A method for preparing a dual-dynamic network crosslinked bio-based composite

Abstract

The application relates to the technical field of biological composite materials, and particularly relates to a preparation method of a double-dynamic-network-crosslinked biological-based composite material, which comprises the following steps: S1, stirring an ENR emulsion, and simultaneously adding 3 phr of tartaric acid and 6 phr of 3-amino phenylboronic acid in rubber dry weight, and stirring until no obvious solid particles are observed in the emulsion to obtain an E-TA / APBA composite emulsion; S2, adding curdlan into deionized water to prepare a water dispersion; S3, adding the water dispersion into the E-TA / APBA composite emulsion to obtain an E-T3A6Ca mixed solution, wherein a represents the component of curdlan in the rubber dry weight, and a is one of 3, 6, 9 or 12; and S4, pouring the E-T3A6Ca mixed solution into a mold, water-bath heating and curing, and air-drying until the weight is constant to obtain the biological-based composite material. The application can realize network rearrangement at a relatively low temperature, and the composite material has the properties of recycling, self-repairing and shape memory. The introduction of functional fillers such as carbon nanotubes and ammonium polyphosphate endows the biological-based composite material with the properties of electromagnetic shielding, flame retardation and photo-thermal conversion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biological composites, in particular to a preparation method of a double dynamic network cross-linked bio-based composite material. BACKGROUND

[0002] Elastomers are well known for their high elasticity, high elongation at break, excellent impact strength, and are widely used in tire production, sealing devices, soft robots, flexible wearable electronic devices, electromagnetic shielding elements and other fields. However, the chemical synthesis of elastomers is difficult to recycle, which easily causes environmental pollution and waste of resources. Therefore, in recent years, the research on bio-based elastomers has become a hot topic.

[0003] Compared with traditional petroleum-based elastomers, the main raw material of bio-based elastomers is derived from renewable biomass resources, and the carbon emissions generated during production are lower, which helps to slow down the trend of global warming.

[0004] Renewable bio-based polymer epoxidized natural rubber (ENR) is gradually becoming an indispensable important material in the preparation process of bio-based elastomers due to its high activity and good processing characteristics. The processing conditions of biomass polysaccharide curdlan are mild and environmentally friendly, which can well improve the physical and mechanical properties of epoxidized natural rubber (ENR) elastomer. In addition, bio-based elastomers also need to introduce dynamic cross-linking network to realize recyclability, self-repair and other properties. Dynamic cross-linking network can undergo reversible reaction under external stimuli (such as light, heat, pH, etc.), forming dynamic bonds such as beta-hydroxy ester bond, disulfide bond, borate ester bond, hydrogen bond, etc., which provides a feasible strategy for the repeated use of bio-based elastomers. SUMMARY

[0005] In view of the shortcomings of the prior art, the present application provides a preparation method of a double dynamic network cross-linked bio-based composite material, which can realize network rearrangement at a relatively low temperature, so as to have recyclability, self-repair and shape memory performance.

[0006] The present application is realized by the following technical scheme:

[0007] A preparation method of a double dynamic network cross-linked bio-based composite material is provided, comprising the following steps:

[0008] S1, slowly stirring the ENR emulsion, and adding 3 phr of tartaric acid and 6 phr of 3-aminophenylboronic acid based on the dry weight of the rubber into the emulsion, and continuously stirring until there are no obvious solid particles in the emulsion, to obtain an E-TA / APBA composite emulsion;

[0009] S2, adding curdlan into deionized water to prepare a water dispersion;

[0010] S3, adding the water dispersion prepared in S2 into the E-TA / APBA composite emulsion under stirring to obtain an E-T3A6Ca mixture, wherein a represents a component of guayule in the dry rubber, and a is one of 3, 6, 9 or 12;

[0011] S4, pouring the E-T3A6Ca mixture into a mold, and after water bath heating and curing, taking out and air drying to constant weight to obtain a bio-based composite material.

[0012] Further, in step S4, the E-T3A6Ca mixture is continuously stirred for 30-60 min before being poured into the glass mold.

[0013] As preferred, in step S4, the temperature of the water bath heating is 90℃.

[0014] A bio-based composite material prepared by the preparation method of the bio-based composite material using double dynamic network crosslinking.

[0015] A preparation method of an electromagnetic shielding and heat-conducting bio-based composite material, wherein the E-T3A6Ca mixture prepared in steps S1-S3 of the preparation method of the bio-based composite material using double dynamic network crosslinking is used, and a is 9, and a CNTs dispersion liquid of a certain amount of dry rubber is further added dropwise to obtain an E-T3A6C9Nc mixture, wherein c represents a component of CNTs in the dry rubber, and c is one of 2, 4, 6 or 8, and after the E-T3A6C9Nc mixture is stirred uniformly, after water bath heating and curing, taking out and air drying to constant weight, an electromagnetic shielding and heat-conducting bio-based composite material is prepared.

[0016] A preparation method of a flame-retardant bio-based composite material, wherein the E-T3A6C9Nc mixture obtained by the preparation method of the bio-based composite material using double dynamic network crosslinking is used, and c is 8, and a 50wt% water-soluble ammonium polyphosphate aqueous solution is further added dropwise to obtain an E-T3A6C9N8Fd mixture, wherein d represents a component of water-soluble ammonium polyphosphate, and d=60, and after the E-T3A6C9N8Fd mixture is stirred and mixed uniformly, after water bath heating and curing, taking out and air drying to constant weight, a flame-retardant bio-based composite material is obtained.

[0017] A preparation method of a conductive bio-based composite material, wherein the bio-based composite material obtained in step S4 of the preparation method of the bio-based composite material using double dynamic network crosslinking is used, and a conductive paste is applied to the surface thereof, and after 120℃ drying and curing for 30 min, the conductive bio-based composite material is obtained after cooling to room temperature.

[0018] The beneficial effects of the present application are as follows:

[0019] The application constructs a double dynamic network cross-linked bio-based elastomer with boron-oxygen dynamic bond and beta-hydroxy ester bond by using 3-aminophenylboronic acid (APBA) / tartaric acid (TA) as the base material of epoxidized natural rubber (ENR) / cis-1,4-polyisoprene (CD), and the composite material can realize network rearrangement at a relatively low temperature due to the existence of reversible boron-oxygen bond and beta-hydroxy ester bond, so the composite material has the properties of recyclability, self-repairing and shape memory. The tensile stress of the elastomer can be up to 9.07 MPa, the self-repairing efficiency can be up to 84.4% in 1 hour, and the introduction of functional fillers such as carbon nanotubes (CNTs) and ammonium polyphosphate (APP) endows the bio-based composite material with electromagnetic shielding, flame retardant and light-heat conversion properties, the highest electromagnetic shielding efficiency of the X waveband can be up to 39.72 dB, the flame retardant burning time can be up to 20 s, and the bio-based composite material has the properties of shape memory and light-heat conversion, and has potential application value in the field of bio-based elastomer electronic shielding components. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The flow chart of the bio-based composite material of the application.

[0021] Figure 2 The XRD pattern of CD, ENR and E-T3A6C12 composite material in the application.

[0022] Figure 3 The FTIR infrared spectrum of E-TA / APBA / CD composite material in the application.

[0023] Figure 4 The loss factor diagram of ENR, E-T3A6C6 and E-T3A6C12 in the application.

[0024] Figure 5 The DSC curve of TA / APBA / ENR composite material in the application.

[0025] Figure 6 The C1s peak diagram of E-T3A6C12 in the application.

[0026] Figure 7 The stress-strain curve image of E-T3A3C3, E-T3A6C3 and E-T3A3C12 in the application.

[0027] Figure 8 The stress-strain curve image of ENR and E-TA / APBA / CD composite material in the application.

[0028] Figure 9 The Mooney-Rivlin curve of ENR and E-TA / APBA / CD in the application.

[0029] Figure 10The cyclic tensile curve diagram of E-TA / APBA / CD composite material in the application when the strain is fixed at 300%.

[0030] Figure 11 The super-depth microscope photos of E-T3A6C9 composite material before and after healing in the application.

[0031] Figure 12 The stress-strain curve diagram of ENR and recycled E-T3A6C12 in the application.

[0032] Figure 13 The FTIR spectra of E-T3A6C12 material before and after curing in the application.

[0033] Figure 14 The FTIR spectra of E-T3A6C12 material before and after three mechanical recycling in the application.

[0034] Figure 15 The electromagnetic shielding efficiency diagram of E-TA / APBA / CD / CNTs composite material in the application under X-band.

[0035] Figure 16 The micro-scale combustion calorimetry test diagram of E-T3A6C9N8 and E-T3A6C9N8F60 in the application.

[0036] Figure 17 The TGA test diagram of E-T3A6C9N8 and E-T3A6C9N8F60 in the application.

[0037] Figure 18 The DTG test diagram of E-T3A6C9N8 and E-T3A6C9N8F60 in the application. DETAILED DESCRIPTION

[0038] In order to clearly illustrate the technical features of the scheme, the scheme will be described below through specific embodiments.

[0039] The various raw materials used in the present application can be purchased from the market, the epoxidized natural rubber (ENR) latex (solid content 30%, epoxy degree 40%) is purchased from the Institute of Agricultural Products Processing of the Chinese Academy of Tropical Agricultural Sciences (Zhanjiang), DL-tartaric acid (TA, 99%) is purchased from China Macklin Co., Ltd., 3-aminophenylboronic acid (APBA, 97%) is purchased from Anjie (Shanghai) Pharmaceutical Chemical Co., Ltd., food-grade curdlan (CD) is purchased from Haiose Biotechnology Co., Ltd., 1,2-dimethylimidazole (DMI, 99%) is purchased from China Macklin Co., Ltd., and carbon nanotube dispersion (CNTs, 10%) is provided by Shenzhen Hongdachangjin Evolution Technology Co., Ltd. Water-soluble ammonium polyphosphate (APP) powder is purchased from Shandong Kaimik New Material Co., Ltd. Conductive paste LY-560 is purchased from Shenzhen Yilei Technology Co., Ltd.

[0040] A preparation method of a double-dynamic network cross-linked bio-based composite material, comprising the following steps:

[0041] S1, slowly stir the ENR emulsion, and add 3 phr of tartaric acid and 6 phr of 3-aminophenylboronic acid based on the dry weight of the rubber into the emulsion, and continue stirring until there are no obvious solid particles in the emulsion, to obtain an E-TA / APBA composite emulsion.

[0042] S2, add curdlan to deionized water to prepare a water dispersion.

[0043] S3, add the water dispersion prepared in S2 to the E-TA / APBA composite emulsion under stirring to obtain an E-T3A6Ca mixture, wherein a represents the curdlan component in the dry weight of the rubber, and a takes one of 3, 6, 9 or 12.

[0044] S4, pour the E-T3A6Ca mixture into a mold after continuous stirring for 30 min, and then heat and cure in a water bath at 90°C, take out and air dry to constant weight to obtain a bio-based composite material.

[0045] A bio-based composite material prepared by a preparation method of a double-dynamic network cross-linked bio-based composite material.

[0046] A preparation method of an electromagnetic shielding and heat-conducting bio-based composite material, using the E-T3A6Ca mixture prepared in steps S1-S3 of the preparation method of a double-dynamic network cross-linked bio-based composite material, and a taking 9, and then adding a certain amount of CNTs dispersion based on the dry weight of the rubber to obtain an E-T3A6C9Nc mixture, wherein c represents the CNTs component in the dry weight of the rubber, and c takes one of 2, 4, 6 or 8, and then stirring the E-T3A6C9Nc mixture uniformly, heating and curing in a water bath, taking out and air drying to constant weight to prepare an electromagnetic shielding and heat-conducting bio-based composite material.

[0047] A preparation method of a flame-retardant bio-based composite material, using the E-T3A6C9Nc mixed solution obtained by the preparation method of the bio-based composite material with double dynamic network crosslinking, and c is 8, then 50wt% water-soluble ammonium polyphosphate aqueous solution is added dropwise to obtain an E-T3A6C9N8Fd mixed solution, wherein: d represents the component of water-soluble ammonium polyphosphate, d=60, after the E-T3A6C9N8Fd mixed solution is stirred and mixed uniformly, it is heated in a water bath for curing, then it is taken out and air dried to constant weight to obtain a flame-retardant bio-based composite material.

[0048] A preparation method of a conductive bio-based composite material, using the bio-based composite material obtained in step S4 of the preparation method of the bio-based composite material with double dynamic network crosslinking, a conductive slurry is applied to the surface, and the conductive bio-based composite material is obtained after drying and curing at 120°C for 30min and cooling to room temperature.

[0049] For comparison, an E-CD composite material was prepared according to the above experimental steps. Specifically, a certain amount of curdene gum was added to 10ml deionized water to prepare a water dispersion. The curdene gum water dispersion was poured into the ENR emulsion under stirring for 30min, and then poured into a glass mold and placed in a 90°C water bath for 10min. After the gel was formed, the mold was taken out and placed in a fume hood for air drying to constant weight. The sample prepared in this step is coded as E-Cb, and b is one of 3, 6, 9, and 12.

[0050] Construction and structure characterization of E-TA / APBA / CD composite material:

[0051] To verify the crystal structure of CD and its distribution state in ENR, XRD was used to test CD, ENR and their composite materials. It can be seen from Figure 2 that CD appears crystallization peaks at 2θ=11.26° and 2θ=20.54°, which is due to the crystallization region caused by intermolecular hydrogen bonding. ENR appears a wide peak near 2θ=18.92°, which is an amorphous diffraction peak. For the E-T3A6C12 composite elastomer, only one amorphous diffraction peak appears at 2θ=18.62, and no CD crystallization peak appears, which may be because the helical structure of CD is re-coiled after heating, and the newly generated helical chains are tightly entangled with the ENR molecular chains and uniformly dispersed in the ENR matrix. The hydrogen bonding between the hydroxyl groups on the CD matrix and the epoxy groups on the ENR causes the hydrogen bonding between the CD molecules to be weakened, resulting in a decrease in crystallinity. At the same time, the size of the CD network generated by heating is small, and the CD crystallization peak may be shielded by ENR, so that the CD crystallization peak cannot be detected, and therefore the XRD pattern of the obtained E-T3A6C12 composite material is similar to that of ENR and no CD crystallization peak is observed, which indicates that the filler is uniformly dispersed in the ENR.

[0052] To verify the interface interaction between CD and ENR and the cross-linking effect of APBA on ENR, FTIR spectroscopy was used to characterize CD, ENR and bio-based composites.

[0053] From Figure 3 It can be seen that for ENR, characteristic peaks appear at 877 cm -1 and 1244 cm -1 , which are formed by the stretching vibration of epoxy groups. For ENR / TA / APBA / CD composites, a characteristic peak of fatty amine appears at 1072 cm -1 , indicating the successful grafting reaction between the amino group on APBA and the epoxy group on ENR. B3O3 characteristic peaks appear at 760 cm -1 and 705 cm -1 , proving the existence of boron-oxygen rings and indicating that the composites successfully introduced boron-oxygen ring dynamic bonds. With the increase of CD content from 0 to 12 phr, the hydroxyl absorption peak at 3336 cm -1 blue shifts to 3288 cm -1 , which also indicates the formation of hydrogen bonding interaction between CD and ENR.

[0054] Figure 4 shows the tan δ of ENR / TA / APBA / CD composites as a function of temperature. With the increase of CD content, the tan δ of ENR / TA / APBA / CD composites continuously shifts to higher temperatures. The tan δ of ENR is only -10.23°C, and due to the restriction of CD and boron-oxygen dynamic bonds on the migration of ENR chains, the tan δ of ENR / TA / APBA / CD composites increases to -5.83°C.

[0055] To study the effect of CD filler and boron-oxygen dynamic bonds formed by APBA on the glass transition temperature of ENR, DSC was used to test the composites, and the results are shown in Figure 5 . Due to the interface hydrogen bonding and covalent cross-linking, the CD network structure and boron-oxygen ring dynamic bonds restrict the migration of ENR molecular chains, so the glass transition temperature (Tg) of E-CD samples increases with the increase of CD content. The Tg of pure ENR is about -20°C, and with the increase of CD content, the Tg of the composites also increases, for example, the Tg of E-T3A6C12 increases to -18.25°C, which is about 1.75°C higher than that of pure ENR.

[0056] The XPS spectrum of the ENR / TA / APBA / CD composite material shows that the ENR / TA / APBA / CD composite material contains N element, which is related to the introduction of APBA in the ENR / TA / APBA / CD composite material. Since the ENR / TA / APBA / CD composite material introduces APBA, it also contains B element in addition to N element. The specific changes of the chemical bond type of the bio-based composite material are studied by XPS peak fitting, as shown in Figure 6 For the ENR / TA / APBA / CD composite material, the C1s peak fitting shows five peak components, respectively 288.5 (C=O), 286.4 (C-O), 285.8 (C-N), 285.1 (C-C), and 284.8 (C=C) eV. C=O comes from the carboxyl group of TA, which can indicate that TA is introduced into the system, and the appearance of C-N bond can indicate that the amino group of APBA is successfully crosslinked with the epoxy group of ENR.

[0057] In summary, it can be shown that APBA successfully undergoes ring-opening reaction to introduce boronic acid groups, and a boron-oxygen six-membered ring dynamic bond is formed.

[0058] The mechanical properties of the E-TA / APBA / CD composite material were studied.

[0059] To explore the best amount of APBA, three groups of tensile tests, E-T3A3C3, E-T3A6C3 and E-T3A12C3, were set. Figure 7 It can be found from that when the amount of APBA is small, the covalent crosslinking produced is less, and the improvement of the mechanical properties is limited. When the amount of APBA is large, the mechanical properties of the material decrease, because there is part of free APBA that does not form covalent crosslinking in the composite material, which affects the chain migration of the material, resulting in a decrease in the mechanical properties.

[0060] The reinforcing effect of the filler network and dynamic covalent crosslinking in the E-TA / APBA / CD composite material on ENR was studied by tensile test on pure ENR and E-CD series samples. The stress-strain curves of ENR and E-TA / APBA / CD samples are shown in Figure 8 .

[0061] CD achieves excellent dispersion in the rubber, forming a continuous network framework. The abundant hydroxyl groups on the CD surface form strong hydrogen bonds with epoxy groups. The dehydration of the APBA-grafted ENR emulsion upon drying, resulting in the formation of hexacyclic boranes and hydrogen bonds, enhances the interfacial interaction between CD and ENR, effectively enhancing the mechanical properties of the composite. However, due to the rigid structure of CD fillers, the network formed when filling the ENR matrix increases the rigidity of the composite. Therefore, as the filler dosage increases, the elongation at break of the composite decreases compared to pure ENR. However, the material's elasticity remains excellent, with the pure ENR composite achieving a tensile strength of 1.26 MPa and an elongation at break of 1403%. The E-CD12 material, on the other hand, achieves a tensile strength of 9.07 MPa, nearly eight times that of the pure ENR sample, and an elongation at break of 1016%, only 72% of that of the pure ENR sample. This demonstrates the significant improvement of the mechanical properties of ENR materials by CD fillers.

[0062] In order to study the interaction between fillers and polymer chains, the Mooney-Rivlin equation was used to further evaluate the stress-strain curves.

[0063]

[0064] Where: σ* is the reduced stress, σ and λ are the true stress and expansion ratio (λ = strain / 100 + 1) calculated from the stress-strain test, and C1 and C2 are constants that are independent of λ. Figure 9 As shown, with increasing strain, the σ* of the composite material first decreases, then levels off, and then declines. At higher elongations, the σ* of ENR does not increase with increasing strain, indicating minimal bonding between ENR chains. However, a significant sudden increase in the σ* of the E-TA / APBA / CD composite is observed at high elongation ratios (λ-1) less than 0.2, which is attributed to the limited extensibility of the ENR chains and the interfacial interactions between the rubber chains and the CD filler, which restrict rubber chain motion. At low elongation ratios (λ-1 greater than 0.9), σ* decreases sharply at the beginning of stretching as the CD network framework emerges.

[0065] In order to further test the dynamic reversibility of hydrogen bonding interactions in E-TA / APBA / CD materials, cyclic tensile tests were performed, e.g. Figure 10The residual strain of ENR is the lowest in the cyclic stretching process, because the network almost recovers to the original state due to the physical entanglement of ENR chains itself on the entropy. With the increase of CD content, the hysteresis loss increases significantly, which indicates that more energy is dissipated during the loading-unloading cycle due to the reconstruction of the supramolecular hydrogen bond network, which is similar to ionic crosslinking. The residual strain of pure ENR is 37.5% at 300% strain cycle, while with the increase of CD content, the residual strain of the composite in the cyclic stretching process shows an upward trend, and the residual strain of E-T3A6C3 and E-T3A6C12 in the 300% cycle reaches 42.4% and 49.7% respectively. This is mainly due to the formation of a continuous interpenetrating network of CD in the rubber matrix, and this network structure presents a rigid structure, which affects the stability of the network structure in the stretching process, and more energy dissipation occurs in the loading-unloading cycle. In order to analyze the energy dissipation in the stretching process, the dissipation energy of the composite can be obtained by calculating the area inside the cyclic stretching curve. When the CD content increases to 12 phr, the dissipation energy of the composite reaches 225.8 kJ / m 3 , which is 9.1 times that of the composite without CD. This shows that the hydrogen bond interaction between CD and ENR molecular chains is broken and recovered in the stretching cycle, which makes the composite consume more energy. Therefore, the hydrogen bond interaction between CD and ENR can effectively consume more external force, and at the same time improve the mechanical strength of the composite while maintaining the excellent elasticity of the material.

[0066] Study the healing behavior of E-TA / APBA / CD composite material:

[0067] The E-TA / APBA / CD composite material formed by CD enhances the mechanical properties of the material through hydrogen bond interaction and boron-oxygen hexacyclic dynamic crosslinking, and improves the self-healing performance through hydrogen bond interaction and boron-oxygen dynamic bond.

[0068] The self-healing performance of the composite material under the influence of temperature, time and different content of CD was studied through the self-healing experiment. Alkaline fuchsin and methylene blue were used to dye during the preparation of E-T3A6C9, and then two dumbbell-shaped samples were cut in the middle with a blade. The fractured surfaces were immediately brought into contact at room temperature, and then healed at 80°C for 1h. The healed samples can be tested for twisting, stretching, etc. It is found that, as shown in Figure 11 , the wound is basically healed, leaving only a shallow mark. The healed sample can load a 500g weight without breaking.

[0069] Study the solvent recovery and mechanical recovery of E-TA / APBA / CD composite material:

[0070] To explore the basic properties of the recycled material, the stress-strain curves of the recycled material and the ENR without CD filler were compared to analyze the changes in the mechanical properties of the material, and the results are shown in Figure 12 The mechanical properties of E-12 recovered by soaking in alkaline solution were significantly lower than those of the sample without soaking, but were still slightly higher than those of pure ENR samples. This is because a small amount of CD was still not removed during the soaking process and remained in the rubber matrix, improving the mechanical properties of the material through weak hydrogen bonding between interfaces.

[0071] 3-aminophenylboronic acid (APBA) has active amino groups that can undergo ring-opening reaction with the epoxy groups of ENR for grafting, while the boron hydroxyl group at the other end can form a boron-oxygen dynamic bond through dehydration condensation. The strong hydrogen bonds between the curd (CD) and the epoxy groups of ENR can endow the material with temperature-sensitive self-healing function. During the hot pressing of ENR, the carboxyl groups of tartaric acid (TA) introduced into the system can form β-hydroxy ester bonds with the epoxy groups of ENR, making the material have recyclable performance as shown in Figure 1 After being crushed, the sample after the first processing (conditions: 120°C, 15MPa, 30min) can be mechanically recycled after repeated primary processing. To explore the structural changes of the material before and after vulcanization and mechanical recycling, the material was tested by FTIR spectroscopy. The cured composite material showed a C=O characteristic peak at 1666cm -1 , indicating that β-hydroxy ester bonds were formed inside the cured material, confirming the successful reaction of TA with the epoxy groups of ENR, as shown in Figure 13 The FTIR spectrum of the sample recycled three times was similar to the initial spectrum, indicating that the material could be mechanically recycled without significant structural changes, as shown in Figure 14

[0072] The electromagnetic shielding properties and electrical conductivity of E-TA / APBA / CD / CNTs composite materials were studied:

[0073] The heterogeneous interface between the CNTs conductive network and the ENR latex network can accumulate free charges, while the functional groups of CNTs molecules can act as electric dipoles. The resulting interface and dipole polarization loss are beneficial to electromagnetic interference shielding. To characterize the electromagnetic shielding effect of the composite material, the electromagnetic shielding efficiency of the material with different amounts of CNTs was tested in the X-band (8.2GHz-12.4GHz). As shown in Figure 15 , with the amount of CNTs increasing from 2phr to 8phr, the electromagnetic shielding efficiency of the material gradually increased, with the maximum value increasing from 12.68dB of E-T3A6C9N2 to 39.72dB of E-T3A6C9N8, indicating that the electromagnetic shielding effect of the material can be adjusted by changing the amount of additives. ​

[0074] To evaluate the electrical conductivity of the composite, the conductive paste was applied to the surface of the elastomer, placed in a 120°C oven for 30 min, and the sample was removed and cooled to room temperature for use. After connecting the composite to the circuit, the small bulb lit up, indicating that the material was conductive. After the sample was cut, the circuit was disconnected, so the bulb went out, and after the material healed, the bulb lit up again, indicating that the composite remained conductive after healing.

[0075] The flame retardant properties of the E-TA / APBA / CD / CNTs / APP composite were studied:

[0076] Because APP was added to the ENR / TA / APBA / CD / CNTs / APP composite, its presence can improve the flame retardant properties of the system. The burning behavior of the two materials was characterized by a micro-scale combustion calorimeter, as shown in Figure 16 The HRR value of the film material decreased significantly after the addition of APP, from 288.64 W / g to 148.40 W / g, indicating that E-T3A6C12N8 released a lot of heat during combustion, and the addition of APP reduced the heat release of the material, indicating that it could improve the flame retardant properties of the material, making the ENR / TA / APBA / CD / CNTs / APP composite have flame retardant properties.

[0077] To analyze the changes in the thermal stability of the elastomer after the combination of APP and CD, APBA, the composite without and with the addition of APP were selected as the test objects. From Figure 17 and Figure 18 It can be seen that, compared with the composite without the addition of APP, the thermal stability of the composite with the addition of APP decreased, because APP preferentially decomposes in the rubber matrix, and NH3 and H2O produced at temperatures above 300°C accelerate the decomposition of rubber molecular chains. The composite without the addition of APP had a higher temperature corresponding to the maximum weight loss rate peak of 428°C, and the final mass retention rate was only 6.7%. Compared with E-T3A6C12N8F60, the temperature corresponding to the maximum weight loss rate of the composite moved to lower temperatures, the peak area decreased significantly, and the final mass retention rate improved significantly, indicating that the addition of the flame retardant promoted the formation of the intumescent barrier layer, delayed the thermal degradation of the composite at high temperatures, promoted the carbonization of the substrate, and improved the flame retardant properties of the rubber. After the composite was burned by the flame for a long time, a carbon residue layer was formed at the burning site. APP, as an intumescent flame retardant, releases metaphosphoric acid when subjected to high temperatures, which catalyzes the formation of a carbon layer. Subsequently, the ammonia gas generated by the thermal decomposition of APP causes the carbon layer to expand, hindering the inward transmission of oxygen and heat, and imparting good flame retardant properties to the composite.

[0078] In the present application, by taking ENR / CD as the base material and CNTs and APP as functional fillers, a recyclable, self-healing and shape memory bio-based elastomer is successfully prepared, which has electromagnetic shielding, flame retardant, light-heat conversion and conductive properties. CD and ENR jointly construct a structure similar to steel-reinforced concrete, which increases the Young's modulus of the composite material by 5.45 times, and the highest electromagnetic shielding X wave band is 39.72 dB. This kind of bio-based elastomer provides potential possibilities in the field of electronic shielding component preparation.

[0079] Of course, the above description is not limited to the above examples, and the technical features not described in the present application can be realized by or using the prior art, which will not be repeated here; the above examples and drawings are only used to illustrate the technical solutions of the present application and are not a limitation on the present application, and the preferred embodiments of the present application are described in detail, and those skilled in the art should understand that the changes, modifications, additions or substitutions made by those skilled in the art within the essential scope of the present application do not deviate from the purpose of the present application, and should also belong to the protection scope of the claims of the present application.

Claims

1. A method for preparing a dual dynamic network cross-linked bio-based composite material, characterized by: The following steps are involved: S1. Slowly stirring the ENR emulsion, while adding 3 phr of tartaric acid (TA) and 6 phr of 3-aminophenylboronic acid (APBA) based on the dry weight of rubber, and continuing stirring until no obvious solid particles are left in the emulsion, to obtain an E-TA / APBA composite emulsion; S2. adding curdlan (CD) into deionized water to prepare an aqueous dispersion; S3. Add the aqueous dispersion prepared in S2 to the E-TA / APBA composite emulsion while stirring to obtain an E-T3A6Ca mixed solution, wherein: a represents the content of the curdlan component in the dry weight of the rubber, in phr, and a is one of 3, 6, 9 or 12; S4. Pour the E-T3A6Ca mixed solution into a mold, heat and cure it in a water bath, and then take it out and air-dry it to a constant weight to obtain a bio-based composite material.

2. The method for preparing a dual dynamic network cross-linked bio-based composite material according to claim 1, characterized in that: In step S4, the E-T3A6Ca mixture is stirred for 30 to 60 minutes before being poured into the mold.

3. The method for preparing a dual dynamic network cross-linked bio-based composite material according to claim 1, characterized in that: In step S4, the water bath is heated to a temperature of 90°C.

4. A bio-based composite material prepared using the method for preparing a dual dynamic network cross-linked bio-based composite material according to claim 1.

5. A method for preparing an electromagnetic shielding and thermally conductive bio-based composite material, characterized by: An E-T3A6Ca mixed solution is prepared in steps S1-S3 of the preparation method according to claim 1, and a is taken as 9. A CNTs dispersion with a certain amount of rubber dry weight is then added dropwise thereto to obtain an E-T3A6C9Nc mixed solution, wherein: c represents the component content of CNTs in the rubber dry weight, in phr, and c is one of 2, 4, 6 or 8. After the E-T3A6C9Nc mixed solution is uniformly stirred, heated in a water bath for curing, and then taken out and air-dried to constant weight, an electromagnetic shielding and thermal conductive bio-based composite material is prepared.

6. A method for preparing a flame-retardant bio-based composite material, characterized by: The E-T3A6C9Nc mixed liquid obtained by the preparation method according to claim 5, where c is 8, is then dropwise added with a 50wt% water-soluble ammonium polyphosphate aqueous solution to obtain an E-T3A6C9N8Fd mixed liquid, wherein: d represents the component content of the water-soluble ammonium polyphosphate, in phr, d=60, and the E-T3A6C9N8Fd mixed liquid is stirred and mixed evenly, heated in a water bath for curing, and then taken out and air-dried to constant weight to obtain a flame-retardant bio-based composite material.

7. A method for preparing a conductive bio-based composite material, characterized by: The conductive bio-based composite material obtained in step S4 of the preparation method according to claim 1 is used to apply a conductive paste to its surface, dry and cure at 120° C. for 30 minutes, and then cool to room temperature to obtain a conductive bio-based composite material.

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