Thermotropic expansion-retraction silicone rubber material as well as preparation method and application thereof

Abstract

The invention belongs to the field of fiber preparation, and particularly discloses a preparation method of a thermally-induced expansion-retraction silicone rubber material, which comprises the following steps: uniformly mixing a silicone rubber prepolymer and thermal expansion microspheres to form a prepolymer mixture, and connecting the prepolymer mixture to an inner spinning head through a first injection tube; connecting a sodium alginate aqueous solution to an outer spinning head through a second injection tube, wherein the mass ratio of the thermal expansion microspheres to the prepolymer mixture is 5-10%; the core-shell fibers are pushed out under the condition that the flow velocity ratio of the inner spinning head to the outer spinning head is set to be 0.8-1.2, the thermal expansion silicon rubber fibers are obtained after cross-linking curing and shell removal, and the elastic modulus of the cross-linked silicon rubber prepolymer is smaller than 1 MPa. The continuous thermal expansion silicon rubber fiber which has stable thermal expansion-retraction capability and retains good mechanical properties such as elasticity of silicon rubber can be prepared only by using low-content thermal expansion microspheres, and secondary macroscale and performance change can be generated when the continuous thermal expansion silicon rubber fiber is heated; therefore, the method has application prospects in the fields of thermal insulation fabrics, thermal driving assemblies, temperature sensors and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation, and more particularly to a thermo-expanding-shrinking silicone rubber material, its preparation method, and its application. Background Technology

[0002] Thermally responsive materials, capable of changing volume and shape with temperature variations, hold immense promise for applications in temperature sensing, controlled drug release, thermal energy storage, and soft robotics. Thermally expandable microspheres, a representative of thermally responsive materials, expand in volume upon heating. When incorporated into other polymer matrix materials, they can modulate the material's macro- and micro-structure, density, and mechanical properties. Currently, thermoplastic elastomers (such as polyurethane) are typically used as the polymer matrix, combining them with thermally expandable microspheres. However, during thermoplastic processing, the thermal expansion of the microspheres occurs simultaneously. This results in the microspheres remaining in an expanded state after the material is solidified, losing their thermal expansion capacity. Even if unexpanded microspheres are incorporated, these thermoplastic polymers tend to melt upon thermal expansion, making it difficult to maintain a solid state. Silicone rubber, an elastomer based on siloxane polymers, is highly favored in numerous applications due to its excellent physical and chemical properties. The preparation of thermally responsive materials using silicone rubber as a substrate has become a research hotspot. For example, Chinese Patent 202411505841.8 discloses a temperature-responsive expandable silicone rubber-based sealing material and its preparation method. The material is prepared by uniformly mixing room-temperature vulcanizing silicone rubber, expandable polymer microspheres, carbon black, etc., followed by the addition of a crosslinking agent and catalyst for curing. This yields a temperature-responsive expandable silicone rubber-based sealing agent that expands upon temperature increase, thus providing a sealing effect. However, this silicone rubber-based sealing material is a large block, which limits its practical application, and it also presents the problem of not being able to simultaneously achieve both expansion performance and elasticity.

[0003] Compared to larger bulk materials, fibrous materials can be woven into ropes or fabrics, with diverse and wide-ranging applications. Introducing thermally expandable microspheres into silicone rubber fibers could potentially control the diameter, length, density, surface roughness, thermal conductivity, and mechanical properties of the fibers and spheres through thermal expansion and contraction, enabling applications in sealing, cushioning, insulation, and biomimetic deformation. However, due to the poor processability of silicone rubber, research on silicone rubber fibers is limited, and no thermally expandable fibers based on silicone rubber or their preparation methods have been proposed. Although Chinese patent (202111314133.2) establishes a cross-linked polymer spinning technology including silicone rubber, it does not address composite materials combining silicone rubber fibers and thermally expandable microspheres, nor their preparation methods. Therefore, how to combine silicone rubber with thermally expandable microspheres so that its expansion rate is not limited by the stress of silicone rubber, and obtain silicone rubber fiber materials with stable and considerable thermal expansion and contraction capabilities, is an urgent problem to be solved. Summary of the Invention

[0004] In view of this, the present invention provides a method for preparing a thermo-expanding-shrinking silicone rubber material, thereby solving the problems existing in the prior art.

[0005] This invention provides a method for preparing a thermo-expanding-shrinking silicone rubber material, comprising the following steps:

[0006] S101 Take silicone rubber prepolymer and thermally expanded microspheres, mix them evenly to form a prepolymer mixture, and connect it to the inner spinning head through the first injection tube; take sodium alginate aqueous solution and connect it to the outer spinning head through the second injection tube, wherein the mass concentration of the thermally expanded microspheres and the prepolymer mixture is 2-20%.

[0007] S102, under the condition that the flow rate ratio of the inner spinning head and the outer spinning head is 0.6-1.5, extrudes a core-shell fiber with a fibrous silicone rubber / thermal expansion microsphere prepolymer as the core and an alginate hydrogel as the outer shell into a calcium chloride aqueous solution. After cross-linking and curing, the outer shell is removed by immersion in sodium citrate solution, and then the fiber is obtained by cleaning and drying.

[0008] Preferably, in step S102, the mass ratio of the thermally expanded microspheres to the prepolymer mixture is 5-10%.

[0009] Preferably, in step S102, the flow rate ratio between the inner spinning head and the outer spinning head is 0.8-1.2.

[0010] Preferably, in step S101, the inner spinning head uses a 16-22 G needle, and the outer spinning head uses a 12-16 G needle.

[0011] Preferably, the particle size of the thermally expandable microspheres before expansion is less than 3% of the diameter of the thermally expandable silicone rubber fiber, and the particle size after expansion does not exceed 10% of the diameter of the thermally expandable silicone rubber fiber.

[0012] Preferably, in step S101, the mass concentration of the sodium alginate aqueous solution is 1.5 wt%; in step S102, the mass concentration of the calcium chloride aqueous solution is 2 wt%.

[0013] Preferably, in step S101, two or more types of thermally expandable microspheres can be selected, and the thermal expansion-retraction capability of the thermally expandable silicone rubber fiber can be controlled by utilizing the expansion-retraction temperature range of the thermally expandable microspheres.

[0014] Preferably, in step S101, the prepolymer mixture of silicone rubber prepolymer and thermally expanded microspheres is subjected to a polymerization reaction time of 0.1 s. -1 Viscosities at shear rates ranging from 1 to 12000 Pa·s, 1 s -1 Viscosities at shear rates ranging from 1 to 1500 Pa·s, 10 s⁻¹ -1 Viscosities at shear rates range from 1 to 200 Pa·s.

[0015] Preferably, in step S101, two or more types of thermally expandable microspheres can be selected, and the thermal expansion-retraction capability of the thermally expandable silicone rubber fiber can be controlled by utilizing the expansion-retraction temperature range of the thermally expandable microspheres.

[0016] Another aspect of the present invention provides thermo-expanding-shrinking silicone rubber materials and their applications in the preparation of thermal insulation fabrics, thermal response actuators or temperature sensors.

[0017] In summary, this invention provides a method for preparing thermotropically expanding-retracting silicone rubber fibers. Through coaxial spinning, core-shell fibers are obtained with a thermotropically expanding microsphere / silicone rubber hybrid prepolymer as the core and sodium alginate hydrogel as the outer shell. The sodium alginate hydrogel provides shaping and protection for the core during its curing process. Subsequent deshelling yields continuous thermotropically expanding silicone rubber fibers with uniform diameter. The method is simple, low-cost, and easy to promote. The thermotropically expanding-retracting silicone rubber fibers prepared using this method exhibit considerable and stable thermotropic expansion-retracting capacity under specific flow rates and thermotropically expanding microsphere content, with the microsphere expansion rate not limited by rubber stress, while retaining good elastic and other comprehensive mechanical properties.

[0018] Furthermore, when the thermally expandable silicone rubber fiber of this invention is heated to the expansion temperature of the thermally expandable microspheres, it undergoes a one-time, large-scale expansion on a macroscopic scale due to the one-time and significant thermal expansion of the microspheres, resulting in changes in its diameter, length, and mechanical properties. After being overheated to the maximum tolerance temperature of the thermally expandable microspheres, it shrinks back, causing the changes in properties to disappear and restoring the diameter, length, and mechanical properties to a state close to the initial state. Utilizing its thermal expansion-shrinkage characteristics, it has promising applications in fields such as thermal insulation fabrics, thermally driven components, temperature sensors, and floating materials. Attached Figure Description

[0019] Figure 1 These are scanning tunneling microscopy images of the surface of thermally expanded silicone rubber fibers prepared with different contents of thermally expanded microspheres, in their initial and heated expansion states.

[0020] Figure 2 These are cross-sectional scanning tunneling microscopy images of thermally expanded silicone rubber fibers prepared with different contents of thermally expanded microspheres, in their initial and heated expansion states.

[0021] Figure 3 Photographs of the spinning process when preparing thermally expandable silicone rubber fibers for different flow rate ratios.

[0022] Figure 4 The images show the initial and thermally expanded states of thermally expandable silicone rubber fibers prepared using needles of different sizes, with ink marks indicating the length of the fibers.

[0023] Figure 5 The image shows the thermally expandable silicone rubber fiber prepared in Example 1 in its initial, heated expansion, and shrinkage states. The fiber has ink marks indicating its length.

[0024] Figure 6 These are the stress-strain curves of the thermally expandable silicone rubber fiber prepared in Example 1 in its initial, heated expansion, and heated shrinkage states.

[0025] Figure 7 The images show the thermally expandable fabric prepared in Example 7 in its initial and heated expansion states.

[0026] Figure 8 The images shown are from Example 7, showing the preparation of a thermally expanded fabric from thermally expanded silicone rubber fibers. 8a is a photograph of a roll of silicone rubber fibers; 8b is a photograph of a roll of thermally expanded silicone rubber fibers prepared in Example 1; 8c is a photograph of the weaving process of a continuous thermally expanded silicone rubber fiber; and 8d is a photograph of the woven thermally expanded silicone rubber fiber fabric.

[0027] Figure 9 To obtain the thermal insulation performance test results of the silicone rubber fiber in Comparative Example 3 and the thermally expanded silicone rubber fiber in Example 1, both fibers were placed on a flat heating platform at the same time, and the temperature data above the fibers was collected using an infrared thermal imager.

[0028] Figure 10 The images show the actual fiber samples prepared in Comparative Example 1 and Comparative Example 2, where 10a is the polydimethylsiloxane fiber without the addition of thermally expanding microspheres, and 10b and 10c are the initial and heated expansion states of the polydimethylsiloxane fiber with the addition of 10 wt% thermally expanding microspheres, respectively. Detailed Implementation

[0029] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0030] Example 1: A method for preparing thermo-expanding-shrinking silicone rubber fibers, comprising the following steps:

[0031] S101 prepares a coaxial spinning device consisting of an inner spinning head of 22 G (inner diameter 0.4 mm, outer diameter 0.7 mm) and an outer spinning head of 16 G (inner diameter 1.2 mm, outer diameter 1.64 mm).

[0032] S102: 9 g of silicone rubber prepolymer (Smooth-On, Ecoflex 00-30, thermosetting temperature 80℃) and 1 g of thermally expandable microspheres (Dongjin, MS140WS, expansion temperature 100℃) were mixed evenly, and the prepolymer mixture was connected to the inner spinning head of the coaxial spinning device through the first injection tube. A 1.5 wt% sodium alginate aqueous solution was connected to the outer spinning head of the coaxial spinning device through the second injection tube. The thermally expandable microspheres were added at a content of 10 wt%. The expansion temperature of the thermally expandable microspheres was higher than the thermosetting temperature of silicone rubber but lower than the thermal decomposition temperature of silicone rubber. In this embodiment, the elastic modulus of the silicone rubber prepolymer after crosslinking was 0.14 MPa. The silicone rubber prepolymer and the thermally expandable microsphere prepolymer mixture were subjected to crosslinking at 0.1 s... -1 The viscosity at the shear rate is 3.0 Pa·s, and at 1 s⁻¹... -1 The viscosity at the shear rate is 2.9 Pa·s, and at 10 s⁻¹... -1 The viscosity at the shear rate is 2.8 Pa·s. The average particle size of the thermally expanded microspheres before expansion is 23 μm, and the average particle size after expansion is 74 μm.

[0033] S103 sets the inner spinning head flow rate to 10 mL / h and the outer spinning head flow rate to 10 mL / h. With an inner-outer flow rate ratio of 1.0, core-shell fibers with a fibrous silicone rubber / thermal expansion microsphere prepolymer core and an alginate hydrogel shell are spun into a 2 wt% calcium chloride aqueous solution. The fibers are then crosslinked and cured at room temperature (25℃) for 3 h to obtain the silicone rubber / thermal expansion microsphere prepolymer. The prepolymer is then removed by immersion in a 1.5% sodium citrate solution, rinsed with running water, and dried to obtain thermal expansion silicone rubber fibers with a diameter of approximately 1.0 mm.

[0034] Example 2: The difference between Example 2 and Example 1 is that the content of thermally expandable microspheres added is 0, 2 wt%, 5 wt%, 20 wt%, and 30 wt%, respectively. The prepared thermally expandable silicone rubber fibers are heated to 100℃ for expansion treatment. Their thermal expansion and mechanical properties are shown in Table 1 and Table 2. Figure 1The results show that when the addition amount of thermally expandable microspheres is 2%, the thermal expansion effect is not obvious; when the thermal expansion concentration reaches 10%, the growth rate of the diameter and length of the thermally expandable fibers increases, while still maintaining a pre-break elongation greater than 3 times, achieving the optimal balance between thermal expansion capacity and mechanical properties. Therefore, the weaving effect and the resulting woven fabric have good thermal insulation and deformation resistance. When the content of thermally expandable microspheres is higher (20% and 30%), although the thermal expansion capacity is further improved, the mechanical properties decrease too much, and the microspheres are subjected to stress compression inside the silicone rubber (e.g., Figure 2 The elasticity and toughness are significantly reduced. Therefore, in Example 1, the fiber prepared with a thermal expansion microsphere concentration of 10 wt% exhibits the best thermal expansion and overall mechanical properties.

[0035] Table 1. Effect of the amount of thermally expandable microspheres added on the properties of the prepared thermally expandable silicone rubber fibers.

[0036] Mass concentration (wt%) Diameter growth rate (%) Length growth rate (%) Fracture strength (MPa) Young's modulus (MPa) strain(%) 0 0 0 1.28 0.143 892 2 35.4 35.4 0.93 0.127 730 5 64.9 62.8 0.9 0.141 635 10 77.2 95.3 0.75 0.196 382 20 87.5 112.7 0.55 0.265 207 30 114.6 129.1 0.41 0.953 43

[0037] Example 3: The difference between Example 3 and Example 1 is that the flow rate ratio between the inner spinning head and the outer spinning head is 0.1 to 1.5 (e.g., Figure 3 It was found that when the flow rate ratio between the inner and outer spinning heads was 0.6-1.5, continuous thermally expanding silicone rubber fibers were spun. In particular, when the flow rate ratio was 0.8-1.2, the spun fibers had a uniform diameter and a circular cross-section. However, when the ratio exceeded 1.2, the extrusion resistance was relatively large. When the flow rate of the sodium alginate aqueous solution was set to 10 mL / h, the material prepared was discontinuous fiber when the internal-external flow rate ratio was below 0.4; and thermally expanding silicone rubber balls were prepared when the internal-external flow rate ratio was below 0.2.

[0038] Example 4: The effect of silicone rubber prepolymers of different viscosities on thermally induced expansion-retraction silicone rubber fibers was studied. The results showed that the silicone rubber prepolymer needed to be within 0.1 s... -1 Viscosities at shear rates ranging from 1 to 12000 Pa·s, and at 1 s -1 Viscosities at shear rates ranging from 1 to 1500 Pa·s, at 10 s⁻¹ -1 Only silicone rubber prepolymers with a viscosity of 1 to 200 Pa·s at a shear rate that meet this range, and which are either liquid silicone rubber prepolymers or grease-like semi-solid silicone rubber prepolymers, can be used to prepare continuous thermo-expanding-shrinking silicone rubber fibers.

[0039] Example 5: The difference between Example 5 and Example 1 lies in the different sizes of the inner and outer spinning needles used. Specifically, the inner spinning needle is 12G paired with an 8G outer spinning needle; the inner spinning needle is 16G paired with a 12G needle-shaped outer spinning needle; and the outer spinning needle is 24G paired with an 18G needle-shaped inner spinning needle. Figure 4The results show that in Example 1, the fiber preparation effect is better when using a 22G inner spinning head and a 16G outer spinning head, while the preparation effect is worse when using a 12G inner needle with an 8G outer needle or a 24G inner needle with an 18G outer needle. This is because when the selected inner needle size is larger than 16G, the prepared fiber diameter is too large, and the thermal expansion microspheres need to overcome more constraints from the surrounding material during expansion, resulting in a significant decrease in their thermal expansion capacity. When the inner needle size is smaller than 22G, it is difficult to extrude and the fiber diameter is uneven. Therefore, the preparation range of the inner needle is controlled within 16G and 22G to prepare continuous fibers of different diameters as shown. The fibers of different sizes all exhibit a consistent regular shape, and the fiber size difference after foaming is large, which is more conducive to deformation-driven applications.

[0040] Example 6: The thermal expansion-shrinkage properties of the thermally expanding silicone rubber fiber from Example 1 were tested, such as... Figure 6 and Figure 7 As shown, the prepared thermally expandable silicone rubber fiber (first state) expands to a second state after being heated to 100°C, which is used to fill channels or gaps, providing sealing, sound insulation, and cushioning. It can also be further heated to 140°C to shrink back to the first state, facilitating removal, disassembly, or replacement. This demonstrates that the thermally expandable silicone rubber fiber prepared in Example 1 not only possesses thermal expansion-shrinkage characteristics but also exhibits excellent comprehensive mechanical properties. The volume changes generated by the thermally expandable silicone rubber fiber during heating expansion and shrinkage can be used as a drive component for soft robots or a temperature sensor.

[0041] Example 7: Using the materials prepared in Example 1, thermally expandable silicone rubber fibers were woven into fabrics, such as... Figure 8 and Figure 9 As shown, using the method of Example 1, approximately 50 meters of continuous silicone rubber fiber and thermally expanded silicone rubber fiber can be continuously prepared. The entire fiber exhibits a consistent shape and diameter. Based on the excellent elasticity of silicone rubber itself, a single thermally expanded silicone rubber fiber can be woven using a hand braiding machine without fiber breakage, demonstrating excellent weavability. These results demonstrate that the fiber of this invention can meet the laboratory-level requirements for subsequent fabrication and application testing. Furthermore, as... Figure 10 The thermal insulation performance test results show that, compared with silicone rubber fibers without thermal expansion microspheres, the thermal expansion silicone rubber fibers prepared in Example 1 have superior thermal insulation performance.

[0042] Example 8: The study investigated the effect of the selection of thermally expandable microsphere particle size on thermally expandable silicone rubber fibers. It was found that the particle size of the thermally expandable microspheres before expansion was less than 3% of the diameter of the thermally expandable silicone rubber fibers, and the particle size after expansion was no more than 10% of the diameter of the thermally expandable silicone rubber fibers, so that continuous thermally expandable silicone rubber fibers with uniform diameter in the initial and heated expansion states could be obtained.

[0043] Example 9: The difference between Example 9 and Example 1 is the addition of 8% thermal expansion microspheres (Dongjin, MS140WS, initial expansion temperature 80℃) and 8% thermal expansion microspheres (Expancel, 920 DU 40, initial expansion temperature 130℃). Experimental results show that two or more types of thermal expansion microspheres can be selected. When the mixed thermal expansion microspheres are two types with different expansion temperatures and heat resistance temperatures, by setting the expansion temperature of the high-temperature microspheres (thermal expansion microspheres with higher expansion and heat resistance temperatures) to be higher than the heat resistance temperature of the low-temperature microspheres (thermal expansion microspheres with lower expansion and heat resistance temperatures), the thermal expansion silicone rubber fibers or spheres can exhibit a multi-stage thermal expansion capability of expansion, contraction, expansion, and contraction in sequence as the temperature increases; or, by setting the high... The expansion temperature of the high-temperature microspheres is lower than that of the low-temperature microspheres, but higher than that of the low-temperature microspheres. This allows the thermally expandable silicone rubber fibers or spheres to exhibit a multi-stage thermal expansion capability as the temperature rises, sequentially exhibiting small expansion, large expansion, small expansion, and shrinkage. Alternatively, by setting the expansion temperature of the high-temperature microspheres to be equal to the heat resistance temperature of the low-temperature microspheres, the temperature range in which the thermally expandable silicone rubber fibers or spheres are in the expansion state can be broadened from the expansion-temperature resistance temperature range of a single thermally expandable microsphere to the range between the lowest expansion temperature and the highest temperature resistance temperature of multiple thermally expandable microspheres.

[0044] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the silicone rubber prepolymer used is Dow Chemical's SYLGARD 184 polydimethylsiloxane, and the thermally expandable microspheres are Expansionl 920 DU40, which can also be used to prepare thermally expandable silicone rubber fibers. However, due to the high modulus (approximately 1.5 MPa) of this crosslinked silicone rubber, the constraint stress on the thermally expandable microspheres is relatively large, resulting in only a low level of diameter and length growth at a thermally expandable microsphere concentration of 10 wt%. Figure 10 As shown in the figure. This indicates that the elastic modulus of the cross-linked silicone rubber prepolymer must be less than 1 MPa in order to prepare thermally expandable silicone rubber fibers that have both excellent thermal expansion capacity and elasticity.

[0045] Comparative Example 2: The difference between Comparative Example 2 and Comparative Example 3 is that no thermally expandable microspheres were added, and polydimethylsiloxane fibers were prepared.

[0046] Comparative Example 3: The difference between Comparative Example 2 and Comparative Example 3 is that thermally expandable microspheres were not added in this case to obtain silicone rubber fibers.

[0047] In summary, this invention provides a method for preparing thermo-expandable-shrinkable silicone rubber fibers. Through coaxial spinning, a core-shell fiber is obtained with a thermo-expandable microsphere / silicone rubber mixed prepolymer as the core and sodium alginate hydrogel as the outer shell. The sodium alginate hydrogel provides shaping and protection for the core during the core curing process. The thermo-expandable silicone rubber fiber is then obtained by deshelling. Because the thermo-expandable microspheres are uniformly dispersed in the silicone rubber matrix, thermo-expandable silicone rubber fibers with uniform diameter and circular cross-section can be prepared under specific flow rate ratios (0.8-1.2) and thermo-expandable microsphere content (5-10%). By selecting a suitable silicone rubber with a modulus (less than 1 MPa), the expansion rate of the thermo-expandable microspheres is less limited by the silicone rubber stress, exhibiting considerable and stable thermal expansion capacity at low microsphere concentrations. Furthermore, the thermo-expanded silicone rubber fiber possesses excellent comprehensive mechanical properties, including elasticity, and undergoes macroscopic dimensional and performance changes upon heating, making it valuable for applications in thermal insulation, sealing, cushioning, and actuation.

[0048] Furthermore, after thermal expansion, the silicone rubber fibers, upon overheating to the maximum tolerance temperature of the thermally expanded microspheres, will shrink back, causing the aforementioned morphological changes to disappear and restoring them to a diameter, length, and mechanical properties close to their initial state. Utilizing its thermal expansion-shrinkage characteristics, the morphological changes caused by thermal expansion can be activated as needed. By leveraging the thermal insulation, sealing, shock absorption, actuation, and buoyancy capabilities imparted to the fibers by the porous structure of the thermally expanded microspheres, applications such as thermal insulation fabrics, thermally driven components, temperature sensors, and floating materials on water surfaces can be realized.

Claims

1. A method for preparing a thermo-expanding-retracting silicone rubber material, characterized in that... Includes the following steps: S101 Take silicone rubber prepolymer and thermally expandable microspheres and mix them evenly to form a prepolymer mixture, and connect it to the inner spinning head through the first injection tube; take sodium alginate aqueous solution and connect it to the outer spinning head through the second injection tube. The mass ratio of the thermally expandable microspheres to the prepolymer mixture is 2-20%. The elastic modulus of the silicone rubber prepolymer after crosslinking is less than 1 MPa. The expansion temperature of the thermally expandable microspheres is higher than the thermosetting temperature of silicone rubber. S102, with the inner and outer spinning head flow rate ratio set at 0.6-1.5, extrudes core-shell fibers with a fibrous silicone rubber / thermal expansion microsphere prepolymer core and an alginate hydrogel shell into a calcium chloride aqueous solution. After cross-linking and curing, immersion in sodium citrate solution to remove the shell, cleaning and drying, thermal expansion silicone rubber fibers are obtained.

2. The method for preparing a thermo-expanding-shrinking silicone rubber material according to claim 1, characterized in that, In step S102, the mass ratio of the thermally expanded microspheres to the prepolymer mixture is 5-10%.

3. In the method for preparing a thermo-expanding-shrinking silicone rubber material according to claim 1, in step S102, the flow rate ratio between the inner spinning head and the outer spinning head is 0.8-1.

2.

4. In the method for preparing a thermo-expanding-shrinking silicone rubber material according to claim 1, in step S101, the inner spinning head uses a 16-22 G needle and the outer spinning head uses a 12-16 G needle.

5. The method for preparing a thermo-expanding-shrinking silicone rubber material according to claim 1, wherein in step S101, the particle size of the thermo-expanding microspheres before expansion is less than 3% of the diameter of the thermo-expanding silicone rubber fiber, and the particle size after expansion does not exceed 10% of the diameter of the thermo-expanding silicone rubber fiber.

6. The method for preparing a thermo-expanding-shrinking silicone rubber material according to claim 1, wherein in step S101, the mass concentration of the sodium alginate aqueous solution is 1.5 wt%; and in step S102, the mass concentration of the calcium chloride aqueous solution is 2 wt%.

7. The method for preparing a thermo-expanding-shrinking silicone rubber material according to claim 1, wherein in step S101, the prepolymer mixture of silicone rubber prepolymer and thermo-expanding microspheres is subjected to a reaction time of 0.1 s. -1 Viscosities at shear rates range from 1 to 12000 Pa·s, 1 s -1 Viscosities at shear rates ranging from 1 to 1500 Pa·s, 10 s⁻¹ -1 Viscosities at shear rates range from 1 to 200 Pa·s.

8. In the method for preparing a thermo-expanding-shrinking silicone rubber material according to claim 1, in step S101, two or more types of thermo-expanding microspheres may be selected.

9. A thermotropic expansion-retraction silicone rubber material prepared according to any one of claims 1 to 8.

10. The use of the thermotropic expansion-retraction silicone rubber material of claim 9 in the preparation of thermal insulation fabrics, thermal response actuators, or temperature sensors.

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