Core-shell silicone rubber-functional nano-microsphere as well as preparation method and application thereof

Abstract

The invention belongs to the field of functional polymer composite materials, and particularly relates to a core-shell silicone rubber-functional nano-microsphere as well as a preparation method and application thereof. The preparation method of the core-shell silicone rubber-functional nano-microspheres comprises synthesis of silicone rubber microspheres and synthesis of silver-coated silicone rubber microspheres. The invention develops a novel universal and universal functional polymer composite material processing method, namely a solution shearing precipitation method, and provides a core-shell silicone rubber-functional nano-microsphere as well as a preparation method and application thereof, so that the structural design and functional network regulation and control of the functional polymer composite material are realized. The problems that in a composite material prepared through a traditional method, effective lap joint between functional filler is difficult to achieve, the filler is wrapped by a polymer, and intrinsic performance is difficult to fully reflect are solved. It needs to be emphasized that the composite material is more excellent in heat conduction and electric conduction, and can be widely applied to thermal protection of aerospace crafts, packaging of electronic components and the like.

Description

Technical Field

[0001] The present invention belongs to the field of functional polymer composites, and particularly relates to a core-shell silicone rubber-functional nanospheres, a preparation method thereof, and an application thereof. Background Art

[0002] In contrast, metal nanomaterials, especially silver nanoparticles (nano-Ag), have received increasing attention due to their high metallic conductivity (6.3×10 5 S cm -1 ) and the ability to construct microscopic networks. To prepare a composite conductor, the content of nano-Ag must be higher than a critical value (threshold) to develop a three-dimensional interconnected conductive network. It has been reported that for a composite conductor composed of silver nanosheets (AgNFs), fluororubber, and a surfactant, when the filler content is close to 4.6 vol.%, the conductor has a significant conductance promotion effect; however, a plateau appears when it exceeds the threshold. In Ag-based composite conductors, although the mass fraction of Ag is very high (generally >80 wt.%), the conductance is reduced by one order of magnitude compared to the inherent Ag. This phenomenon can be explained by the presence of a polymer insulating layer, which acts as a physical barrier separating adjacent conductive components, thus suppressing the ohmic conduction behavior and limiting the number of conduction paths. Although the use of a thermal sintering process can partially solve this obstacle, this strategy has limitations in its adverse effects on the use of high-temperature substrates (>150°C).

[0003] Adding a high amount of nano-Ag to a bulky composite conductor has an adverse effect on its mechanical properties. On the one hand, due to the high Young's modulus of Ag, the interconnected silver network significantly increases the Young's modulus, which is not conducive to practical applications in soft and stretchable electronics. On the other hand, the fracture strain of the composite material depends to a large extent on the filler content. For example, Matsuhisa et al. formulated a printable conductor ink using an elastomeric fluoropolymer and AgNFs. When the content of AgNFs increased from 43% to 56%, the fracture strain of the conductor decreased significantly from 194% to 8%. To achieve electrical connection while reducing the filler content, constructing a conductive network structure has become an alternative method to alleviate the filler-dependent conductive behavior. For example, an Ag nanowire (AgNWs) framework filled with poly(n-isopropylacrylamide) hydrogel shows that the conductive load is significantly reduced (≈6 wt.%), but its conductivity is limited (93 S cm -1 ). Similarly, porous NWs-reinforced polydimethylsiloxane (PDMS) (2 wt.%) and 3D-segregated Ag NWs / PDMS (2.5 wt.%) form conduction paths at low filling concentrations, while their conductances are limited to 42 and 21.5 S cm -1。The conductivity and filler loading are positively correlated in a system. Currently, achieving high conductivity (>1000 S cm -1 ) with a filler addition amount of <50 wt.% remains a challenging problem.

[0004] In addition, it is also equally important for the composite conductor to maintain its conductivity under large deformation conditions. However, due to the lack of crack energy dissipation, randomly dispersed silver nanocomposites are prone to losing network connection, resulting in a significant conductivity decay under tensile strain. For example, the conductor consists of merged silver nanowires (41245 cm -1 ), pre-constructed copper nanonetworks (>1000 cm -1 ), and in-situ synthesized silver nanoparticles (silver nano) wrapped poly(styrene-styrene) based fibers (5500 cm -1 ) has a relatively high conductivity, but due to percolation, the main conductivity behavior is limited to <300%. In addition, conductors with self-aligned AgNFs, in-situ generated AgNFs, and ternary honeycomb NWs assemblies show better network connections and can resist large deformations without losing conductivity, but the initial conductivity is usually <100 S cm -1 . Despite many efforts in stretchable conductors, it is still difficult to achieve high initial conductivity and maintain good electrical connections in a single material system in terms of the rational design and construction of the structure of the conductive network.

[0005] Therefore, based on this, the technical solution of the present invention is proposed. Summary of the Invention

[0006] The present invention develops a universal and general new method for processing functional polymer composites - solution shear precipitation method, and invents a core-shell silicone rubber-functional nanospheres, its preparation method and application, realizing the structural design and functional network regulation of functional polymer composites. It solves the problem that it is difficult to achieve effective lap between functional fillers in the composites prepared by traditional methods, and the fillers are wrapped by polymers and it is difficult to fully exhibit their intrinsic properties.

[0007] The present invention provides a method for preparing core-shell silicone rubber-functional nanospheres, and the preparation method includes the following steps:

[0008] (I) Synthesis of silicone rubber microspheres:

[0009] (1) Mix the base rubber and the curing agent to obtain a viscous silicone rubber mixture;

[0010] (2) Add the viscous silicone rubber mixture to deionized water and carry out high-speed stirring to obtain a mixed solution;

[0011] (3) Carry out low-speed stirring on the high-speed shear mixed solution until polymerization is completed to obtain silicone rubber microspheres;

[0012] (II) Synthesis of silver-coated silicone rubber microspheres (in practical applications, the coating material can also be other functional materials such as gold, graphite, carbon powder, graphene, etc.):

[0013] (4) Treat the silicone rubber microspheres with air plasma to obtain activated silicone rubber microspheres;

[0014] (5) Mix AgCF 3 COO with tetrahydrofuran to obtain a silver ion-containing solution;

[0015] (6) Immerse the activated silicone rubber microspheres in the silver ion-containing solution to cause the activated silicone rubber microspheres to swell and absorb silver ions, obtaining silver ion-swollen silicone rubber microspheres;

[0016] (7) Immerse the silver ion-swollen silicone rubber microspheres in a mixture of hydrazine and ethanol to reduce silver ions to silver metal, obtaining silicone rubber microspheres with a silver nanoparticle coating, which are the core-shell silicone rubber-functional nanomicrospheres.

[0017] Preferably, in step (1), the base rubber is silicone rubber;

[0018] And / or, the curing agent is hydrogen-containing silicone oil;

[0019] And / or, the volume ratio of the base rubber to the curing agent is 20:2;

[0020] And / or, the conditions for mixing are: the rotation speed is 500 - 1000 r / min.

[0021] Preferably, in step (2), the temperature of the deionized water is 78 - 82 °C;

[0022] And / or, the rotation speed of the high-speed shearing is 4800 - 5200 rpm, and the time of high-speed shearing is 13 - 17 min;

[0023] And / or, the volume ratio of the viscous silicone rubber mixture to the deionized water is 0.73 - 1.28:10.

[0024] Preferably, in step (3), the rotation speed of the low-speed stirring is 480 - 520 rpm.

[0025] Preferably, in step (4), for the air plasma treatment, the time of the air plasma treatment is 15 - 25 min.

[0026] Preferably, in step (5), in the silver ion ink, the concentration of silver ions is 780 - 820 mg / mL.

[0027] Preferably, in step (6), the immersion time is 5 - 40 min;

[0028] And / or, in step (7), the immersion time is 25 to 35 min;

[0029] And / or, in the mixed solution of hydrazine and ethanol in step (7), the volume ratio of hydrazine to ethanol is 1:1.

[0030] Based on the same inventive concept, the present invention also provides a core-shell silicone rubber-functional nanospheres obtained by the above preparation method.

[0031] Based on the same inventive concept, another aspect of the present invention is to provide an application of the core-shell silicone rubber-functional nanospheres in the preparation of a stretchable conductor, and the method of the application is as follows:

[0032] (S1) Mix the core-shell silicone rubber-functional nanospheres with ethanol to obtain a mixed suspension;

[0033] (S2) Place the mixed suspension in a mold, and after the ethanol evaporates, a tight conductive channel is formed;

[0034] (S3) Vigorously mix the commercially available silicone rubber A and B components in a mass ratio of 1:1 to obtain a silicone rubber mixture;

[0035] (S4) Pour the silicone rubber mixture onto the surface of the core-shell silicone rubber-functional nanospheres, and let it penetrate into the gaps between the microspheres and solidify to obtain a stretchable conductor.

[0036] Preferably, in step (S1), the mass ratio of the core-shell silicone rubber-functional nanospheres to the ethanol is 1:10;

[0037] And / or, in step (S4), the curing temperature is 23 to 27 °C, and the curing time is 3 to 5 h.

[0038] It should be noted that the application directions of the core-shell silicone rubber-functional nanospheres are extremely extensive, such as heat conduction, electricity conduction, etc. By changing the doping method of the filler, the morphology of the unit cell, etc., the contact points / surfaces are increased to form more connectivity effects, thereby enhancing the electrical and thermal conductivity.

[0039] The beneficial effects of the present invention are as follows:

[0040] The present invention uses an evaporation-induced capillary force strategy to construct a closely arranged conductive path composed of densely packed core-shell PDMS@Ag microspheres (PDMS@Ag MPs) in the matrix. The closely arranged stretchable conductors (CPSC) interconnected in three-dimensional space form a dense and strong conductive network, which is beneficial for effective electrical connection in both static and stretched states, with a conductivity as high as 67185 S / cm at a low silver content (19.5 wt.%). -1, at large deformation (820 Scm at 400%) -1 ). In addition, the minimum inclusion of locally distributed rigid Ag contributes to significantly suppressing the enhancement of elastic modulus and the attenuation of tensile strain (0.79 MPa, 613% for consumer product 4). In addition, CPSC also exhibits strong hydrophobicity (WCA = 149.8°) and self-cleaning ability, which is attributed to the hierarchical surface microstructure, ensuring stable electrical conductivity when exposed to harsh environments. Finally, through extremely high electrical conductivity and rationally designed core-shell PDMS@Ag MPs, significant high electromagnetic interference (EMI) shielding (108 dB) and strain-tolerant EMI shielding are demonstrated. These stretchable conductors with closely arranged conductive networks open up a new way to fabricate composite conductors with high electrical conductivity, strain-tolerant electrical conductivity, and low filler content. It should be emphasized that the present invention makes the composite material perform more excellently in terms of heat conduction and electricity conduction, and can be widely applied to thermal protection of aerospace vehicles, electronic component packaging, and other aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0042] Figure 1 is a schematic diagram of the core-shell silicone rubber-functional nanospheres of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope protected by the present invention.

[0044] Example 1

[0045] This example provides a preparation method for core-shell silicone rubber-functional nanospheres, and the preparation method includes the following steps:

[0046] (I) Synthesis of silicone rubber microspheres:

[0047] (1) Mix 20 mL of base rubber and 2 mL of curing agent to obtain 22 mL of viscous silicone rubber mixture;

[0048] (2) Load the silicone rubber mixture into a needle (10G) and slowly inject it into deionized water at 78 °C (the volume ratio of the silicone rubber mixture to deionized water is 0.73:10). Use a stirrer to vigorously stir the deionized water at a speed of 4800 rpm for 17 min. During this vigorous stirring process, continuous silicone rubber mixture is torn out and transformed into cross-linked microspheres, obtaining a high-speed shear mixture;

[0049] (3) Transfer the high-speed shear mixture to a low-speed stirring condition (480 rpm) until polymerization is completed, obtaining silicone rubber microspheres with an average size of 26 μm. Subsequently, wash them with deionized water and then dry them at 60 °C for standby;

[0050] (II) Synthesis of silver-coated silicone rubber microspheres:

[0051] (4) Treat the dried silicone rubber microspheres with air plasma at 580 W for 25 min to obtain activated silicone rubber microspheres;

[0052] (5) Mix AgCF 3 COO with tetrahydrofuran to obtain a silver ion-containing solution (the silver ion concentration is 780 mg / mL);

[0053] (6) Immerse the activated silicone rubber microspheres in the silver ion-containing solution for 5 min to allow the activated silicone rubber microspheres to swell and absorb silver ions, obtaining silver ion-swollen silicone rubber microspheres;

[0054] (7) Immerse the silver ion-swollen silicone rubber microspheres in a mixture of hydrazine and ethanol (the volume ratio of hydrazine to ethanol is 1:1) for 25 min to reduce silver ions to silver metal, obtaining silicone rubber microspheres with a silver nanoparticle coating (referred to as: PDMS@AgMPs), which are the core-shell silicone rubber-functional nanomicrospheres.

[0055] Example 2

[0056] This example provides a method for preparing core-shell silicone rubber-functional nanomicrospheres, and the preparation method includes the following steps:

[0057] (I) Synthesis of silicone rubber microspheres:

[0058] (1) Mix 20 mL of base rubber and 2 mL of curing agent to obtain 22 mL of viscous silicone rubber;

[0059] (2) Load the silicone rubber mixture into a needle (10G), slowly inject it into deionized water at 82 °C (the volume ratio of silicone rubber to deionized water is 1.03:10), and use a stirrer to stir the deionized water at a speed of 5200 rpm for 13 min. During the high-speed stirring process, continuous silicone rubber mixture is torn out and transformed into cross-linked microspheres to obtain a high-speed shear mixture;

[0060] (3) Transfer the high-speed shear mixture to a low-speed stirring condition (520 rpm) until polymerization is completed to obtain silicone rubber microspheres with an average size of 49 μm. Then wash them with deionized water and dry them at 60 °C for standby;

[0061] (II) Synthesis of silver-coated silicone rubber microspheres:

[0062] (4) Treat the dried silicone rubber microspheres with air plasma at 620 W for 15 min to obtain active silicone rubber microspheres;

[0063] (5) Mix AgCF 3 COO with tetrahydrofuran to obtain a silver ion-containing solution (the silver ion concentration is 820 mg / mL);

[0064] (6) Immerse the active silicone rubber microspheres in the silver ion-containing solution for 40 min to allow the active silicone rubber microspheres to swell and absorb silver ions to obtain silver ion-swollen silicone rubber microspheres;

[0065] (7) Immerse the silver ion-swollen silicone rubber microspheres in a mixture of hydrazine and ethanol (the volume ratio of hydrazine to ethanol is 1:1) for 35 min to reduce silver ions to silver metal to obtain silicone rubber microspheres with a silver nanoparticle coating (referred to as: PDMS@AgMPs), which are the core-shell silicone rubber-functional nanomicrospheres.

[0066] Example 3

[0067] This example provides a method for preparing core-shell silicone rubber-functional nanomicrospheres, and the preparation method includes the following steps:

[0068] (I) Synthesis of silicone rubber microspheres:

[0069] (1) Mix 20 mL of base gum and 2 mL of curing agent to obtain 22 mL of viscous silicone rubber mixture;

[0070] (2) Load the silicone rubber mixture into a needle (10G), slowly inject it into deionized water at 80 °C (the volume ratio of the silicone rubber mixture to deionized water is 0.128:1), and use a stirrer to stir the deionized water at a speed of 5000 rpm for 15 min. During the high-speed stirring process, a continuous silicone rubber mixture is torn out and transformed into cross-linked microspheres to obtain a high-speed shear mixed solution;

[0071] (3) Transfer the high-speed shear mixed solution to a low-speed stirring condition (500 rpm) until the polymerization is completed to obtain silicone rubber microspheres with an average size of 73 μm. Then wash them with deionized water and dry them at 60 °C for later use;

[0072] (II) Synthesis of silver-coated silicone rubber microspheres:

[0073] (4) Treat the dried silicone rubber microspheres with air plasma at 600 W for 20 min to obtain activated silicone rubber microspheres;

[0074] (5) Mix AgCF 3 COO with tetrahydrofuran to obtain a silver ion-containing solution (the silver ion concentration is 800 mg / mL);

[0075] (6) Immerse the activated silicone rubber microspheres in the silver ion-containing solution for 20 min to allow the activated silicone rubber microspheres to swell and absorb silver ions to obtain silver ion-swollen silicone rubber microspheres;

[0076] (7) Immerse the silver ion-swollen silicone rubber microspheres in a mixed solution of hydrazine and ethanol (the volume ratio of hydrazine to ethanol is 1:1) for 30 min to reduce silver ions to silver metal to obtain silicone rubber microspheres with a silver nanoparticle coating (referred to as: PDMS@AgMPs), which are the core-shell silicone rubber-functional nanomicrospheres.

[0077] Example 4

[0078] This example provides a preparation method of a stretchable conductor, including the following steps:

[0079] (S1) Mix the core-shell silicone rubber-functional nanomicrospheres and ethanol according to a mass ratio of 1:10 to obtain a mixed suspension;

[0080] (S2) Place the mixed suspension in a polytetrafluoroethylene mold. After the solvent ethanol evaporates, PDMS@AgMPs are firmly stacked together to form a closely arranged conductive path;

[0081] (S3) Vigorously mix the commercially available silicone rubber components A and B according to a mass ratio of 1:1 to prepare a silicone rubber mixture. Pour the silicone rubber mixture on the surface of the microspheres and infiltrate into the gaps between the microspheres due to capillary action and pressure difference;

[0082] (S4) Cure the mixture at 23 °C for 5 h to obtain a stretchable conductor.

[0083] Example 5

[0084] This example provides a method for preparing a stretchable conductor, including the following steps:

[0085] (S1) Mix the core-shell silicone rubber-functional nanospheres and ethanol at a mass ratio of 1:10 to obtain a mixed suspension;

[0086] (S2) Place the mixed suspension into a polytetrafluoroethylene mold. After the solvent ethanol evaporates, the PDMS@AgMPs are firmly stacked together to form a closely arranged conductive path;

[0087] (S3) Mix commercially available silicone rubber components A and B vigorously at a mass ratio of 1:1 to prepare a silicone rubber mixture. Pour the silicone rubber mixture onto the surface of the microspheres and infiltrate into the gaps between the microspheres due to capillary action and pressure difference;

[0088] (S4) Cure the mixture at 27 °C for 3 h to obtain a stretchable conductor.

[0089] Example 6

[0090] This example provides a method for preparing a stretchable conductor, including the following steps:

[0091] (S1) Mix the core-shell silicone rubber-functional nanospheres and ethanol at a mass ratio of 1:10 to obtain a mixed suspension;

[0092] (S2) Place the mixed suspension into a polytetrafluoroethylene mold. After the solvent ethanol evaporates, the PDMS@AgMPs are firmly stacked together to form a closely arranged conductive path;

[0093] (S3) Mix commercially available silicone rubber components A and B vigorously at a mass ratio of 1:1 to prepare a silicone rubber mixture. Pour the silicone rubber mixture onto the surface of the microspheres and infiltrate into the gaps between the microspheres due to capillary action and pressure difference;

[0094] (S4) Cure the mixture at 25 °C for 4 h to obtain a stretchable conductor.

[0095] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, and all should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for preparing core-shell silicone rubber-functional nano-microspheres, characterized in that: The preparation method comprises the following steps: (I) Synthesis of silicone rubber microspheres: (1) mixing the base rubber and the curing agent to obtain a viscous silicone rubber mixture; (2) adding the viscous silicone rubber mixture into deionized water and stirring at high speed to obtain a mixed solution; (3) stirring the mixed solution at a low speed until polymerization is completed to obtain silicone rubber microspheres; (II) Synthesis of silver-coated silicone rubber microspheres: (4) treating the silicone rubber microspheres with air plasma to obtain active silicone rubber microspheres; (5) mixing AgCF3COO with tetrahydrofuran to obtain a silver ion-containing solution; (6) immersing the active silicone rubber microspheres in the silver ion-containing solution to allow the active silicone rubber microspheres to swell and absorb silver ions, thereby obtaining silver ion-swollen silicone rubber microspheres; (7) Immersing the silver ion-swollen silicone rubber microspheres in a mixture of hydrazine and ethanol to reduce the silver ions to elemental silver, thereby obtaining silicone rubber microspheres with a silver nanoparticle coating, namely the core-shell silicone rubber-functional nano-microspheres.

2. The method for preparing core-shell silicone rubber-functional nano-microspheres according to claim 1, characterized in that: In step (1), the base rubber is silicone rubber; And / or, the curing agent is hydrogen-containing silicone oil; And / or, the volume ratio of the base glue and the curing agent is 20:2; And / or, the mixing condition is: the rotation speed is 500-1000r / min.

3. The method for preparing core-shell silicone rubber-functional nano-microspheres according to claim 1, characterized in that: In step (2), the temperature of the deionized water is 78-82° C.; And / or, the high-speed shearing speed is 4800-5200 rpm, and the high-speed shearing time is 13-17 min; And / or, the volume ratio of the viscous silicone rubber mixture to deionized water is 0.73-1.28:

10.

4. The method for preparing core-shell silicone rubber-functional nano-microspheres according to claim 1, characterized in that: In step (3), the rotation speed of the low-speed stirring is 480 to 520 rpm.

5. The method for preparing core-shell silicone rubber-functional nano-microspheres according to claim 1, characterized in that: In step (4), the air plasma treatment is performed for 15 to 25 minutes.

6. The method for preparing core-shell silicone rubber-functional nano-microspheres according to claim 1, characterized in that: In step (5), the concentration of silver ions in the silver ion solution is 780-820 mg / mL.

7. The method for preparing core-shell silicone rubber-functional nano-microspheres according to claim 1, characterized in that: In step (6), the immersion time is 5 to 40 minutes; And or, in step (7), the immersion time is 25 to 35 minutes; And / or, in step (7), in the mixed solution of hydrazine and ethanol, the volume ratio of hydrazine to ethanol is 1:

1.

8. Core-shell silicone rubber-functional nano-microspheres obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the core-shell silicone rubber-functional nano-microspheres according to claim 8 in preparing stretchable conductors, characterized in that: The method of application is: (S1) mixing the core-shell silicone rubber-functional nanospheres with ethanol to obtain a mixed solution; (S2) placing the mixed suspension into a mold, and forming a tight conductive path after ethanol evaporates; (S3) vigorously mixing commercially available silicone rubber components A and B at a mass ratio of 1:1 to obtain a silicone rubber mixture; (S4) pouring the silicone rubber mixture on the surface of the core-shell silicone rubber-functional nano-microspheres, allowing it to penetrate into the gaps between the microspheres and solidify, thereby obtaining a stretchable conductor.

10. The use according to claim 9, characterized in that: In step (S1), the mass ratio of the core-shell silicone rubber-functional nano-microspheres to the ethanol is 1:10; And / or, in step (S4), the curing temperature is 23-27° C., and the curing time is 3-5 hours.

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