WO2024109838A1

WO2024109838A1 - Shape memory composite material, preparation method therefor and use thereof

Info

Publication number: WO2024109838A1
Application number: PCT/CN2023/133432
Authority: WO
Inventors: 丁振; 张敬一; 蔡唯; 王亚飞
Original assignee: 中国科学院深圳先进技术研究院
Priority date: 2022-11-24
Filing date: 2023-11-22
Publication date: 2024-05-30
Also published as: CN115891135A

Abstract

The present invention provides a shape memory composite material, a preparation method therefor and an application thereof. The shape memory composite material comprises a polymer matrix and a support structure arranged in the polymer matrix; the support structure has a truss lattice structure, and the material of the support structure is a first polymer; the material of the polymer matrix is a second polymer; the glass transition temperature of the first polymer is greater than that of the second polymer, and the difference between the two is greater than or equal to 40°C. In the present invention, a support structure having a truss lattice structure is embedded into a matrix as a reinforcing phase, and by means of the design of the support structure and the design and compounding of two polymers, a strong interface bonding force between the matrix and the reinforcing phase is achieved. This significantly improves the modulus of the shape memory composite material, and enables the shape memory composite material to have an excellent shape memory function and withstand substantial deformations, thereby greatly expanding the wide application of 4D printing technology based on shape memory materials in engineering.

Description

A shape memory composite material and its preparation method and application

Technical Field

The present invention belongs to the technical field of 4D printing materials, and in particular relates to a shape memory composite material and a preparation method and application thereof.

Background technique

4D printing refers to the property that the shape of 3D printed materials/structures changes over time under the stimulation of the external environment. Because of the addition of a dimension (time), the shape of 4D printed parts is no longer static, but presents a controllable dynamic form. Under environmental stimulation, its shape can be transformed into a new shape in an expected way to adapt to new needs. In other words, 4D printing is based on 3D printing and implants intelligence into the parts, and its application prospects are very broad.

Most of the current 4D printing is based on the principle of polymer shape memory effect, that is, mechanical deformation of polymer materials at high temperature (polymers are in rubber state), cooling under the condition of maintaining deformation constraints, lowering the temperature of the polymer materials (polymers are in glass state), and the deformation of the materials is basically maintained after the constraints are released; by heating again, the material releases stress and realizes shape recovery. Therefore, polymer materials are natural shape memory materials.

However, current 4D printing shape memory polymer materials have a natural defect, that is, when the temperature of the polymer material is higher than its own glass transition temperature, its elastic modulus is very small, making it difficult to apply to strong and stable structures. Therefore, improving the modulus of 4D printing shape memory polymer materials is an important research topic in the field of materials.

In order to overcome the natural defect of low modulus of shape memory polymers, researchers have tried to enhance its modulus by means of composite materials. For example, CN109897375A discloses a high-strength flexible epoxy resin modified cyanate resin/carbon fiber composite shape memory material, which is composited with a carbon fiber material reinforcement phase and a modified cyanate resin matrix, wherein the modified cyanate resin matrix comprises the following components: 2-4 parts of carboxyl-terminated liquid nitrile rubber, 2-5 parts of flexible epoxy resin, and 8-12 parts of cyanate resin; wherein the cyanate resin is the matrix resin, the carboxyl-terminated liquid nitrile rubber and the flexible epoxy resin are used as toughening agents, the carbon fiber material is the reinforcement phase, and the material is cured by vacuum heating, and the carbon fiber material accounts for 40-60% of the total mass of the shape memory material; the surface of the shape memory material is flat, without obvious defects, and has high tensile strength, tensile modulus, shear strength and bending strength. CN111171520A discloses a modified carbon nanotube reinforced shape memory epoxy resin composite material, which is prepared by heating epoxy resin, modified carbon nanotubes and curing agent under vacuum conditions in the presence of a catalyst; wherein the modified carbon nanotubes are carbon nanotube powders with epoxy groups modified on the surface, and the addition amount is 0.05-1.5wt.%; the modified carbon nanotube reinforced shape memory epoxy resin composite material has good mechanical strength, toughness and shape memory performance. CN103897337A discloses a nanographite sheet reinforced shape memory composite material, including a thermosetting resin, a flaky nano-scale graphite reinforcement material and a curing agent, wherein the weight ratio of the thermosetting resin to the flaky nano-scale graphite reinforcement material is 100:(0.5-4), and the weight ratio of the thermosetting resin to the curing agent is 100:(10-20); the shape memory composite material has an extremely wide temperature adjustment range, and exhibits good practical performance in terms of tensile strength, elastic modulus and shape memory performance.

technical problem

In general, the most common modulus enhancement method is to add ultra-high modulus second phases such as carbon fiber, carbon nanotubes, graphene, carbon black, ceramic sheets, etc. to shape memory polymers. However, these reinforcing phases and polymer matrices differ greatly in material properties and basically belong to different material categories. The binding force of the materials themselves belongs to different categories, so the interface binding force between the materials is poor, and the deformation of the composite material cannot be too large, otherwise the reinforcing phase is prone to fall off; on the other hand, the reinforcing phase material is basically randomly distributed in the matrix, which reduces the shape memory performance of the shape memory polymer material and makes it difficult to meet the performance requirements of 4D printing.

Therefore, developing a material with good shape memory properties, high modulus, and the ability to withstand large deformations is an urgent problem to be solved in this field.

Technical Solutions

In view of the deficiencies in the prior art, the purpose of the present invention is to provide a shape memory composite material and a preparation method and application thereof. By introducing a support structure with a truss lattice structure and through the material design of the support structure and the polymer matrix, the shape memory composite material has both high modulus and excellent shape memory properties, and can withstand a large degree of deformation, thereby greatly expanding the application of 4D printing technology based on shape memory materials.

In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a shape memory composite material, comprising a polymer matrix and a support structure arranged in the polymer matrix; the support structure has a truss lattice structure, and its material is a first polymer; the material of the polymer matrix is a second polymer; the glass transition temperature of the first polymer is greater than the glass transition temperature of the second polymer, and the difference between the two is ≥40°C.

In the shape memory composite material provided by the present invention, a support structure with a truss lattice structure having a high glass transition temperature is embedded as a reinforcing phase in a polymer matrix with a low glass transition temperature, so that the modulus of the shape memory composite material is significantly improved; at the same time, the reinforcing phase has a regular truss lattice structure, so that the shape memory composite material has excellent shape memory properties; and the support structure and the polymer matrix are both polymer materials, and the interface bonding force between the matrix and the reinforcing phase is good, so that the shape memory composite material can withstand large deformation. Therefore, the present invention, through the design of the support structure and the design and compounding of the two polymers, enables the shape memory composite material to have both high modulus and excellent shape memory function, and can be deformed to a large extent, thereby greatly expanding the wide application of 4D printing technology based on shape memory materials in engineering.

In the present invention, the material of the support structure is a first polymer having a high glass transition temperature, preferably a glassy polymer with a high modulus at a use temperature (e.g., room temperature). The material of the polymer matrix is a second polymer having a low glass transition temperature, preferably a rubbery state at a use temperature (e.g., room temperature). Based on the screening and design of the first polymer and the second polymer having a specific glass transition temperature, the high modulus glassy polymer is integrally embedded in the low modulus rubbery polymer with a high modulus, lightweight truss lattice structure, and the formed shape memory composite material can withstand large deformation, the interface bonding force between the matrix and the reinforcement phase is high, and the support structure basically only undergoes elastic deformation within the deformation range set by the shape memory composite material, thereby not affecting the shape memory characteristics of the polymer matrix, and giving the shape memory composite material excellent shape memory function.

In the _present invention, the difference between the glass transition temperature ( Tg1 ) of the first polymer and _{the glass transition temperature (Tg2} ) of the second polymer is ≥40°C, for example, it can be 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C or 140°C, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the said range.

Thus, the shape memory composite material can have a wide temperature adjustment range and deformation range, and within the deformation range, the _{support structure basically only undergoes elastic deformation, which will not affect/reduce the shape memory function of the polymer matrix, so that the shape memory composite material has excellent shape memory properties. In particular, the shape memory composite material is in a rubber state in the temperature range of Tg2} _to Tg1 , has excellent shape programming and memory capabilities, and has a high modulus.

In the present invention, the term "modulus" refers to "elastic modulus" and "storage modulus", and unless otherwise specified, refers to the modulus at room temperature (25°C).

Preferably, the truss lattice structure is an octet-truss truss lattice structure.

Preferably, the diameter of a single cell rod of the octet-truss truss lattice structure is 0.2-2 mm, for example, it can be 0.3 mm, 0.5 mm, 0.8 mm, 1 mm, 1.1 mm, 1.3 mm, 1.5 mm, 1.7 mm or 1.9 mm, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range, and 0.6-1.8 mm is further preferred.

Preferably, the volume percentage of the support structure in the shape memory composite material is 3-30%, for example, it can be 4%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 27% or 29%, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range, and 5-28% is further preferred.

As a preferred technical solution of the present invention, the truss lattice structure is an octet-truss truss lattice structure (octagonal truss lattice structure), and the rod size of the unit cell is determined based on the mechanical properties of the material and through mechanical simulation calculations, preferably with a diameter of 0.2-2 mm, and more preferably 0.6-1.8 mm. Based on the geometric size design of the truss lattice structure (rod size, pores inside the unit cell; the larger the rod size, the smaller the pores inside the unit cell), the volume percentage of the support structure in the shape memory composite material can be adjusted, thereby obtaining a shape memory composite material with different mechanical properties, deformation size and modulus.

In a preferred technical solution, the support structure with an octet-truss lattice structure can be digitally designed and digitally manufactured by a computer, and its geometric dimensions can be precisely controlled; since the support structure and the polymer matrix form a solid structure with 100% volume, namely the shape memory composite material, after the support structure is designed, a Boolean operation is performed on it, and the remaining structure after removing the support structure is the structure of the polymer matrix. In the present invention, a high-precision complex composite material structure (the structure of the support structure and the polymer matrix) is designed based on a computer and prepared non-destructively by 3D printing technology, and the design is the result, so that the shape memory composite material is structurally precise and controllable, and can be customized according to actual needs.

Preferably, the difference in glass transition temperature between the first polymer and the second polymer is 40-130°C, more preferably 50-100°C.

Preferably, the glass transition temperature of the first polymer is 40-190°C, for example, it can be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range, and 50-160°C is further preferred.

Preferably, the first polymer includes any one of acrylic polymer, epoxy polymer, polysulfone, polycarbonate, polyvinyl chloride or a combination of at least two thereof, and is more preferably an acrylic polymer.

Preferably, the first polymer is a photocurable acrylate polymer.

Preferably, the first polymer is a photocurable acrylic polymer having a glass transition temperature of 50-60°C.

The first polymer can be obtained through commercial channels. Preferably, the first polymer is a photocurable polymer, which is convenient for 3D printing. Exemplarily, the first polymer is Veroblue, which is light blue in color and has a glass transition temperature of about 58°C. It is in a glassy state at room temperature and has a high modulus (elastic modulus/storage modulus).

Preferably, the glass transition temperature of the second polymer is -10°C to 80°C, for example, it can be -5°C, 0°C, 5°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 75°C, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range, and -5°C to 65°C is further preferred.

Preferably, the second polymer includes any one of acrylic polymer, polylactic acid, polystyrene, polyvinyl acetate, or a combination of at least two thereof, and is more preferably an acrylic polymer.

Preferably, the second polymer is a photocurable acrylate polymer.

Preferably, the second polymer is a photocurable acrylic polymer having a glass transition temperature of -5°C to 5°C.

The second polymer can be obtained through commercial channels. Preferably, the second polymer is a photocurable polymer, which is convenient for 3D printing. Exemplarily, the second polymer is Tangoblack+, which is black in color and has a glass transition temperature of about -0.5°C. It is in a rubber state at room temperature and has a low modulus (elastic modulus/storage modulus).

In a preferred technical solution, the first polymer is a photocurable acrylate polymer Veroblue, and the second polymer is a photocurable acrylate polymer Tangoblack+. The two polymers can be arbitrarily distributed in space, and the interface bonding force between the support structure prepared by them and the polymer matrix is good, so that the shape memory composite material has a high modulus and excellent shape memory function, and can withstand large deformation, thereby expanding the application of 4D printing technology based on shape memory materials.

In another technical solution, the first polymer may be polysulfone (PSF) having a glass transition temperature of about 190°C, and the second polymer may be polylactic acid having a glass transition temperature of about 60°C; the two polymers are compounded to serve as a support structure and a polymer matrix, respectively, so that the shape memory composite material is in a rubber state within a temperature range of 60-190°C, has excellent shape editing and memory functions, and has a significantly improved rubber modulus.

In another technical solution, the first polymer may be polycarbonate, whose glass transition temperature is about 120°C, and the second polymer may be polylactic acid, whose glass transition temperature is about 60°C; the two polymers are compounded to serve as a support structure and a polymer matrix, respectively, so that the shape memory composite material is in a rubber state within a temperature range of 60-120°C, has excellent shape editing and memory functions, and has a significantly improved rubber modulus.

Preferably, the elastic modulus of the first polymer is greater than the elastic modulus of the second polymer.

Preferably, the elastic modulus of the first polymer is ≥500 MPa, for example, it may be 600 MPa, 800 MPa, 1000 MPa, 1200 MPa, 1500 MPa, 1800 MPa, 2000 MPa, 2200 MPa, 2500 MPa, 2800 MPa, 3000 MPa, 3200 MPa or 3500 MPa, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range, and 800-3000 MPa is further preferred.

Preferably, the elastic modulus of the second polymer is ≤100 MPa, for example, it can be 0.5 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa, 60 MPa, 70 MPa, 80 MPa or 90 MPa, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range, and it is further preferably ≤10 MPa.

In a second aspect, the present invention provides a method for preparing the shape memory composite material as described in the first aspect, the preparation method comprising: 3D printing a first polymer material and a second polymer material to obtain the shape memory composite material.

Preferably, the 3D printing method is inkjet 3D printing.

Preferably, the preparation method specifically comprises: placing the first polymer material and the second polymer material in different printing channels respectively, and performing inkjet 3D printing based on a preset graphic structure to obtain the shape memory composite material.

The first polymer material may be understood as the raw material of the first polymer forming the support structure, and the second polymer material may be understood as the raw material of the second polymer forming the polymer matrix.

The first polymer material and the second polymer material are placed in different printing channels of the 3D printer. Based on the imported 3D graphic structure (pre-designed support structure, polymer matrix structure), the printing software of the 3D printer will automatically slice the 3D model and assign injection positions of different materials. During the printing process, the printer nozzle moves in the horizontal direction and sprays out the polymer material, and solidifies it at the same time (for example, using ultraviolet light for curing). In this way, layer by layer is printed, solidified and stacked until the height of the printing design is reached, thereby obtaining the shape memory composite material.

It should be noted that the shape memory composite material provided by the present invention is not limited to being prepared by the aforementioned preparation method.

Exemplarily, the method for preparing the shape memory composite material further includes: first preparing (for example, preparing by 3D printing) a polymer matrix, and then injecting a first polymer material into the internal voids of the polymer matrix and curing the first polymer material to obtain the shape memory composite material.

Exemplarily, the method for preparing the shape memory composite material further includes: first preparing (for example, preparing by 3D printing) a support structure, and then placing the support structure in a second polymer material and curing it to obtain the shape memory composite material.

Preferably, the curing method includes light curing and/or heat curing.

In a third aspect, the present invention provides an application of the shape memory composite material as described in the first aspect in a 4D printing material.

Beneficial Effects

Compared with the prior art, the present invention has the following beneficial effects:

(1) In the shape memory composite material provided by the present invention, a support structure with a truss lattice structure is embedded in the matrix as a reinforcing phase. Through the design of the support structure and the design and compounding of the two polymers, the interface bonding force between the matrix and the reinforcing phase is good, which significantly improves the modulus of the shape memory composite material and enables it to have excellent shape memory function and withstand a large degree of deformation, thereby greatly expanding the wide application of 4D printing technology based on shape memory materials in engineering.

(2) The present invention can adjust the volume percentage of the support structure in the shape memory composite material through the size design and optimization of the truss lattice structure, thereby obtaining a shape memory composite material with different mechanical properties, deformation size and modulus, so that the elastic modulus of the shape memory composite material can be designed and customized within the range of 22.4-54.1 MPa to meet the differentiated mechanical performance requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a graph showing a loss tangent-temperature curve of a first polymer and a second polymer in a specific embodiment;

FIG2 is a storage modulus-temperature graph of a first polymer and a second polymer in one embodiment;

FIG3 is a schematic structural diagram of a support structure in a specific implementation manner;

FIG4 is a schematic diagram of the structure of a polymer matrix in one embodiment;

FIG5 is a schematic diagram of the structure of a shape memory composite material in a specific embodiment;

FIG6 is a physical picture of the shape memory composite material provided in Example 1;

FIG7 is a stress-strain curve diagram of the shape memory material provided in Comparative Example 1;

FIG. 8 is a stress-strain curve diagram of the shape memory composite material provided in Example 1.

Embodiments of the present invention

The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

As used herein, the terms "comprises," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

"Optionally" or "either" means that the subsequently described matter or event can or cannot occur, and that the description includes instances where the event occurs and instances where it does not.

The indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirements (i.e. the number of occurrences) of the elements or components. Therefore, "a" or "an" should be interpreted as including one or at least one, and the elements or components in the singular form also include the plural form, unless the quantity obviously refers to the singular form only.

In the present invention, the features defined as "first" or "second" may include one or more of the features explicitly or implicitly, and are used to distinguish and describe the features, without distinction of order or importance. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

The terms "one embodiment", "some embodiments", "exemplarily", "specific examples" or "some examples" described in the present invention mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this document, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

In a specific embodiment, the first polymer is a light-curable acrylic polymer Veroblue, which is light blue in color, and the second polymer is a light-curable acrylic polymer Tangoblack+, which is black in color.

Dynamic thermomechanical analysis (DMA, Q800, TA) was performed on the first polymer Veroblue and the second polymer Tangoblack+, and the obtained loss tangent-temperature curve is shown in Figure 1. It can be seen from Figure 1 that the glass transition temperature of Veroblue is about 58°C, and it is in a glassy state at room temperature; the glass transition temperature of Tangoblack+ is about -0.5°C, and it is in a rubbery state at room temperature.

Dynamic thermomechanical analysis (DMA) was performed on the first polymer Veroblue and the second polymer Tangoblack+, and the storage modulus-temperature curve obtained is shown in Figure 2. It can be seen from Figure 2 that the modulus of Veroblue at room temperature is nearly 1000 MPa; the modulus of Tangoblack+ at room temperature is less than 1 MPa.

In the following specific embodiments of the present invention, the first polymer used is Veroblue, and the second polymer is Tangoblack+.

In a specific embodiment, the support structure in the shape memory composite material is an octet-truss truss lattice structure, and its structural schematic diagram is shown in Figure 3. The unit cell geometric parameters (rod size) of the octet-truss truss lattice structure are determined based on the mechanical properties of the material and through mechanical simulation calculations.

In a specific embodiment, the shape memory composite material is a cubic structure, wherein the embedded support structure is the octet-truss truss lattice structure shown in FIG3, and a Boolean operation is performed on it. After removing the support structure, the remaining structure is the structure of the polymer matrix, and its structural schematic diagram is shown in FIG4. The octet-truss truss lattice structure shown in FIG3 is combined with the polymer matrix shown in FIG4 to form a 100% solid cube, that is, the shape memory composite material of the present invention is constituted, and its structural schematic diagram is shown in FIG5.

In the following specific embodiments of the present invention, the support structure has the octet-truss lattice structure shown in Figure 3, and the volume percentage of the support structure in the shape memory composite material is adjusted by designing the diameter of the unit cell rod (as the diameter of the rod increases, the pores inside the unit cell decrease and the volume percentage of the support structure increases).

In a specific embodiment, the shape memory composite material is prepared by inkjet 3D printing, which specifically includes: designing the support structure and the polymer matrix structure by computer drawing software to generate an stl format file; importing the stl format file into the printing software of the 3D printer, and then assigning material properties to each component. The software will automatically slice the three-dimensional model and assign the injection position of each polymer material. During the printing process, the printer nozzle moves in the horizontal direction to spray the polymer material, and at the same time uses ultraviolet light to cure. In this way, layer by layer of printing and light curing are stacked until the height of the printing design is stopped.

Example 1

A shape memory composite material and a preparation method thereof, the structural schematic diagram of the shape memory composite material is shown in FIG5, comprising a polymer matrix and a support structure arranged in the polymer matrix, the structural schematic diagrams of the polymer matrix and the support structure are shown in FIG4 and FIG3 respectively; the support structure is an octet-truss truss lattice structure, and the diameter of a single cell rod is 1 mm; the volume percentage of the support structure in the shape memory composite material is 11.4%. The material of the support structure is a first polymer Veroblue, and the material of the polymer matrix is a second polymer Tangoblack+.

The preparation method of the shape memory composite material comprises:

The preparation was carried out by using a 3D printer (Connex350 from Stratasys) and an inkjet 3D printing method, and the above two polymer materials were printed simultaneously in one component. Specifically, the Veroblue material and the Tangoblack+ material were placed in different printing channels of the 3D printer respectively. Based on the imported preset 3D graphic structure, the printing software automatically sliced the 3D model and assigned the injection positions of different materials. During the printing process, the printer nozzle moved in the horizontal direction to eject the polymer material, and ultraviolet light curing was performed at the same time. The printing, curing and stacking were carried out layer by layer until the printing design height was reached, thereby obtaining the shape memory composite material.

The actual image of the shape memory composite material provided in this embodiment is shown in FIG6 , wherein the dark area is the polymer matrix (the second polymer Tangoblack+), and the light area is the external support structure (the first polymer Veroblue).

Comparative Example 1

A shape memory material, which is different from Example 1 only in that it does not contain a support structure, that is, it is a shape memory material consisting only of the second polymer Tangoblack+.

The mechanical properties of the shape memory composite materials provided in Example 1 and Comparative Example 1 were investigated in the following specific methods:

The stress-strain curve of the material to be tested was tested using a Zwick/Roell Z020 universal materials testing machine. The stress-strain curve of the shape memory material in Comparative Example 1 is shown in FIG7 , which is the stress-strain curve of the second polymer Tangoblack+ at room temperature (25° C.). According to the slope of the curve, the elastic modulus of the material at room temperature can be obtained to be 0.37 MPa.

The stress-strain curve of the shape memory composite material provided in Example 1 is shown in FIG8 . Different curves in FIG8 represent the total strain of different experimental loadings. The same composite material sample was subjected to multiple experiments at room temperature (25° C.), with cyclic loading-unloading, and the total strain increased successively. It can be calculated from FIG8 that the elastic modulus of the shape memory composite material at room temperature is 26.6 MPa, which is about 70 times the elastic modulus of the Tangoblack+ material at room temperature.

At the same time, the curves in Figure 8 have a horizontal section at the end of the unloading section, which coincides with the X-axis. This is due to the viscoelasticity of the first polymer Veroblue as the support structure. Due to the viscoelastic properties, the deformation of the Veroblue polymer material has a hysteresis effect, and the horizontal section on the curve that coincides with the X-axis is not caused by plasticity. These residual deformations can be accelerated by simply increasing the temperature, especially by heating the temperature of the shape memory composite material to above the glass transition temperature of the Veroblue material, the residual deformation of the material can be eliminated instantly, and the shape memory composite material can quickly return to its initial size without leaving permanent residual deformation.

It can be seen that the shape memory composite material provided by the present invention is in a rubbery state as a whole at room temperature (25°C) and has the characteristics of high elasticity; at the same time, its elastic modulus is much higher than that of the matrix material Tangoblack+ that constitutes it, thereby greatly expanding the application space of the matrix material Tangoblack+ at room temperature (rubbery state).

Since the volume percentage of the support structure in the shape memory composite material provided in Example 1 is only 11.4%, which is relatively low, it can well preserve the original properties of the polymer matrix Tangoblack+ material, is in a rubbery state at room temperature, and has high elasticity and shape programming capabilities. At the same time, the shape memory composite material of the present invention can achieve the effect of enhancing the elastic modulus of the original matrix phase Tangoblack+ at room temperature by 70 times with an extremely low volume fraction of the reinforcing phase.

In addition, after the shape memory composite material structure is deformed at room temperature, its shape can be fixed below 0°C. Once the temperature rises to room temperature again, the 4D printed shape memory composite material structure can return to its original shape. Due to its ultra-high rubber modulus, it can be widely used in some application scenarios with certain constrained deformation.

Embodiment 2-5

A shape memory composite material, which differs from Example 1 only in that the diameters of the unit cell rods of the octet-truss lattice structure as the support structure are different, thereby making the volume percentage of the support structure in the shape memory composite material different, as shown in Table 1; other structures, materials and preparation methods are the same as those in Example 1. The modulus test of the shape memory composite materials provided in Examples 2-5 was carried out by the same method as in Example 1, and the data are shown in Table 1.

Table 1

Combined with the performance test results of Examples 1-5, it can be seen that the present invention adopts a 3D printing method to form a shape memory composite material with a specific structure of two polymer materials, Veroblue and Tangoblack+. The new shape memory composite material has higher modulus, hardness and other mechanical properties in the rubber state (at room temperature), and has excellent properties such as high elasticity and programmable shape when the polymer is in the rubber state. At the same time, through the geometric parameter design of the octet-truss truss lattice structure in the support structure, a shape memory composite material with different volume fractions of the reinforcing phase can be obtained, so that the modulus and other mechanical properties of the shape memory composite material can be adjusted, and the elastic modulus is 22.4-54.1 MPa, which meets the performance requirements of 4D printing materials in different application scenarios.

The applicant declares that the present invention uses the above embodiments to illustrate the shape memory composite material and its preparation method and application, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

A shape memory composite material, characterized in that the shape memory composite material comprises a polymer matrix and a support structure arranged in the polymer matrix;

The support structure has a truss lattice structure, and its material is a first polymer;

The material of the polymer matrix is a second polymer;

The glass transition temperature of the first polymer is greater than the glass transition temperature of the second polymer, and the difference between the two is ≥40°C.
The shape memory composite material according to claim 1, characterized in that the truss lattice structure is an octet-truss truss lattice structure;

Preferably, the diameter of a unit cell member of the octet-truss lattice structure is 0.2-2 mm, and more preferably 0.6-1.8 mm.
The shape memory composite material according to claim 1 or 2, characterized in that the volume percentage of the support structure in the shape memory composite material is 3-30%, preferably 5-28%.
The shape memory composite material according to any one of claims 1 to 3, characterized in that the difference in glass transition temperature between the first polymer and the second polymer is 40-130°C, preferably 50-100°C.
The shape memory composite material according to any one of claims 1 to 4, characterized in that the glass transition temperature of the first polymer is 40-190° C., preferably 50-160° C.;

Preferably, the first polymer comprises any one of an acrylic polymer, an epoxy polymer, a polysulfone, a polycarbonate, and a polyvinyl chloride, or a combination of at least two thereof, preferably an acrylic polymer;

Preferably, the first polymer is a light-curable acrylate polymer;

Preferably, the first polymer is a photocurable acrylic polymer having a glass transition temperature of 50-60°C.
The shape memory composite material according to any one of claims 1 to 5, characterized in that the glass transition temperature of the second polymer is -10°C to 80°C, preferably -5°C to 65°C;

Preferably, the second polymer includes any one of acrylic acid ester polymer, polylactic acid, polystyrene, polyvinyl acetate or a combination of at least two thereof, preferably an acrylic acid ester polymer;

Preferably, the second polymer is a light-curable acrylic polymer;

Preferably, the second polymer is a photocurable acrylic polymer having a glass transition temperature of -5°C to 5°C.
The shape memory composite material according to any one of claims 1 to 6, characterized in that the elastic modulus of the first polymer is greater than the elastic modulus of the second polymer;

Preferably, the elastic modulus of the first polymer is ≥500 MPa, more preferably 800-3000 MPa;

Preferably, the elastic modulus of the second polymer is ≤100 MPa, more preferably ≤10 MPa.
A method for preparing the shape memory composite material as described in any one of claims 1 to 7, characterized in that the preparation method comprises: 3D printing a first polymer material and a second polymer material to obtain the shape memory composite material.
The preparation method according to claim 8, characterized in that the 3D printing method is inkjet 3D printing;

Preferably, the preparation method specifically comprises: placing the first polymer material and the second polymer material in different printing channels respectively, and performing inkjet 3D printing based on a preset graphic structure to obtain the shape memory composite material.
An application of the shape memory composite material as claimed in any one of claims 1 to 7 in 4D printing materials.