A preparation method for improving the driving performance of a stimuli-responsive polymer film

Abstract

The application discloses a preparation method for improving the driving performance of a stimulus-responsive polymer film, which comprises the following steps: preparing stimulus-responsive synergistic nanoparticles; blending, extruding polyvinyl acetate copolymer, benzoyl peroxide and the synergistic nanoparticles to obtain a film matrix; performing crosslinking hot-pressing treatment on the film matrix by using hot extrusion to prepare a film primary body; and performing heat setting treatment on the film primary body, and then performing cooling to obtain a polymer film, and regulating the molecular grid structure and the crystalline structure of the film. By introducing the stimulus-responsive synergistic nanoparticles into the polymer film, the sensing effect of the polymer film on external stimuli such as light, electricity and heat is improved, and then the driving response effect of the film is improved. By regulating the extrusion temperature and the hot-pressing temperature, the molecular chain segment network structure and the crystalline structure of the polymer film are controlled, the driving performance of the bidirectional reversible polymer is improved, and large driving deformation and bidirectional reversible deformation stability are realized.

Description

Technical Field

[0001] This invention relates to the field of polymer film technology, specifically to a method for preparing a polymer film with enhanced stimulus-responsive driving performance. Background Technology

[0002] Shape memory polymer materials are a class of smart materials that can respond to changes in external conditions. Under external stimuli such as temperature, light, humidity, electric field, magnetic field or pH, the shape of the material can also change accordingly. However, current shape memory polymer materials are generally unidirectional shape memory, that is, the deformation is irreversible. At the same time, it is difficult to achieve large driven deformation of polymer films, which limits the application range of shape memory polymer materials in different fields.

[0003] The existing defects of polymer films are:

[0004] Patent document CN108688252B mainly describes the assembly of multilayer films to enable the composite film to exhibit rapid and sensitive reversible bending deformation behavior under stimuli such as light, heat, and humidity. However, the aforementioned patent does not consider how to improve the large driven deformation capability of polymer materials, or how to enable the polymer film to have bidirectional reversible deformation capability. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a stimulus-responsive polymer film with improved driving performance, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a stimulus-responsive polymer film with improved driving performance, comprising the following steps:

[0007] Step 1: Preparation of stimulus-responsive synergistic nanoparticles;

[0008] Step 2: Co-extrusion of polyethylene vinyl acetate copolymer, benzoyl peroxide and synergistic nanoparticles to obtain film matrix;

[0009] Step 3: Crosslink the film substrate using hot extrusion and hot pressing to prepare the primary film body;

[0010] Step 4: Heat-set the primary film body, then cool it to obtain the polymer film;

[0011] In steps 3 and 4, the molecular network structure and crystal structure of the thin film are controlled.

[0012] Preferably, the method for preparing the stimulus-responsive synergistic nanoparticles is as follows: deionized water and graphene oxide powder are added to a magnetic stirrer and mixed with ultrasonic assistance to obtain a suspension. Then, NH4VO3 solution is added dropwise to the suspension, followed by the addition of citric acid to adjust the pH of the suspension to neutral to obtain a mixture.

[0013] The mixture was heat-treated at 120–150°C for 4–6 hours, and then centrifuged to obtain particulate precipitate. The particulate precipitate was then washed and dried to obtain stimulus-responsive synergistic nanoparticles.

[0014] Preferably, the graphene oxide powder is 40 mg, the deionized water is 100 ml, the NH4VO3 solution concentration is 0.05 mol / L, the NH4VO3 solution addition amount is 15 ml, and the stimulus-responsive synergistic nanoparticle particle size is 40-150 nm.

[0015] Preferably, the preparation of the film matrix in step 2 includes feeding 20g of polyethylene vinyl acetate copolymer and 12wt% benzoyl peroxide into a small twin-screw extruder and mixing at 10rpm for 5min, then feeding 5wt% of irritation-responsive synergistic nanoparticles into the small twin-screw extruder and mixing at 10rpm for 15min, and obtaining the film matrix after melt blending and extrusion.

[0016] Preferably, the thin film substrate is cooled to room temperature at a cooling rate of 5°C / min.

[0017] Preferably, the cooled film substrate is placed in a hot press for thermal crosslinking treatment, and the thermal crosslinking treatment temperature is 110-150°C, the thermal crosslinking treatment pressure is 10MPa, and the thermal crosslinking treatment time is 20min, to obtain a primary film with a thickness of 0.1-1.2mm.

[0018] Preferably, the heat setting treatment of the primary film body involves placing the primary film body at 40-70°C for 30 minutes, followed by cooling the primary film body to room temperature at a cooling rate of 5°C / min to obtain a polymer film.

[0019] Preferably, the extrusion temperature of the small twin-screw extruder is 90–110°C.

[0020] Preferably, the polymer polyethylene vinyl acetate has a number average molecular weight of 2000 and the benzoyl peroxide has a number average molecular weight of 242.23.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. This invention introduces stimulus-responsive synergistic nanoparticles into polymer films to achieve multiple stimulus-response modes of electricity, light, and temperature, thereby improving the polymer film's perception of external stimuli such as light, electricity, and heat, and thus enhancing the film's driving response effect. By controlling the extrusion temperature and hot-pressing temperature, the molecular chain network structure and crystal structure of the polymer film are controlled, which helps to improve the driving performance of bidirectional reversible polymers and achieve large driving deformation and bidirectional reversible deformation stability.

[0023] 2. This invention enhances the stimulus response capability of thin films by using GO-VO2 composite stimulus-responsive synergistic nanoparticles. The synergistic nanoparticles are blended with polyethylene vinyl acetate copolymer, so that the copolymer molecular chains entangle the nanoparticles. During the hot pressing process to prepare the thin film, the nanoparticles form a particle network in the molecular chain segments of the thin film, which is beneficial to improving the uniformity of the film's response deformation.

[0024] 3. This invention uses heat treatment on polymer films to facilitate control of the distribution of crystalline regions and enhance the stability and driving performance of polymer films during shape memory recovery.

[0025] 4. By controlling the cooling rate of the polymer film, this invention ensures the full crystallization of the polymer film molecular chain segments, which is beneficial to improving the original shape memory effect and enhancing the bidirectional shape memory capability of the film. Attached Figure Description

[0026] Figure 1 This is a driving performance curve diagram of the present invention;

[0027] Figure 2 These are electron microscope images of the polymer film surfaces corresponding to Examples 1, 2, and 3 of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1:

[0030] A method for preparing a stimulus-responsive polymer film with enhanced driving performance involves adding 100 ml of deionized water and 40 mg of graphene oxide powder to a magnetic stirrer and mixing with ultrasonic assistance to obtain a suspension. Then, 15 ml of a 0.05 mol / L NH4VO3 solution is added dropwise to the suspension while stirring slowly. Citric acid is then added to adjust the pH of the suspension to neutral, resulting in a mixture. The mixture is then heat-treated at 135°C for 5 hours. Afterward, the mixture is centrifuged to obtain a particulate precipitate. The precipitate is then washed and dried to obtain GO-VO2 composite stimulus-responsive synergistic nanoparticles with a particle size of 80 nm.

[0031] 20g of polyethylene vinyl acetate copolymer and 12wt% benzoyl peroxide were fed into a small twin-screw extruder and blended at 10rpm for 5min. Then, 5wt% of irritant-responsive synergistic nanoparticles were fed into the small twin-screw extruder and blended at 10rpm for 15min. After melt blending and extrusion, a film matrix was obtained. The film matrix was cooled to room temperature at a cooling rate of 5°C / min.

[0032] The cooled film substrate was placed in a hot press for thermal crosslinking treatment at a temperature of 110°C, a pressure of 10 MPa, and a time of 20 min to obtain a primary film with a thickness of 1 mm. The primary film was then heat-set at 60°C for 30 min, followed by cooling to room temperature at a rate of 5°C / min to obtain a polymer film.

[0033] Example 2:

[0034] A method for preparing a stimulus-responsive polymer film with enhanced driving performance involves adding 100 ml of deionized water and 40 mg of graphene oxide powder to a magnetic stirrer and mixing with ultrasonic assistance to obtain a suspension. Then, 15 ml of a 0.05 mol / L NH4VO3 solution is added dropwise to the suspension while stirring slowly. Citric acid is then added to adjust the pH of the suspension to neutral, resulting in a mixture. The mixture is then heat-treated at 135°C for 5 hours. Afterward, the mixture is centrifuged to obtain a particulate precipitate. The precipitate is then washed and dried to obtain GO-VO2 composite stimulus-responsive synergistic nanoparticles with a particle size of 80 nm.

[0035] 20g of polyethylene vinyl acetate copolymer and 12wt% benzoyl peroxide were fed into a small twin-screw extruder and blended at 10rpm for 5min. Then, 5wt% of irritant-responsive synergistic nanoparticles were fed into the small twin-screw extruder and blended at 10rpm for 15min. After melt blending and extrusion, a film matrix was obtained. The film matrix was cooled to room temperature at a cooling rate of 5°C / min.

[0036] The cooled film substrate was placed in a hot press for thermal crosslinking treatment at a temperature of 130°C, a pressure of 10 MPa, and a time of 20 min to obtain a primary film with a thickness of 1 mm. The primary film was then heat-set at 60°C for 30 min, followed by cooling to room temperature at a rate of 5°C / min to obtain a polymer film.

[0037] Example 3:

[0038] A method for preparing a stimulus-responsive polymer film with enhanced driving performance involves adding 100 ml of deionized water and 40 mg of graphene oxide powder to a magnetic stirrer and mixing with ultrasonic assistance to obtain a suspension. Then, 15 ml of a 0.05 mol / L NH4VO3 solution is added dropwise to the suspension while stirring slowly. Citric acid is then added to adjust the pH of the suspension to neutral, resulting in a mixture. The mixture is then heat-treated at 135°C for 5 hours. Afterward, the mixture is centrifuged to obtain a particulate precipitate. The precipitate is then washed and dried to obtain GO-VO2 composite stimulus-responsive synergistic nanoparticles with a particle size of 80 nm.

[0039] 20g of polyethylene vinyl acetate copolymer and 12wt% benzoyl peroxide were fed into a small twin-screw extruder and blended at 10rpm for 5min. Then, 5wt% of irritant-responsive synergistic nanoparticles were fed into the small twin-screw extruder and blended at 10rpm for 15min. After melt blending and extrusion, a film matrix was obtained. The film matrix was cooled to room temperature at a cooling rate of 5°C / min.

[0040] The cooled film substrate was placed in a hot press for thermal crosslinking treatment at a temperature of 150°C, a pressure of 10 MPa, and a time of 20 min to obtain a primary film with a thickness of 1 mm. The primary film was then heat-set at 60°C for 30 min, followed by cooling to room temperature at a rate of 5°C / min to obtain a polymer film.

[0041] For performance testing, dumbbell-shaped films with dimensions of 10mm*30mm were taken from the polymer films prepared in Examples 1-3 as test specimens. The surface of the polymer films was observed using a microscope, and microscopic images of the structure were obtained. Figure 2 As shown;

[0042] Thermomechanical curves of the driving properties of stimuli-responsive polymer films were obtained using a thermomechanical analyzer, such as... Figure 1 As shown;

[0043] according to Figure 2 It can be seen that the wrinkled and blocky phenomenon on the surface structure of the polymer film corresponding to Example 3 is the most obvious. Figure 1 The test results show that the polymer film corresponding to Example 3 has the best driving performance. The specific reason is that polyethylene vinyl acetate copolymer (PEVA) is a semi-crystalline polymer with a crystalline structure. Free radicals are initiated during the extrusion process of blending PEVA with benzamide peroxide (BPO) initiator. During the hot-press crosslinking process using a hot press, the free radicals are triggered to capture hydrogen atoms from the main chain and side chain of the polymer PEVA, making the carbon atoms of the main chain and side chain of the polymer PEVA become active nodes. These active nodes on the macromolecular chains combine with each other (covalent bonding) to generate interconnected C-C single chemical bonds, which makes the polymer PEVA change from a linear structure to a network structure. Therefore, the polymer film has both a network crosslinking structure and a crystalline structure.

[0044] Polyethylene vinyl acetate copolymer, synergistic nanoparticles, and benzoyl peroxide are co-extruded and hot-pressed to obtain a polymer film. This allows the synergistic nanoparticles to be uniformly distributed in the polymer film, forming a modified graphene network. Graphene has a very wide spectral absorption range, which can efficiently convert light energy into heat energy. When a voltage is applied to the polymer composite film, current flows through the graphene conductive network. Due to the resistance of graphene itself and the contact points, Joule heating is generated, driving the polymer film to deform and realizing a multi-stimulus response mode of the polymer film based on electricity, light, and temperature.

[0045] Polyethylene vinyl acetate copolymer, benzoyl peroxide, and synergistic nanoparticles were co-extruded at an extruder chamber temperature of 90℃-110℃, higher than the melt temperature of polymer PEVA (87℃) and the initiation temperature of thermal initiator BPO (80℃-95℃). This resulted in a long strip-shaped film matrix. The thermal initiation of the initiator generated free radicals, and the free radical initiation rate could be controlled by adjusting the extrusion temperature. The film matrix was then placed in a hot press for hot-press crosslinking to obtain a polymer film. During hot pressing, free radicals abstracted hydrogen, turning the carbon atoms of the PEVA main chain and side chains into active junctions. These active junctions combined to form a network-like crosslinked structure. Furthermore, as the hot-pressing temperature increased, more energy (heat) was provided to the polymer molecular chains, promoting the bonding of active junctions and forming more chemical bonds. This increased the crosslinking density of the crosslinking network, resulting in a denser, blocky, three-dimensional network crosslinked structure, increasing intramolecular stress, and enhancing the polymer's driven strain.

[0046] Thermosetting of hot-pressed polymer films involves thermal annealing followed by cooling. The films are held at a temperature below the melting point (Tm) but above the glass transition temperature (Tg) for an extended period, providing sufficient energy and time for molecular chain rearrangement. Simultaneously, holding at a specific temperature promotes the continuation of residual cross-linking reactions, leading to the formation of more covalent bonds between molecular chains and a denser, more complete three-dimensional network structure. This enhances the thermomechanical properties of the polymer, facilitates control over the distribution of crystalline regions, and strengthens the stability and driving performance during the shape memory recovery process. By controlling the cooling rate of the polymer film, sufficient time is provided for the polymer molecular chains to rearrange, fold, and embed into the lattice, ensuring that molecular chain segments can fully crystallize.

[0047] In summary, by regulating the crosslinking density of polymer molecular chains through hot pressing temperature, the molecular network structure of polymer films can be controlled, thereby improving the driving performance of polymer films. Furthermore, by heat-treating polymer films and controlling the cooling rate, the crystallinity and stability of polymer film molecular chain segments can be improved, thus achieving large driving deformation and bidirectional reversible deformation stability of polymer films.

[0048] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a stimulus-responsive polymer film with enhanced driving performance, characterized in that, Includes the following steps: Step 1: Preparation of stimulus-responsive synergistic nanoparticles; Step 2: Co-extrusion of polyethylene vinyl acetate copolymer, benzoyl peroxide and synergistic nanoparticles to obtain film matrix; Step 3: Crosslink the film substrate using hot extrusion and hot pressing to prepare the primary film body; Step 4: Heat-set the primary film body, then cool it to obtain the polymer film; In steps 3 and 4, the molecular network structure and crystal structure of the thin film are controlled; The method for preparing the stimulus-responsive synergistic nanoparticles is as follows: deionized water and graphene oxide powder are added to a magnetic stirrer and mixed with ultrasonic assistance to obtain a suspension. Then, NH4VO3 solution is added dropwise to the suspension, followed by the addition of citric acid to adjust the pH of the suspension to neutral to obtain a mixture. The mixture was placed at 120-150℃ for 4-6 hours for heat treatment. Then the mixture was centrifuged to obtain particulate precipitate. The particulate precipitate was washed and dried to obtain stimulus-responsive synergistic nanoparticles. The amount of graphene oxide powder is 40 mg, the amount of deionized water is 100 ml, the concentration of NH4VO3 solution is 0.05 mol / L, the amount of NH4VO3 solution added is 15 ml, and the particle size of the stimulus-responsive synergistic nanoparticles is 40-150 nm.

2. The method for preparing a stimulus-responsive polymer film with enhanced driving performance according to claim 1, characterized in that: The preparation of the film matrix in step 2 includes feeding 20g of polyethylene vinyl acetate copolymer and 12wt% benzoyl peroxide into a small twin-screw extruder and mixing at 10rpm for 5min. Then, 5wt% of irritant-responsive synergistic nanoparticles are fed into the small twin-screw extruder and mixed at 10rpm for 15min. After melt blending and extrusion, the film matrix is ​​obtained.

3. The method for preparing a stimulus-responsive polymer film with enhanced driving performance according to claim 2, characterized in that: The film substrate is cooled to room temperature at a cooling rate of 5°C / min.

4. The method for preparing a stimulus-responsive polymer film with enhanced driving performance according to claim 3, characterized in that: The cooled film substrate is placed in a hot press for thermal crosslinking treatment, and the thermal crosslinking treatment temperature is 110-150℃, the thermal crosslinking treatment pressure is 10MPa, and the thermal crosslinking treatment time is 20min, to obtain a primary film with a thickness of 0.1-1.2mm.

5. The method for preparing a stimulus-responsive polymer film with enhanced driving performance according to claim 4, characterized in that: The heat setting treatment of the primary film is to place the primary film at 40-70°C for 30 minutes, and then cool the primary film to room temperature at a cooling rate of 5°C / min to obtain a polymer film.

6. The method for preparing a stimulus-responsive polymer film with enhanced driving performance according to claim 2, characterized in that: The extrusion temperature of the small twin-screw extruder is 90–110°C.

7. The method for preparing a stimulus-responsive polymer film with enhanced driving performance according to claim 1, characterized in that: The number-average molecular weight of the polyethylene vinyl acetate copolymer is 2000, and the number-average molecular weight of benzoyl peroxide is 242.23.

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