Method for synthesizing polyurea elastomer in one step without chain extender

Abstract

The invention relates to a method for synthesizing a polyurea elastomer in one step without a chain extender, which abandons the necessary chain extender component in the traditional polyurethane / polyurea synthesis, and carries out direct addition polymerization on excessive isocyanate and hydroxyl-terminated polyether. The core mechanism is that excessive isocyanate and reactive hydrogen in carbamate bonds generated by reaction are subjected to secondary reaction, and a cross-linked structure is constructed in situ. The process is carried out in a specific good solvent, and the solvent not only has the effects of adjusting the reaction rate and enhancing the process controllability, but also provides entropy elasticity contribution for the final product. Therefore, the formed large-ring-shaped multi-crosslinking-point topological network effectively improves the deformation uniformity and the elastic recovery capability of the elastomer. According to the invention, the production process is obviously simplified, the cost is reduced, and the polyurea elastomer product with excellent comprehensive mechanical properties is finally obtained.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a method for one-step synthesis of polyurea elastomers without chain extenders. Background Technology

[0002] Polyurea elastomers, due to their good mechanical strength, chemical corrosion resistance, wear resistance, low-temperature resistance, and aging resistance, are widely used in various applications such as waterproofing, corrosion protection, impact and wear resistance, and surface decoration. Generally speaking, polyurea elastomers consist of soft segments composed of flexible long chains of oligomeric polyols or amines, and hard segments composed of diisocyanates and chain extenders. The ratio of soft to hard segments, the microphase separation structure, the crosslinking method, and the crosslinking density have a significant impact on the final performance behavior of polyurea elastomers. Currently, the industrial preparation of polyurea elastomers mainly adopts a one-step synthesis method and a two-step prepolymer chain extension method. Although the one-step method can achieve a simpler processing technology and a shorter production cycle by mixing polyols, isocyanates, chain extenders, and other additives (such as catalysts and foaming agents) in one step, it is not conducive to the control of the reaction process and the improvement of product performance. The prepolymer method can solve the problems of one-step synthesis, but it will increase the cost of the process and production cycle. Meanwhile, purely linear polyurea elastomers may undergo creep under static pressure conditions. To achieve long-term performance of the elastomer, it is sometimes necessary to introduce multifunctional monomers to provide crosslinking sites, thereby limiting molecular chain slippage and reducing its permanent deformation rate. Therefore, the synthesis of crosslinked polyurea elastomers with good performance and controllable structure through a one-step method is of great significance for its industrial production and practical applications. Summary of the Invention

[0003] Based on this, the present invention provides a method for one-step synthesis of polyurea elastomers without chain extenders. By directly adding excess isocyanate to terminal hydroxyl polyether and simultaneously controlling the solubility parameters of a good solvent, a polyurea elastomer with excellent performance is finally prepared.

[0004] First aspect: A method for one-step synthesis of polyurea elastomer without chain extender includes the following steps: The polyether diol is dissolved in a solvent, a diisocyanate curing agent is added, the mixture is stirred, and then allowed to stand and cure to obtain the polyurea elastomer. The solvent has a solubility parameter > 8.9; the diisocyanate curing agent is calculated based on NCO groups, the polyether diol is calculated based on hydroxyl groups, the molar ratio of the NCO groups to the hydroxyl groups is 1.5~2.4, and the mass ratio of the polyether diol to the solvent is 1:(0.8~2). Specifically, the mass ratio of the polyether diol to the solvent can be 1:(1~2), 1:(1.2~2), or 1:(1.4~2).

[0005] This invention develops a one-step synthesis process for polyurea elastomers without chain extenders. Isocyanate components (such as MDI or HDI) are rapidly added to hydroxyl-terminated polyethers to form the elastomer. Simultaneously, chain extension is achieved by utilizing the secondary addition reaction of excess isocyanate components and the active hydrogen on the urethane functional groups to form crosslinking sites. Controlling the solvent solubility parameter has a dual effect: on the one hand, it slows down the reaction rate increase, improving the controllability of the reaction process; on the other hand, it provides entropic elasticity to the polyurea elastomer, thereby improving mechanical properties. The synthesis process of the polyurea elastomer in this invention does not require the addition of additional chain extender components (unlike polyurethane). The crosslinked elastomer formed in this way has crosslinking sites that differ from simple multifunctional linear crosslinking sites. It combines multiple isocyanate monomers to form large-ring crosslinking sites, improving the uniformity of deformation and enhancing the elastic recovery ability of the polyurea elastomer. This provides a new approach to simplifying the production process and improving product performance.

[0006] like Figure 1 As shown in the figure, the diisocyanate curing agent used is diphenylmethane diisocyanate (MDI), which is the diisocyanate curing agent actually used in the example. This figure is only for example and does not mean that the present invention can only use this diisocyanate curing agent.

[0007] The reaction process of this invention can be divided into two stages: First stage: Polyether diol reacts with diisocyanate to generate an isocyanate-terminated intermediate.

[0008] The second stage involves the unreacted isocyanate in the system undergoing a further cross-linking reaction with the intermediate. This second stage is crucial for chain extension, and the cross-linking reaction must be carried out in a good solvent with a solubility parameter > 8.9. Under these conditions, the unreacted isocyanate can be fully mixed with the intermediate in the solvent, thereby effectively interacting with the active hydrogen reaction sites on the urethane groups in the intermediate. Furthermore, the reaction process is more controllable, ultimately forming a urea elastomer with a multi-crosslinking structure.

[0009] It is important to emphasize that only in good solvent systems with a solubility parameter > 8.9 is it conducive to the formation of multi-ring cross-linked structures with more than 4 rings, thereby achieving a high ring content in the system and a relatively uniform number of cyclizations in the cyclized structures. This multi-ring cross-linked system with more than 4 rings ultimately constructs a highly branched three-dimensional network topology. In addition, the good solvent also provides a good contribution to the elasticity of the final product.

[0010] As a preferred embodiment, the polyether diol comprises at least one of polyethylene glycol and polytetrahydrofuran.

[0011] As a preferred embodiment, the polyethylene glycol and polytetrahydrofuran have a molecular weight of 200-20000 Da.

[0012] As a preferred embodiment, the solvent includes at least one of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF).

[0013] As a preferred embodiment, the diisocyanate curing agent includes at least one selected from isoflurane diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, L-lysine diisocyanate, phenyl diisocyanate, terephthalic diisocyanate, diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate, and 2,6-toluene diisocyanate.

[0014] As a preferred embodiment, the following steps are also included: after the polyether diol is dissolved in the solvent, the temperature is raised to 40-80°C, the diisocyanate curing agent is added, and the mixture is stirred at a speed of 1800-2500 r / min for 3-10 min to obtain a mixture.

[0015] As a preferred embodiment, the following steps are also included: the mixture is placed at 60-100℃ for 6-12 hours to cure, thereby obtaining the polyurea elastomer.

[0016] The second aspect: A polyurea elastomer prepared by the method described in the first aspect for one-step synthesis of polyurea elastomer without chain extender has an elongation at break ≥500% and a tensile strength ≥3 MPa. Attached Figure Description

[0017] Figure 1 Schematic diagram of the reaction process for one-step synthesis of polyurea elastomers without chain extenders; Figure 2 Polyurea elastomers prepared for Example 1, Comparative Example 2, and Comparative Example 4 1 H NMR spectrum; Figure 3 As in Example 1 1 H- 13 C NMR spectrum; Figure 4 For Comparative Example 4 1 H- 13 C NMR spectrum; Figure 5 The GPC map is shown in Comparative Example 2; Figure 6 The attenuated total reflectance infrared spectra of the polyurea elastomers prepared in Examples 1, 2, and 4 are shown. Detailed Implementation

[0018] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of the embodiments of this application.

[0019] A method for one-step synthesis of polyurea elastomer without chain extender includes the following steps: Dissolve polyether diol in a solvent, add diisocyanate curing agent, heat to 40-80℃, add the diisocyanate curing agent, stir at 1800-2500 r / min for 3-10 min to obtain a mixture, then place the mixture at 60-100℃ for 6-12 h to cure, and obtain polyurea elastomer.

[0020] The solvent has a solubility parameter > 8.9; the diisocyanate curing agent is calculated based on NCO groups, and the polyether diol is calculated based on hydroxyl groups, with a molar ratio of NCO groups to hydroxyl groups of 1.5~2.4, and a mass ratio of polyether diol to solvent of [value missing]. Preferably, the mass ratio of polyether diol to solvent is 1:(1~2).

[0021] Polyether diols include at least one of polyethylene glycol and polytetrahydrofuran, and have a molecular weight of 200-20000 Da.

[0022] The solvent includes at least one of N,N-dimethylformamide and tetrahydrofuran.

[0023] Diisocyanate curing agents include at least one of isoflurone diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, L-lysine diisocyanate, phenyl diisocyanate, terephthalic diisocyanate, diphenylmethane diisocyanate, 2,4-toluene diisocyanate, and 2,6-toluene diisocyanate.

[0024] In an embodiment of the present invention, 1 H-NMR spectra and 13 C-NMR spectra were analyzed using a Bruker 600 MHz Fourier transform nuclear magnetic resonance spectrometer. Specifically, the sample was dissolved in deuterated chloroform at a concentration of 10 wt.%, and chemical shifts were measured at room temperature using tetramethylsilane (TMS) as an internal standard.

[0025] The molecular weight of the non-crosslinked polyurea elastomer was determined using Waters 150CV gel permeation chromatography (GPC), specifically a GPC instrument equipped with a differential refractive index detector. The mobile phase was degassed dimethylformamide (DMF), and the standard was polystyrene particles of known molecular weight. Experimental conditions included a flow rate of 0.5 mL / min and a column temperature of 40 °C. For sample preparation, approximately 5-10 mg of dried polyurea elastomer was weighed and dissolved in an appropriate amount of solvent, with a concentration controlled at 0.1-1% w / w. After ensuring system stability, the test was performed, and the weight-average molecular weight (Mb) was calculated using calibration curves and data analysis software. w ).

[0026] The structure of the polyurea elastomer was analyzed using a Fourier transform infrared spectroscopy (ThermoNicolet 6500) instrument. The sample was placed directly on the surface of a ZnSe crystal with an ATR-IR attachment, and the scanning range was 400–4000 cm⁻¹. -1 4cm resolution -1 The number of scans was 32. Before the test, the blank background was measured to ensure the baseline was smooth. After the sample was placed on the detection stage and the infrared spectrum was acquired, the position and intensity of the functional group absorption peaks were analyzed by software and compared with the standard spectrum to confirm the material structure characteristics.

[0027] Polyurea elastomer samples were cut using a dumbbell-shaped cutter to dimensions of 1 mm × 2 mm × 12 mm, with a quantity of n=5. Tensile tests were then performed using an Instron 5966 electronic universal testing machine equipped with a 1 kN load sensor, stretched at a rate of 10 mm / min until fracture. The elastic modulus, breaking strength, and elongation at break were calculated from the resulting engineering stress-strain curves. The elastic modulus was calculated using the secant modulus at 2% strain.

[0028] Example 1 A method for one-step synthesis of polyurea elastomer without chain extender includes the following steps: 10g of polyethylene glycol with a molecular weight of 4000 Da was dissolved in 10ml of DMF solution (solubility parameter ≈ 12.1) and heated to 60℃; then 1.5g of MDI was melted at 60℃ and added to the DMF solution containing polyethylene glycol; the mixture was stirred at 2500r / min for 3min to ensure that all components were fully mixed and to remove any air bubbles or dissolved gases, resulting in a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, resulting in polyurea elastomer.

[0029] Example 2 A method for one-step synthesis of polyurea elastomer without chain extender includes the following steps: 10g of polyethylene glycol with a molecular weight of 4000 Da was dissolved in 10ml of DMF solution and heated to 60℃; then 0.94g of MDI was melted at 60℃ and added to the DMF solution containing polyethylene glycol; the mixture was stirred at 2500r / min for 3min to ensure that all components were fully mixed and to remove any air bubbles or dissolved gases, resulting in a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, resulting in polyurea elastomer.

[0030] Example 3 A method for one-step synthesis of polyurea elastomer without chain extender includes the following steps: 10g of polyethylene glycol with a molecular weight of 4000 Da was dissolved in 10ml of THF solution (solubility parameter ≈ 9.3) and heated to 60℃; then 1.5g of MDI was melted at 60℃ and added to the THF solution containing polyethylene glycol; the mixture was stirred at 2500r / min for 3min to ensure that all components were fully mixed and to remove any air bubbles or dissolved gases, resulting in a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, resulting in polyurea elastomer.

[0031] Example 4 A method for one-step synthesis of polyurea elastomer without chain extender includes the following steps: 10g of polyethylene glycol with a molecular weight of 2000 Da was dissolved in 10ml of DMF solution and heated to 60℃; then 3g of MDI was melted at 60℃ and added to the DMF solution containing polyethylene glycol; the mixture was stirred at 2500r / min for 3min to ensure that the components were fully mixed and to remove any air bubbles or dissolved gases, resulting in a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, resulting in polyurea elastomer.

[0032] Example 5 A method for one-step synthesis of polyurea elastomer without chain extender includes the following steps: 10g of polyethylene glycol with a molecular weight of 6000 Da was dissolved in 10ml of DMF solution and heated to 60℃; then 1g of MDI was melted at 60℃ and added to the DMF solution containing polyethylene glycol; the mixture was stirred at 2500r / min for 3min to ensure that the components were fully mixed and to remove any air bubbles or dissolved gases, resulting in a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, resulting in polyurea elastomer.

[0033] Example 6 A method for one-step synthesis of polyurea elastomer without chain extender includes the following steps: 10g of polyethylene glycol with a molecular weight of 6000 Da was dissolved in 12ml of DMF solution and heated to 60℃; then 1g of MDI was melted at 60℃ and added to the DMF solution containing polyethylene glycol; the mixture was stirred at 2500r / min for 3min to ensure that the components were fully mixed and to remove any air bubbles or dissolved gases, resulting in a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, resulting in polyurea elastomer.

[0034] Example 7 A method for one-step synthesis of polyurea elastomer without chain extender includes the following steps: 10g of polyethylene glycol with a molecular weight of 6000 Da was dissolved in 15ml of THF solution and heated to 60℃; then 1g of MDI was melted at 60℃ and added to the DMF solution containing polyethylene glycol; the mixture was stirred at 2500r / min for 3min to ensure that the components were fully mixed and to remove any air bubbles or dissolved gases, resulting in a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, resulting in polyurea elastomer.

[0035] Comparative Example 1 A method for producing a polyurea elastomer includes the following steps: 10g of polyethylene glycol with a molecular weight of 4000 Da was heated to 60℃ and melted; then 0.75g of MDI was melted at 60℃. The two were mixed and stirred at 2500r / min for 3min to ensure that the components were fully mixed and to remove any air bubbles or dissolved gases, thus obtaining a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, thus obtaining polyurea elastomer.

[0036] Comparative Example 2 A method for producing a polyurea elastomer includes the following steps: 10g of polyethylene glycol with a molecular weight of 4000 Da was heated to 60℃ and melted; then 1.46g of MDI was melted at 60℃. The two were mixed and 0.037g of chain extender 1,4-butanediol was added. The mixture was then stirred at 2500r / min for 3min to ensure that all components were fully mixed and to remove any air bubbles or dissolved gases, resulting in a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, resulting in polyurea elastomer.

[0037] Comparative Example 3 A method for producing a polyurea elastomer includes the following steps: 10g of polyethylene glycol with a molecular weight of 2000 Da was heated to 60℃ and melted; then 3g of MDI was melted at 60℃. The two were mixed and stirred at 2500r / min for 3min to ensure that the components were fully mixed and to remove any air bubbles or dissolved gases, thus obtaining a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, thus obtaining polyurea elastomer.

[0038] Comparative Example 4 A method for producing a polyurea elastomer includes the following steps: 10g of polyethylene glycol with a molecular weight of 4000 Da was heated to 60℃ and melted; then 1.5g of MDI was melted at 60℃. The two were mixed and stirred at 2500r / min for 3min to ensure that the components were fully mixed and to remove any air bubbles or dissolved gases, thus obtaining a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, thus obtaining polyurea elastomer.

[0039] Comparative Example 5 A method for producing a polyurea elastomer includes the following steps: 10g of polyethylene glycol with a molecular weight of 6000 Da was heated to 60℃ and melted; then 1g of MDI was melted at 60℃. The two were mixed and stirred at 2500r / min for 3min to ensure that the components were fully mixed and to remove any air bubbles or dissolved gases, thus obtaining a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, thus obtaining polyurea elastomer.

[0040] Comparative Example 6 A method for producing a polyurea elastomer includes the following steps: 10g of polyethylene glycol with a molecular weight of 4000 Da was dissolved in 10ml of toluene solution (solubility parameter 8.9) and heated to 60℃; then 1.5g of MDI was melted at 60℃ and added to the toluene solution containing polyethylene glycol; the mixture was stirred at 2500r / min for 3min to ensure that all components were fully mixed and to remove any air bubbles or dissolved gases, resulting in a mixture. The mixture was then placed in a 60℃ oven for 8h to cure completely, resulting in polyurea elastomer.

[0041] To confirm the successful synthesis and precise construction of the topology of polyurea, this invention selected three representative samples (Example 1, Comparative Example 2, and Comparative Example 4) for systematic structural characterization. The chemical structure was verified by 1H and 1C NMR spectroscopy; the degree of reaction of characteristic functional groups was confirmed by infrared spectroscopy. Furthermore, for Comparative Example 2, which did not undergo crosslinking, molecular weight testing was performed, confirming that it had been successfully synthesized as a linear prepolymer with the expected structure, thus laying the foundation for the subsequent formation of the crosslinked network.

[0042] like Figure 2 As shown, the characteristic peaks at 9.6 ppm and 8.5 ppm belong to urea groups (-NC(=O)-NH-) and carbamate groups (-OC(=O)-NH-), respectively, while the signal in the 7.0-7.35 ppm range corresponds to aromatic protons. The intensity of these characteristic peaks shows a regular variation in Example 1, Comparative Example 2, and Comparative Example 4, confirming that their chemical composition is consistent with the design expectations.

[0043] like Figure 3-4 As shown, both Example 1 and Comparative Example 4 exhibit peak broadening due to the cross-linking structure, a typical characteristic of enhanced network structure rigidity. Specifically, the main signal appears at 3.6 ppm, corresponding to the methylene groups in the polyethylene glycol backbone, confirming that different polymer topologies can be effectively constructed by controlling the isocyanate stoichiometry.

[0044] like Figure 5 As shown, gel permeation chromatography confirmed that the polyurea elastomer prepared in Comparative Example 2 had a high molecular weight, indicating that the chain extension reaction proceeded efficiently, consistent with the observed curing process.

[0045] like Figure 6 As shown, the stretching vibration peak of the urea carbonyl group in the cyclic cross-linked topology (~1650 cm⁻¹) -1 The peak of the carbonyl stretching vibration of carbamate (~1725 cm⁻¹) -1 The intensity of ) increased significantly, while the characteristic peak of imine (NH) (1540 cm⁻¹) also increased. -1 This demonstrates that Example 1, Comparative Example 2, and Comparative Example 4 all formed macrocyclic oligourea linkage structures.

[0046] Table 1. Low-field NMR and crosslinking specific gravity data of polyurea elastomers of Examples 1-7 and Comparative Examples 1-6

[0047] The crosslinking ratio in Table 1 can be calculated using the following formula (1): Formula (1) in, It is the crosslinking ratio; T2A and T2B are relaxation times, respectively; and It is a coefficient, given by the testing instrument; Low-field NMR analysis revealed that the crosslinking density of polyurea elastomers was significantly affected by the isocyanate index (R value, i.e., the [NCO] / [OH] molar ratio) and the reaction medium (i.e., the solubility parameter). When the R value was between 1.5 and 2.4 (Examples 1-3), the crosslinking density of the material was higher than 40%. However, for the same R value, the higher the molecular weight of polyethylene glycol, the lower the crosslinking density. This is because the chain segments become longer, resulting in a longer average distance between urethane bonds and an increased degree of freedom in the molecular chain. On the other hand, the crosslinking point density decreased, ultimately leading to a decrease in the crosslinking density as the molecular weight of polyethylene glycol in the system increased. Conversely, when the R value was below 1.5 (Comparative Examples 1-3), even under solvent-free conditions, the crosslinking density decreased to below 25% due to the intrinsic insufficiency of the crosslinking point density in the system. If the reaction was carried out in a solvent with a solubility parameter less than or equal to 8.9 (Comparative Example 6), the crosslinking density increased to 67.2%.

[0048] Table 2 Mechanical properties of polyurea elastomers from Examples 1-7 and Comparative Examples 1-6

[0049] As can be seen from Tables 1 and 2, when the R value drops below 1.5, the crosslinking density of the polyurea system is significantly too low. This structural defect directly leads to the elastomer's mechanical strength failing to meet application requirements. As shown in Comparative Examples 1 and 2, their fracture strength (both <2 MPa) is far below the benchmark, experimentally confirming that the proportion of functional groups below the critical threshold cannot support the formation of a sufficiently complete crosslinked network.

[0050] Under a fixed R value, comparisons of Example 1, Comparative Example 4, and Comparative Example 6 show that the introduction of the solvent and its solubility parameter have a decisive influence on the mechanical properties of polyurea elastomers. Specifically: the solvent-free system (Comparative Example 4) can achieve a breaking strength of 6 MPa, but the elongation at break is only 42%, exhibiting brittleness; when using the poor solvent toluene (solubility parameter = 8.9, Comparative Example 6), the poor dispersion of the raw materials leads to an abnormally high crosslinking density. Although the strength is increased to 12 MPa, the elongation at break is still limited to 89%, exhibiting strong and tough characteristics; while when a good solvent is used (Example 1), it plays the role of a "molecular lubricant" in the system, significantly promoting the topological reconstruction ability of polymer segments, thereby achieving an elongation at break of up to 1600% while maintaining a crosslinking density of 41.2% and high breaking strength, demonstrating an excellent combination of strength and toughness.

[0051] The above embodiments are merely illustrative of several implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the invention patent. For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A process for the one-step synthesis of polyurea elastomers without chain extender, characterized in that, Includes the following steps: The polyether diol was dissolved in a solvent, a diisocyanate curing agent was added, and the mixture was stirred to obtain the polyurea elastomer. Wherein, the solubility parameter of the solvent is >8.9; the diisocyanate curing agent is calculated based on NCO groups, the polyether diol is calculated based on hydroxyl groups, the molar ratio of the NCO groups to the hydroxyl groups is 1.5~2.4, and the mass ratio of the polyether diol to the solvent is 1:(0.8~2).

2. A process for one step synthesis of polyurea elastomer without chain extender as claimed in claim 1 wherein, The polyether diol includes at least one of polyethylene glycol and polytetrahydrofuran.

3. A process for one step synthesis of polyurea elastomer without chain extender as claimed in claim 2 wherein, The molecular weight of the polyethylene glycol and polytetrahydrofuran is 200-20000 Dal.

4. A process for one step synthesis of polyurea elastomer without chain extender as claimed in claim 1 wherein, The solvent includes at least one of N,N-dimethylformamide and tetrahydrofuran.

5. The method for one-step synthesis of polyurea elastomer without chain extender according to claim 1, wherein the diisocyanate curing agent comprises at least one selected from isoflurane diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, L-lysine diisocyanate, phenyl diisocyanate, terephthalic diisocyanate, diphenylmethane diisocyanate, 2,4-toluene diisocyanate, and 2,6-toluene diisocyanate.

6. The process for one step synthesis of polyurea elastomers without chain extender as claimed in claim 1 wherein, The process also includes the following steps: after the polyether diol is dissolved in the solvent, the temperature is raised to 40-80°C, the diisocyanate curing agent is added, and the mixture is stirred at a speed of 1800-2500 r / min for 3-10 min to obtain a mixture.

7. A process for one step synthesis of polyurea elastomer without chain extender as claimed in claim 6 wherein, The process also includes the following steps: the mixture is placed at 60-100℃ and cured for 6-12 hours to obtain the polyurea elastomer.

8. A polyurea elastomer prepared by the method of one-step synthesis of polyurea elastomer without chain extender according to any one of claims 1 to 7, characterized in that, Elongation at break ≥500%, breaking strength ≥3 MPa.

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