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

Abstract

The invention discloses a thermoplastic elastomer with shape memory and self-repairing properties as well as a preparation method and application thereof, and belongs to the technical field of preparation of rubber elastomer materials. The thermoplastic elastomer is prepared from the following preparation raw materials in parts by weight: 10 to 50 parts of caprolactone compounds; 50 to 90 parts of epoxidized natural rubber; 0.1 to 10 parts of phytic acid; and 0.1 to 10 parts of a metal compound. The preparation raw materials are stirred and blended through a one-step method to obtain the thermoplastic elastomer. Through the synergistic effect of the components, the thermoplastic elastomer has good mechanical properties, self-repairing ability and shape memory performance, the preparation method is simple, convenient, efficient and green, and the thermoplastic elastomer can be widely applied to common materials for medicine, food packaging and the like.

Description

Technical Field

[0001] The invention relates to the technical field of rubber elastic material preparation, and in particular to a thermoplastic elastomer with shape memory and self-healing properties, and a preparation method and application thereof. Background Art

[0002] Since most polymers are non-biodegradable, they have caused serious environmental problems, making biodegradable polymers and their blends a research hotspot. Polycaprolactone (PCL) is widely used in biomedicine, production and processing of plastic materials due to its degradability and good shape memory temperature control properties. Thermoplastic elastomers prepared with PCL and epoxidized natural rubber (ENR) as the main raw materials have attracted attention, but the existing related technologies have shortcomings.

[0003] For example, Chinese invention patent CN116218060A discloses a self-healing epoxidized natural rubber composite material and its preparation method, which utilizes the dynamic reversible interface between surface hydroxyl porous MXene and modified latex ENR to improve the mechanical properties and self-healing properties of the elastomeric material. This method optimizes the performance of the self-healing elastomer to a certain extent, but the preparation process of this method is relatively cumbersome, and the method does not design and explore the shape memory properties of the composite material. The single self-healing performance research will restrict its application field and cannot meet the current sustainable development needs; Chinese invention patent CN116376251A discloses a polyester hybrid nano-TiO2 film with shape memory and antibacterial properties, which utilizes carboxylated polycaprolactone (PCL-COOH) and silane-modified TiO2 to generate PCL-TiO2 through amide bond grafting reaction, and then blends with PLA to cast the film. The material prepared by this method has repeatable shape memory properties and excellent antibacterial properties. However, this method has a complicated preparation process and only explores the shape memory and antibacterial properties of the composite material. The self-healing properties of the composite material have not yet been functionally designed, resulting in reduced material utilization.

[0004] Therefore, it is of great significance to provide a thermoplastic elastomer with shape memory properties and self-healing properties. Summary of the invention

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

[0006] The invention also provides a method for preparing the thermoplastic elastomer.

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

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

[0009] 10 to 50 parts of caprolactone compounds;

[0010] Epoxidized natural rubber 50-90 parts;

[0011] Phytic acid 0.1-10 parts;

[0012] 0.1 to 10 parts of metal compound.

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

[0014] The present invention uses natural rubber derivative epoxidized natural rubber (ENR) and polycaprolactone (PCL) as main raw materials, and uses organic phosphorus compound phytic acid (PA) extracted from plant seeds and metal compounds as vulcanizing agents to prepare thermoplastic elastomers with 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 make the rubber-based elastomer have a good shape memory effect; the phosphoric acid group in PA and the epoxy group in ENR are covalently cross-linked to form a reversible phosphate bond, and PA has a strong coordination interaction with the metal compound. Therefore, phytic acid and metal compounds are used together in the PCL / ENR blend to construct a double cross-linked network based on phosphate bond / coordination bond, 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 present invention introduces PA and metal compounds into PCL / ENR rubber-based elastomers, which not only significantly improves the mechanical strength thereof, but also makes it have excellent self-repairing properties, thereby improving the reliability and service life of rubber-based elastomer products. The preparation raw material PCL of the present invention is biodegradable, and ENR and PA are renewable biological resources, which meet the needs of sustainable development.

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

[0017] 40-50 parts of polycaprolactone;

[0018] Epoxidized natural rubber 50-60 parts;

[0019] Phytic acid 1.2-8 parts;

[0020] 0.3 to 1.2 parts of metal compound.

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

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

[0023] According to some embodiments of the present invention, the epoxidized natural rubber includes two types: dry rubber and latex.

[0024] According to some embodiments of the present invention, the epoxidation degree of the epoxidized natural rubber is 25 mol% to 75 mol%.

[0025] Preferably, the epoxidation degree of the epoxidized natural rubber is 25 mol% to 50 mol%.

[0026] Epoxidation degree refers to the molar percentage of epoxidized double bonds in natural rubber molecules. The degree of epoxidation directly affects the reactivity of ENR molecules and their compatibility with other components. When the epoxidation degree is too low, fewer epoxy groups can participate in the reaction, resulting in a lower degree of crosslinking of the rubber-based elastomer. When the epoxidation degree is too high, the movement of the molecular chain is restricted, which increases the modulus of the rubber-based elastomer and deteriorates the fluidity during processing.

[0027] According to some embodiments of the present invention, the number average molecular weight of the polycaprolactone is 30,000 to 300,000.

[0028] According to some embodiments of the present invention, the usage ratio of the epoxidized natural rubber and the polycaprolactone derivative is (50-60):(40-50), for example, it can be 60:40 or 50:50.

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

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

[0031] The proportion of phytic acid and metal compounds will significantly affect the density and strength of the cross-linked network. When the proportion is too high, the strength and modulus of the rubber-based elastomer are increased, the molecular chain movement ability is limited, and it is not conducive to achieving self-healing performance; when it is too low, the degree of cross-linking is low and the shape memory performance is poor.

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

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

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

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

[0036] The preparation method according to the second aspect of the present invention has at least the following beneficial effects:

[0037] The present invention prepares a thermoplastic elastomer with self-healing and shape memory properties through a simple, efficient and green process flow and preparation method. In the process of preparing the rubber-based elastomer, polycaprolactone, epoxidized natural rubber, phytic acid and metal compounds are fully blended in an extruder, internal mixer or open mixer through a one-step method to improve the shape memory property of the rubber-based elastomer.

[0038] The preparation method and process flow adopted by the present invention 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 invention, the phytic acid is a 20 wt % to 80 wt % phytic acid aqueous solution.

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

[0041] According to some embodiments of the present invention, the temperature of the melt blending is 70-90°C.

[0042] Preferably, the melt blending temperature is 80°C.

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

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

[0045] According to some embodiments of the present invention, the melt blending time is 8 to 15 minutes.

[0046] Preferably, the melt blending time is 10 to 12 minutes.

[0047] The third aspect of the present invention provides the application of the above-mentioned thermoplastic elastomer in food packaging, biomedicine, and flexible wearable products.

[0048] If there is no special explanation, the actual meaning of “about” in the present invention is that the error is allowed to be within the range of ±2%, for example, about 100 is actually 100±2%×100.

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

[0050] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0051] Figure 1 This is a three-dimensional ultra-depth video microscope image of ENR and PCL after simple blending and compression molding in Example 1 of the present application.

[0052] Figure 2 : are stress-strain curves of Example 1, Example 2, and Example 7 of the present invention;

[0053] Figure 3 The three-dimensional ultra-depth video microscope images of Example 4 and Example 6 of the present invention after self-repairing in a vacuum oven at 170° C. for 3 hours;

[0054] Figure 4 This is a digital photo of the thermally induced shape recovery process of Example 5 of the present invention. DETAILED DESCRIPTION

[0055] The embodiments of the present invention are described in detail below, and the same or similar reference numerals throughout the embodiments represent the same or similar elements or elements with the same or similar functions. The embodiments described below are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

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

[0057] The words "preferably", "more preferably", etc. in the present invention refer to embodiments of the present invention that may provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention.

[0058] When a numerical range is disclosed herein, the above range is considered to be 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 features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included 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 described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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 embodiments and control examples of the present invention, the caprolactone compound is polycaprolactone (Perstorp, 6500), 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 the epoxidized natural rubber (Chinese Academy of Tropical Agricultural Sciences) is the dry rubber, which is plasticized on an open mill before use. The phytic acid used is a phytic acid aqueous solution with a content of 50%, and the metal compound used is FeCl3 (analytical purity 99%) as an example.

[0062] Example 1

[0063] This embodiment provides a thermoplastic elastomer, which includes the following preparation raw materials, epoxidized natural rubber and polycaprolactone, in weight percentage, wherein:

[0064] 40 parts of polycaprolactone;

[0065] Epoxidized natural rubber 60 parts;

[0066] Phytic acid 1.2 parts;

[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 ratio of epoxidized natural rubber with an epoxidation degree of 50 mol% to polycaprolactone is 60 / 40. Epoxidized natural rubber, polycaprolactone, phytic acid and FeCl3 powder are mixed in an internal mixer (temperature and speed are 80° C. and 60 rpm, respectively) for 11 minutes to obtain a rubber-based elastomer, which is then compression molded.

[0070] Example 2

[0071] This embodiment provides a thermoplastic elastomer, which includes the following preparation raw materials, epoxidized natural rubber and polycaprolactone, in weight percentage, wherein:

[0072] 40 parts of polycaprolactone;

[0073] Epoxidized natural rubber 60 parts;

[0074] Phytic acid 1.2 parts;

[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 is 60 / 40. Epoxidized natural rubber, polycaprolactone, phytic acid and FeCl3 powder are mixed in an internal mixer (temperature and speed are 80°C and 60 rpm, respectively) for 11 minutes to obtain a rubber-based elastomer and then compression molded. The three-dimensional super-depth video microscope image of ENR and PCL after simple blending and compression molding is shown in the figure. Figure 1 As shown, 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 the whole material in a network form, while the rest is the PCL matrix. This phase separation structure and the continuous network distribution of ENR help the rubber-based elastomer to produce a good shape memory effect due to the entanglement and intermolecular interaction between ENR and PCL.

[0078] Example 3

[0079] This embodiment provides a thermoplastic elastomer, which includes the following preparation raw materials, epoxidized natural rubber and polycaprolactone, in weight percentage, wherein:

[0080] 50 parts of polycaprolactone;

[0081] Epoxidized natural rubber 50 parts;

[0082] Phytic acid 1.2 parts;

[0083] 0.6 parts of metal compound.

[0084] This embodiment also provides a method for preparing the above-mentioned thermoplastic elastomer, comprising the following steps:

[0085] The ratio of epoxidized natural rubber with an epoxidation degree of 50 mol% to polycaprolactone is 50 / 50. Epoxidized natural rubber, polycaprolactone, phytic acid and FeCl3 powder are mixed in an internal mixer (temperature and speed are 80° C. and 60 rpm, respectively) for 11 minutes to obtain a rubber-based elastomer, which is then compression molded.

[0086] Example 4

[0087] This embodiment provides a thermoplastic elastomer, which includes the following preparation raw materials, epoxidized natural rubber and polycaprolactone, in weight percentage, wherein:

[0088] 40 parts of polycaprolactone;

[0089] Epoxidized natural rubber 60 parts;

[0090] Phytic acid 1.2 parts;

[0091] 0.3 parts of metal compound.

[0092] This embodiment also provides a method for preparing the above-mentioned thermoplastic elastomer, comprising the following steps:

[0093] The ratio of epoxidized natural rubber with an epoxidation degree of 50 mol% to polycaprolactone is 60 / 40. Epoxidized natural rubber, polycaprolactone, phytic acid and FeCl3 powder are mixed in an internal mixer (temperature and speed are 80° C. and 60 rpm, respectively) for 11 minutes to obtain a rubber-based elastomer, which is then compression molded.

[0094] Example 5

[0095] This embodiment provides a thermoplastic elastomer, which includes the following preparation raw materials, epoxidized natural rubber and polycaprolactone, in weight percentage, wherein:

[0096] 40 parts of polycaprolactone;

[0097] Epoxidized natural rubber 60 parts;

[0098] Phytic acid 1.2 parts;

[0099] 0.9 parts of metal compound.

[0100] This embodiment also provides a method for preparing the above-mentioned thermoplastic elastomer, comprising the following steps:

[0101] The ratio of epoxidized natural rubber with an epoxidation degree of 50 mol% to polycaprolactone is 60 / 40. Epoxidized natural rubber, polycaprolactone, phytic acid and FeCl3 powder are mixed in an internal mixer (temperature and speed are 80° C. and 60 rpm, respectively) for 11 minutes to obtain a rubber-based elastomer, which is then compression molded.

[0102] Example 6

[0103] This embodiment provides a thermoplastic elastomer, which includes the following preparation raw materials, epoxidized natural rubber and polycaprolactone, in weight percentage, wherein:

[0104] 40 parts of polycaprolactone;

[0105] Epoxidized natural rubber 60 parts;

[0106] Phytic acid 1.2 parts;

[0107] 1.2 parts of metal compound.

[0108] This embodiment also provides a method for preparing the above-mentioned thermoplastic elastomer, comprising the following steps:

[0109] The ratio of epoxidized natural rubber with an epoxidation degree of 50 mol% to polycaprolactone is 60 / 40. Epoxidized natural rubber, polycaprolactone, phytic acid and FeCl3 powder are mixed in an internal mixer (temperature and speed are 80° C. and 60 rpm, respectively) for 11 minutes to obtain a rubber-based elastomer, which is then compression molded.

[0110] Example 7

[0111] This embodiment provides a thermoplastic elastomer, which includes the following preparation raw materials, epoxidized natural rubber and polycaprolactone, in weight percentage, wherein:

[0112] 40 parts of polycaprolactone;

[0113] Epoxidized natural rubber 60 parts;

[0114] Phytic acid 1.2 parts;

[0115] 0.6 parts of metal compound.

[0116] This embodiment also provides a method for preparing the above-mentioned thermoplastic elastomer, comprising the following steps:

[0117] The ratio of epoxidized natural rubber with an epoxidation degree of 50 mol% to polycaprolactone is 60 / 40. Epoxidized natural rubber, polycaprolactone, phytic acid and FeCl3 powder are mixed in an internal mixer (temperature and speed are 170°C and 60 rpm, respectively) for 11 minutes to obtain a rubber-based elastomer, which is then compression molded.

[0118] Example 8

[0119] This embodiment provides a thermoplastic elastomer, which includes the following preparation raw materials, epoxidized natural rubber and ε-caprolactone, in weight percentage, wherein:

[0120] 40 parts of ε-caprolactone;

[0121] Epoxidized natural rubber 60 parts;

[0122] Phytic acid 1.2 parts;

[0123] 0.6 parts of metal compound.

[0124] This embodiment also provides a method for preparing the above-mentioned thermoplastic elastomer, comprising the following steps:

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

[0126] Comparative Example 1

[0127] This comparative example provides a thermoplastic elastomer, which comprises the following preparation raw materials, epoxidized natural rubber and polycaprolactone, in weight percentage, wherein:

[0128] 40 parts of polycaprolactone;

[0129] 60 parts of epoxidized natural rubber.

[0130] This comparative example also provides a method for preparing the above thermoplastic elastomer, comprising the following steps:

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

[0132] Comparative Example 2

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

[0134] Epoxidized natural rubber 60 parts;

[0135] Phytic acid 1.2 parts;

[0136] 0.6 parts of metal compound.

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

[0138] The epoxidized natural rubber with an epoxy degree of 50 mol% is plasticized, and then phytic acid is dropped into the plasticized rubber and mixed evenly before molding.

[0139] Comparative Example 3

[0140] This comparative example provides a thermoplastic elastomer, which comprises the following preparation raw materials, epoxidized natural rubber and polycaprolactone, in weight percentage, wherein:

[0141] 40 parts of polycaprolactone;

[0142] Epoxidized natural rubber 60 parts;

[0143] 1.2 parts of phytic acid.

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

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

[0146] Comparative Example 4

[0147] This comparative example provides a thermoplastic elastomer, which comprises the following preparation raw materials, epoxidized natural rubber and polycaprolactone, in weight percentage, wherein:

[0148] 40 parts of polycaprolactone;

[0149] Epoxidized natural rubber 60 parts;

[0150] 0.6 parts of metal compound.

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

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

[0153] Comparative Example 5

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

[0155] 40 parts of polycaprolactone;

[0156] Epoxidized natural rubber 60 parts;

[0157] 1.2 parts of dicumyl peroxide.

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

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

[0160] Test Case

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

[0162] Mechanical properties test:

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

[0164] Self-healing 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 radially using a homemade device to ensure that the depth of the damaged cracks was 50% of the thickness of the sample and the length of the cracks 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 splines, damaged splines and repaired splines 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 to 7 and Comparative Examples 1 to 5 are shown in Table 3. The thermally induced shape memory performance of the rubber-based elastomer was tested using a high and low temperature tensile machine, and the specific process is as follows: (1) Draw a line segment L0 with a length of 20 mm in the middle area of ​​the dumbbell spline (thickness of 1 mm); (2) Place the spline at 60°C for 5 minutes to ensure that the spline is heated evenly, and then deform it to 100% strain at a rate of 50 mm / min, and then immediately pass liquid nitrogen to cool the experimental cavity. The load remains unchanged during the cooling process, and the deformed sample is cooled to 0°C and then unloaded, and the length L1 at both ends is recorded; (3) The sample is allowed to stand at room temperature, and the length L2 at both ends is recorded after standing for 2 hours; (4) The sample is placed in a 60°C oven and heated for 5 minutes to cause the spline to recover its shape, and then the length L3 at both ends of the spline is recorded. The shape fixation rate (R) of the rubber-based elastomer can be calculated by formulas (1) and (2), respectively. f ) and shape recovery rate (R r ):

[0169]

[0170] Table 1 Mechanical properties test results of Examples 1 to 7 and Comparative Examples 1 to 5

[0171]

[0172]

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

[0174]

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

[0176]

[0177]

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

[0179] As shown in Table 1, compared with the direct addition of phytic acid and metal compounds to epoxidized natural rubber (Comparative Example 2), the addition of polycaprolactone contributes to the improvement of its mechanical properties, and the tensile strength and elongation at break are increased from 8.3MPa, 206.6% (Comparative Example 2) to 11.3MPa, 325.2% (Example 1). At the same time, as shown in 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). It can be seen from this that the low melting point of polycaprolactone gives the rubber-based elastomer a more excellent shape memory property.

[0180] It can be seen from Table 1 that compared with the blend of epoxidized natural rubber and polycaprolactone (Comparative Example 1), the addition of phytic acid and metal compounds is beneficial to the improvement of its mechanical properties, and the tensile strength is increased from 1.8 MPa (Comparative Example 1) to more than 6.4 MPa (Examples 1 to 7), and compared with the introduction of only phytic acid (Comparative Example 3) or metal compounds (Comparative Example 4), the tensile strength is also significantly improved (Examples 1, 4, 5, 6), indicating that a double cross-linked network based on phosphate bonds / coordination bonds is constructed in the PCL / ENR blend, so that the mechanical strength of the rubber-based elastomer is enhanced. At the same time, it can be seen from Table 2 that, compared with the addition of phytic acid and metal compounds (Comparative Example 1) and the addition of diisopropylbenzene peroxide, a common vulcanizing agent in the art (Comparative Example 5), with the addition of phytic acid and metal compounds, the tensile strength self-repair efficiency of the rubber-based elastomer is increased from 37.4% (Comparative Example 1) and 75.3% (Comparative Example 5) to more than 90% (Examples 1-6); In addition, it can be seen from Table 3 that, compared with the addition of phytic acid and metal compounds (Comparative Example 1) and the addition of vulcanizing agent diisopropylbenzene 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% and 67.4% (Comparative Example 1), 78.4% and 88.9% (Comparative Example 5) to more than 93.6% and 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 by the present invention can effectively balance various functions and has broad application prospects.

[0181] In addition, it can be seen from Example 2 that the tensile strength, elongation at break, tensile strength self-repair performance, shape fixation rate, and shape recovery rate of the epoxidized natural rubber with an epoxidation degree of 25 mol% are lower than those measured in Example 1, indicating that the epoxidation degree of the epoxidized natural rubber has an important influence on the mechanical properties of the rubber-based elastomer. As the epoxidation degree increases, the interaction between the epoxidized natural rubber and phytic acid and metal compounds will be enhanced. The stress-strain curves of Examples 1, 2, and 7 ( Figure 2 , 34. The test method steps used are consistent with the test method mentioned in the test example). It can be seen that the overall performance of the epoxidized natural rubber with an epoxidation degree of 50 mol% is better than that of 25 mol%. The results are as follows Figure 2 Moreover, the rubber-plastic ratio of Example 3 is 50 / 50, and compared with Example 1, the content of polycaprolactone is increased, and the tensile strength and shape fixation rate of the rubber-based elastomer are significantly improved (the tensile strength of Example 3 is 13.4 MPa, 95.6%), but the increase in the amount of polycaprolactone inevitably causes a decrease in the elongation at break.

[0182] like Figure 3 As shown, by comparing the three-dimensional super-depth video microscope images of the materials of Example 4 and Example 6 of the present application before and after self-repairing in a vacuum oven at 170°C for 3 hours, it can be seen that after 3 hours of self-repairing, the rubber-based elastomer has been basically repaired completely, indicating that phytic acid and metal compounds construct a double cross-linked network based on phosphate bonds / coordination bonds in the PCL / ENR blend, thereby improving the self-repairing ability of the rubber-based elastomer.

[0183] like Figure 4 As shown, this is the thermal shape recovery process of Example 5 of the present application (the test method process is consistent with the above-mentioned collision memory test process). It can be seen that the rubber-based elastomer can respond within 2 seconds, can achieve shape recovery within 6 seconds, and the shape recovery rate can reach more than 98%, indicating that the rubber-based elastomer has excellent thermal shape memory performance.

[0184] In summary, the present invention realizes the functionalization of rubber-based elastomer by adding phytic acid in rubber-plastic blends. It is proved by experiments that the introduction of polycaprolactone makes the rubber-based elastomer have more excellent shape memory performance, 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 the fields of food packaging, biomedicine, flexible wear, etc. In addition, the raw materials involved in the present invention are all environmentally friendly materials, meet the needs of sustainable development of social economy, and have broad application prospects.

[0185] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention 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 preparation raw materials in parts by weight: 10 to 50 parts of caprolactone compounds; Epoxidized natural rubber 50-90 parts; Phytic acid 0.1-10 parts; 0.1 to 10 parts of metal compound.

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 epoxidation degree of the epoxidized natural rubber is 25 mol% to 75 mol%.

4. The thermoplastic elastomer according to claim 1, characterized in that The caprolactone compound includes at least one of ε-caprolactone monomer, polycaprolactone and polycaprolactone derivatives; preferably, the polycaprolactone derivative includes at least one of polycaprolactone, polycaprolactone diol and methoxypolyethylene glycol polycaprolactone.

5. The thermoplastic elastomer according to claim 4, characterized in that The number average molecular weight of the polycaprolactone is 30,000 to 300,000.

6. The thermoplastic elastomer according to claim 1, characterized in that The usage ratio of the epoxidized natural rubber and the polycaprolactone derivative is (50-60): (40-50); preferably, the metal compound includes at least one of ferric chloride, copper sulfate, zinc chloride and zinc oxide.

7. A method for preparing a thermoplastic elastomer according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: melt-blending epoxidized natural rubber, polycaprolactone, phytic acid and a metal compound in one step, and vulcanizing to obtain the thermoplastic elastomer.

8. The preparation method according to claim 7, characterized in that: The phytic acid is a 20wt% to 80wt% phytic acid aqueous solution.

9. The preparation method according to claim 7, characterized in that: The melt blending includes internal mixing, open mixing and melt extrusion; preferably, the temperature of the melt blending is 80-170° C.; preferably, the rotation speed of the melt blending is 50-70 rpm; preferably, the time of the melt blending is 8-15 min.

10. Use of the thermoplastic elastomer according to any one of claims 1 to 6 in food packaging, biomedicine, and flexible wearable products.

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