethane, its preparation method and application.

[0005] This invention provides a polyoxime urethane, characterized in that the polyoxime urethane has the following general structural formula:

[0006] Where y = 1~3 and z = 20 or more;

[0007] Where R is an isocyanate residue;

[0008] The isocyanate residues are the groups remaining after the isocyanate groups are removed.

[0009] The M is , where n=1~3; x=6~8.

[0010] Furthermore, n is 1, 2, or 3.

[0011] Furthermore, as mentioned above, n=1, x=2, y=1, and z is 20 or more.

[0012] The isocyanate is one or more of isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), and diphenylmethane diisocyanate (MDI).

[0013] The corresponding structure of isocyanate: , , .

[0014] The preparation of polyoxime esters involves reacting polyester polyol and dimethylglyoxime as soft segments and chain extenders, respectively, with different isocyanates under the action of a catalyst.

[0015] This invention provides a method for preparing polyoxime urethane, comprising:

[0016] Polyester polyol, solvent, and catalyst are mixed, and isocyanate is added dropwise for reaction. Then, dimethylglyoxime solution is added for reaction, followed by post-treatment to obtain polyoxime urethane.

[0017] The preferred embodiment of the above preparation method is as follows:

[0018] The structure of the polyester polyol:

[0019] Where n = 1~3; x = 6~8;

[0020] Furthermore, n can be 1, 2, or 3.

[0021] Furthermore, the polyester polyol is an alcoholysis polyester polyol, such as an alcoholysis polyester polyol obtained by alcoholysis of waste PET.

[0022] The alcoholysis polyester polyol is prepared by alcoholysis of waste PET, including: mixing and reacting pretreated waste PET, ethylene glycol and zinc acetate of PET, then adding adipic acid for esterification and chain extension, taking a sample to measure the acid value, continuing the reaction, and obtaining the alcoholysis polyester polyol after the reaction is completed.

[0023] The isocyanate is one or more of isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), and diphenylmethane diisocyanate (MDI).

[0024] The solvent includes N,N-dimethylformamide; the catalyst includes dibutyltin dilaurate; and the solvent for the dimethylglyoxime solution includes N,N-dimethylformamide.

[0025] The molar ratio of the polyester polyol to the isocyanate is 1:4~6.

[0026] The catalyst is fed in an amount of 0.4% to 0.6% of the total mass of the three monomers (polyester polyol, isocyanate and dimethylglyoxime); the dimethylglyoxime is 2 to 4 times the molar amount of the polyester polyol.

[0027] The preparation process includes: heating the polyester polyol to 110-120℃ and then evacuating it under vacuum; cooling it to 80-90℃ and then adding solvent and catalyst; stirring; adding isocyanate dropwise for 2-4 hours; then cooling it to 55-65℃ and adding dimethylglyoxime solution for 14-18 hours; all reactions are carried out under protective gas conditions.

[0028] The post-treatment involves reacting at 55-65℃ for 12-24 hours, followed by heating to 80-85℃ and vacuuming for 20-30 hours.

[0029] This invention provides an application of any of the polyoxime esters in the field of self-healing, such as self-healing polyoxime ester elastomers.

[0030] Beneficial effects

[0031] The present invention uses polyester polyol and dimethylglyoxime as soft segment and chain extender, respectively, and the polyoxime elastomer obtained by reacting with isocyanates of different structures has good self-healing and mechanical properties.

[0032] This invention belongs to the field of environmentally friendly flexible polymer material preparation technology, and also relates to a low-cost, high-value-added recycling process for waste plastic products. The self-healing polyoxime elastomer of this invention combines rapid self-healing properties with high mechanical strength. Attached Figure Description

[0033] Figure 1 These are the UV-Vis spectral test curves for Examples 1-3;

[0034] Figure 2 Examples 1-3 are surface height maps and phase curves obtained from atomic force microscopy (AFM).

[0035] Figure 3 These are the stress-strain curves for Examples 1-3;

[0036] Figure 4 These are images of the self-healing scratches in Example 3 under a digital microscope;

[0037] Figure 5 This is the self-healing efficiency of the specimens at different temperatures in Example 3.

[0038] Figure 6 This is a flowchart of the synthesis process of POU elastomer. Detailed Implementation

[0039] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0040] The sources and specifications of the raw materials and reagents used in the experiment are shown in Table 1.

[0041] Table 1 Experimental materials and reagents

[0042]

[0043] Preparation of polyester polyol by alcoholysis: PET bottle flakes were washed three times with anhydrous ethanol and dried in a 60℃ forced-air oven for later use. When ready for use, waste PET bottle flakes, ethylene glycol, and 0.5 wt% PET zinc acetate were added to a three-necked flask and placed in an oil bath. The mixture was heated to 220℃, and the equipped mechanical stirrer and oil-sealed condenser were started. The reaction was carried out, and the hydroxyl value was measured. The temperature was then lowered to 170℃, and adipic acid was added at a molar ratio of n(ethylene glycol):n(adipic acid) = 1:0.65 for esterification and chain extension. After 60 min of reaction, the acid value was measured again. Simultaneously, the reaction system was heated back to 220℃, and the apparatus was changed, replacing the spherical condenser with a straight condenser. The reaction continued, and then a vacuum was applied to the system, adjusting the vacuum level to 0.1 MPa. Finally, the reaction was completed, yielding a brown paste-like product, PEO.

[0044] Example 1

[0045] In this embodiment, isophorone diisocyanate (IPDI) was used for synthesis.

[0046] Preparation of polyoxime urethane containing isophorone diisocyanate (IPDI): Alcohololyzed polyester polyol (2.362 g, 0.500 mmol) was added to a reaction flask, and the mixture was heated to 120 °C and vacuum-treated to remove water and residual anhydrous ethanol for 2 h. While maintaining a nitrogen atmosphere, the mixture was cooled to 85 °C, and N,N-dimethylformamide (DMF, 2 mL) and dibutyltin dilaurate (DBTDL, 0.5 wt%, 0.015 g) were added to the reaction flask. After magnetic stirring at 600 r / min for 20 min, isophorone diisocyanate (IPDI, 0.467 g, 2.1 mmol) was added dropwise using a syringe, and the reaction proceeded for 3 h. Subsequently, the temperature was lowered to 60 °C, and a solution of dimethylglyoxime (DMG, 0.174 g, 1.5 mmol) dissolved in 2 mL of DMF was added to the flask, and the reaction proceeded for 16.5 h. Finally, the product was poured into a polytetrafluoroethylene mold and transferred to a 60°C vacuum oven to continue the reaction for 24 h. The oven was then heated to 80°C and vacuumed for 27 h to obtain a yellow solid, which is POU-IPDI.

[0047] Example 2

[0048] In this embodiment, dicyclohexylmethane diisocyanate (HMDI) was used for synthesis.

[0049] Preparation of polyoxime urethane containing dicyclohexylmethane diisocyanate (HMDI): Alcohololyzed polyester polyol (2.362 g, 0.500 mmol) was added to a reaction flask, and the mixture was heated to 120 °C and vacuum-treated to remove water and residual anhydrous ethanol for 2 h. While maintaining a nitrogen atmosphere, the mixture was cooled to 85 °C, and N,N-dimethylformamide (DMF, 2 mL) and dibutyltin dilaurate (DBTDL, 0.5 wt%, 0.015 g) were added to the reaction flask. After magnetic stirring at 600 r / min for 20 min, dicyclohexylmethane diisocyanate (HMDI, 0.551 g, 2.1 mmol) was added dropwise using a syringe, and the reaction proceeded for 3 h. Subsequently, the temperature was lowered to 60 °C, and a solution of dimethylglyoxime (DMG, 0.174 g, 1.5 mmol) dissolved in 2 mL of DMF was added to the flask, and the reaction proceeded for 16.5 h. Finally, the product was poured into a polytetrafluoroethylene mold and transferred to a 60 °C vacuum oven to continue the reaction for 24 h. The oven was then heated to 80 °C and vacuumed for 27 h to obtain a yellow solid, which is POU-HMDI.

[0050] Example 3

[0051] In this embodiment, diphenylmethane diisocyanate (MDI) was used for synthesis.

[0052] Preparation of polyoxime urethane containing diphenylmethane diisocyanate (MDI): Alcohololyzed polyester polyol (2.362 g, 0.500 mmol) was added to a reaction flask, and the mixture was heated to 120 °C and vacuum-treated to remove water and residual anhydrous ethanol for 2 h. While maintaining a nitrogen atmosphere, the mixture was cooled to 85 °C, and N,N-dimethylformamide (DMF, 2 mL) and dibutyltin dilaurate (DBTDL, 0.5 wt%, 0.015 g) were added to the reaction flask. After magnetic stirring at 600 r / min for 20 min, diphenylmethane diisocyanate (MDI, 0.526 g, 2.1 mmol) was added dropwise using a syringe, and the reaction proceeded for 3 h. Subsequently, the temperature was lowered to 60 °C, and a solution of dimethylglyoxime (DMG, 0.174 g, 1.5 mmol) dissolved in 2 mL of DMF was added to the flask, and the reaction proceeded for 16.5 h. Finally, the product was poured into a polytetrafluoroethylene mold and transferred to a 60 °C vacuum oven to continue the reaction for 24 h. The oven was then heated to 80 °C and vacuumed for 27 h to obtain a yellow solid, which is POU-MDI.

[0053] Performance tests were conducted on Examples 1, 2, and 3.

[0054] 1. Gel permeation chromatography (GPC) test:

[0055] The molecular weight of POU was determined using a GPC equipped with an RI detector and an MG300 column. All solvents used were N-methylpyrrolidone, and the concentration was prepared at 1.0 mg / mL.

[0056] 2. Ultraviolet-Vis Spectroscopy (UV-Vis) Testing:

[0057] The intensity of π-π interactions in POU was characterized using UV-Vis with a slow response rate, a scan rate of 100 nm / min, and a scan range of 230–300 nm.

[0058] 3. Atomic Force Microscope (AFM):

[0059] The surface morphology and phase separation of POU were determined by AFM characterization of height maps and phase maps. The scanning range was 500 nm. The images were processed and analyzed using Nano-Scope-Analysis and Gwyddion software.

[0060] 4. Uniaxial tensile test:

[0061] The tensile properties of POU were characterized using a universal testing machine. The sample size was 15×3×0.5 mm. 3 The rectangular spline was stretched at a rate of 50 mm / min, and the result was the average of three data points.

[0062] 5. Surface scratch self-healing test:

[0063] The self-healing property of scratches on the surface of POU-MDI was characterized using a digital microscope. The PU surface was scratched with a razor blade, and the scratches were about 1.2 mm long. The changes of the scratches over time were observed at room temperature (25℃).

[0064] 6. Spline cutting self-healing test:

[0065] The tensile properties of the cut and self-healing specimens of Example 3 were characterized using a universal testing machine. The cut rectangular specimens of Example 3 were placed in ovens at 25 ℃, 55 ℃ and 70 ℃ for 24 h and then removed. The self-healing performance of POU-MDI was evaluated by the tensile strength of the healed specimens. The average of the three tensile strengths was taken as the result, and the ratio of the tensile strength after self-healing to the original tensile strength was defined as the self-healing efficiency.

[0066] Examples 1-3 used GPC to characterize the molecular weight and distribution of POU, as shown in Table 2. Under the same reaction conditions and ratios, the reactivity of alcoholysis polyester polyols and isocyanates with different structures differed, with M in Example 3 being particularly significant. n and M w The values ​​were 23535 and 62374 g / mol, respectively, which were significantly higher than the other two sets of examples, indicating that the reaction between alcoholysis polyol and MDI has higher reactivity and the reaction between the two can easily yield products with excellent mechanical properties.

[0067] Table 2. Molecular weight and distribution of POU

[0068]

[0069] Examples 1-3 characterized the samples using UV-Vis spectra, such as... Figure 1 As shown, under essentially the same solution concentration, a broad characteristic absorption peak appeared in all three sets of POU spectra, indicating the presence of π-π interactions in the materials. Furthermore, the absorption peak intensities of Examples 1 and 2 were essentially the same, with the highest values ​​both around 243.8 nm. The absorption peak signal of Example 3 was significantly stronger than that of Examples 1 and 2, with its highest absorption peak value near 246.1 nm, exhibiting a clear red shift, indicating that the π-π interactions in Example 3 were stronger than in the other two sets of POUs.

[0070] Examples 1-3 used AFM to test the surface area of ​​the material at 500×500 nm. 2 The height map and corresponding phase map of the scanned dimensions, such as Figure 2As shown. The adhesion strength of the material surface determines the phase value of the corresponding region. Generally, bright areas in the phase diagram represent domains aggregated by interactions, while broad dark areas represent soft segments with lower modulus. From Figure 2 It can be seen that no obvious hard segment microdomains appeared in any of the three sets of examples, indicating that the domains in the material are uniformly distributed in the soft segments. To further compare the degree of microphase separation among the three sets of examples while keeping the material color range consistent, it can be seen that the color of Example 1 is the brightest, followed by Example 3, while the color of Example 2 is the darkest. In addition, a 500 nm long straight line region with the largest phase difference was selected in the phase diagram of the three sets of examples, and the average phase value of this region was calculated. The average phase value of Example 1 is the largest and two sets of phase difference peaks appear, indicating the largest degree of microphase separation; Example 3 has only one set of phase difference peaks and the peak value is smaller than that of Example 1, indicating a relatively small degree of microphase separation; Example 2 has a basically consistent average phase and no obvious phase difference peaks appear, indicating the smallest degree of microphase separation.

[0071] The mechanical properties of Examples 1-3 can be investigated using stress-strain curves, such as... Figure 3 As shown in Table 3, POU exhibits different mechanical properties with changes in isocyanate structure. The Young's modulus of POU is negatively correlated with chain segment regularity. However, with increasing elongation and stress, the physical crosslinking points (hydrogen bonds and π-π interactions) in POU begin to dissipate mechanical energy. Examples 1 and 3 have relatively more physical crosslinking points, thus their tensile strength is higher than that of Example 2. Compared to Example 2, Example 3 exhibits a higher tensile strength (6.6 ± 0.1 MPa), an increase of 2.0 times; compared to Example 1, the elongation at break of Example 3 (903.6 ± 50.8%) is significantly increased by 1.4 times. Therefore, Example 3 has the best mechanical properties.

[0072] Table 3 Mechanical properties of POU

[0073]

[0074] The reversible hydrogen bonds, oxime-carbamate bonds, and π-π interactions in Example 3 enable it to possess good room-temperature self-healing ability, which is investigated through room-temperature scratch self-healing and spline cut self-healing experiments. Figure 4As shown in Table 4, the healing process of the scratched film of Example 3 was observed under a digital microscope at room temperature (25 °C). The micrographs show that only a small portion of the deepest scratches remained unhealed at 25 min, and the scratches completely disappeared at 30 min, indicating that Example 3 has good room temperature scratch self-healing ability. The self-healing ability of Example 3 was further evaluated by testing the mechanical properties of cut rectangular specimens of Example 3 after healing at different temperatures. The cut rectangular specimens were placed at the fracture surfaces in contact and then placed in environments at room temperature, 55 °C, and 70 °C for 24 h before being removed. The mechanical properties of the specimens after cooling are shown in Table 4. Figure 5 As shown, under the same healing time, the tensile strength, elongation at break, and self-healing efficiency of Example 3 all increased with increasing temperature. After healing at 70 °C for 24 h, the self-healing efficiency of Example 3 reached 83.0 ± 4.9%, which was 24.1% higher than that of the self-healing specimen at 55 °C. This is because heating can promote the dissociation and recombination rate of reversible dynamic bonds at the fracture site of Example 3, which macroscopically manifests as an improvement in material mechanics and self-healing efficiency. The above research shows that Example 3 is a room-temperature self-healing elastomer with temperature response capability, which can effectively repair material damage and extend service life.

[0075] Table 4 Self-healing performance of Example 3

[0076]

Claims

1. A polyoxime urethane, characterized in that, The general structural formula of the polyoxime ester is: Where y = 1~3 and z = 20 or more; Where R is an isocyanate residue; The M is , where n=1-3; x=6~8.

2. The polyoxime urethane according to claim 1, characterized in that, The isocyanate is one or more of isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), and diphenylmethane diisocyanate (MDI).

3. A method for preparing polyoxime urethane, comprising: Polyester polyol, solvent, and catalyst are mixed, and isocyanate is added dropwise for reaction. Then, dimethylglyoxime solution is added for reaction, followed by post-treatment to obtain polyoxime urethane.

4. The preparation method according to claim 3, characterized in that, The structure of the polyester polyol: Where n=1~3; x=6~8; the isocyanate is one or more of isophorone diisocyanate IPDI, dicyclohexylmethane diisocyanate HMDI, and diphenylmethane diisocyanate MDI.

5. The preparation method according to claim 3, characterized in that, The solvent includes N,N-dimethylformamide; the catalyst includes dibutyltin dilaurate; and the solvent for the dimethylglyoxime solution includes N,N-dimethylformamide.

6. The preparation method according to claim 3, characterized in that, The molar ratio of the polyester polyol to the isocyanate is 1:4~6.

7. The preparation method according to claim 3, characterized in that, The catalyst is fed at a rate of 0.4-0.6% of the total mass of the three monomers; the dimethylglyoxime is 2-4 times the molar amount of the polyester polyol.

8. The preparation method according to claim 3, characterized in that, Preparation includes: After the polyester polyol is heated to 110-120℃, a vacuum is drawn, and after cooling to 80-90℃, solvent and catalyst are added, stirred, and isocyanate is added dropwise for 2-4 hours. Then, the temperature is lowered to 55-65℃ and dimethylglyoxime solution is added for 14-18 hours. All reactions are carried out under protective gas conditions.

9. The preparation method according to claim 3, characterized in that, The post-treatment involves reacting at 55-65℃ for 12-24 hours, followed by heating to 80-85℃ and vacuuming for 20-30 hours.

10. The use of the polyoxime urethane according to any one of claims 1-2 in the field of self-healing.

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