Low-density high-strength organosilicon microporous foam material and preparation method thereof

Abstract

The invention relates to the field of organic silicon microporous foam materials, and discloses a low-density high-strength organic silicon microporous foam material, which is composed of an organic silicon matrix, a reinforcing filler and a microporous structure formed by a two-stage composite foaming process, the microporous structure has a micron-sized average pore size and a high closed porosity, the average pore size is adjustable in a range of 10-100 [mu] m, and the density of the foam material is adjustable in a range of 0.1-0.5 g / cm < 3 >; the reinforcing filler comprises SiO2 aerogel particles and hollow glass beads, and the filler is subjected to surface modification treatment so as to improve the dispersity and interface bonding strength of the filler in an organic silicon matrix; the foam material is prepared by a two-stage composite foaming process in which supercritical fluid physical foaming and chemical foaming are coordinated. Compared with the prior art, the organic silicon foam material has the advantage that the technical problem that an organic silicon foam material in the prior art is difficult to give consideration to low density, high mechanical strength and excellent heat insulation performance is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicone microporous foam materials, in particular to a low-density high-strength silicone microporous foam material and a preparation method thereof. BACKGROUND

[0002] Silicone foam materials have application prospects in the fields of aerospace, new energy vehicles and building insulation due to their excellent high and low temperature resistance, chemical stability and flexibility. In the prior art, silicone foam materials are mainly prepared by chemical foaming method. The material prepared by this method usually has problems such as high density, insufficient compressive strength and large thermal conductivity. In order to improve the performance, some technical solutions try to introduce lightweight fillers (such as hollow glass microspheres) or use supercritical fluid foaming process. However, the fillers are prone to agglomeration in the matrix, which leads to weak interfacial bonding and limited performance improvement. The single foaming method has insufficient control ability on the pore structure, and it is difficult to balance the low density, high mechanical strength and high thermal insulation performance at the same time. SUMMARY

[0003] (I) Technical problems to be solved

[0004] The technical problem to be solved by the present application is to provide a low-density high-strength silicone microporous foam material and a preparation method thereof, in order to solve the technical problem that the existing silicone foam material is difficult to balance low density, high mechanical strength and excellent thermal insulation performance.

[0005] (II) Technical solutions

[0006] To solve the above technical problems, the technical solution provided by the present application is: a low-density high-strength silicone microporous foam material, the foam material is composed of a silicone matrix, a reinforcing filler and a microporous structure formed by a two-stage composite foaming process;

[0007] The microporous structure has a micrometer-level average pore size and a high closed porosity, wherein the average pore size is adjustable in the range of 10-100 pm, and the density of the foam material is adjustable in the range of 0.1-0.5 g / cm 3 ;

[0008] The reinforcing filler includes SiO2 aerogel particles and hollow glass microspheres, and the filler is subjected to surface modification treatment to improve its dispersibility and interfacial bonding strength in the silicone matrix;

[0009] The foam material is prepared by a two-stage composite foaming process of supercritical fluid physical foaming and chemical foaming. In the first stage, supercritical CO2 is dissolved in the silicone prepolymer under high pressure and then rapidly depressurized to form initial bubble nucleation points. In the second stage, the temperature rising rate is accurately controlled to initiate the decomposition of the chemical foaming agent to produce gas, and the initial bubble nucleation points are subjected to secondary expansion and stabilization.

[0010] As an improvement, the mass ratio of SiO2 aerogel particles to hollow glass microspheres in the reinforcing filler is 1:5 to 1:1.

[0011] As an improvement, the surface modification treatment of the reinforcing filler is chemical modification with a silane coupling agent or physical activation with plasma treatment.

[0012] As an improvement, the silicone matrix is a room temperature vulcanizing or heat vulcanizing type silicone rubber, and the crosslinking system is an addition reaction system of hydrogen-containing silicone oil and platinum catalyst or a peroxide-initiated free radical crosslinking system.

[0013] As an improvement, the foaming agent system further includes a foam stabilizer, which is a polyether-modified silicone surfactant with an HLB value in the range of 8-14.

[0014] A method for preparing a low-density high-strength silicone microcellular foam material, comprising the following steps:

[0015] (1) providing a silicone prepolymer, a reinforcing filler, a foam stabilizer, a crosslinking agent, and a foaming agent system including supercritical CO2 physical foaming agent and chemical foaming agent azodicarbonamide;

[0016] (2) mixing the surface-modified reinforcing filler with the silicone prepolymer to form a uniform prepolymer mixture;

[0017] (3) dissolving supercritical CO2 at high pressure in the prepolymer mixture to form a saturated solution in a supercritical CO2 foaming experiment platform;

[0018] (4) rapidly releasing pressure to allow supercritical CO2 to escape from the saturated solution to form initial cell nucleation points;

[0019] (5) controlling the temperature rise rate to initiate decomposition of the chemical foaming agent to produce gas, and to perform secondary expansion and stabilization of the initial cell nucleation points to form a microcellular structure;

[0020] (6) curing reaction by the crosslinking agent to obtain the low-density high-strength silicone microcellular foam material.

[0021] As an improvement, in step (3), the pressure of the supercritical CO2 is 8-30 MPa, and the dissolution temperature is 40-80°C.

[0022] As an improvement, in step (4), the rate of rapid pressure release is controlled in the range of 0.5-5 MPa / s.

[0023] As an improvement, in step (5), the heating rate is 1-5℃ / min, and the decomposition temperature of the chemical foaming agent is 150-200℃.

[0024] As an improvement, the curing reaction is carried out at a temperature ranging from room temperature to 200℃, and the curing time is 10 minutes to 4 hours.

[0025] (III) Beneficial effects

[0026] The present application has the advantages compared with the prior art: through the two-stage foaming mechanism of "physical nucleation-chemical expansion", the separation and accurate control of the processes of cell nucleation, growth and stabilization are realized. The method helps to form the ideal microcellular structure with uniform pore size and high closed cell rate, and provides the material with better mechanical properties and lower thermal conductivity.

[0027] The multi-scale reinforcing fillers after surface modification, i.e. SiO2 aerogel and hollow glass microspheres, are used to construct gradient reinforced interface with the organic silicone matrix, which effectively improves the dispersibility of the fillers and the interfacial bonding force with the matrix, reduces the material density, and enhances the compressive strength and dimensional stability. DETAILED DESCRIPTION

[0028] The invention content of the present application will be further described in detail below in combination with specific embodiments, but it should not be understood that the scope of the subject matter of the present application is limited to the following examples only.

[0029] Example 1

[0030] A low-density high-strength silicone microcellular foam material, the foam material is composed of an organic silicone matrix, reinforcing fillers and a microcellular structure formed by a two-stage composite foaming process; the microcellular structure has a micron-level average pore size and a high closed cell rate, wherein the average pore size is adjustable within the range of 100μm, the foam material density is 0.5g / cm 3Adjustable within a certain range; the reinforcing filler includes SiO2 aerogel particles and hollow glass microspheres, and the filler is surface modified to improve its dispersibility and interfacial bonding strength in the organosilicon matrix; the foam material is prepared by a two-stage composite foaming process that combines supercritical fluid physical foaming and chemical foaming, wherein: in the first stage, supercritical CO2 is rapidly depressurized after high-pressure dissolution in the organosilicon prepolymer to form initial cell cores; in the second stage, by precisely controlling the heating rate, the chemical foaming agent is decomposed to generate gas, which further expands and stabilizes the initial cell cores; the mass ratio of SiO2 aerogel particles to hollow glass microspheres in the reinforcing filler is 1:1; the surface modification treatment of the reinforcing filler is physical activation by plasma treatment; the organosilicon matrix is ​​room temperature vulcanized or heated vulcanized organosilicon rubber; the crosslinking system is a peroxide-induced free radical crosslinking system; the foaming agent system also includes a foam stabilizer, which is a polyether-modified organosilicon surfactant with an HLB value in the range of 14.

[0031] A method for preparing a low-density, high-strength organosilicon microporous foam material includes the following steps:

[0032] (1) Provides a system of organosilicon prepolymer, reinforcing filler, foam stabilizer, crosslinking agent and foaming agent, wherein the foaming agent system includes supercritical CO2 physical foaming agent and chemical foaming agent azodicarbonamide;

[0033] (2) The reinforcing filler is surface modified and then mixed with organosilicon prepolymer to form a uniform prepolymer mixture;

[0034] (3) In the supercritical CO2 foaming experimental platform, supercritical CO2 is dissolved in the prepolymer mixture under high pressure to form a saturated solution;

[0035] (4) Rapidly depressurize to allow supercritical CO2 to escape from the saturated solution and form initial bubble cores. The rate of rapid depressurization is controlled within the range of 5 MPa / s.

[0036] (5) Control the heating rate to induce the chemical foaming agent to decompose and generate gas, thereby expanding and stabilizing the initial bubble core points to form a microporous structure. The heating rate is 5℃ / min and the decomposition temperature of the chemical foaming agent is 200℃.

[0037] (6) The low-density, high-strength organosilicon microporous foam material is obtained by a curing reaction through a crosslinking agent. The curing reaction is carried out in a temperature range of room temperature to 200°C and the curing time is 4 hours.

[0038] Example 2

[0039] A low-density, high-strength organosilicon microporous foam material is disclosed, comprising an organosilicon matrix, reinforcing fillers, and a microporous structure formed through a two-stage composite foaming process. The microporous structure exhibits a micron-level average pore size and a high closed-cell ratio, wherein the average pore size is adjustable within the range of 100 μm, and the foam material density is 0.5 g / cm³. 3 Adjustable within a certain range; the reinforcing filler includes SiO2 aerogel particles and hollow glass microspheres, and the filler is surface modified to improve its dispersibility and interfacial bonding strength in the organosilicon matrix; the foam material is prepared by a two-stage composite foaming process combining supercritical fluid physical foaming and chemical foaming, wherein: in the first stage, supercritical CO2 is rapidly depressurized after high-pressure dissolution in the organosilicon prepolymer to form initial cell cores; in the second stage, by precisely controlling the heating rate, the chemical foaming agent is decomposed to generate gas, which further expands and stabilizes the initial cell cores. The mass ratio of SiO2 aerogel particles to hollow glass microspheres in the reinforcing filler is 1:5. The surface modification treatment of the reinforcing filler is chemical modification using a silane coupling agent. The organosilicon matrix is ​​room temperature vulcanized or heat-vulcanized organosilicon rubber. The crosslinking system is an addition reaction system of hydrogen-containing silicone oil and platinum catalyst. The foaming agent system also includes a foam stabilizer, which is a polyether-modified organosilicon surfactant with an HLB value in the range of 8.

[0040] A method for preparing a low-density, high-strength organosilicon microporous foam material includes the following steps:

[0041] (1) Provides a system of organosilicon prepolymer, reinforcing filler, foam stabilizer, crosslinking agent and foaming agent, wherein the foaming agent system includes supercritical CO2 physical foaming agent and chemical foaming agent azodicarbonamide;

[0042] (2) The reinforcing filler is surface modified and then mixed with organosilicon prepolymer to form a uniform prepolymer mixture;

[0043] (3) In the supercritical CO2 foaming experimental platform, supercritical CO2 is dissolved in the prepolymer mixture under high pressure to form a saturated solution;

[0044] (4) Rapidly depressurize to allow supercritical CO2 to escape from the saturated solution and form initial bubble cores. The rate of rapid depressurization is controlled within the range of 0.5 MPa / s.

[0045] (5) Control the heating rate to induce the chemical foaming agent to decompose and generate gas, and perform secondary expansion and stabilization on the initial bubble core points to form a microporous structure. The heating rate is 1℃ / min and the decomposition temperature of the chemical foaming agent is 150℃.

[0046] (6) The low-density, high-strength organosilicon microporous foam material is obtained by a curing reaction through a crosslinking agent. The curing reaction is carried out in a temperature range of room temperature to 200°C and the curing time is 10 minutes.

[0047] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents. In short, if those skilled in the art are inspired by these claims and design similar structural methods and embodiments without departing from the inventive spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A low-density, high-strength organosilicon microporous foam material, characterized in that: The foam material consists of an organosilicon matrix, reinforcing fillers, and a microporous structure formed through a two-stage composite foaming process. The microporous structure has a micron-level average pore size and a high closed-cell ratio, wherein the average pore size is adjustable in the range of 10-100 μm, and the density of the foam material is 0.1-0.5 g / cm³. 3 Adjustable within a range; The reinforcing filler includes SiO2 aerogel particles and hollow glass microspheres. The filler is surface modified to improve its dispersibility and interfacial bonding strength in the organosilicon matrix. The foam material is prepared by a two-stage composite foaming process that combines supercritical fluid physical foaming and chemical foaming. In the first stage, supercritical CO2 is dissolved in organosilicon prepolymer under high pressure and then rapidly depressurized to form initial cell cores. In the second stage, the heating rate is precisely controlled to induce the decomposition of the chemical foaming agent to generate gas, which then expands and stabilizes the initial cell cores.

2. The low-density, high-strength organosilicon microporous foam material according to claim 1, characterized in that: The mass ratio of SiO2 aerogel particles to hollow glass microspheres in the reinforcing filler is 1:5 to 1:

1.

3. The low-density, high-strength organosilicon microporous foam material according to claim 1, characterized in that: The surface modification treatment of the reinforcing filler is either chemical modification using silane coupling agents or physical activation using plasma treatment.

4. The low-density, high-strength organosilicon microporous foam material according to claim 1, characterized in that: The organosilicon matrix is ​​a room temperature vulcanizing or heated vulcanizing type organosilicon rubber, and the crosslinking system is an addition reaction system of hydrogen-containing silicone oil and platinum catalyst, or a free radical crosslinking system initiated by peroxide.

5. The low-density, high-strength organosilicon microporous foam material according to claim 1, characterized in that: The foaming agent system also includes a foam stabilizer, which is a polyether-modified silicone surfactant with an HLB value in the range of 8-14.

6. The method for preparing a low-density, high-strength organosilicon microporous foam material according to claims 1-5, characterized in that, Includes the following steps: (1) Provides a system of organosilicon prepolymer, reinforcing filler, foam stabilizer, crosslinking agent and foaming agent, wherein the foaming agent system includes supercritical CO2 physical foaming agent and chemical foaming agent azodicarbonamide; (2) The reinforcing filler is surface modified and then mixed with organosilicon prepolymer to form a uniform prepolymer mixture; (3) In the supercritical CO2 foaming experimental platform, supercritical CO2 is dissolved in the prepolymer mixture under high pressure to form a saturated solution; (4) Rapidly release pressure to allow supercritical CO2 to escape from the saturated solution and form initial bubble cores; (5) Control the heating rate to induce the chemical foaming agent to decompose and generate gas, thereby expanding and stabilizing the initial bubble core points to form a microporous structure. (6) The low-density, high-strength organosilicon microporous foam material is obtained by a curing reaction using a crosslinking agent.

7. The method for preparing a low-density, high-strength organosilicon microporous foam material according to claim 1, characterized in that: In step (3), the pressure of the supercritical CO2 is 8-30 MPa and the dissolution temperature is 40-80℃.

8. The method for preparing a low-density, high-strength organosilicon microporous foam material according to claim 1, characterized in that: In step (4), the rate of rapid depressurization is controlled within the range of 0.5-5 MPa / s.

9. The method for preparing a low-density, high-strength organosilicon microporous foam material according to claim 1, characterized in that: In step (5), the heating rate is 1-5℃ / min, and the decomposition temperature of the chemical foaming agent is 150-200℃.

10. The method for preparing a low-density, high-strength organosilicon microporous foam material according to claim 1, characterized in that: The curing reaction is carried out in a temperature range of room temperature to 200°C, and the curing time is from 10 minutes to 4 hours.