Thermoplastic elastomer with shape memory and self-repairing properties, and preparation method and application thereof

Abstract

The application discloses a thermoplastic elastomer with shape memory and self-repairing properties, and a preparation method and application thereof, and belongs to the technical field of rubber elastomer material preparation.The thermoplastic elastomer comprises the following preparation raw materials in parts by weight: a caprolactone compound 10-50 parts; an epoxidized natural rubber 50-90 parts; phytic acid 0.1-10 parts; and a metal compound 0.1-10 parts.The preparation raw materials are stirred and blended through a one-step method to obtain the thermoplastic elastomer.The thermoplastic elastomer has good mechanical properties, self-repairing capability and shape memory performance through the synergistic effect among the components, and the preparation method is simple, efficient and green, and can be widely used in common materials such as medical treatment, food packaging and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rubber elastomer material preparation, and particularly relates to a thermoplastic elastomer with shape memory and self-repairing properties and a preparation method and application thereof. BACKGROUND

[0002] Because most polymers are not biodegradable, they have caused serious environmental problems, prompting biodegradable polymers and their blends to become a research hotspot. Poly (caprolactone) (PCL) is widely used in the fields of biomedical materials, shaping materials production and processing, etc. due to its biodegradability, good shape memory temperature control properties, etc. The thermoplastic elastomer prepared by taking PCL and epoxidized natural rubber (ENR) as main raw materials has attracted attention, but the existing related technologies have defects.

[0003] For example, Chinese invention patent CN116218060A discloses a self-repairing epoxidized natural rubber composite material and a preparation method thereof. The method utilizes the dynamic reversible interfacial action between surface hydroxyl porous MXene and modified latex ENR to improve the mechanical properties and self-repairing properties of the elastomer material. This method optimizes the performance of the self-repairing elastomer to a certain extent, but the preparation process of the method is relatively complicated, and the method does not design and explore the shape memory properties of the composite material, and the single self-repairing property research will limit its application field, which cannot meet the current demand for sustainable development; Chinese invention patent CN116376251A discloses a polyester hybrid nano TiO2 film with shape memory and antibacterial properties. The method utilizes carboxyl-terminated poly (caprolactone) (PCL-COOH) and silane-modified TiO2 to generate PCL-TiO2 through amide bond grafting reaction, and then the PCL-TiO2 is blended with PLA to cast a film. The material prepared by the method has repeatable shape memory properties and excellent antibacterial properties. However, the preparation process of this method is complex, and only the shape memory properties and antibacterial properties of the composite material are explored, and the self-repairing properties of the composite material are not functionally designed, which reduces the utilization rate of the material.

[0004] Therefore, it is of great significance to provide a thermoplastic elastomer with shape memory properties and self-repairing properties. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a thermoplastic elastomer with good mechanical properties, self-repairing ability and shape memory properties, and a simple, efficient and green preparation method.

[0006] The present application also provides a preparation method of the thermoplastic elastomer.

[0007] The present application also provides an application of the thermoplastic elastomer.

[0008] The first aspect of the present application provides a thermoplastic elastomer, which comprises the following raw materials in parts by weight:

[0009] Caprolactone compound 10-50 parts;

[0010] Epoxidized natural rubber 50-90 parts;

[0011] Phytic acid 0.1-10 parts;

[0012] Metal compound 0.1-10 parts.

[0013] The thermoplastic elastomer according to the first aspect of the present application has at least the following beneficial effects:

[0014] The thermoplastic elastomer prepared by using epoxidized natural rubber (ENR) and polycaprolactone (PCL) as main raw materials, and phytic acid (PA) and metal compound extracted from plant seeds as vulcanizing agents has good self-repairing ability, shape memory performance and mechanical properties. There is phase separation between ENR and PCL, and the ENR phase is distributed in the PCL matrix in a continuous network structure. The entanglement and intermolecular interaction between ENR and PCL enable the rubber-based elastomer to have good shape memory effect. The covalent crosslinking of the phosphate groups in PA and the epoxy groups in ENR forms reversible phosphate ester bonds, and PA has strong coordination interaction with the metal compound. Therefore, the application of phytic acid and metal compound in the PCL / ENR blend together constructs a double crosslinking network based on phosphate ester bonds / coordination bonds, so that the rubber-based elastomer has self-repairing performance, good shape memory performance and mechanical properties, and effectively improves the utilization rate of the material.

[0015] The application of PA and metal compound in the PCL / ENR rubber-based elastomer not only significantly improves the mechanical strength, but also has excellent self-repairing performance, thereby improving the reliability and service life of the rubber-based elastomer product. The raw materials PCL, ENR and PA used in the application are biodegradable and belong to renewable biological resources, which meets the demand of sustainable development.

[0016] According to some embodiments of the present application, the thermoplastic elastomer comprises the following raw materials in parts by weight, wherein epoxidized natural rubber and polycaprolactone are 100 parts, and wherein:

[0017] Polycaprolactone 40-50 parts;

[0018] Epoxidized natural rubber 50-60 parts;

[0019] Phytic acid 1.2-8 parts;

[0020] metal compound 0.3-1.2 parts.

[0021] According to some embodiments of the present application, the caprolactone compound includes at least one of ε-caprolactone monomer, polycaprolactone, polycaprolactone diol, and methoxypolyethylene glycol polycaprolactone.

[0022] Preferably, the caprolactone compound includes ε-caprolactone monomer or polycaprolactone.

[0023] According to some embodiments of the present application, the epoxidized natural rubber includes both dry rubber and latex.

[0024] According to some embodiments of the present application, the epoxidized natural rubber has an epoxidation degree of 25-75 mol%.

[0025] Preferably, the epoxidized natural rubber has an epoxidation degree of 25-50 mol%.

[0026] The epoxidation degree refers to the molar percentage of the double bonds in the natural rubber molecules that are epoxidized, and the epoxidation degree directly affects the reactivity of the ENR molecules and the compatibility with other components. When the epoxidation degree is too low, there are few epoxide groups that can participate in the reaction, resulting in a low degree of crosslinking of the rubber-based elastomer. When the epoxidation degree is too high, the molecular chain movement is restricted, increasing the modulus of the rubber-based elastomer and reducing the flowability during processing.

[0027] According to some embodiments of the present application, the polycaprolactone has a number average molecular weight of 30,000-300,000.

[0028] According to some embodiments of the present application, the epoxidized natural rubber and the polycaprolactone derivative are used in a ratio of (50-60):(40-50), for example, 60:40 or 50:50.

[0029] According to some embodiments of the present application, the mass percentage of the phytic acid is 2-16% of the epoxidized natural rubber.

[0030] According to some embodiments of the present application, the mass percentage of the metal compound is 0.5-2.4% of the epoxidized natural rubber.

[0031] The proportions of the phytic acid and the metal compound significantly affect the density and strength of the crosslinking network. When the proportions are too high, the strength and modulus of the rubber-based elastomer increase, and the molecular chain movement is restricted, which is not conducive to achieving self-repairing performance. When the proportions are too low, the degree of crosslinking is low, and the shape memory performance is poor.

[0032] According to some embodiments of the present application, the mass ratio of the phytic acid to the metal compound is (1-4):1.

[0033] According to some embodiments of the present application, the metal compound comprises at least one of ferric chloride (FeCl3), copper sulfate (CuSO4), zinc chloride (ZnCl2), zinc oxide (ZnO).

[0034] The second aspect of the present application provides a method for preparing the thermoplastic elastomer as described above, the method comprising the following steps:

[0035] The epoxidized natural rubber, polycaprolactone, phytic acid and metal compound are melt-blended by one step to vulcanize to obtain the thermoplastic elastomer.

[0036] According to the method for preparing the thermoplastic elastomer according to the second aspect of the present application, at least the following beneficial effects are achieved:

[0037] The present application prepares the thermoplastic elastomer with self-repairing and shape memory properties by a simple, efficient and green process and preparation method. In the preparation of the rubber-based elastomer, polycaprolactone, epoxidized natural rubber, phytic acid and metal compound are fully blended in an extruder, internal mixer or open mill by one step, which can improve the shape memory properties of the rubber-based elastomer.

[0038] The preparation method and process flow adopted by the present application are simple, efficient and green, and the equipment used only needs to be selected according to the needs.

[0039] According to some embodiments of the present application, the phytic acid is a 20wt%-80wt% aqueous solution of phytic acid.

[0040] According to some embodiments of the present application, the melt blending comprises internal mixing, open mixing and melt extrusion.

[0041] According to some embodiments of the present application, the temperature of the melt blending is 70-90℃.

[0042] Preferably, the temperature of the melt blending is 80℃.

[0043] According to some embodiments of the present application, the rotational speed of the melt blending is 50-70rpm.

[0044] Preferably, the rotational speed of the melt blending is 60rpm.

[0045] According to some embodiments of the present application, the time of the melt blending is 8-15min.

[0046] Preferably, the time of the melt blending is 10-12min.

[0047] The third aspect of the present application provides the use of the thermoplastic elastomer as described above in food packaging, biomedical and flexible wearable products.

[0048] Unless otherwise defined, "about" as used herein is intended to provide an allowance, for example, ± 2%, of the value for the term that it is modifying, such that "about 100" is intended to mean 100 ± 2% x 100.

[0049] Other features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0050] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the appended drawings, wherein:

[0051] Figure 1 Three-dimensional super depth of field video microscope images of simple blend of Example 1 ENR and PCL, compression molded in this application.

[0052] Figure 2 Stress-strain curves of Example 1, Example 2, Example 7 in this application;

[0053] Figure 3 Three-dimensional super depth of field video microscope images of self-repair of Example 4, Example 6 in this application for 3h in a vacuum oven at 170°C;

[0054] Figure 4 Digital photos of the thermal induced shape recovery process of Example 5 in this application. DETAILED DESCRIPTION

[0055] Embodiments of the present application are described in detail below, with like or similar components being referred to with like or similar reference numerals throughout the embodiments. The embodiments described below are exemplary only, and are not intended to be limiting of the present application.

[0056] In the description of the present application, if there is a description to first, second, etc., it is only for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying relative importance or implying the number of the indicated technical features or implying the order of the indicated technical features.

[0057] The words "preferably," "more preferably," and the like used herein mean that under certain circumstances one or more of the described implementations of the application are preferred. However, other implementations can also be preferred to varying degrees depending on the particular circumstances, and the language "preferably" is not used to imply that a feature is essential to an implementation or that an implementation cannot be utilized without the feature. Furthermore, the recitation of one or more preferred implementations does not imply that other implementations are not useful, and is not intended to exclude other implementations from the scope of the application.

[0058] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0059] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of the present invention.

[0060] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0061] In the examples and control examples of the present invention, the caprolactone compound is polycaprolactone (Perstorp, 6500) and ε-caprolactone (CAS No.: 502-44-3), wherein the polycaprolactone (Perstorp, 6500) is dried in a vacuum drying oven at 35°C for 8 hours before use, and epoxidized natural rubber (Chinese Academy of Tropical Agricultural Sciences) is used as dry rubber, which is masticated on an open mill before use. The phytic acid used is a 50% phytic acid aqueous solution, and the metal compound used is FeCl3 (analytical purity 99%) as an example.

[0062] Example 1

[0063] This embodiment provides a thermoplastic elastomer, which comprises the following raw materials, epoxidized natural rubber and polycaprolactone, in 100 parts by weight:

[0064] 40 parts of polycaprolactone;

[0065] 60 parts of epoxidized natural rubber;

[0066] 1.2 parts of phytic acid;

[0067] 0.6 parts of metal compound.

[0068] This embodiment also provides a method for preparing the above-mentioned thermoplastic elastomer, comprising the following steps:

[0069] The epoxidized natural rubber (epoxidized degree 50 mol%) and polycaprolactone were used in a 60 / 40 ratio. The epoxidized natural rubber, polycaprolactone, phytic acid, and FeCl3 powder were blended in an internal mixer (temperature and speed of 80°C and 60 rpm, respectively) for 11 minutes to obtain a rubber-based elastomer, which was then compression molded.

[0070] Example 2

[0071] This embodiment provides a thermoplastic elastomer, which comprises the following raw materials, epoxidized natural rubber and polycaprolactone, in 100 parts by weight:

[0072] 40 parts of polycaprolactone;

[0073] 60 parts of epoxidized natural rubber;

[0074] 1.2 parts of phytic acid;

[0075] 0.6 parts of metal compound.

[0076] This embodiment also provides a method for preparing the above-mentioned thermoplastic elastomer, comprising the following steps:

[0077] The ratio of epoxidized natural rubber with an epoxy degree of 25 mol% and polycaprolactone was 60 / 40. Epoxidized natural rubber, polycaprolactone, phytic acid, and FeCl3 powder were blended in an internal mixer (temperature and speed were 80°C and 60 rpm, respectively) for 11 minutes to obtain a rubber-based elastomer, which was then compression molded. The 3D super-depth video microscope image of ENR and PCL after simple blending and compression molding is shown below. Figure 1 As shown in the figure, the phase separation between ENR (epoxidized natural rubber) and PCL (polycaprolactone) can be seen. The continuous network structure corresponds to the ENR phase, which is distributed in a network-like manner throughout the material, while the rest is the PCL matrix. This phase separation structure and the continuous network distribution of ENR contribute to the good shape memory effect of the rubber-based elastomer due to the entanglement and intermolecular interactions between ENR and PCL.

[0078] Example 3

[0079] This embodiment provides a thermoplastic elastomer, which comprises the following raw materials, epoxidized natural rubber and polycaprolactone, in 100 parts by weight:

[0080] 50 parts of polycaprolactone;

[0081] 50 parts of epoxidized natural rubber;

[0082] 1.2 parts of phytic acid;

[0083] 0.6 parts of metal compound.

[0084] The embodiment also provides a preparation method of the thermoplastic elastomer, comprising the following steps:

[0085] The epoxy degree of the epoxidized natural rubber is 50 mol%, and the use ratio of the epoxidized natural rubber and the polycaprolactone is 50 / 50. The epoxidized natural rubber, the polycaprolactone, the phytic acid and FeCl3 powder are blended in a mixer (the temperature and the rotating speed are 80 °C and 60 rpm respectively) for 11 min to obtain a rubber-based elastomer, and then the rubber-based elastomer is molded.

[0086] Embodiment 4

[0087] The embodiment provides a thermoplastic elastomer, the thermoplastic elastomer comprising the following preparation raw materials in percentage by weight, wherein the epoxidized natural rubber and the polycaprolactone are 100 parts, and wherein:

[0088] The polycaprolactone is 40 parts;

[0089] The epoxidized natural rubber is 60 parts;

[0090] The phytic acid is 1.2 parts;

[0091] The metal compound is 0.3 parts.

[0092] The embodiment also provides a preparation method of the thermoplastic elastomer, comprising the following steps:

[0093] The epoxy degree of the epoxidized natural rubber is 50 mol%, and the use ratio of the epoxidized natural rubber and the polycaprolactone is 60 / 40. The epoxidized natural rubber, the polycaprolactone, the phytic acid and FeCl3 powder are blended in a mixer (the temperature and the rotating speed are 80 °C and 60 rpm respectively) for 11 min to obtain a rubber-based elastomer, and then the rubber-based elastomer is molded.

[0094] Embodiment 5

[0095] The embodiment provides a thermoplastic elastomer, the thermoplastic elastomer comprising the following preparation raw materials in percentage by weight, wherein the epoxidized natural rubber and the polycaprolactone are 100 parts, and wherein:

[0096] The polycaprolactone is 40 parts;

[0097] The epoxidized natural rubber is 60 parts;

[0098] The phytic acid is 1.2 parts;

[0099] The metal compound is 0.9 parts.

[0100] The embodiment also provides a preparation method of the thermoplastic elastomer, comprising the following steps:

[0101] The epoxy degree of the epoxidized natural rubber is 50 mol%, and the ratio of the amount of the epoxidized natural rubber to the amount of the polycaprolactone is 60 / 40. The epoxidized natural rubber, the polycaprolactone, the phytic acid and the FeCl3 powder are blended in a mixer (the temperature and the rotating speed are 80°C and 60 rpm respectively) for 11 minutes to obtain a rubber-based elastomer, and then the rubber-based elastomer is molded.

[0102] Example 6

[0103] The present example provides a thermoplastic elastomer, the thermoplastic elastomer comprising, in percentage by weight, the following raw materials, the epoxidized natural rubber and the polycaprolactone being 100 parts, wherein:

[0104] The polycaprolactone is 40 parts;

[0105] The epoxidized natural rubber is 60 parts;

[0106] The phytic acid is 1.2 parts;

[0107] The metal compound is 1.2 parts.

[0108] The present example also provides a preparation method of the thermoplastic elastomer, comprising the following steps:

[0109] The epoxy degree of the epoxidized natural rubber is 50 mol%, and the ratio of the amount of the epoxidized natural rubber to the amount of the polycaprolactone is 60 / 40. The epoxidized natural rubber, the polycaprolactone, the phytic acid and the FeCl3 powder are blended in a mixer (the temperature and the rotating speed are 80°C and 60 rpm respectively) for 11 minutes to obtain a rubber-based elastomer, and then the rubber-based elastomer is molded.

[0110] Example 7

[0111] The present example provides a thermoplastic elastomer, the thermoplastic elastomer comprising, in percentage by weight, the following raw materials, the epoxidized natural rubber and the polycaprolactone being 100 parts, wherein:

[0112] The polycaprolactone is 40 parts;

[0113] The epoxidized natural rubber is 60 parts;

[0114] The phytic acid is 1.2 parts;

[0115] The metal compound is 0.6 parts.

[0116] The present example also provides a preparation method of the thermoplastic elastomer, comprising the following steps:

[0117] The epoxy degree of the epoxidized natural rubber is 50 mol%, and the ratio of the amount of the epoxidized natural rubber to the amount of the polycaprolactone is 60 / 40. The epoxidized natural rubber, the polycaprolactone, the phytic acid and the FeCl3 powder are blended in a mixer (the temperature and the rotating speed are 80°C and 60 rpm respectively) for 11 minutes to obtain a rubber-based elastomer, and then the rubber-based elastomer is molded.

[0118] Example 8

[0119] The present example provides a thermoplastic elastomer, which comprises the following raw materials by weight percentage, 100 parts of epoxidized natural rubber and ε-caprolactone, wherein:

[0120] 40 parts of ε-caprolactone;

[0121] 60 parts of epoxidized natural rubber;

[0122] 1.2 parts of phytic acid;

[0123] 0.6 parts of metal compound.

[0124] The present example also provides a preparation method of the above thermoplastic elastomer, comprising the following steps:

[0125] The amount ratio of epoxidized natural rubber with an epoxidation degree of 50 mol% and ε-caprolactone is 60 / 40. The epoxidized natural rubber, ε-caprolactone, phytic acid and FeCl3 powder are blended in an internal mixer (temperature and rotating speed are 80℃ and 60rpm respectively) for 11 min to obtain a rubber-based elastomer, which is then molded.

[0126] Comparative Example 1

[0127] The present comparative example provides a thermoplastic elastomer, which comprises the following raw materials by weight percentage, 100 parts of epoxidized natural rubber and polycaprolactone, wherein:

[0128] 40 parts of polycaprolactone;

[0129] 60 parts of epoxidized natural rubber.

[0130] The present comparative example also provides a preparation method of the above thermoplastic elastomer, comprising the following steps:

[0131] The amount ratio of epoxidized natural rubber with an epoxidation degree of 50 mol% and polycaprolactone is 60 / 40. The epoxidized natural rubber and polycaprolactone are blended for 11 min to obtain a rubber-based elastomer, which is then molded.

[0132] Comparative Example 2

[0133] The present comparative example provides a thermoplastic elastomer, which comprises the following raw materials by weight percentage, wherein:

[0134] 60 parts of epoxidized natural rubber;

[0135] 1.2 parts of phytic acid;

[0136] 0.6 parts of metal compound.

[0137] The present comparative example also provides a method for preparing the thermoplastic elastomer described above, comprising the following steps:

[0138] The epoxidized natural rubber with an epoxidation degree of 50 mol% was plasticized, and then the phytic acid was added dropwise into the plasticized rubber and mixed uniformly before being molded.

[0139] Comparative Example 3

[0140] The present comparative example provides a thermoplastic elastomer, which comprises the following raw materials by weight percentage, 100 parts of epoxidized natural rubber and polycaprolactone, wherein:

[0141] 40 parts of polycaprolactone;

[0142] 60 parts of epoxidized natural rubber;

[0143] 1.2 parts of phytic acid.

[0144] The present comparative example also provides a method for preparing the thermoplastic elastomer described above, comprising the following steps:

[0145] The epoxidized natural rubber with an epoxidation degree of 50 mol% and polycaprolactone are used in a proportion of 60 / 40. The epoxidized natural rubber, polycaprolactone and phytic acid are blended in an internal mixer (temperature and rotating speed are 80°C and 60 rpm, respectively) for 11 min to obtain a rubber-based elastomer, which is then molded.

[0146] Comparative Example 4

[0147] The present comparative example provides a thermoplastic elastomer, which comprises the following raw materials by weight percentage, 100 parts of epoxidized natural rubber and polycaprolactone, wherein:

[0148] 40 parts of polycaprolactone;

[0149] 60 parts of epoxidized natural rubber;

[0150] 0.6 parts of metal compound.

[0151] The present comparative example also provides a method for preparing the thermoplastic elastomer described above, comprising the following steps:

[0152] The epoxidized natural rubber with an epoxidation degree of 50 mol% and polycaprolactone are used in a proportion of 60 / 40. The epoxidized natural rubber, polycaprolactone and FeCl3 powder are blended in an internal mixer (temperature and rotating speed are 80°C and 60 rpm, respectively) for 11 min to obtain a rubber-based elastomer, which is then molded.

[0153] Comparative Example 5

[0154] This comparative example provides a thermoplastic elastomer, which comprises the following raw materials, epoxidized natural rubber and polycaprolactone, in 100 parts by weight, wherein:

[0155] 40 parts of polycaprolactone;

[0156] 60 parts of epoxidized natural rubber;

[0157] 1.2 parts of dicumyl peroxide.

[0158] This comparative example also provides a method for preparing the above-mentioned thermoplastic elastomer, comprising the following steps:

[0159] The epoxidized natural rubber with an epoxy degree of 50 mol% and polycaprolactone were used in a ratio of 60 / 40. The epoxidized natural rubber, polycaprolactone, and dicumyl peroxide were blended in an internal mixer (temperature and speed of 80°C and 60 rpm, respectively) for 11 minutes to obtain a rubber-based elastomer, which was then compression molded.

[0160] Test Case

[0161] In order to test the mechanical, self-repair, shape memory and other performances of the examples and comparative samples, the following treatment was performed: the prepared samples were crushed and then compression molded to obtain test specimens, and the molding conditions were: molding temperature 170°C, pressure 5 MPa.

[0162] Mechanical properties test:

[0163] The tensile properties of all samples were measured according to the national standard GB / T 1040.1-2006 using a universal testing machine (INSTRON 5966) at 25°C and a tensile speed of 50 mm / min. Five samples were tested for each measurement and the average value was calculated. The mechanical property test results of Examples 1-7 and Comparative Examples 1-5 are shown in Table 1.

[0164] Self-repair performance test:

[0165] The self-healing performance test results of Examples 1 to 7 and Comparative Examples 1 to 5 are shown in Table 2. The deformed dumbbell splines were damaged in the radial direction using a homemade device to ensure that the depth of the damaged crack was 50% of the thickness of the sample and the length of the crack was 50% of the width of the sample. The sample was then placed in a vacuum oven at 170°C for repair for 3 hours. Subsequently, the original spline, damaged spline and repaired spline were tested using a universal testing machine at a tensile speed of 10 mm / min. The repair efficiency of the tensile strength of the rubber-based elastomer can be calculated according to the following formula, where α is the tensile strength of the original spline, β is the tensile strength of the damaged spline, and γ is the tensile strength of the repaired spline:

[0166]

[0167] Shape memory performance test:

[0168] The shape memory performance test results of Examples 1-7 and Comparative Examples 1-5 are shown in Table 3. The thermal induced shape memory performance of the rubber-based elastomer was tested by using a high-low temperature tensile machine, and the specific process was as follows: (1) a line segment L0 with a length of 20 mm was drawn in the middle region of the dumbbell-shaped sample (thickness of 1 mm); (2) the sample was placed at 60℃ for 5 min to ensure uniform heating, and then deformed to 100% strain at a rate of 50 mm / min, and then immediately cooled by liquid nitrogen to cool the experimental cavity, and the load was kept unchanged during the cooling process, and the deformed sample was unloaded after cooling to 0℃, and the length L1 of the two ends was recorded; (3) the sample was placed in a 60℃ oven for 5 min to recover the shape, and then the length L3 of the two ends of the sample was recorded. The shape fixing rate (R f ) and shape recovery rate (R r ) of the rubber-based elastomer can be calculated by formulas (1) and (2), respectively:

[0169]

[0170] Table 1 Mechanical property test results of Examples 1-7 and Comparative Examples 1-5

[0171]

[0172]

[0173] Table 2 Self-repairing performance test results of Examples 1-7 and Comparative Examples 1-5

[0174]

[0175] Table 3 Shape memory performance test results of Examples 1-7 and Comparative Examples 1-5

[0176]

[0177]

[0178] It should be noted that the samples of Examples 1-7 were complete and defect-free during the molding process.

[0179] As can be seen from Table 1, compared with the addition of phytic acid and metal compounds directly to epoxidized natural rubber (Comparative Example 2), the addition of polycaprolactone helps to improve the mechanical properties, and the tensile strength and elongation at break are increased from 8.3 MPa, 206.6% (Comparative Example 2) to 11.3 MPa, 325.2% (Example 1). Meanwhile, as can be seen from Table 3, the addition of polycaprolactone significantly improves the shape fixation rate of the rubber-based elastomer, and the shape fixation rate is increased from 40.5% (Comparative Example 2) to more than 89% (Examples 1-8). Accordingly, it can be seen that the low melting point of polycaprolactone endows the rubber-based elastomer with more excellent shape memory properties.

[0180] As can be seen from Table 1, compared with the blending of epoxidized natural rubber and polycaprolactone (Comparative Example 1), the addition of phytic acid and metal compounds helps to improve the mechanical properties, and the tensile strength is increased from 1.8 MPa (Comparative Example 1) to more than 6.4 MPa (Examples 1-7), and compared with the introduction of phytic acid (Comparative Example 3) or metal compounds (Comparative Example 4) alone, the tensile strength is also significantly improved (Examples 1, 4, 5, 6), indicating that the construction of a double crosslinking network based on phosphate ester bond / coordination bond in the PCL / ENR blend enhances the mechanical strength of the rubber-based elastomer. Meanwhile, as can be seen from Table 2, compared with no addition of phytic acid and metal compounds (Comparative Example 1) and the addition of the vulcanizing agent dicumyl peroxide commonly used in the art (Comparative Example 5), with the addition of phytic acid and metal compounds, the self-repairing efficiency of the tensile strength of the rubber-based elastomer is increased from 37.4% (Comparative Example 1), 75.3% (Comparative Example 5) to more than 90% (Examples 1-6); in addition, as can be seen from Table 3, compared with no addition of phytic acid and metal compounds (Comparative Example 1) and the addition of the vulcanizing agent dicumyl peroxide (Comparative Example 5), with the addition of phytic acid and metal compounds, the shape fixation rate and shape recovery rate of the rubber-based elastomer are increased from 66.5%, 67.4% (Comparative Example 1), 78.4%, 88.9% (Comparative Example 5) to more than 93.6%, 96.8% (Examples 1-8), indicating that the addition of phytic acid and metal compounds not only does not destroy the structure of the rubber-based elastomer, but also helps to improve the self-repairing performance and shape memory performance of the rubber-based elastomer. Therefore, the rubber-based elastomer prepared in the present application can effectively balance various functions, and has a broad application prospect.

[0181] In addition, as can be seen from Example 2, the tensile strength, elongation at break, tensile strength self-repairing performance, shape fixation rate and shape recovery rate of the rubber-based elastomer prepared by using epoxidized natural rubber with an epoxide degree of 25 mol% are lower than those of Example 1, indicating that the epoxide degree of the epoxidized natural rubber has an important influence on the mechanical properties of the rubber-based elastomer. With the increase of the epoxide degree, the interaction between the epoxidized natural rubber and phytic acid and metal compounds will be enhanced, and the stress-strain curves of Examples 1, 2 and 7 are as shown in FIG. 1. Figure 2 、 3, 4, the test method steps used are consistent with the test method described in the test examples) can be seen that the overall performance of the epoxidized natural rubber with an epoxide degree of 50 mol% is better than that with an epoxide degree of 25 mol%, and the results are shown in Table 1. Figure 2 As shown in Table 1, the tensile strength and shape fixing rate of the rubber-based elastomer of Example 3 are obviously improved (the tensile strength of Example 3 is 13.4 MPa, and the shape fixing rate is 95.6%) compared with Example 1, and the content of polycaprolactone is increased. However, the increase in the amount of polycaprolactone inevitably leads to a decrease in the elongation at break.

[0182] As shown in Table 1, the tensile strength and shape fixing rate of the rubber-based elastomer of Example 3 are obviously improved (the tensile strength of Example 3 is 13.4 MPa, and the shape fixing rate is 95.6%) compared with Example 1, and the content of polycaprolactone is increased. However, the increase in the amount of polycaprolactone inevitably leads to a decrease in the elongation at break. Figure 3 As shown in Table 1, the tensile strength and shape fixing rate of the rubber-based elastomer of Example 3 are obviously improved (the tensile strength of Example 3 is 13.4 MPa, and the shape fixing rate is 95.6%) compared with Example 1, and the content of polycaprolactone is increased. However, the increase in the amount of polycaprolactone inevitably leads to a decrease in the elongation at break.

[0183] As shown in Table 1, the tensile strength and shape fixing rate of the rubber-based elastomer of Example 3 are obviously improved (the tensile strength of Example 3 is 13.4 MPa, and the shape fixing rate is 95.6%) compared with Example 1, and the content of polycaprolactone is increased. However, the increase in the amount of polycaprolactone inevitably leads to a decrease in the elongation at break. Figure 4 As shown in Table 1, the tensile strength and shape fixing rate of the rubber-based elastomer of Example 3 are obviously improved (the tensile strength of Example 3 is 13.4 MPa, and the shape fixing rate is 95.6%) compared with Example 1, and the content of polycaprolactone is increased. However, the increase in the amount of polycaprolactone inevitably leads to a decrease in the elongation at break.

[0184] In summary, the present application realizes the functionalization of the rubber-based elastomer by adding phytic acid in the rubber-plastic blend. The experiments show that the introduction of polycaprolactone improves the shape memory performance of the rubber-based elastomer, the introduction of phytic acid improves the self-repairing ability of the rubber-based elastomer, and the two synergistically improve the mechanical properties of the rubber-based elastomer. The rubber-based elastomer can be widely used in food packaging, biomedical, flexible wear and other fields. In addition, the raw materials involved in the present application are all environmentally friendly materials, which meet the needs of sustainable social and economic development, and have wide application prospects.

[0185] The above describes the embodiments of the present application in detail, but the present application is not limited to the above-described embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A thermoplastic elastomer, characterized in that The thermoplastic elastomer comprises the following raw materials in parts by weight: 10-50 parts of caprolactone compounds; Epoxidized natural rubber 50-90 parts; Phytic acid 0.1~10 parts; 0.1-10 parts of metal compound; The caprolactone compound includes at least one of ε-caprolactone monomer, polycaprolactone, polycaprolactone diol, and methoxy polyethylene glycol polycaprolactone; The epoxidation degree of the epoxidized natural rubber is 25 mol% to 75 mol%; The metal compound includes at least one of ferric chloride, copper sulfate, zinc chloride and zinc oxide.

2. The thermoplastic elastomer according to claim 1, characterized in that The epoxidized natural rubber includes two types: dry rubber and latex.

3. The thermoplastic elastomer according to claim 1, characterized in that The number average molecular weight of the polycaprolactone is 30,000-300,000.

4. A method for preparing a thermoplastic elastomer according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: melt-blending epoxidized natural rubber, caprolactone compound, phytic acid and metal compound in one step, and vulcanizing to obtain the thermoplastic elastomer.

5. The preparation method according to claim 4, characterized in that The phytic acid is a phytic acid aqueous solution with a concentration of 20 wt% to 80 wt%.

6. The preparation method according to claim 4, characterized in that The melt blending includes internal mixing, open mixing, and melt extrusion; the temperature of the melt blending is 80-170° C.; the rotation speed of the melt blending is 50-70 rpm; and the time of the melt blending is 8-15 minutes.

7. Use of the thermoplastic elastomer according to any one of claims 1 to 3 in food packaging, biomedical products for non-diagnostic and therapeutic purposes, and flexible wearable products.

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