A polyurea composite and a method for producing the same

Abstract

The application discloses a kind of polyurea composite and preparation method thereof, it is related to composite field, by isocyanate component and amino component reaction formation;The amino component includes polyether amine and the amino compound containing polycaprolactone chain segment;The polycaprolactone chain segment is crystallizable chain segment, and the number average molecular weight of the polycaprolactone chain segment is 1000~4000g / mol;The mass ratio of the amino compound containing polycaprolactone chain segment and the polyether amine is (1:9)~(5:5);Wherein, the polycaprolactone chain segment can form stress-induced crystalline phase under high strain rate.The application can simultaneously improve the flexibility and impact resistance of polyurea composite.

Description

Technical Field

[0001] This invention relates to the field of composite materials, and more specifically to a polyurea composite material and its preparation method. Background Technology

[0002] Polyurea materials are polymers formed by the rapid reaction of isocyanate and amino components. They possess characteristics such as fast curing speed, excellent mechanical properties, good wear resistance, and strong corrosion resistance, and are widely used in protective coatings, energy-absorbing structures, transportation, construction engineering, and special protection applications. Particularly in the field of impact protection, polyurea materials can absorb the energy carried by external loads through their own deformation, thereby reducing impact damage, and have therefore attracted widespread attention.

[0003] As the application scenarios of polyurea materials continue to expand, the requirements for their impact resistance are constantly increasing. In existing technologies, to improve the impact resistance of polyurea materials, modifications to the polyurea system are typically made by increasing the crosslinking density, introducing rigid segments, or adding reinforcing fillers. Increasing the crosslinking density or introducing rigid segments can improve the material strength, while adding inorganic fillers or fiber reinforcements can improve the material's load-bearing capacity, thereby improving the impact resistance of polyurea materials.

[0004] However, the aforementioned methods of improving material rigidity or crosslinking density can easily affect the material's flexibility, making it difficult for polyurea composites to simultaneously meet the requirements for impact resistance and flexibility. Summary of the Invention

[0005] This invention aims to address, to a certain extent, one of the technical problems in related technologies. To this end, this invention provides a polyurea composite material and its preparation method, which can simultaneously improve the flexibility and impact resistance of the polyurea composite material.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A polyurea composite material is formed by reacting an isocyanate component and an amino component; The amino component includes polyetheramines and amino compounds containing polycaprolactone segments; The polycaprolactone segment is a crystallizable segment, and the number average molecular weight of the polycaprolactone segment is 1000-4000 g / mol. The mass ratio of the amino compound containing the polycaprolactone segment to the polyetheramine is (1:9) to (5:5). The polycaprolactone segments can form a stress-induced crystalline phase under high strain rates.

[0007] Polyetheramine molecular segments have good flexibility, which can improve the deformation ability of polyurea composites; amino compounds containing polycaprolactone segments can introduce crystallizable segments into the polyurea system, enabling the material to form a stress-induced crystalline phase under high strain rate conditions, thereby improving the impact resistance of the material.

[0008] In this application, polyetheramine forms polyether segments in the polyurea composite material. These polyether segments possess good segmental mobility and flexible deformation capabilities, thus imparting high elongation at break and flexibility to the polyurea composite material. Simultaneously, an amino compound containing polycaprolactone segments introduces polycaprolactone segments into the polyurea network. These polycaprolactone segments are crystallizable and, under normal conditions, can maintain the material's flexible characteristics together with the polyether segments. However, under high strain rate impact conditions, they can undergo orientational alignment and form a stress-induced crystalline phase. It should be noted that not all polycaprolactone segments can undergo orientational alignment and form a stress-induced crystalline phase under high strain rate impact conditions; only the polycaprolactone segments defined in this application (i.e., polycaprolactone segments with a number average molecular weight of 1000–4000 g / mol and located in the polyurea system of this application) have the ability to form a stress-induced crystalline phase. The formed stress-induced crystalline phase can serve as a temporary reinforcing structure, improving the material's ability to absorb impact energy. Furthermore, by controlling the number-average molecular weight of the polycaprolactone segments within the range of 1000–4000 g / mol, and by controlling the mass ratio of the amino compound containing the polycaprolactone segments to the polyetheramine within the range of (1:9)–(5:5), a balance is maintained between the flexibility provided by the polyether segments and the impact reinforcement provided by the polycaprolactone segments. Therefore, this application can improve impact resistance while maintaining the material's flexibility, achieving a balance between strength and toughness.

[0009] Optionally, the polyetheramine is selected from at least one of polyetheramine D2000 and polyetheramine D400; the amino compound containing the polycaprolactone segment is selected from at least one of amino-terminated polycaprolactone and polycaprolactone diol-terminated urethane prepolymers.

[0010] Optionally, the -NCO content of the isocyanate component is 5 to 15 wt%.

[0011] Optionally, the isocyanate component is prepared by reacting diisocyanate with a polyol, wherein the diisocyanate is selected from one or more of isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate and dicyclohexylmethane diisocyanate.

[0012] Optionally, the polyurea composite material further includes dynamic crosslinking units containing disulfide bonds or borate ester bonds.

[0013] Optionally, the dynamic crosslinking unit is introduced by 4,4'-dithiodiphenylamine or 4-hydroxyphenylboronic acid.

[0014] Optionally, after the polyurea composite material is heat-treated at 80–120°C, the stress-induced crystalline phase formed by the polycaprolactone segments is at least partially melted.

[0015] Optionally, the high strain rate is not less than 10. 3 s -1 The strain rate.

[0016] Furthermore, the present invention also provides a method for preparing a polyurea composite material, the method comprising the following steps: S1, Prepare an isocyanate component, wherein the isocyanate component is prepared by reacting diisocyanate with a polyol, wherein the polyol includes polyether polyol and / or polyester polyol, and the molar ratio of the diisocyanate to the polyol is (1.5:1) to (2.5:1). S2, mixing polyetheramine with an amino compound containing polycaprolactone segments to obtain an amino component; S3, the isocyanate component and the amino component are mixed and cured to obtain the aforementioned polyurea composite material.

[0017] Optionally, in step S1, the polyol and the diisocyanate are reacted at 70-90°C for 2-4 hours to obtain the isocyanate component; in step S2, the amino component is mixed at 40-60°C to obtain the isocyanate component; in step S3, the curing is carried out at 60-100°C for 12-36 hours.

[0018] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments and accompanying drawings. The preferred embodiments or means of the present invention will be shown in detail in conjunction with the accompanying drawings, but are not intended to limit the technical solutions of the present invention. In addition, each of these features, elements and components appearing in the following text and drawings is a plurality of, and different symbols or numbers are used for convenience of representation, but all represent parts with the same or similar construction or function. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings: Figure 1 This is a schematic flowchart of the preparation method of the polyurea composite material of the present invention. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described are intended to explain the present invention and should not be construed as limiting the invention.

[0021] The terms "an embodiment," "example," or "example" used in this specification refer to a particular feature, structure, or characteristic described in connection with the embodiment itself that may be included in at least one embodiment disclosed in this application. The phrase "in an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0022] Example: This example provides a polyurea composite material formed by the reaction of isocyanate component and amino component.

[0023] In this process, the isocyanate component refers to the reactive component containing isocyanate groups (-NCO), which can undergo an addition reaction with amino groups to form a urea bond structure. The amino component refers to the reactive component containing active amino groups, which can react with the isocyanate component to construct a polyurea network. By reacting the isocyanate and amino components, different chain segments can be chemically bonded to the same polyurea network, thereby forming a polyurea composite material with a continuous network structure. Therefore, the isocyanate and amino components are not simply physically mixed, but together constitute the main structure of the polyurea composite material after the reaction.

[0024] In this embodiment, the amino component includes polyetheramine and an amino compound containing polycaprolactone segments (PCL). Polyetheramine is a compound whose molecular chain contains polyether segments and has amino groups at its ends; it can react with the isocyanate component and enter the polyurea network. The polyether segments formed by polyetheramine have good segment mobility, providing deformability and flexibility to the polyurea composite material. The amino compound containing polycaprolactone segments is an amino compound whose molecular structure contains polycaprolactone segments and can participate in the isocyanate reaction; it can introduce polycaprolactone segments into the polyurea network after the reaction. Polycaprolactone segments are polyester segments formed from caprolactone structural units; they have crystallizable properties and can undergo segment orientation and form a crystalline structure under certain external forces. By simultaneously incorporating polyetheramine and an amino compound containing polycaprolactone segments into the amino component, the polyurea composite material can possess both flexible and crystallizable segments, thereby providing a structural basis for stress-induced crystallization under impact conditions.

[0025] Specifically, the polycaprolactone (PCL) segments are crystallizable segments with a number-average molecular weight (NMR) of 1000–4000 g / mol. NMR is a parameter characterizing the average length of polymer segments, which can be determined by gel permeation chromatography or supplier calibration data. In this embodiment, the NMR of the PCL segments is within the range of 1000–4000 g / mol. At this range, the PCL segments have the segment length required to form a crystalline structure and can maintain a certain degree of mobility within the polyurea network. If the PCL segments are too short, their ability to arrange themselves regularly is insufficient, which is not conducive to forming effective crystalline regions. If the PCL segments are too long, their own crystallization tendency is enhanced, which can easily lead to excessive hardening or decreased flexibility of the material under non-impact conditions. Therefore, by controlling the NMR of the PCL segments, a balance can be achieved between segment mobility and crystallization ability, allowing the material to maintain flexibility under normal conditions and form a crystalline reinforced structure under high strain rates.

[0026] In this embodiment, the mass ratio of the amino compound containing polycaprolactone segments to the polyetheramine is (1:9) to (5:5). This mass ratio is the feeding mass ratio between the amino compound containing polycaprolactone segments that participate in forming the amino component and the polyetheramine. By controlling this mass ratio, the ratio between crystallizable segments and flexible segments in the polyurea composite material can be adjusted. When the proportion of the amino compound containing polycaprolactone segments is too low, the number of crystallizable segments in the polyurea network is insufficient, resulting in fewer stress-induced crystalline phases formed under high strain rates, and the impact enhancement effect of the material is limited. When the proportion of the amino compound containing polycaprolactone segments is too high, the proportion of crystallizable segments in the polyurea network is too large, which can easily affect the flexibility of the material under normal conditions. Therefore, by controlling the mass ratio of the two within the range of (1:9) to (5:5), a suitable ratio of flexible segments and crystallizable segments in the polyurea composite material can be maintained, thereby taking into account both flexibility and impact resistance.

[0027] In this embodiment, the polyetheramine can be selected from at least one of polyetheramine D2000 and polyetheramine D400. Polyetheramine D2000 is a polyetheramine with a relatively high number-average molecular weight and longer chain segments, which can improve the flexibility and elongation of the polyurea composite material. Polyetheramine D400 is a polyetheramine with a relatively low number-average molecular weight and shorter chain segments, which can improve the structural density and dimensional stability of the polyurea network. Both can be used alone or in combination. When used in combination, the flexibility, strength, and post-curing network structure of the polyurea composite material can be further controlled by adjusting their ratio.

[0028] In this embodiment, the amino compound containing polycaprolactone segments can be selected from at least one of amino-terminated polycaprolactone and polycaprolactone diol-terminated urethane prepolymers. Amino-terminated polycaprolactone is a compound whose molecular chain contains polycaprolactone segments and has amino groups at its ends; it can directly react with isocyanate components and enter the polyurea network. Polycaprolactone diol-terminated urethane prepolymers are prepolymers based on polycaprolactone diol and incorporating urethane structures; their molecular structure contains polycaprolactone segments and can participate in the construction of the polyurea system as reactive components containing polycaprolactone segments. For this prepolymer, the end-capping method can be controlled to give it active groups capable of reacting with isocyanate components, thereby introducing polycaprolactone segments into the polyurea composite material. Both types of compounds can provide polycaprolactone segments, giving the polyurea network a source of crystallizable segments.

[0029] In this embodiment, the -NCO content of the isocyanate component is 5–15 wt%. The -NCO content refers to the percentage of isocyanate groups in the total mass of the isocyanate component, which can be determined by di-n-butylamine back titration. The -NCO content characterizes the reactivity of the isocyanate component and its ability to form a network structure after reacting with the amino component. When the -NCO content is too low, there are insufficient reactive groups in the isocyanate component, which may lead to insufficient polyurea network formation. When the -NCO content is too high, the reactivity is too strong or the degree of crosslinking is too high, which may make the material too hard and affect its flexibility. Controlling the -NCO content within the range of 5–15 wt% ensures sufficient reaction between the isocyanate component and the amino component, while also ensuring that the formed polyurea network has suitable structural stability.

[0030] In this embodiment, the isocyanate component is prepared by reacting diisocyanate with a polyol. The diisocyanate can be selected from one or more of isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate. Specifically, isophorone diisocyanate can provide an alicyclic structure, which is beneficial to improving the weather resistance and structural stability of the material. Hexamethylene diisocyanate can provide flexible aliphatic segments, which is beneficial to improving the flexibility of the material. Diphenylmethane diisocyanate can provide an aromatic rigid structure, which is beneficial to improving the strength of the material. Dicyclohexylmethane diisocyanate can provide an alicyclic rigid structure, which is beneficial to improving the mechanical stability of the material. After the above diisocyanates react with the polyol, an isocyanate component is formed, allowing the isocyanate groups to participate in the subsequent polyurea reaction in the form of prepolymers, thereby improving component compatibility and reaction uniformity, and thus obtaining a polyurea composite material with a more uniform structure.

[0031] In this embodiment, the polyurea composite material may further include dynamic crosslinking units containing disulfide bonds or borate ester bonds. Dynamic crosslinking units refer to structural units capable of reversible breakage, recombination, or bond exchange under certain external conditions. Disulfide bonds refer to structures containing -SS- bonds, which can undergo dynamic exchange under thermal, mechanical, or redox conditions. Borate ester bonds refer to reversible bonding structures formed by boric acid groups and hydroxyl groups, which can undergo reversible dissociation and recombination under certain conditions. By introducing the aforementioned dynamic crosslinking units into the polyurea composite material, an adjustable dynamic bonding structure can be provided in the polyurea network, giving the material better structural rearrangement capabilities under impact or subsequent heat treatment.

[0032] In this embodiment, the dynamic crosslinking unit can be introduced by 4,4'-dithiodiphenylamine or 4-hydroxyphenylboronic acid. 4,4'-dithiodiphenylamine contains a disulfide bond structure and also has an amino group structure capable of participating in the reaction of the polyurea system. Its introduction allows for the formation of dynamic crosslinking units containing disulfide bonds within the polyurea network. 4-hydroxyphenylboronic acid contains borate groups and hydroxyl structures, enabling the formation of dynamic crosslinking units containing borate ester bonds within the system. By selecting the above compounds, the dynamic crosslinking structure can be stably introduced into the polyurea composite material. Therefore, the polyurea composite material not only possesses the stress-induced crystallization ability provided by the polycaprolactone segments but also enhances the adjustability of the network structure through the dynamic crosslinking unit.

[0033] In this embodiment, the polycaprolactone segments can form a stress-induced crystalline phase under high strain rates. High strain rate refers to a strain rate of not less than 10... 3 s -1 The deformation conditions. Strain rate is the rate at which the strain changes in a material per unit time, used to describe the deformation speed of the material. Stress-induced crystalline phase is a crystalline structure formed by the orientation and alignment of crystallizable chain segments under external stress. Specifically, when polyurea composites are subjected to high strain rate impact, the polycaprolactone segments in the polyurea network rapidly orient along the direction of force, increasing the regularity of the chain segment arrangement, thereby forming a stress-induced crystalline phase. This stress-induced crystalline phase can serve as a temporary physical reinforcement structure, limiting excessive chain segment slippage and participating in load transfer, thereby improving the material's ability to absorb impact energy.

[0034] Furthermore, to ensure that the formation of stress-induced crystalline phases can be confirmed by those skilled in the art, this embodiment also provides corresponding characterization methods. These methods can be applied to unimpacted polyurea composite materials and those subjected to strain rates of not less than 10... 3 s -1Polyurea composite materials subjected to impact under certain conditions were subjected to differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAN), or small-angle X-ray scattering (SAXS). When the impacted sample showed enhanced melting peaks, enhanced crystallization diffraction peaks, or changes in scattering signals corresponding to polycaprolactone segments compared to the unimpacted sample, it could be confirmed that polycaprolactone segments formed a stress-induced crystalline phase under high strain rate conditions. DSC was used to detect the melting behavior of the crystalline phase in the material, WAN was used to detect the crystal structure and crystallization peaks, and SAXS was used to observe segment aggregation and phase structure changes. These detection methods make the formation process of the stress-induced crystalline phase verifiable.

[0035] In this embodiment, after heat treatment at 80–120°C, the stress-induced crystalline phase formed by the polycaprolactone segments of the polyurea composite material at least partially melts. Heat treatment refers to placing the impacted polyurea composite material at a set temperature for a certain period to adjust its internal crystalline structure. Because the crystalline phase formed by the polycaprolactone segments has thermal response characteristics, when the heat treatment temperature reaches 80–120°C, the stress-induced crystalline phase can at least partially melt, reducing or eliminating the crystalline regions. After the crystalline phase melts, the polycaprolactone segments regain their mobility, and the temporary reinforcing structure formed by impact is weakened or eliminated, thereby restoring the material's good flexible deformation capacity. This process can be confirmed by differential scanning calorimetry or X-ray diffraction. If the melting peak corresponding to the polycaprolactone segments weakens or the diffraction peak decreases after heat treatment, it indicates that the stress-induced crystalline phase has at least partially melted.

[0036] Furthermore, the polyurea composite material in this embodiment can be prepared in the following manner. For example... Figure 1 As shown, an isocyanate component is first prepared by reacting diisocyanate with a polyol. The polyol includes one or both of polyether polyols and polyester polyols, with a molar ratio of diisocyanate to polyol of 1.5:1 to 2.5:1. This molar ratio is used to control the content of residual -NCO groups in the isocyanate component, ensuring that the isocyanate component meets the requirements for subsequent reaction with the amino component. Next, a polyether amine is mixed with an amino compound containing polycaprolactone segments to obtain the amino component. Since both the polyether amine and the amino compound containing polycaprolactone segments have active groups that participate in the reaction, pre-mixing improves the uniformity of the subsequent reaction. Subsequently, the isocyanate component and the amino component are mixed and cured, allowing the isocyanate groups to react with the amino groups to form a polyurea network, ultimately yielding a polyurea composite material. The polyether polyol can be polytetramethylene ether glycol (PTMEG) or polypropylene glycol (PPG), etc. The polyester polyol can also be polyadipate glycol, polycaprolactone glycol, etc.

[0037] In the preparation process, polyols and diisocyanates can react at 70–90°C for 2–4 hours to obtain the isocyanate component. This temperature and time range allows the diisocyanate and polyol to react fully and form an isocyanate component with the target -NCO content. The amino component can be mixed at 40–60°C, which is beneficial for reducing the viscosity of the system and improving the mixing uniformity. After mixing the isocyanate component and the amino component, it can be cured at 60–100°C for 12–36 hours to allow the polyurea reaction to proceed fully and form a stable polyurea network. As a result, the obtained polyurea composite material has flexible segments provided by polyetheramine, crystallizable segments provided by polycaprolactone segments, and optional dynamic crosslinking units, thereby forming a stress-induced crystalline phase and improving impact resistance under high strain rate impact conditions.

[0038] In summary, this embodiment forms a polyurea composite material through the reaction of isocyanate and amino components, and incorporates polyetheramine and amino compounds containing polycaprolactone segments into the amino component, giving the material both flexible and crystallizable segments. By controlling the number-average molecular weight of the polycaprolactone segments and the mass ratio between the amino compounds containing polycaprolactone segments and the polyetheramine, the polycaprolactone segments can form a stress-induced crystalline phase under high strain rate conditions. Furthermore, by incorporating dynamic crosslinking units and heat treatment conditions, the internal structure of the material can be further adjusted. Therefore, this embodiment improves the impact energy absorption capacity and impact resistance of the polyurea composite material under high strain rate impact conditions while maintaining the material's flexibility.

[0039] Preparation Example 1: This preparation example provides a method for preparing a polyurea composite material, including the following steps.

[0040] 50g of dehydrated polytetramethylene ether glycol was added to a three-necked flask and stirred under vacuum at 120°C for 2 hours to remove residual moisture. The temperature was then lowered to 50°C, and 12g of isophorone diisocyanate and a catalyst were added. The mixture was then heated to 80°C under nitrogen protection and reacted for 3 hours to obtain the isocyanate component. This isocyanate component is an isocyanate-terminated prepolymer with a -NCO content of approximately 6 wt%. The catalyst was an organometallic catalyst or a tertiary amine catalyst. Specifically, the organometallic catalyst was dibutyltin dilaurate, dibutyltin oxide, bismuth 2-ethylhexanoate, etc. The tertiary amine catalyst could be triethylamine (TEA).

[0041] 20g of terminal amino-terminated polycaprolactone and 80g of polyetheramine D2000 were added to a container and stirred at 50°C for 1 hour to obtain the amino component. The number-average molecular weight of the polycaprolactone segments in the terminal amino-terminated polycaprolactone was 2000 g / mol, and the mass ratio of terminal amino-terminated polycaprolactone to polyetheramine D2000 was 2:8.

[0042] The obtained amino component was added to the isocyanate component and mixed rapidly. The mixture was then poured into a mold and cured at 80°C for 24 hours. After demolding, a polyurea composite material was obtained.

[0043] Preparation Example 2: This preparation example provides a method for preparing a polyurea composite material, including the following steps.

[0044] This preparation example is basically the same as Preparation Example 1, except that 5g of 4,4'-dithiodiphenylamine was added during the preparation of the amino component. Specifically, 20g of terminal amino polycaprolactone, 80g of polyetheramine D2000, and 5g of 4,4'-dithiodiphenylamine were stirred and mixed at 50°C for 1 hour to obtain an amino component containing a disulfide bond structure. Subsequently, this amino component was mixed with the isocyanate component and cured to obtain a polyurea composite material containing disulfide bond dynamic crosslinking units.

[0045] Preparation Example 3: This preparation example provides a method for preparing a polyurea composite material, including the following steps.

[0046] This preparation example is basically the same as Preparation Example 1, except that 3g of 4-hydroxyphenylboronic acid was added during the preparation of the amino component. Specifically, 20g of terminal amino polycaprolactone, 80g of polyetheramine D2000, and 3g of 4-hydroxyphenylboronic acid were stirred and mixed at 50°C for 1 hour to obtain an amino component with a borate ester bond structure. Subsequently, this amino component was mixed with the isocyanate component and cured to obtain a polyurea composite material with borate ester bond dynamic crosslinking units.

[0047] Preparation Example 4: This preparation example provides a method for preparing a polyurea composite material, including the following steps.

[0048] This preparation example is basically the same as Preparation Example 1, except that the terminal amino-terminated polycaprolactone in Preparation Example 1 is replaced with terminal amino-terminated polycaprolactone with a number-average molecular weight of 3000 g / mol. In the resulting polyurea composite material, the number-average molecular weight of the polycaprolactone segment is 3000 g / mol, and the mass ratio of terminal amino-terminated polycaprolactone to polyetheramine D2000 remains 2:8.

[0049] Preparation Example 5: This preparation example provides a method for preparing a polyurea composite material, including the following steps.

[0050] This preparation example is basically the same as Preparation Example 1, except that the terminal amino polycaprolactone in Preparation Example 1 is replaced with terminal amino polycaprolactone with a number average molecular weight of 1000 g / mol. In the resulting polyurea composite material, the number average molecular weight of the polycaprolactone segment is 1000 g / mol, and the mass ratio of terminal amino polycaprolactone to polyetheramine D2000 remains 2:8.

[0051] Preparation Example 6: This preparation example provides a method for preparing a polyurea composite material, including the following steps.

[0052] This preparation example is basically the same as Preparation Example 1, except that the amounts of terminal amino-terminated polycaprolactone and polyetheramine D2000 in the amino component are adjusted. Specifically, 40g of terminal amino-terminated polycaprolactone and 60g of polyetheramine D2000 are stirred and mixed at 50°C for 1 hour to obtain the amino component. In this amino component, the mass ratio of terminal amino-terminated polycaprolactone to polyetheramine D2000 is 4:6. Subsequently, this amino component is mixed with the isocyanate component and cured to obtain the polyurea composite material.

[0053] Preparation Example 7: This preparation example provides a method for preparing a polyurea composite material, including the following steps.

[0054] This preparation example is basically the same as Preparation Example 1, the main difference being the adjustment of the amount of isophorone diisocyanate in the isocyanate component. Specifically, when preparing the isocyanate component, the amount of isophorone diisocyanate was adjusted to 18g, resulting in an isocyanate component with an -NCO content of approximately 9wt%. Subsequently, the amino component was prepared according to the method of Preparation Example 1, and the isocyanate component and amino component were mixed and cured to obtain a polyurea composite material.

[0055] Comparative Example 1: This comparative example provides a method for preparing a polyurea composite material, comprising the following steps.

[0056] This comparative example is essentially the same as Preparation Example 1, except that terminal amino-terminated polycaprolactone is not added to the amino component; instead, 20g of terminal amino-terminated polycaprolactone is replaced with an equal mass of polyetheramine D2000. The resulting amino component contains only polyetheramine D2000 and no polycaprolactone segments.

[0057] Comparative Example 2: This comparative example provides a method for preparing a polyurea composite material, comprising the following steps.

[0058] This comparative example is essentially the same as Preparation Example 1, except that the terminal amino-terminated polycaprolactone in Preparation Example 1 was replaced with terminal amino-terminated polycaprolactone with a number-average molecular weight of 5000 g / mol. In the resulting polyurea material, the number-average molecular weight of the polycaprolactone segments exceeds the range of 1000–4000 g / mol.

[0059] Comparative Example 3: This comparative example provides a method for preparing a polyurea composite material, comprising the following steps.

[0060] This comparative example is basically the same as Comparative Example 1, except that 5 wt% nano-silica was added as a reinforcing filler when the isocyanate component and amino component were mixed, and the mixture was stirred at high speed for 3 minutes to disperse the nano-silica in the reaction system. The mixture was then injected into a mold and cured to obtain a filler-reinforced polyurea material.

[0061] Test example: Performance tests were conducted on the samples obtained from each preparation example and comparative example. Static tensile strength and static elongation at break were tested according to ASTM D638 standard, at a test temperature of 25℃ and a tensile rate of 50 mm / min. High-speed impact absorption energy was tested according to ASTM D7136 standard, at a test temperature of 25℃ and an impact velocity of 10 m / s. The impact absorption energy improvement rate was based on the impact absorption energy of the polyurea composite material prepared in Comparative Example 1. The heat treatment recovery rate was tested as follows: the sample was first subjected to a high-speed impact test, then the impacted sample was placed in an 80℃ oven for 1 hour, followed by another high-speed impact absorption energy test. The heat treatment recovery rate was calculated based on the ratio of the high-speed impact absorption energy after heat treatment to the initial high-speed impact absorption energy. Material density was tested according to ASTM D792 standard using the Archimedes' displacement method, at a test temperature of 25℃. The test results are shown in Table 1.

[0062] Table 1. Test results of polyurea composite materials prepared in each comparative example and preparation example.

[0063] The test results from Preparation Example 1 and Comparative Examples 1 to 3 show that the high-velocity impact absorption capacity of the polyurea composite material is significantly improved after introducing an amino compound containing polycaprolactone segments. Comparative Example 1, without the introduction of polycaprolactone segments, has a high-velocity impact absorption energy of 24.8 J / m³. Although nano-silica was added as a reinforcing filler in Comparative Example 3, its high-velocity impact absorption energy was only 35.1 J / m³, showing a limited improvement, and the material density increased. In Preparation Example 1, after introducing polycaprolactone segments with a number-average molecular weight of 2000 g / mol, the high-velocity impact absorption energy increased to 76.8 J / m³ while maintaining a high elongation at break. This indicates that the introduction of polycaprolactone segments can effectively improve the impact energy absorption capacity of the polyurea composite material, and this improvement does not depend on the addition of a large amount of rigid filler.

[0064] The test results from Preparation Examples 1, 2, and 3 show that, based on the introduction of polycaprolactone segments, further introducing dynamic crosslinking units containing disulfide or borate ester bonds can further improve the high-speed impact absorption capacity and heat treatment recovery performance of polyurea composites. In Preparation Example 2, the introduction of disulfide bonds increased the high-speed impact absorption energy to 95.2 J / m³, and the heat treatment recovery rate reached 97%. In Preparation Example 3, the introduction of borate ester bonds increased the high-speed impact absorption energy to 90.5 J / m³, and the heat treatment recovery rate reached 95%. Compared to Preparation Example 1 without the introduction of dynamic crosslinking units, Preparation Examples 2 and 3 both exhibited higher impact absorption capacity and recovery performance. This demonstrates that dynamic crosslinking units can improve the structural recovery capacity of polyurea composites after impact.

[0065] The test results from Preparation Examples 1, 4, and 5, and Comparative Example 2, show that the number-average molecular weight of the polycaprolactone segments affects the flexibility and impact resistance of the polyurea composite material. In Preparation Example 5, the number-average molecular weight of the polycaprolactone segments was 1000 g / mol, resulting in a material with high elongation at break, but lower high-speed impact absorption energy than Preparation Examples 1 and 4. In Preparation Examples 1 and 4, the number-average molecular weights of the polycaprolactone segments were 2000 g / mol and 3000 g / mol, respectively, resulting in materials that maintained good elongation at break while exhibiting high high-speed impact absorption energy. In Comparative Example 2, the number-average molecular weight of the polycaprolactone segments was 5000 g / mol, resulting in a significantly decreased elongation at break and lower high-speed impact absorption energy than Preparation Examples 1 and 4. This indicates that controlling the number-average molecular weight of the polycaprolactone segments within the range of 1000–4000 g / mol is beneficial for polyurea composite materials to balance flexibility and impact resistance.

[0066] The test results from Preparation Examples 1, 6, and 7 show that the mass ratio of the amino compound containing polycaprolactone segments to the polyetheramine, as well as the -NCO content of the isocyanate component, affects the overall performance of the polyurea composite material. In Preparation Example 6, the mass ratio of the amino compound containing polycaprolactone segments to the polyetheramine was 4:6, resulting in improved tensile strength but decreased elongation at break and lower high-speed impact absorption energy compared to Preparation Example 1. In Preparation Example 7, the -NCO content of the isocyanate component was increased to approximately 9 wt%, resulting in improved tensile strength, but lower elongation at break and lower high-speed impact absorption energy compared to Preparation Example 1. This indicates that controlling the mass ratio of the amino compound containing polycaprolactone segments to the polyetheramine, as well as the -NCO content of the isocyanate component, is beneficial for achieving a balance between material strength, flexibility, and impact resistance.

[0067] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments above. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A polyurea composite material, characterized in that, Formed by the reaction of isocyanate and amino components; The amino component includes polyetheramines and amino compounds containing polycaprolactone segments; The polycaprolactone segment is a crystallizable segment, and the number average molecular weight of the polycaprolactone segment is 1000-4000 g / mol. The mass ratio of the amino compound containing the polycaprolactone segment to the polyetheramine is (1:9) to (5:5). The polycaprolactone segments can form a stress-induced crystalline phase under high strain rates; The polyetheramine is selected from at least one of polyetheramine D2000 and polyetheramine D400; the amino compound containing polycaprolactone segments is selected from at least one of amino-terminated polycaprolactone and polycaprolactone diol-terminated urethane prepolymers. The -NCO content of the isocyanate component is 5-15 wt%; The isocyanate component is prepared by reacting diisocyanate with polyol, wherein the diisocyanate is selected from one or more of isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate and dicyclohexylmethane diisocyanate; After the polyurea composite material is heat-treated at 80-120°C, the stress-induced crystalline phase formed by the polycaprolactone segments is at least partially melted. The high strain rate is not less than 10. 3 s -1 The strain rate.

2. The polyurea composite material according to claim 1, characterized in that, The polyurea composite material also includes dynamic crosslinking units containing disulfide bonds or borate ester bonds.

3. The polyurea composite material according to claim 2, characterized in that, The dynamic crosslinking unit is introduced by 4,4'-dithiodiphenylamine or 4-hydroxyphenylboronic acid.

4. A method for preparing a polyurea composite material, characterized in that, The preparation method includes the following steps: S1, Prepare an isocyanate component, wherein the isocyanate component is prepared by reacting diisocyanate with a polyol, wherein the polyol includes polyether polyol and / or polyester polyol, and the molar ratio of the diisocyanate to the polyol is (1.5:1) to (2.5:1). S2, mixing polyetheramine with an amino compound containing polycaprolactone segments to obtain an amino component; S3, the isocyanate component is mixed with the amino component and cured to obtain the polyurea composite material as described in any one of claims 1 to 3.

5. The preparation method according to claim 4, characterized in that, In step S1, the polyol and the diisocyanate are reacted at 70-90°C for 2-4 hours to obtain the isocyanate component; in step S2, the amino component is mixed at 40-60°C to obtain the product; in step S3, the curing is carried out at 60-100°C for 12-36 hours.

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