A kind of anti-overload silicone potting adhesive based on nano-microspheres and preparation method thereof

Abstract

The invention provides a method for preparing an anti-overload organosilicon potting glue based on nano-microspheres, comprising: preparing a first mixture formed by organosilicon rubber, a solvent and nano-silicon dioxide microspheres or surface-modified nano-silicon dioxide microspheres; preparing a second mixture formed by a curing agent and a catalyst; and subjecting the first mixture and the second mixture to stirring degassing, pouring degassing and curing to form an anti-overload organosilicon potting glue. The nano-silicon dioxide microspheres are monodisperse silica microspheres with Si-OH surface groups in the range of 50-500nm, or a composite mixture composed of several monodisperse microspheres; the organosilicon rubber is methyl vinyl silicone rubber or hydroxyl silicone rubber; the solvent is one or more of ethyl acetate solvent, cyclohexane solvent or anhydrous ethanol; or one or more of benzene, cyclohexane or n-hexane solvent; the curing agent is an organic silicate or a hydrogen-containing silicone oil; the catalyst includes an organic tin catalyst or an organic platinum catalyst; and the corresponding anti-overload organosilicon potting glue is also disclosed.

Description

Technical Field

[0001] The invention relates to the technical field of potting material preparation, and in particular to an anti-overload organic silicon potting adhesive based on nano-microspheres and a preparation method thereof. Background Art

[0002] Silicone potting materials have been widely used in missile-borne electronic devices due to their excellent high and low temperature performance, non-corrosiveness, good fluidity, mild curing conditions, and simple and easy-to-control process. Through the elastic deformation of the circuit board fixing frame and the potting colloid, the overload impact energy generated during the launch can be absorbed, thereby ensuring the normal operation of the missile-borne circuit. Usually, the impact overload of missile-borne electronic devices during the launch and penetration process is about 5000g to 10000g, and even reaches 50,000 to 100,000g in the penetration weapon. Under the overload impact of 5000g to 20,000g, the traditional potting glue for potting circuit boards is not strong enough and has insufficient overload energy absorption capacity, which causes the circuit board to be easily distorted and deformed, and the circuit function fails and cannot play the combat function. Under this condition, in addition to the design of the protective structure of missile-borne electronic devices, the composition and strength of the potting glue, especially the dynamic strength under loading conditions, and whether it can attenuate and filter out the interference signals of the penetration process become the key factors affecting whether the missile-borne electronic devices can function normally.

[0003] At present, the elastic silicone potting glue usually uses micron-scale silicon powder, white carbon black and other particles to adjust the compressive strength, hardness and energy absorption capacity of the potting glue; the silicone rubber matrix is ​​usually a dealcoholized silicone rubber system or an addition-type silicone system. The dealcoholized silicone consists of a hydroxyl silicone rubber base and an organic silicate curing agent plus an organic tin catalyst. The strength and hardness of this type of silicone rubber system are relatively low, and white carbon black is often added as a reinforcing filler; even so, there are still disadvantages of low hardness and easy breakage. Addition-type silicone rubber is composed of a vinyl silicone rubber matrix, hydrogen-containing silicone rubber and a platinum catalyst. The mechanical strength and toughness of this type of silicone rubber system are better than those of dealcoholized silicone rubber, but in terms of anti-overload protection applications, these two types of silicone rubber still need to add a certain amount of solid powder fillers such as white carbon black, silicon powder, etc. to enhance their mechanical strength and adjust their hardness, and usually can only meet the overload protection of 2500 to 5000g. Since the size of inorganic fillers is usually between microns and tens of microns and the particle size is uneven, the surface interface between the silicone potting glue matrix and the particles is not rich enough, the synergistic energy absorption capacity is weak, and the dynamic strength is not high, which cannot meet the application requirements of overload resistance of missile-borne electronic systems under high overload conditions of 5000-200000g. Summary of the invention

[0004] In order to overcome the deficiencies and shortcomings of the prior art, an anti-overload silicone potting compound based on nano-microspheres and a preparation method thereof are provided. Nano-silica microspheres are used to replace traditional silicon micropowder, white carbon black and other inorganic fillers, and a solvent-assisted ultrasonic dispersion process is adopted to achieve uniform dispersion of the nano-microspheres in a silicone rubber matrix with a relatively high viscosity, thereby solving the application problems of insufficient dynamic impact energy absorption and insufficient signal highlighting of traditional micron particle-filled anti-overload potting compounds. At the same time, the nano-silica microspheres and the nano-silica microspheres modified by surface groups have the characteristics of uniform particle size, high sphericity and smooth surface. The scale less than 1um can be more conducive to reflecting the rigid-flexible synergistic energy absorption effect on the microstructure of the silicone composite system under the action of dynamic overload impact.

[0005] The object of the present invention is to provide a method for preparing an anti-overload silicone potting adhesive based on nano-microspheres, comprising the following steps:

[0006] S1, preparing a first mixture consisting of organic silicone rubber, a solvent and nano-silica microspheres or surface-modified nano-silica microspheres;

[0007] S2, preparing a second mixture formed of a curing agent and a catalyst;

[0008] S3, the first mixture and the second mixture are subjected to stirring degassing, pouring degassing and curing to form the anti-overload silicone potting glue.

[0009] Preferably, the organic silicone rubber is methyl vinyl silicone rubber or hydroxy silicone rubber, the hydroxy silicone rubber includes terminal hydroxy methyl silicone rubber, and the terminal hydroxy methyl silicone rubber is ω-dihydroxy methyl silicone rubber.

[0010] Preferably, the solvent is one or more of ethyl acetate solvent, cyclohexane solvent or anhydrous ethanol; or one or more of benzene, cyclohexane or n-hexane solvent.

[0011] Preferably, the surface-modified nano-silica microspheres are nano-silica microspheres whose surfaces are modified to hydrophobic groups (-CH3); the nano-silica microspheres or surface-modified nano-silica microspheres are monodisperse silica microspheres in the range of 50-500nm with surface groups being Si-OH, or a composite mixture of several monodisperse microspheres, wherein the monodisperse microspheres include a composite mixture of silica microspheres with surface groups being Si-OH, methyl and alkyl.

[0012] Preferably, the S1 comprises:

[0013] S11, ultrasonically stirring and dispersing the measured nano-silica microspheres or surface-modified nano-silica microspheres in the solvent until no precipitation occurs, to form a uniform white emulsion;

[0014] S12, adding a measured amount of the silicone rubber matrix to the white emulsion, and continuing ultrasonic stirring and dispersion for 0.5-3 hours to form a first mixed solution;

[0015] S13, removing the solvent from the first mixed liquid at 40-60° C. to obtain a first mixture in which nano-silica microspheres or surface-modified nano-silica microspheres are uniformly dispersed in a matrix of organic silicone rubber; the solvent removal method is a method of removing the solvent by reduced pressure distillation, a method of removing the solvent by rotary evaporation, or a method of removing the solvent by heating, stirring, and vacuuming.

[0016] Preferably, the curing agent is an organic silicate or a hydrogen-containing silicone oil, the organic silicate includes a ethyl orthosilicate crosslinking agent or vinyl polydimethylsiloxane; the hydrogen-containing silicone oil is a hydrogen-containing silicone oil crosslinking agent and a crosslinking inhibitor.

[0017] Preferably, the catalyst comprises an organotin catalyst or an organoplatinum catalyst.

[0018] Preferably, S2 comprises: stirring and mixing the curing agent and the catalyst in a stoichiometric ratio at room temperature to obtain a second mixed liquid of the curing system.

[0019] Preferably, S3 includes:

[0020] S31, stirring and degassing the measured first mixed solution and the second mixed solution for 3-5 minutes using a mechanical stirrer or a planetary stirring deaerator;

[0021] S32, pouring into the device to be potted, and performing vacuum degassing again for 1-3 minutes;

[0022] S33, curing at 40-80°C for 2-4h to form the anti-overload silicone potting adhesive.

[0023] The second aspect of the present invention provides an anti-overload organosilicon potting adhesive based on nano-microspheres, which is prepared by a preparation method of an anti-overload organosilicon potting adhesive based on nano-microspheres.

[0024] Beneficial effects of the present invention:

[0025] Nano-silica microspheres are used to replace traditional silicon micropowder, white carbon black and other inorganic fillers, and a solvent-assisted ultrasonic dispersion process is adopted to achieve uniform dispersion of nano-microspheres in a silicone rubber matrix with higher viscosity, solving the application problems of insufficient dynamic impact energy absorption and insufficient signal highlighting of traditional micron-particle-filled anti-overload potting glue; at the same time, the use of nano-silica microspheres and surface group-modified nano-silica microspheres has the characteristics of uniform particle size, high sphericity and smooth surface. The scale less than 1um can be more conducive to reflecting the rigid-flexible synergistic energy absorption effect of the microstructure of the silicone composite system under dynamic overload impact.

[0026] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. The objects and features of the present invention will become more apparent in view of the following description in conjunction with the accompanying drawings, in which:

[0028] Figure 1 The figure is a schematic flow chart of a method for preparing an anti-overload silicone potting adhesive based on nano-microspheres according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0030] like Figure 1 As shown, this embodiment provides a method for preparing an anti-overload silicone potting adhesive based on nano-microspheres, comprising the following steps:

[0031] S1, preparing a first mixture consisting of organic silicone rubber, a solvent and nano-silica microspheres or surface-modified nano-silica microspheres;

[0032] S2, preparing a second mixture formed of a curing agent and a catalyst;

[0033] S3, the first mixture and the second mixture are subjected to stirring degassing, pouring degassing and curing to form the anti-overload silicone potting glue.

[0034] As a preferred embodiment, the organic silicone rubber is methyl vinyl silicone rubber or hydroxy silicone rubber, the hydroxy silicone rubber includes terminal hydroxy methyl silicone rubber, and the terminal hydroxy methyl silicone rubber is ω-dihydroxy methyl silicone rubber.

[0035] As a preferred embodiment, the solvent is one or more of ethyl acetate solvent, cyclohexane solvent or anhydrous ethanol; or one or more of benzene, cyclohexane or n-hexane solvent.

[0036] As a preferred embodiment, the surface-modified nano-silica microspheres are nano-silica microspheres whose surfaces are modified to hydrophobic groups (-CH3); the nano-silica microspheres or surface-modified nano-silica microspheres are monodisperse silica microspheres in the range of 50-500nm with surface groups of Si-OH, or can be a composite mixture of several monodisperse microspheres. In order to facilitate rapid and uniform dispersion, silica microspheres with methyl or other alkyl surfaces are preferred.

[0037] As a preferred embodiment, the S1 includes:

[0038] S11, ultrasonically stirring and dispersing the measured nano-silica microspheres or surface-modified nano-silica microspheres in the solvent until no precipitation occurs, to form a uniform white emulsion;

[0039] S12, adding a measured amount of the silicone rubber matrix to the white emulsion, and continuing ultrasonic stirring and dispersion for 0.5-3 hours to form a first mixed solution;

[0040] S13, removing the solvent from the first mixed liquid at 40-60° C. to obtain a first mixture in which nano-silica microspheres or surface-modified nano-silica microspheres are uniformly dispersed in a matrix of organic silicone rubber; the solvent removal method is a method of removing the solvent by reduced pressure distillation, a method of removing the solvent by rotary evaporation, or a method of removing the solvent by heating, stirring, and vacuuming.

[0041] As a preferred embodiment, the curing agent is an organic silicate or a hydrogen-containing silicone oil, the organic silicate includes an ethyl orthosilicate crosslinking agent or vinyl polydimethylsiloxane; the hydrogen-containing silicone oil is a hydrogen-containing silicone oil crosslinking agent and a crosslinking inhibitor.

[0042] As a preferred embodiment, the catalyst includes an organic tin catalyst or an organic platinum catalyst.

[0043] As a preferred embodiment, the S2 comprises: stirring and mixing the curing agent and the catalyst in a metered ratio at room temperature to obtain a second mixed liquid of the curing system.

[0044] As a preferred implementation, S3 includes:

[0045] S31, stirring and degassing the measured first mixed solution and the second mixed solution for 3-5 minutes using a mechanical stirrer or a planetary stirring deaerator;

[0046] S32, pouring into the device to be potted, and performing vacuum degassing again for 1-3 minutes;

[0047] S33, curing at 40-80°C for 2-4h to form the anti-overload silicone potting adhesive.

[0048] A second aspect of the present embodiment provides an anti-overload organosilicon potting compound based on nano-microspheres, which is prepared by a preparation method of an anti-overload organosilicon potting compound based on nano-microspheres.

[0049] Example 1

[0050] (1) adding 10-50 parts of nano-silica microspheres into 200-300 parts of ethyl acetate solvent, stirring and ultrasonically dispersing for 3-5 hours until a white emulsion without precipitation is formed;

[0051] (2) Add 50-100 parts of α, ω-dihydroxy polydimethylsiloxane to the above white emulsion, stir and disperse by ultrasonic for 10-30 minutes, then heat at 40-60° C. to remove the solvent ethyl acetate under reduced pressure to obtain a viscous white liquid component A;

[0052] (3) adding 0.1-1 part of a catalyst to 5-10 parts of an ethyl orthosilicate crosslinking agent to form component B;

[0053] (4) The prepared components A and B are mixed at a stirring rate of 100-500 rpm for 3-5 min, degassed at 50-70 kPa for 30-50 s, and then poured into a mold or a device to be encapsulated, and vulcanized at RH 40-60% and 20-80° C. for 24-6 h.

[0054] The obtained nano-silica microsphere reinforced anti-overload potting material is a white opaque solid with a Shore A hardness of 25-50, a tensile strength greater than 3MPa, and a loss factor of 0.1-0.3 at 25°C, and can meet the anti-overload potting application of 5000-10000g.

[0055] Example 2

[0056] (1) adding 10-50 parts of nano-silica microspheres whose surfaces are modified to hydrophobic groups (-CH3) into 200-300 parts of cyclohexane solvent, stirring and ultrasonically dispersing for 3-5 hours until a white emulsion without precipitation is formed;

[0057] (2) Add 50-100 parts of vinyl polydimethylsiloxane to the above white emulsion, stir and disperse by ultrasonication for 10-30 minutes, then heat at 40-60° C. under reduced pressure to remove the solvent cyclohexane, add 5-20 parts of hydrogenated silicone oil crosslinking agent and crosslinking inhibitor, stir thoroughly and evenly to obtain a viscous white liquid component A;

[0058] (3) adding 0.5-1 part of a platinum catalyst to 10-50 parts of vinyl polydimethylsiloxane and stirring for 3-5 minutes to obtain component B;

[0059] (4) 100 parts of component A and 5-10 parts of component B are stirred and mixed at 100-300rpm for 3-5 minutes, and degassed at a vacuum degree of 0.06-0.1MPa to obtain a high-strength anti-overload silicone potting glue. The potting glue has excellent fluidity, an operating time of more than 1.5 hours at room temperature, and a curing time of 48 hours at 25°C. The obtained cured product is a white opaque solid with a Shore A hardness of 35-50, a tensile strength of more than 6MPa, an operating temperature range of -45°C to 200°C, and a loss factor of 0.25-0.3 at 0-120°C.

[0060] This potting compound is widely used in the potting of high and low temperature wide temperature range overload resistant electronic devices. It has good mechanical properties and dynamic impact energy absorption performance, and can meet the 5000-25000g overload resistant potting application.

[0061] Example 3

[0062] (1) adding 10-50 parts of nano-silica microspheres whose surfaces are modified to hydrophobic groups (-CH3) into 200-300 parts of cyclohexane solvent, stirring and ultrasonically dispersing for 3-5 hours until a white emulsion without precipitation is formed;

[0063] (2) Add 50-100 parts of vinyl polydimethylsiloxane to the above white emulsion, stir and disperse by ultrasonication for 10-30 minutes, then heat at 40-60° C. under reduced pressure to remove the solvent cyclohexane, add 5-20 parts of hydrogenated silicone oil crosslinking agent and crosslinking inhibitor, stir thoroughly and evenly to obtain a viscous white liquid component A;

[0064] (3) adding 0.1-0.3 parts of a platinum catalyst to 10-50 parts of vinyl polydimethylsiloxane and stirring for 3-5 minutes to obtain component B;

[0065] (4) 100 parts of component A and 5-10 parts of component B are stirred and mixed at 100-300rpm for 3-5 minutes, and degassed at a vacuum degree of 0.06-0.1MPa to obtain a high-strength anti-overload silicone potting glue. The potting glue has excellent fluidity, an operating time of more than 1.5 hours at room temperature, and a curing time of 4 hours at 80°C. The obtained cured product is a white opaque solid with a Shore A hardness of 35-50, a tensile strength of more than 6MPa, an operating temperature range of -45°C to 200°C, and a loss factor of 0.25-0.3 at 0-120°C.

[0066] This potting compound is widely used in the potting of high and low temperature wide temperature range overload resistant electronic devices. It has good mechanical properties and dynamic impact energy absorption performance, and can meet the 5000-25000g overload resistant potting application.

[0067] Nano-silica microspheres are used to replace traditional silicon micropowder, white carbon black and other inorganic fillers, and a solvent-assisted ultrasonic dispersion process is adopted to achieve uniform dispersion of nano-microspheres in a silicone rubber matrix with higher viscosity, solving the application problems of insufficient dynamic impact energy absorption and insufficient signal highlighting of traditional micron-particle-filled anti-overload potting glue; at the same time, the use of nano-silica microspheres and surface group-modified nano-silica microspheres has the characteristics of uniform particle size, high sphericity and smooth surface. The scale less than 1um can be more conducive to reflecting the rigid-flexible synergistic energy absorption effect of the microstructure of the silicone composite system under dynamic overload impact.

[0068] Although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing an anti-overload silicone potting compound based on nano-microspheres, characterized in that: The steps include: S1, preparing a first mixture consisting of organic silicone rubber, a solvent and nano-silica microspheres or surface-modified nano-silica microspheres; wherein the particle size of the nano-silica microspheres or surface-modified nano-silica microspheres is less than 1 um; The S1 includes: S11, ultrasonically stirring and dispersing the measured nano-silica microspheres or surface-modified nano-silica microspheres in the solvent until no precipitation occurs, to form a uniform white emulsion; the mass ratio of the nano-silica microspheres or surface-modified nano-silica microspheres to the solvent is (10-50): (200-300); the ultrasonic stirring time is 3-5 hours; S12, adding a measured amount of the silicone rubber matrix to the white emulsion, and continuing ultrasonic stirring and dispersion for 0.5-3 hours to form a first mixed solution; The organic silicon rubber matrix is ​​50-100 parts, and the ultrasonic stirring time is 10-30 minutes; S13, removing the solvent from the first mixed liquid at 40-60° C. to obtain a first mixture in which the nano-silica microspheres or surface-modified nano-silica microspheres are uniformly dispersed in a matrix of the silicone rubber; the solvent removal method is a method of removing the solvent by reduced pressure distillation, a method of removing the solvent by rotary evaporation, or a method of removing the solvent by heating, stirring, and vacuuming; S2, preparing a second mixture formed of a curing agent and a catalyst; S2 comprises: stirring and mixing the curing agent and the catalyst at room temperature in a metered ratio to obtain a second mixed solution of the curing system; the metered ratio is adding 0.1-0.3 parts of the catalyst to 10-50 parts of the curing agent, and stirring for 3-5 minutes to obtain the second mixture of the curing system; S3, subjecting the first mixture and the second mixture to stirring degassing, pouring degassing and curing to form the anti-overload silicone potting glue; The S3 includes: S31, stirring and defoaming the measured first mixture and second mixture for 3-5 minutes using a mechanical stirrer or a planetary stirring deaerator; S32, pouring into the device to be potted, and performing vacuum degassing again for 1-3 minutes; S33, curing at 40-80°C for 2-4h to form the anti-overload silicone potting adhesive.

2. The method for preparing the nano-microsphere-based overload-resistant silicone potting adhesive according to claim 1, characterized in that: The organic silicone rubber is methyl vinyl silicone rubber or hydroxy silicone rubber, the hydroxy silicone rubber includes terminal hydroxy methyl silicone rubber, and the terminal hydroxy methyl silicone rubber is ω-dihydroxy methyl silicone rubber.

3. The method for preparing the nano-microsphere-based overload-resistant silicone potting adhesive according to claim 2, characterized in that: The solvent is one or more of ethyl acetate solvent, cyclohexane solvent or anhydrous ethanol; or one or more of benzene or n-hexane solvent.

4. The method for preparing the nano-microsphere-based overload-resistant silicone potting adhesive according to claim 3, characterized in that: The surface-modified nano-silica microspheres are nano-silica microspheres whose surfaces are modified to hydrophobic groups; the nano-silica microspheres or surface-modified nano-silica microspheres are monodisperse silica microspheres in the range of 50-500nm whose surface groups are Si-OH.

5. The method for preparing the nano-microsphere-based overload-resistant silicone potting adhesive according to claim 4, characterized in that: The curing agent is organic silicate, and the organic silicate includes a ethyl orthosilicate crosslinking agent or vinyl polydimethylsiloxane.

6. The method for preparing the nano-microsphere-based overload-resistant silicone potting adhesive according to claim 5, characterized in that: The catalyst includes an organic tin catalyst or an organic platinum catalyst.

7. An anti-overload silicone potting adhesive based on nano-microspheres, characterized in that: The invention is prepared by the preparation method of the nano-microsphere-based overload-resistant silicone potting adhesive according to any one of claims 1 to 6.

Images