Recyclable composite of thermoplastic polyacrylic-polyurea with hindered urea bonds and its preparation method and application

Abstract

The application discloses a recyclable composite material of thermoplastic polyacrylic acid-polyurea with a blocked urea bond and a preparation method and application thereof, and belongs to the technical field of high polymer materials. The application introduces a dynamic blocked urea bond, combines acrylic polyurea as a dynamic component with polyurea, forms a semi-interpenetrating network structure, improves compatibility and increases bond exchange efficiency; realizes high-temperature melting recycling, while maintaining excellent mechanical properties; at high temperature, the urea bond reversibly breaks and recombines, and the recycling efficiency is more than 90%, which is much higher than the 50-70% of traditional polyurea. This benefit is due to the dynamic nature of the bond, allowing the material to be recycled multiple times without additional energy input; the initial mechanical properties of the composite material are excellent, the tensile strength is 18-22 MPa, the modulus is 1.2-1.8 GPa, the elongation at break is 150-200%, the performance retention rate after recycling is as high as 92-98% (once) and 88-94% (second), the recycling efficiency is more than 90%, and the problem of performance degradation of existing materials after recycling is solved.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a recyclable thermoplastic polyacrylic acid-polyurea composite material with hindered urea bonds, its preparation method, and its application. Background Technology

[0002] Thermoplastic polyurea, as a high-performance engineering plastic, possesses excellent mechanical strength, chemical resistance, and thermal stability, and is widely used in automotive, electronics, and construction industries. However, traditional polyurea materials typically employ a cross-linked structure, making them difficult to melt and reshape during recycling, resulting in significant resource waste and environmental pollution. According to existing technology reports, the recycling rate of conventional polyurea is often below 50%, and its mechanical properties degrade significantly after recycling, for example, tensile strength decreases by more than 20%, failing to meet the demands of high-performance applications. This is mainly because the molecular chains of traditional polyurea are linked by irreversible chemical bonds, which are difficult to reverse once formed, making it difficult to reuse waste materials.

[0003] To improve the recyclability of polyurea, some studies have introduced dynamic bonds, such as hydrogen bonds or transesterification bonds. However, these bonds lack stability at high temperatures and are prone to degradation, resulting in low recycling efficiency (typically <70%). While this method achieves reversibility to some extent, it often sacrifices the initial mechanical properties of the material; for example, the modulus decreases to below 1.0 GPa, and the elongation at break is less than 150%. Furthermore, existing polyurea materials are relatively homogeneous in composition and lack synergistic effects with other polymers, often resulting in defects in mechanical properties (such as modulus and elongation at break) or recycling mechanisms. For instance, the initial tensile strength of a single polyurea is approximately 10-15 MPa, but after one recycling, the performance retention rate is only 70-80%, and even lower at less than 50% after secondary recycling. This limits its application in the field of sustainable materials.

[0004] Further analysis of existing technologies reveals that current polyurea materials typically rely on the rapid reaction of isocyanates and amines during synthesis to form a highly cross-linked network structure. While this structure provides excellent heat resistance and mechanical strength, it also presents challenges for recycling. Under environmental pressure, countries worldwide are implementing plastic recycling regulations, such as the EU's Circular Economy Directive, which requires material recycling rates of over 80%. However, traditional polyureas struggle to meet this requirement due to their high melting temperature and viscosity, necessitating the addition of solvents or catalysts during recycling. This not only increases costs but may also introduce secondary pollution.

[0005] The limitations of existing technologies are mainly reflected in low recycling efficiency, large performance degradation, and inflexible structural design.

[0006] Furthermore, some improvement schemes attempt to enhance recyclability by doping with other polymers, such as composites of polyurea with polyesters or polyethers. However, these methods often lead to phase separation problems, affecting the uniformity and stability of the material. Although the recycling efficiency of such composites is improved (approximately 60-75%), the mechanical properties still show significant degradation; for example, after multiple recycling cycles, the tensile strength drops to less than 60% of its initial value. Another problem is that existing dynamic bond designs are mostly limited to hydrogen bonds or disulfide bonds, which are unstable in high-temperature or humid environments, easily leading to material aging or performance loss.

[0007] Therefore, how to maintain the high mechanical properties of polyurea composite materials and achieve efficient melt recycling has become an important issue that urgently needs to be addressed. Summary of the Invention

[0008] Therefore, the purpose of this invention is to provide a recyclable thermoplastic polyacrylic acid-polyurea composite material with hindered urea bonds, its preparation method and application, which achieves high-temperature melting and recycling by introducing dynamic hindered urea bonds while maintaining excellent mechanical properties.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] In a first aspect, the present invention provides a recyclable thermoplastic polyacrylic acid-polyurea composite material having hindered urea bonds, which is prepared by composite of acrylic polyurea and polyurea in a mass ratio of 1:5-10, wherein the acrylic polyurea contains a dynamically hindered urea bond structure.

[0011] Based on the above technical solution, the mass ratio of the acrylic polyurea and the polyurea is further 1:6-8.

[0012] In this composite design, the acrylic polyurea portion forms the material's dynamic network, providing reversibility through dynamically hindered urea bonds, while the polyurea portion ensures overall mechanical strength and chemical resistance. This composite design fully leverages the complementary advantages of the two polymers: acrylic polyurea contributes flexibility and recyclability, while polyurea contributes rigidity and stability.

[0013] In the composite process, controlling the doping ratio is crucial. If the ratio is too low (e.g., below 1:5), the dynamic bond density is insufficient, leading to a decrease in recovery efficiency; if the ratio is too high (e.g., above 1:10), it may affect the overall rigidity of the material. Through experimental optimization, a range of 1:5-10 was determined, which can balance performance.

[0014] The structural formula of the dynamically hindered urea bond is as follows: ; In the structural formula: R is an isocyanate group derived from IPDI, and R' is a tert-butyl hindered group derived from TBEMA.

[0015] This structure allows for reversible exchange at high temperatures, enabling the melt recycling of the material. Specifically, at 150-200°C, the steric hindrance effect of the tert-butyl group weakens in the hindered urea bond, leading to bond breakage and recombination, thus transforming the material from a solid to a molten state. This dynamic behavior is similar to self-healing materials, but this invention applies it to a polyurea system, achieving efficient secondary recycling. Compared to other dynamic bonds, the hindered urea bond exhibits better thermal stability and chemical inertness, and is not easily affected by moisture or oxygen.

[0016] Secondly, the present invention provides a method for preparing a recyclable thermoplastic polyacrylic acid-polyurea composite material with hindered urea bonds as described above. Under nitrogen protection, polyurea prepolymer, diethyltoluene diamine and acrylic polyurea containing a dynamically hindered urea bond structure are mixed and heated to 70-90°C for chain extension for 2-4 hours to obtain the composite material. The mass ratio of the polyurea prepolymer to diethyltoluene diamine is 10-20:1, and the mass of the acrylic polyurea is 10-20% of the mass of the polyurea.

[0017] Based on the above technical solution, the mass ratio of the polyurea prepolymer to diethyltoluene diamine is 15:1, and the mass of the acrylic polyurea is 15% of the mass of the polyurea.

[0018] Diethyltoluenediamine provides a multifunctional amine group, which extends the molecular chain.

[0019] Preferably, the temperature is heated to 80°C, and the chain extension is preferably carried out for 3 hours.

[0020] During chain extension, diethyltoluene diamine reacts with the remaining isocyanate groups to elongate the chain segments, while acrylic polyurea integrates into the polyurea network through hydrogen bonds and dynamic bonds, forming a composite material. The reaction is monitored by tracking the disappearance of the NCO peak using FT-IR (Fourier Transform Infrared Spectroscopy). After the reaction, the product is cast or extruded and cooled to obtain the final product. The molding temperature is 100-120℃ to avoid bubble formation.

[0021] The chain extension mechanism involves the integration of dynamic bonds: the hindered urea bonds of acrylic polyurea form a semi-interpenetrating structure with the polyurea chain segments, improving compatibility.

[0022] Based on the above technical solution, further, 1-5 wt% of nano-silica is added before mixing.

[0023] The addition of 1-5 wt% nano-silica as a filler enhances mechanical properties. After composite formation, the material density is 1.1-1.3 g / cm³, as measured by a densitometer.

[0024] Based on the above technical solution, the preparation process of the acrylic polyurea is further as follows: Under nitrogen protection, isophorone diisocyanate and tert-butyl acrylate methylamine in a molar ratio of 1:1-2 are mixed evenly in solvent a and reacted at 50-70°C for 2-4 hours to obtain the acrylic polyurea. The solvent a is N,N-dimethylformamide or N-methylpyrrolidone, and the amount of solvent a is 2-5 times the total mass of the isophorone diisocyanate and the tert-butyl acrylate methylamine.

[0025] The choice of solvent a is crucial to the uniformity of the reaction. N,N-dimethylformamide provides good solubility, while N-methylpyrrolidone is suitable for high-temperature reactions.

[0026] The preferred preparation process for acrylic polyurea is to react at 60°C for 3 hours.

[0027] During the reaction, the isocyanate groups of isophorone diisocyanate undergo an addition reaction with the amino groups of tert-butyl acrylate methylamine to form an acrylic polyurea containing dynamically hindered urea bonds. Specifically, isophorone diisocyanate is first dissolved in a solvent, and tert-butyl acrylate methylamine is slowly added dropwise to control the reaction rate and avoid local overheating. Too low a temperature (e.g., <50°C) will prolong the reaction time, while too high a temperature (e.g., >70°C) may lead to side reactions. After the reaction is complete, the product is purified by precipitation or distillation, for example, by precipitation with diethyl ether followed by vacuum drying. The amount of solvent used is 2-5 times the total mass of the raw materials, preferably 3 times, to ensure a suitable viscosity of the reaction medium.

[0028] The reaction mechanism is as follows: isophorone diisocyanate provides a diisocyanate functional group, and tert-butyl acrylate methylamine introduces a hindered amine structure, forming a dynamic urea bond. The hindered nature of the urea bond makes it stable at room temperature, but reversibly breaks at high temperatures. The specific reaction pathway includes nucleophilic addition and chain growth stages, followed by further polymerization after the formation of oligomers.

[0029] The molecular weight of the purified acrylic polyurea can reach 5000-10000 g / mol, which is determined by GPC (gel permeation chromatography).

[0030] Based on the above technical solution, further, when the isophorone diisocyanate and the tert-butyl acrylate methylamine are mixed in solvent a, 0.1-0.5 wt% dibutyltin lauryl ester is added.

[0031] The percentage of 0.1-0.5 wt% refers to the mass fraction of dibutyltin lauryl ester in the total mass of isophorone diisocyanate and tert-butyl acrylate methylamine.

[0032] Adding dibutyltin laurate as a catalyst can accelerate the reaction, but the reaction temperature, stirring speed, and reaction time need to be controlled to avoid excessive cross-linking.

[0033] Based on the above technical solution, the preparation process of the polyurea prepolymer is further as follows: Under nitrogen protection, isophorone diisocyanate and polyetheramine with a molar ratio of 1:0.8-1.2 are mixed evenly in solvent b, heated to 60-80℃, and prepolymerized for 1-3 hours to obtain the polyurea prepolymer; The prepolymerization process is carried out with stirring at 200-500 rpm; the viscosity of the polyurea prepolymer is controlled at 500-2000 cP by diluting solvent b. The solvent b is N,N-dimethylformamide.

[0034] In the preparation of the polyurea prepolymer: isophorone diisocyanate and polyetheramine are preferably in a molar ratio of 1:1, preferably heated to 70°C, and preferably prepolymerized for 2 hours.

[0035] Among them, polyetheramine provides flexible segments, which improves the toughness of the material.

[0036] During the prepolymerization process, the amine groups of polyetheramine react with some of the isocyanate groups of isophorone diisocyanate to form a low molecular weight prepolymer.

[0037] A stirring speed of 200-500 rpm is required to ensure a uniform reaction; insufficient stirring may lead to uneven polymerization in certain areas.

[0038] Temperature control is crucial; too low a temperature will slow down the reaction, while too high a temperature may trigger self-polymerization.

[0039] After prepolymerization, the NCO (isocyanate) content is tested, and the remaining NCO groups are confirmed by titration to be 40-60% of the initial amount, so as to facilitate subsequent chain extension.

[0040] The viscosity of the prepolymer was monitored using a Brookfield viscometer.

[0041] In this process, polyester adhesive is added in batches. First, 80% of the total amount is added for prepolymerization, allowing the isocyanate groups and hydroxyl groups to react fully in a relatively homogeneous and controlled system, forming a prepolymer with a relatively concentrated molecular weight distribution. After the prepolymerization reaction is basically complete, the remaining polyester adhesive is added for chain extension, thereby suppressing the problem of excessive chain length differences caused by excessively high local concentrations in the early stages of the reaction, and thus effectively optimizing the final polymer chain length distribution. Based on the above technical solution, furthermore, 0.05-0.2 wt% butylated hydroxytoluene is added during the preparation of the polyurea prepolymer.

[0042] The viscosity of the prepolymer should be controlled between 500-2000 cP, monitored using a Brookfield viscometer. If the viscosity is too high, the solvent can be diluted.

[0043] The entire preparation process is carried out under nitrogen protection to isolate water and oxygen from interference, so as to avoid the isocyanate groups from reacting with water or air.

[0044] Based on the above technical solution, further, 0.05-0.2 wt% butylhydroxytoluene is added during the initial preparation process of the polyurea prepolymer.

[0045] The stabilizer butylated hydroxytoluene is added to prevent oxidation.

[0046] The percentage of 0.05-0.2 wt% refers to the percentage of butylated hydroxytoluene in the total mass of isophorone diisocyanate and polyetheramine.

[0047] Thirdly, the present invention provides the application of the above-mentioned recyclable thermoplastic polyacrylic acid-polyurea composite material with hindered urea bonds in the manufacture of automotive parts, electronic device housings or medical devices.

[0048] The recycling method for the composite material involves heating the material to 150-200℃, preferably 180℃, melting it for 0.5-2 hours, and then cooling and reshaping it. The recycling process utilizes the reversibility of dynamically hindered urea bonds to achieve efficient reuse. After multiple recycling cycles, performance degradation is minimal, and the change in Tg (glass transition temperature) is analyzed using DSC (differential scanning calorimetry).

[0049] The composite material has an initial tensile strength of 18–22 MPa, preferably 19–21 MPa; a modulus of 1.2–1.8 GPa, preferably 1.4–1.6 GPa; an elongation at break of 150–200%, preferably 160–180%; a mechanical property retention rate of 92–98% after primary recycling and 88–94% after secondary recycling; and a recycling efficiency of over 90%, preferably 92–96%.

[0050] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention introduces dynamically hindered urea bonds, combining acrylic polyurea as a dynamic component with polyurea to form a semi-interpenetrating network structure, improving compatibility and increasing bond exchange efficiency; achieving high-temperature melt recycling while maintaining excellent mechanical properties; at high temperatures, urea bonds reversibly break and recombine, with a recycling efficiency exceeding 90%, far higher than the 50-70% of traditional polyurea. This benefit stems from the dynamic nature of the bonds, allowing the material to be recycled multiple times without additional energy input; the composite material exhibits excellent initial mechanical properties, with tensile strength reaching 18-22 MPa, modulus 1.2-1.8 GPa, and elongation at break 150-200%, and performance retention rates after recycling as high as 92-98% (primary) and 88-94% (secondary), with a recycling efficiency exceeding 90%, solving the problem of performance degradation after recycling of existing materials.

[0051] 2. The composite material preparation method provided by this invention is simple, the raw materials are readily available, the reaction conditions are mild (50-90℃), and it is easy to carry out industrial production. The doping of acrylic polyurea improves compatibility and stability, avoids the brittleness defects of single polyurea, and increases the tensile strength of the composite by 20-40%.

[0052] 3. The composite material provided by this invention is environmentally friendly, with no harmful emissions during the recycling process. The recycling process does not require additional catalysts and can be achieved simply by heating, which conforms to the principles of green chemistry. It is suitable for sustainable applications, such as automotive parts (reducing waste plastics) and electronic casings (improving durability).

[0053] 4. The synergistic effect of the present invention is significant: when there are no hindered urea bonds, the recovery efficiency drops to below 70%; in addition, the material has good biocompatibility and can be extended to the field of medical devices. Attached Figure Description

[0054] To more clearly illustrate the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below.

[0055] Figure 1 This is a schematic diagram of the preparation route of the present invention; Figure 2 This is a schematic diagram of the hindered urea bond in this invention; Figure 3 This is a comparison chart of the tensile strength of the embodiments and comparative examples of the present invention; Figure 4 This is a graph showing the retention rate of mechanical properties before and after recycling in Example 1 of the present invention. Figure 5 The graphs show the modulus and elongation at break test results for embodiments and comparative examples of the present invention. Figure 6 This is a graph showing the relationship between recovery efficiency and temperature in Example 1 of the present invention; Figure 7 This is a schematic diagram of the polyurea molecular structure of the present invention. Detailed Implementation

[0056] This invention addresses the needs of sustainable development and environmental protection by providing a novel composite material for the recycling of thermoplastic polyurea through the ingenious introduction of dynamic chemical bond structures. It is applicable to engineering plastics, composite materials, and renewable resources. This technical field typically encompasses research on polymer synthesis, composite material preparation, and recycling technologies, aiming to address the challenges of balancing environmental friendliness and performance in traditional polymer materials. The core lies in the application of dynamic hindered urea bonds—an innovative design based on reversible chemical reactions that enables the melting and reshaping of materials at high temperatures, significantly enhancing the material's lifespan and economic value. In the context of a global emphasis on green manufacturing, this material has broad application prospects, particularly playing a crucial role in sustainable product design in the automotive, electronics, and packaging industries. The technical solution of this invention is not limited to material synthesis but extends to the optimization of preparation processes and performance evaluation, aiming to provide an efficient and controllable solution for the field of polymer materials. Through this invention, researchers and engineers can explore more composite systems based on dynamic bonds, further advancing materials science.

[0057] The technical solution of this invention also includes further optimization of material properties. For example, by adjusting the doping ratio, the glass transition temperature (Tg) of the material can be finely adjusted to 80–100°C, ensuring rigidity at room temperature and rapid melting at recycling temperature. Furthermore, the composite material exhibits good solvent resistance and anti-aging properties, with a mass loss rate of less than 5% after immersion in chloroform or DMF for 24 hours. These characteristics make this invention suitable for applications in harsh environments, such as automotive interiors or electronic packaging.

[0058] The preparation route of the present invention is as follows: Figure 1 As shown, firstly, IPDI + TBEMA → polyurea acrylic acid (dynamically hindered urea bonds); then, IPDI + D2000 → prepolymer; finally, prepolymer + E100 + polyurea acrylic acid → composite material. This preparation route emphasizes stepwise construction to ensure a uniform distribution of dynamic bonds.

[0059] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0060] All raw materials used in the examples were commercially available products with a purity >98%. Performance testing adopted standard methods: tensile strength was tested according to GB / T1040.1-2018, with sample size of 50mm×10mm×2mm and tensile speed of 5mm / min; recovery efficiency was calculated by mass recovery rate, i.e., (recovered mass / initial mass)×100%; modulus and elongation were determined using a universal testing machine, with data averaged in triplicate. The recovery process was carried out in a vacuum oven to avoid oxidation. Each example includes detailed parameters, test results, and analysis to verify repeatability. Among them, isophorone diisocyanate is abbreviated as IPDI; tert-butyl acrylate methylamine is abbreviated as TBEMA; polyetheramine is abbreviated as D2000; chain extender diethyltoluene diamine is abbreviated as E100; N,N-dimethylformamide is abbreviated as DMF; N-methylpyrrolidone is abbreviated as NMP; dibutyltin laurate is abbreviated as DBTL; butylated hydroxytoluene is abbreviated as BHT; and isocyanate is abbreviated as NCO.

[0061] Example 1 1 mol of IPDI was dissolved in 3 times its mass of DMF, heated to 60°C, and 1.5 mol of TBEMA was slowly added dropwise. The reaction was carried out for 3 hours with stirring at 300 rpm. After the reaction, the product was precipitated with diethyl ether and dried under vacuum to obtain polyurea acrylic acid (yield 92%).

[0062] Another 1 mol IPDI and 1 mol D2000 were dissolved in DMF and prepolymerized at 70℃ for 2 hours. The NCO content was measured to be 50%.

[0063] After cooling, add 0.07 mol E100 and 15% of the prepolymer mass of acrylic polyurea, extend the chain at 80℃ for 3 hours, and then cast into shape.

[0064] The density of the composite material is 1.2 g / cm³.

[0065] Test results: initial tensile strength 19.98 MPa, modulus 1.5 GPa, elongation 170%; retention rate 95% in the first recovery (melting at 180℃ for 1 h), 91% in the second recovery; recovery efficiency 92%. Analysis shows that dynamic bonds contribute to the recovery capacity, and performance degradation is only due to slight chain breakage.

[0066] Example 2 The differences between this embodiment and Embodiment 1 are as follows: The concentration of TBEMA was adjusted to 1.2 mol, the solvent was NMP, the reaction temperature was 55 °C, the reaction time was 3.5 h, and 0.2 wt% DBTL was added as a catalyst. The yield after purification was 90%.

[0067] Prepolymerization: D2000 0.9mol, prepolymerization at 65℃ for 2.5h, with the addition of 0.1wt% BHT.

[0068] Chain extension: E100 0.06mol, chain extension at 75℃ for 3.5h, acrylic polyurea 12%.

[0069] Post-molding tests: initial tensile strength 20.15 MPa, modulus 1.6 GPa, elongation 175%; primary recovery 96%, secondary recovery 92%; recovery efficiency 93%. Compared with Example 1, the low proportion of TBEMA improved rigidity but slightly reduced the recovery rate; DSC showed Tg 85℃.

[0070] Example 3 The differences between this embodiment and Embodiment 1 are as follows: 1.8 mol of TBEMA was added, and the reaction was carried out at 65°C for 2.5 h without a catalyst. The yield was 93%.

[0071] Prepolymerization: D2000 1.1mol, prepolymerization at 75℃ for 1.5h.

[0072] Chain extension: E100 0.08mol, chain extension at 85℃ for 2.5h, acrylic polyurea 18%, with the addition of 2wt% nano SiO2.

[0073] Tests: Initial tensile strength 19.50 MPa, modulus 1.4 GPa, elongation 165%; primary recovery 94%, secondary recovery 90%; recovery efficiency 91%. The filler enhanced the modulus, but high doping slightly increased viscosity; FT-IR confirmed bond integrity.

[0074] Example 4 The differences between this embodiment and Embodiment 1 are as follows: 1 mol of TBEMA was added, and the reaction was carried out at 50°C for 4 hours. The yield was 91%.

[0075] Prepolymerization: D2000 0.8mol, prepolymerization at 60℃ for 3h.

[0076] Chain extension: E100 0.05mol, chain extension at 70℃ for 4h, acrylic polyurea 10%.

[0077] Test results: Initial tensile strength 18.80 MPa, modulus 1.3 GPa, elongation 160%; 93% recovered in one cycle, 89% in two cycles; recovery efficiency 90%. The low recovery rate results in slightly lower rigidity, but the recovery process is faster, with an energy consumption of 0.6 kWh / kg.

[0078] Example 5 The differences between this embodiment and Embodiment 1 are as follows: 1.6 mol of TBEMA was added, and the reaction was carried out at 62 °C for 2.8 h. The yield was 94%.

[0079] Prepolymerization: D2000 1.05mol, prepolymerization at 72℃ for 1.8h.

[0080] Chain extension: E100 0.075mol, chain extension at 82℃ for 2.8h, acrylic polyurea 16%.

[0081] Test results: Initial tensile strength 20.50 MPa, modulus 1.55 GPa, elongation 172%; single-pass recovery 96.5%, double-pass 92.5%; recovery efficiency 94%. Optimized parameters improved balance, making it suitable for industrial scale-up.

[0082] Comparative Example 1 The difference from Example 1 is that there is no hindered urea bond; specifically, TBEMA is replaced with conventional methylamine.

[0083] Test results: Initial tensile strength 15.20 MPa, modulus 1.0 GPa, elongation 130%; 75% recovered in the first cycle, 60% in the second cycle; recovery efficiency 70%. The lack of dynamic bonds leads to irreversible degradation and significant performance loss.

[0084] Comparative Example 2 The difference from Example 1 is that it is a conventional polyurea, without doping, specifically an acrylic-free polyurea.

[0085] Test results: Initial tensile strength 14.50 MPa, modulus 0.9 GPa, elongation 125%; primary recovery 72%, secondary recovery 58%; recovery efficiency 68%. The structure is simple and cannot be melted.

[0086] Comparative Example 3 The difference from Example 1 is that the doping ratio is low, specifically 5% acrylic polyurea.

[0087] Test results: Initial tensile strength 16.00 MPa, modulus 1.1 GPa, elongation 140%; 80% recovered in the first cycle, 65% in the second cycle; recovery efficiency 75%. Insufficient dynamic bonds led to incomplete recovery.

[0088] Comparative Example 4 The difference from Example 1 is that there is no chain extender, specifically no E100.

[0089] Test results: Initial tensile strength 13.80 MPa, modulus 0.8 GPa, elongation 120%; 70% recycled in the first cycle, 55% in the second cycle; recycling efficiency 65%. Short chains, low strength.

[0090] Comparative Example 5 The difference from Example 1 is that the prepolymerization temperature is higher, specifically 90°C.

[0091] Test results: Initial tensile strength 17.10 MPa, modulus 1.2 GPa, elongation 145%; primary recovery 82%, secondary recovery 68%; recovery efficiency 78%. High-temperature degradation bonds.

[0092] Performance comparison: From Figure 3 It can be seen that the tensile strength of the example is 20-40% higher than that of the comparative example, indicating the strengthening effect of dynamic bonds; Figure 4 The recovery retention rate curve is flat, and the attenuation in the example is <10%. Figure 5 The medium modulus and elongation are better than the comparative example, and the scatter plot shows the optimization points; Figure 6 This indicates that the recovery efficiency reaches 95% at 180℃. Overall, the present invention significantly improves performance through synergistic effects and is suitable for actual production.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A recyclable thermoplastic polyacrylic acid-polyurea composite material having hindered urea bonds, characterized in that, It is prepared by combining acrylic polyurea and polyurea in a mass ratio of 1:5-10, wherein the acrylic polyurea contains a dynamically hindered urea bond structure.

2. A recyclable thermoplastic polyacrylic acid-polyurea composite material with hindered urea bonds according to claim 1, characterized in that, The mass ratio of the acrylic polyurea to the polyurea is 1:6-8.

3. A method for preparing a recyclable thermoplastic polyacrylic acid-polyurea composite material with hindered urea bonds as described in claim 1 or 2, characterized in that, Under nitrogen protection, polyurea prepolymer, diethyltoluene diamine and acrylic polyurea containing a dynamically hindered urea bond structure were mixed and heated to 70-90℃ for chain extension for 2-4 hours to obtain a composite material. The mass ratio of the polyurea prepolymer to diethyltoluene diamine is 10-20:1, and the mass of the acrylic polyurea is 10-20% of the mass of the polyurea.

4. The preparation method according to claim 3, characterized in that, The mass ratio of the polyurea prepolymer to diethyltoluene diamine is 15:1, and the mass of the acrylic polyurea is 15% of the mass of the polyurea.

5. The preparation method according to claim 3, characterized in that, 1-5 wt% nano-silica is added before mixing.

6. The preparation method according to claim 3, characterized in that, The specific preparation process of the acrylic polyurea is as follows: Under nitrogen protection, isophorone diisocyanate and tert-butyl acrylate methylamine in a molar ratio of 1:1-2 are mixed evenly in solvent a and reacted at 50-70°C for 2-4 hours to obtain the acrylic polyurea. The solvent a is N,N-dimethylformamide or N-methylpyrrolidone, and the amount of solvent a is 2-5 times the total mass of the isophorone diisocyanate and the tert-butyl acrylate methylamine.

7. The preparation method according to claim 6, characterized in that, When the isophorone diisocyanate and the tert-butyl acrylate methylamine are mixed in solvent a, 0.1-0.5 wt% dibutyltin lauryl ester is added.

8. The preparation method according to claim 3, characterized in that, The specific preparation process of the polyurea prepolymer is as follows: Under nitrogen protection, isophorone diisocyanate and polyetheramine with a molar ratio of 1:0.8-1.2 are mixed evenly in solvent b, heated to 60-80℃, and prepolymerized for 1-3 hours to obtain the polyurea prepolymer; The prepolymerization process is carried out with stirring at 200-500 rpm; the viscosity of the polyurea prepolymer is controlled at 500-2000 cP by diluting solvent b. The solvent b is N,N-dimethylformamide.

9. The preparation method according to claim 8, characterized in that, 0.05-0.2 wt% butylhydroxytoluene is added during the initial preparation of the polyurea prepolymer.

10. The use of a recyclable thermoplastic polyacrylic acid-polyurea composite material with hindered urea bonds as described in claim 1 or 2 in the manufacture of automotive parts, electronic device housings, or medical devices.

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