A method for preparing an electro-thermal dual-stimulus shape memory composite actuator

Abstract

The present application relates to the technical field of flexible stimulus-responsive self-driven devices, and particularly relates to a preparation method of an electric-temperature dual-stimulus shape-reversible composite material driver, which comprises the following steps: firstly, chemically modifying and modifying conductor particles and ultrasonically dispersing a solution to improve interface adhesion and improve interface bonding between the conductor and the polymer; secondly, using a double-screw mixing device to melt blend and compound polyvinyl acetate to prepare a shape memory semi-crystalline and carbon-carbon single bond network structure; thirdly, uniformly doping and embedding conductor unit particles into the molecular network to construct a three-dimensional conductive network and form a double-continuous phase structure conductive blend; and finally, hot-pressing the conductive blend to initiate a macromolecular radical crosslinking reaction and prepare an electric-temperature dual-stimulus shape-reversible composite material driver with a conductive-semi-crystalline-crosslinking three-dimensional network structure. The present application can realize electric and thermal dual-stimulus reversible deformation response of the shape memory composite material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible stimulus-responsive self-driven devices, and particularly relates to a preparation method of an electric-temperature dual-stimulus shape-reversible composite material driver. BACKGROUND

[0002] Stimulus-responsive polymers refer to a class of intelligent polymer drivers capable of sensing and responding to external stimuli under the condition of external environmental stimuli (temperature, light, pH, electricity, magnetic field, etc.), with the development of bionics and material science.

[0003] However, most stimulus-responsive materials can only respond to a single external stimulus, and only have one-way deformation (i.e., irreversible deformation), which is greatly limited in the application fields of biomedical implant tissue scaffolds, self-driven folding aerospace structures, artificial muscles, etc., and it is imperative to develop flexible materials with dual or multiple stimulus deformation responsiveness. Shape memory polymer materials with reversible deformation function can autonomously and reversibly move under external stimuli without additional mechanical energy, and are increasingly concerned, and have potential application value in the field of lightweight flexible drivers. With the diversification of intelligent driving application scenarios, remote control, local and instantaneous high controllability are increasingly required, and non-thermal energy triggered deformation modes are highly concerned.

[0004] Therefore, in order to solve the above problems, the present application provides a preparation method of an electric-temperature dual-stimulus shape-reversible composite material driver. SUMMARY

[0005] The purpose of the present application is to solve the problems existing in the prior art, and a preparation method of an electric-temperature dual-stimulus shape-reversible composite material driver is provided. By introducing conductive particles, reversible phase crystallization and crosslinked network interconversion are triggered by Joule heat of the internal resistance of the composite material when electrified, realizing the electric and thermal dual-stimulus reversible deformation response of the shape memory composite material. The shape-reversible composite material prepared by the method can not only be driven to deform by temperature, but also can remotely trigger the reversible shape memory deformation effect of the composite material under electric stimulation.

[0006] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0007] A preparation method of an electric-temperature dual-stimulus shape-reversible composite material driver, comprising the following steps:

[0008] Step 1, first, the conductor particles are chemically modified and dispersed in solution to improve the interface adhesion and the interface bonding between the conductor and the polymer;

[0009] Step 2: Using a twin-screw mixer, shape memory semi-crystalline and carbon-carbon single-bond cross-linked molecular network structures are prepared by melt blending and radical bimolecular coupling of polyethylene vinyl acetate.

[0010] Step 3: Uniformly dope and embed conductive unit particles into the molecular network structure to construct a conductive three-dimensional network, forming a conductive blend with a dual continuous phase structure;

[0011] Step 4: Finally, hot-pressing the conductive blend initiates a macromolecular free radical cross-linking reaction, enhancing the orientation structure and density of multi-walled carbon nanotubes, and preparing an electro-temperature dual-stimulation deformation reversible composite material actuator with a conductive-semi-crystalline-crosslinked three-dimensional network structure.

[0012] Preferably, in step 1, the conductor particle is a multi-walled carbon nanotube with a high thermal conductivity >10W / mK; the modification process of the conductor particle is as follows: the multi-walled carbon nanotube is added to a potassium hydroxide aqueous solution with a concentration of 25-40wt% for activation treatment at 400-450℃ for 60min, followed by ultrasonic dispersion for 30min, and then sealed and heated in a stainless steel high-pressure furnace at 160℃ for 2h. Finally, the solution is filtered, and the multi-walled carbon nanotube is washed with distilled water and ethanol until neutral, and then dried in an oven at 50℃ for 8h to constant weight to obtain the modified multi-walled carbon nanotube.

[0013] Preferably, in step 2, the melt blending process involves feeding thermoplastic polyethylene vinyl acetate polymer particles and benzoyl peroxide at a mass percentage ratio of 10:100 into a twin-screw mixer and melt-blending for 3 minutes; the polyethylene vinyl acetate polymer consists of 18 wt% vinyl acetate; the three zones of the twin-screw mixer are preheated to 90°C, 95°C, and 100°C, and equilibrated for 5 minutes to ensure uniform temperature within the machine cavity; the polyethylene vinyl acetate polymer has an average number-average molecular weight of 2000 and a melting point of 87°C; the peroxide initiator benzoyl peroxide has an average molecular weight of 242.23 and a melting point of 104°C-106°C.

[0014] Preferably, in step 3, the conductive three-dimensional network is constructed by slowly feeding modified multi-walled carbon nanotubes into a blend of polyethylene vinyl acetate and benzoyl peroxide through the feed port of a twin-screw mixer, and then circulating and melting the blend at 10 rpm for 10 minutes. The pressure and shear force of the twin-screw mixer ensure that the conductive particles are uniformly dispersed in the homogeneous polymer network. After melt-extrusion-cooling, a cylindrical strip-shaped conductive blend with a diameter of 3 mm is obtained. The multi-walled carbon nanotubes account for 0.1 wt% to 0.5 wt% of the conductive blend by mass.

[0015] Preferably, in step 4, the hot pressing method is as follows: the conductive blend with a dual continuous phase structure is covered with two layers of polytetrafluoroethylene film release paper, and the outer layer is sandwiched with a metal plate and sent into a hot press for peroxide crosslinking reaction. The hot pressing temperature is 130°C, the pressure is 10MPa, and the hot pressing time is 20min, to produce an electro-temperature dual-stimulation deformation reversible composite material actuator with a thickness of about 0.1-1mm.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. This invention ingeniously prepares a flexible intelligent composite material actuator with electro- and thermo-reversible deformation properties by introducing multi-walled carbon nanotubes as conductive particles into a semi-crystalline, network-crosslinked reversible dynamic molecular network. Besides providing a direct temperature-induced heating method to trigger polymer deformation, this invention also offers an indirect heating method for applications where direct thermal triggering is not possible. Multi-walled carbon nanotubes are uniformly embedded in the polymer molecular network, and reversible polymer deformation is triggered by electrical stimulation utilizing the polymer's internal resistance. This method offers high controllability (i.e., remote, local, and instantaneous stimulation deformation), and due to the polymer's low thermal transfer coefficient, it does not transfer excessive heat to the surrounding environment. It has great potential applications in self-deploying and self-folding aerospace structures, biomedical implantable scaffolds, flexible actuators, and sensors.

[0018] 2. The carbon nanotubes in this invention are carbon nanomaterials with outstanding properties in many aspects. This invention combines multi-walled carbon nanotubes with a semi-crystalline, network-crosslinked, reversible dynamic molecular network as both the conductive and deformation-reversible phases. This allows the electro-temperature dual-stimulation composite actuator to exhibit better deformation reversibility, superior mechanical strength, flexibility, and electroactivity, as well as higher conductivity and lower resistance. Furthermore, the chemical functionalization modification of multi-walled carbon nanotubes and the ultrasonic-assisted solution mixing method used in this invention ensure uniform dispersion of multi-walled carbon nanotubes within the polymer network, improving the compatibility of different components in the blend. This is key to the excellent deformation reversible shape memory properties of the electro-temperature dual-stimulation composite actuator. Attached Figure Description

[0019] Figure 1 This is a cyclic curve of the temperature-stimulated deformation reversible driving performance of Embodiment 1 of the present invention;

[0020] Figure 2 Comparison of strain-temperature cycling curves for different multi-walled carbon nanotube contents in Examples 1, 2, and 3 of the present invention;

[0021] Figure 3 This is a schematic diagram of the reversible deformation response to dual electrical and temperature stimuli in Embodiment 1 of the present invention. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the scope of protection of the present invention. The embodiments described in this invention are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] Example 1:

[0024] A method for preparing an electro-temperature dual-stimulation deformation reversible composite actuator involves adding a quantitative amount of multi-walled carbon nanotubes (MWCNTs) to a 25-40 wt% potassium hydroxide aqueous solution. After slow stirring at 400-450°C for 60 min, the solution is ultrasonically dispersed in an ultrasonic disperser for 30 min, followed by sealed heating in a 160°C stainless steel high-pressure furnace for 2 h. The solution is then filtered, and the MCCNTs are washed with distilled water and ethanol until neutral. The MCCNTs are then dried in a 50°C oven for 8 h to constant weight, yielding modified MCCNTs. 15 g of polyethylene vinyl acetate polymer, 10 wt% benzamide peroxide, and 0.1 wt% MCCNTs are sequentially fed into a small twin-screw mixer and internally circulated at 10 rpm for 10 min. The extrudate is collected and cooled to room temperature. The extrudate is then subjected to a peroxide crosslinking reaction in a hot press at 130°C to produce an electro-temperature dual-stimulation deformation reversible composite actuator film EB with a thickness of approximately 0.1-1 mm. 10 C 0.1 .

[0025] Example 2:

[0026] A method for preparing an electro-temperature dual-stimulation deformation reversible composite actuator involves adding a quantitative amount of multi-walled carbon nanotubes (MWCNTs) to a 25-40 wt% potassium hydroxide aqueous solution. After slow stirring at 400-450°C for 60 min, the solution is ultrasonically dispersed in an ultrasonic disperser for 30 min, followed by sealed heating in a 160°C stainless steel high-pressure furnace for 2 h. The solution is then filtered, and the MCCNTs are washed with distilled water and ethanol until neutral. The solution is then dried in a 50°C oven for 8 h to constant weight, yielding modified MCCNTs. 15 g of polyethylene vinyl acetate polymer, 10 wt% benzamide peroxide, and 0.5 wt% MCCNTs are sequentially fed into a small twin-screw mixer and internally circulated at 10 rpm for 10 min. The extrudate is collected and cooled to room temperature. The extrudate is then subjected to a peroxide crosslinking reaction in a hot press at 130°C to produce an electro-temperature dual-stimulation deformation reversible composite actuator film EB with a thickness of approximately 0.1-1 mm. 10 C 0.5 .

[0027] Example 3:

[0028] A method for preparing an electro-temperature dual-stimulation deformation reversible composite actuator involves adding a quantitative amount of multi-walled carbon nanotubes (MWCNTs) to a 25-40 wt% potassium hydroxide aqueous solution. The solution is slowly stirred at 400-450°C for 60 min, then ultrasonically dispersed in an ultrasonic disperser for 30 min. Following this, the solution is sealed and heated in a 160°C stainless steel high-pressure furnace for 2 h. After filtering, the MCCNTs are washed with distilled water and ethanol until neutral, and then dried in a 50°C oven for 8 h to constant weight, yielding modified MCCNTs. 15 g of polyethylene vinyl acetate polymer and 10 wt% benzamide peroxide are sequentially fed into a small twin-screw mixer and internally circulated at 10 rpm for 10 min. The extrudate is collected and cooled to room temperature. The extrudate is then subjected to a peroxide crosslinking reaction in a hot press at 130°C to produce an electro-temperature dual-stimulation deformation reversible composite actuator film EB with a thickness of approximately 0.1-1 mm. 10 C0.

[0029] The electro-temperature dual-stimulation reversible deformation composite materials from Examples 1-3 were cut into dumbbell-shaped films with a length of 10 mm and a width of 2 mm. The temperature-driven deformation reversible shape memory performance cycling curves were tested using a thermomechanical analyzer (TMA), as shown below. Figure 1 , 2 As shown; Schematic diagram of reversible deformation response to dual electrical and temperature stimuli. Figure 3 As shown.

[0030] from Figure 1 As can be seen, under a constant external stress of 0.1 MPa, the sample EB...10 C 0.1 They exhibit elongation deformation during cooling and contraction deformation recovery during heating, and maintain high repeatability and reversible deformation under long-term heating-cooling stimulation cycles; such as Figure 2 This study demonstrates the effect of composite material actuators with different component contents (0.1 wt% and 0.5 wt%) of multi-walled carbon nanotubes (MWCNTs) on the reversible deformation after temperature stimulation. Under constant external force, the composite material exhibits strain elongation upon cooling and strain contraction upon heating with temperature changes. When the mass fraction of MWCNTs is 0.1 wt%, the driven strain and recovery rate reach 3.4% and 99.8%, respectively. During the cooling process of polymer melts, some polymers retain a disordered structure and become amorphous solids. However, the polymer composite material actuator of this invention is composed of multiple linear molecular bridges bonded and cross-linked into a network structure and crystalline regions, and its molecular chains rearrange, exhibiting a cooling-deformation phenomenon. Figure 3 Exhibit sample EB 10 C 0.1 The bending mobility after electrical stimulation shows that under 10V voltage stimulation, the film is driven to open within 5s, and the shape is closed and restored within 20s when the voltage is turned off. It also exhibits long-term reversible deformation under continuous on-off cycles. The essence of the electro-induced deformation of this invention is electro-induced internal resistance Joule heating-thermal triggered deformation.

[0031] In summary, the reversible composite material actuator prepared by the present invention, which is subject to both electrical and temperature stimulation, can trigger the reversible phase crystallization and cross-linking network transformation by the Joule heating of the composite material under the influence of electricity and heating. This enables the shape memory composite material to generate reversible, reciprocating flexible deformation under both electrical and temperature stimulation, and has broad application prospects in the fields of flexible actuators, biomedicine, and soft robotics.

[0032] The descriptions and practices disclosed in this invention are readily apparent and understandable to those skilled in the art, and various modifications and refinements can be made without departing from the principles of this invention. Therefore, any modifications or improvements made without departing from the spirit of this invention should also be considered within the scope of protection of this invention.

Claims

1. A method for preparing a reversible composite material actuator subjected to dual electro-temperature stimulation, characterized in that, Includes the following steps: Step 1: First, the conductor particles are chemically modified and ultrasonically dispersed in solution to improve interfacial adhesion and enhance the interfacial bonding between the conductor and the polymer. Step 2: Using a twin-screw mixer, shape memory semi-crystalline and carbon-carbon single-bond cross-linked molecular network structures are prepared by melt blending and radical bimolecular coupling of polyethylene vinyl acetate. Step 3: Uniformly dope and embed conductive unit particles into the molecular network structure to construct a conductive three-dimensional network, forming a conductive blend with a dual continuous phase structure; Step 4: Finally, hot-pressing the conductive blend initiates a macromolecular free radical cross-linking reaction, enhancing the orientation structure and compactness of multi-walled carbon nanotubes, and preparing an electro-temperature dual-stimulation deformation reversible composite material actuator with a conductive-semi-crystalline-cross-linked three-dimensional network structure. In step 1, the conductor particles are multi-walled carbon nanotubes with high thermal conductivity. The modification process of the conductor particles is as follows: multi-walled carbon nanotubes are added to a potassium hydroxide aqueous solution with a concentration of 25-40 wt% and activated at 400-450℃ for 60 min, followed by ultrasonic dispersion for 30 min, and then heated in a stainless steel high-pressure furnace at 160℃ for 2 h. Finally, the solution is filtered, and the multi-walled carbon nanotubes are washed with distilled water and ethanol until neutral. They are then dried in an oven at 50℃ for 8 h until constant weight is obtained to obtain the modified multi-walled carbon nanotubes. In step 2, the melt blending process involves feeding thermoplastic polyethylene vinyl acetate polymer particles and benzoyl peroxide at a mass percentage ratio of 10:100 into a twin-screw mixer and melt-blending for 3 minutes. The polyethylene vinyl acetate polymer consists of 18 wt% vinyl acetate. The three zones of the twin-screw mixer are preheated to 90°C, 95°C, and 100°C, and equilibrated for 5 minutes to ensure uniform temperature within the machine chamber. In step 3, the conductive three-dimensional network is constructed by slowly feeding modified multi-walled carbon nanotubes into a blend of polyethylene vinyl acetate and benzoyl peroxide through the feed port of a twin-screw mixer. The blend is then internally circulated and melt-blended at 10 rpm for 10 minutes. The pressure and shear force of the twin-screw mixer ensure that the conductive particles are uniformly dispersed in the homogeneous polymer network. After melt-extrusion-cooling, a cylindrical strip-shaped conductive blend with a diameter of 3 mm is obtained. The multi-walled carbon nanotubes account for 0.1 wt% to 0.5 wt% of the conductive blend by mass. In step 4, the hot pressing method is as follows: the conductive blend with a dual continuous phase structure is covered with two layers of polytetrafluoroethylene film release paper, and the outer layer is sandwiched with a metal plate and sent into a hot press for peroxide cross-linking reaction. The hot pressing temperature is 130°C, the pressure is 10MPa, and the hot pressing time is 20min, to produce an electro-temperature dual-stimulation deformation reversible composite material actuator with a thickness of 0.1-1mm.

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