CN111269576A - Hydrophobic silica aerogel nanocomposite for modified silicone rubber and modification method thereof - Google Patents

Abstract

The invention discloses a hydrophobic silica aerogel nano-composite material for modifying silicone rubber and a modification method thereof. The purpose of its hydrophobic modification is to solve the problem that it is easy to agglomerate and cannot be uniformly dispersed in the silicone rubber matrix. Using the nanocomposite material of the present invention as a reinforcing filler can greatly improve the mechanical properties and thermal insulation properties of the silicone rubber.

Description

A kind of hydrophobic silica aerogel nanocomposite for modifying silicone rubber and modification method thereof

technical field

The invention belongs to the field of functional polymer materials, in particular to a hydrophobic silica aerogel nano-composite material for modifying silicone rubber and a modification method thereof.

Background technique

Room temperature vulcanized methyl silicone rubber (MQ) is an addition type rubber, its main component is polydimethylsiloxane, and the side chain contains a small amount of vinyl. RTV methyl silicone rubber is safe, non-toxic, chemically stable, corrosion-resistant, and has good biocompatibility. It has many advantages such as simple process operation and easy processing and molding. The modified liquid silicone rubber has high mechanical strength, good high temperature stability and low compression set, so it has a wide range of applications in electronics, electric power, medical, aerospace, food hygiene and other fields.

The silica aerogel material is formed by the three-dimensional stacking skeleton structure of nano-scale particles, which has a large number of open nano-scale pores. The particle size of the stacking skeleton is 3-20 nm, with low density (kg/m ³ ) and high specific surface area. , which can effectively inhibit gas heat transfer and reduce solid-state heat conduction, has low thermal conductivity, and is a solid material with good thermal insulation performance. The thermal conductivity of aerogel materials is about 50% lower than that of conventional air, so it is used in the field of thermal insulation. particularly extensive. However, since the surface of silica aerogel is usually not modified in the production process, the silanol groups (Si-OH) on the surface are hydrophilic, and there is agglomeration problem in the process of dispersing in the polymer matrix as a filler. The dispersion uniformity of the material is poor.

The influence of silica aerogel on the mechanical properties of liquid silicone rubber is mainly manifested in tensile strength, elongation at break, stress-strain, etc., and the influence on the thermal insulation performance of liquid silicone rubber is mainly manifested by its low thermal conductivity. . Studies have shown that the hydrophilicity or hydrophobicity of silica aerogel plays an important role in its dispersion in the rubber matrix. The graft-modified hydrophobic silica aerogel has less interfacial force with the rubber matrix and better dispersion uniformity in the silicone rubber. However, the unmodified silica aerogel is easy to agglomerate in a large amount during the mixing process, so the improvement of the mechanical properties and thermal insulation properties of the silicone rubber cannot achieve the desired effect.

SUMMARY OF THE INVENTION

In view of the problems existing in the above-mentioned prior art, the present invention discloses a hydrophobic silica aerogel nanocomposite for modifying silicone rubber and a modification method thereof. The surface modification of silica aerogel improves the interfacial compatibility between silica aerogel and silicone rubber, reduces the interfacial force, and improves the performance of silicone rubber.

The present invention adopts the following technical solutions for realizing the purpose of the invention:

The invention firstly discloses a hydrophobic silica aerogel nanocomposite material for modifying silicone rubber, which is characterized in that: the hydrophobic silica aerogel nanocomposite material is formed in silica aerogel There are trimethylsiloxy groups grafted on the surface of the glue.

The preparation method of the hydrophobic silica aerogel nanocomposite material is as follows: adding the silica aerogel into toluene and dispersing it uniformly by ultrasonic wave to obtain a silica aerogel dispersion liquid with a concentration of 0.2 g/mL ; Pour the silica aerogel dispersion and hexamethyldisilazane into a three-necked flask, add ammonia water dropwise to adjust the pH to 7-8, and then heat and stir in a water bath at 60°C under the nitrogen Stir at a speed of 300-400 r/min for 2 hours, and then stir at a speed of 700-800 r/min for 2 hours; after the stirring is completed, set up a reflux device, and conduct a reflux reaction at 100 ° C for 5 hours. The obtained product is washed with toluene and acetone in turn, and then vacuum frozen After drying, the hydrophobic silica aerogel nanocomposite is obtained.

Preferably, the mass ratio of silica aerogel to hexamethyldisilazane is 25:1.

The invention further discloses the application of the hydrophobic silica aerogel nanocomposite material, which is used as a reinforcing filler to modify the room temperature vulcanized methyl vinyl silicone rubber, so as to improve the mechanical properties and the mechanical properties of the silicone rubber. Thermal insulation properties.

Preferably, the method for modifying silicone rubber by using the hydrophobic silica aerogel nanocomposite comprises the following steps:

(1) Take 100 parts of liquid methyl vinyl silicone rubber, 5 parts of tetraethyl orthosilicate (as a crosslinking agent), 2 parts of dibutyltin dilaurate (as an accelerator), 0.5 parts of triethylenetetramine and 2-10 parts of the hydrophobic silica aerogel nanocomposite material are mixed in a homogenizer at 2000 r/min for 2 min, and then mixed at 800 r/min for 3-4 min to obtain a silicone rubber composite material;

(2) The silicone rubber composite material was evacuated for 5 minutes to remove air bubbles, then poured into a mold, cured at room temperature for 24 hours, and then placed in an oven at 100°C for 2 hours; after complete curing, cooled to room temperature to release the mold , that is, a hydrophobic silica aerogel nanocomposite modified methyl vinyl silicone rubber composite material is obtained.

The beneficial effects of the present invention are embodied in:

1. The present invention generates trimethylsiloxy groups through the hydrolysis reaction of hexamethyldisilazane, which is grafted to the surface of the silica aerogel to obtain a hydrophobic silica aerogel, which can be uniformly dispersed in the silica aerogel. In the silicone rubber matrix, the interfacial force between the filler and the rubber is reduced, the interfacial compatibility between the filler and the rubber matrix is improved, and the mechanical properties of the silicone rubber are improved.

2. The trimethylsiloxy-grafted silica aerogel nanocomposite material of the present invention is a three-dimensional porous material, has low thermal conductivity, and forms a uniform network distribution in the silicone rubber matrix, which can hinder the Transferred in silicone rubber to improve heat resistance and thermal insulation.

Description of drawings

Fig. 1 is the SEM image of the hydrophobic silica aerogel nanocomposite (M-SA) prepared by the present invention;

Fig. 2 is the contact angle test chart of the unmodified silica aerogel (SA) and the modified hydrophobic silica aerogel nanocomposite (M-SA) of the present invention;

Fig. 3 shows the stretching of the unmodified silica aerogel prepared by the present invention and the modified hydrophobic silica aerogel nanocomposite modified silicone rubber composite (SA/SR, M-SA/SR) performance test chart;

Figure 4 shows the stress- Strain test chart;

Figure 5 is the tearing of the unmodified silica aerogel prepared by the present invention and the modified hydrophobic silica aerogel nanocomposite modified silicone rubber composite (SA/SR, M-SA/SR) Elongation test chart;

FIG. 6 is a test chart of thermal conductivity of the hydrophobic silica aerogel nanocomposite modified silicone rubber composite (M-SA/SR) prepared by the present invention.

Detailed ways

The embodiments of the present invention are described in detail below. The following embodiments are implemented on the premise of the technical solutions of the present invention, and provide detailed embodiments and specific operation processes, but the protection scope of the present invention is not limited to the following implementations example.

The hydrophobic silica aerogel nanocomposites used in the following examples were prepared as follows:

The silica aerogel was added to toluene and dispersed uniformly by ultrasonic to obtain a silica aerogel dispersion with a concentration of 0.2 g/mL; according to the mass of silica aerogel and hexamethyldisilazane The ratio is 25:1, the silica aerogel dispersion and hexamethyldisilazane are poured into a three-necked flask, and ammonia water is added dropwise to adjust the pH to 7-8, and then a water bath at 60°C is introduced under the condition of nitrogen. Heating and stirring, first stirring at 350r/min for 2h, and then at 750r/min for 2h; after stirring, set up a reflux device, and conduct reflux reaction at 100 ° C for 5h, the obtained product was washed with toluene and acetone in turn, and then vacuumed Freeze-drying, that is, grafting trimethylsiloxy groups on the surface of the silica aerogel, obtains a hydrophobic silica aerogel nanocomposite.

FIG. 1 is a scanning electron microscope (SEM) image of the obtained trimethylsiloxy-modified silica aerogel nanocomposite (M-SA). It can be seen that the silica aerogel has a three-dimensional structure with a large number of pores, so it has a very high porosity, and the pore size is about 30-60 nm.

FIG. 2 is the contact angle test chart of the obtained trimethylsiloxy-modified silica aerogel nanocomposite (M-SA) and unmodified silica aerogel (SA). It can be seen from the figure that the contact angles of the modified and unmodified silica aerogels are 144.4° and 71°, respectively, indicating that the hydrophobicity of the modified silica aerogel has been greatly increased , the interfacial force with the rubber is lower, and it can be better dispersed in the silicone rubber matrix.

Comparative Example 1

The present embodiment prepares the unmodified methyl vinyl silicone rubber composite material according to the following steps:

(1) Take 100 parts of liquid methyl vinyl silicone rubber, add 5 parts of tetraethyl orthosilicate, 2 parts of dibutyltin dilaurate and 0.5 part of triethylene tetramine, and mix at 2000 r/min in a homogenizer 2min, then mix at 800r/min for 3min;

(2) Vacuum the mixed silicone rubber composite material for 5 minutes to remove air bubbles, then pour it into a mold, cure at room temperature for 24 hours, and then put it in an oven at 100 °C for 2 hours; after complete curing, cool to room temperature to remove Then, the unmodified methyl vinyl silicone rubber composite SR (M-SA content is 0%) is obtained.

Comparative Example 2

The present embodiment prepares unmodified silica aerogel (SA) modified methyl vinyl silicone rubber composite material according to the following steps (the amount of SA is 8% of the mass of the silicone rubber):

(1) Take 100 parts of liquid methyl vinyl silicone rubber, 5 parts of tetraethyl orthosilicate, 2 parts of dibutyltin dilaurate, 0.5 parts of triethylenetetramine and 8 parts of unmodified silica aerogel , in a homogenizer at 2000r/min for 2min, and then at 800r/min for 3min to obtain a silicone rubber composite material;

(2) Vacuum the silicone rubber composite material for 5 minutes to remove air bubbles, then pour it into a mold, cure it at room temperature for 24 hours, and then put it in an oven at 100°C for 2 hours; The SA-modified methyl vinyl silicone rubber composite material SA/SR (SA content is 8%) was obtained.

Example 1

In this embodiment, the hydrophobic silica aerogel nanocomposite (M-SA) modified methyl vinyl silicone rubber composite material is prepared according to the following steps (the amount of M-SA is 2% of the mass of the silicone rubber):

(1) Take 100 parts of liquid methyl vinyl silicone rubber, 5 parts of tetraethyl orthosilicate, 2 parts of dibutyltin dilaurate, 0.5 parts of triethylene tetramine and 2 parts of hydrophobic silica aerogel nanoparticle The composite material was mixed in a homogenizer at 2000 r/min for 2 min, and then at 800 r/min for 3 min to obtain a silicone rubber composite material;

(2) Vacuum the silicone rubber composite material for 5 minutes to remove air bubbles, then pour it into a mold, cure it at room temperature for 24 hours, and then put it in an oven at 100°C for 2 hours; The M-SA modified methyl vinyl silicone rubber composite material M-SA/SR (M-SA content is 2%) was obtained.

Example 2

In this example, the hydrophobic silica aerogel nanocomposite (M-SA) modified methyl vinyl silicone rubber composite material is prepared according to the following steps (the amount of M-SA is 4% of the mass of the silicone rubber):

(1) Take 100 parts of liquid methyl vinyl silicone rubber, 5 parts of tetraethyl orthosilicate, 2 parts of dibutyltin dilaurate, 0.5 parts of triethylenetetramine and 4 parts of hydrophobic silica aerogel nanoparticles The composite material was mixed in a homogenizer at 2000 r/min for 2 min, and then at 800 r/min for 3 min to obtain a silicone rubber composite material;

(2) Vacuum the silicone rubber composite material for 5 minutes to remove air bubbles, then pour it into a mold, cure it at room temperature for 24 hours, and then put it in an oven at 100°C for 2 hours; The M-SA modified methyl vinyl silicone rubber composite material M-SA/SR was obtained (the M-SA content was 4%).

Example 3

In this embodiment, the hydrophobic silica aerogel nanocomposite (M-SA) modified methyl vinyl silicone rubber composite material is prepared according to the following steps (the amount of M-SA is 6% of the mass of the silicone rubber):

(1) Take 100 parts of liquid methyl vinyl silicone rubber, 5 parts of tetraethyl orthosilicate, 2 parts of dibutyltin dilaurate, 0.5 parts of triethylenetetramine and 6 parts of hydrophobic silica aerogel nanoparticles The composite material was mixed in a homogenizer at 2000 r/min for 2 min, and then at 800 r/min for 3 min to obtain a silicone rubber composite material;

(2) Vacuum the silicone rubber composite material for 5 minutes to remove air bubbles, then pour it into a mold, cure it at room temperature for 24 hours, and then put it in an oven at 100°C for 2 hours; The M-SA modified methyl vinyl silicone rubber composite material M-SA/SR (the content of M-SA is 6%) is obtained.

Example 4

In this example, the hydrophobic silica aerogel nanocomposite (M-SA) modified methyl vinyl silicone rubber composite material is prepared according to the following steps (the amount of M-SA is 8% of the mass of the silicone rubber):

(1) Take 100 parts of liquid methyl vinyl silicone rubber, 5 parts of tetraethyl orthosilicate, 2 parts of dibutyl tin dilaurate, 0.5 parts of triethylene tetramine and 8 parts of hydrophobic silica aerogel nanoparticles The composite material was mixed in a homogenizer at 2000 r/min for 2 min, and then at 800 r/min for 3 min to obtain a silicone rubber composite material;

(2) Vacuum the silicone rubber composite material for 5 minutes to remove air bubbles, then pour it into a mold, cure it at room temperature for 24 hours, and then put it in an oven at 100°C for 2 hours; The M-SA modified methyl vinyl silicone rubber composite material M-SA/SR was obtained (the M-SA content was 8%).

Example 5

In this example, the hydrophobic silica aerogel nanocomposite (M-SA) modified methyl vinyl silicone rubber composite material is prepared according to the following steps (the amount of M-SA is 10% of the mass of the silicone rubber):

(1) Take 100 parts of liquid methyl vinyl silicone rubber, 5 parts of tetraethyl orthosilicate, 2 parts of dibutyltin dilaurate, 0.5 parts of triethylenetetramine and 10 parts of hydrophobic silica aerogel nanoparticles The composite material was mixed in a homogenizer at 2000 r/min for 2 min, and then at 800 r/min for 3 min to obtain a silicone rubber composite material;

(2) Vacuum the silicone rubber composite material for 5 minutes to remove air bubbles, then pour it into a mold, cure it at room temperature for 24 hours, and then put it in an oven at 100°C for 2 hours; The M-SA modified methyl vinyl silicone rubber composite material M-SA/SR (M-SA content is 10%) was obtained.

Figure 3 shows the tensile strength properties of the samples obtained in each embodiment, in which the samples are SR, 2%M-SA/SR, 4%M-SA/SR, 6%M-SA/SR, 8%M- SA/SR, 8% SA/SR, 10% M-SA/SR. It can be seen from Figure 3 that the addition of hydrophobic silica aerogel and unmodified silica aerogel both increased the tensile strength of silicone rubber, and the modified hydrophobic silica aerogel It can significantly improve the tensile strength of silicone rubber, which is consistent with the performance parameters of each sample in Table 1. The silicone rubber composites with 2wt%, 4wt%, 6wt%, 8wt% and 10wt% of hydrophobic silica aerogel added, compared with the tensile strength of pure silicone rubber of 0.26MPa, the corresponding increase in 158.7%, 258.7%, 496.2%, 569.2%, 669.2%. The tensile strength of the silicone rubber composite with 8wt% unmodified silica aerogel is 0.94MPa, which is 261.5% higher than that of pure silicone rubber, and the tensile strength is obviously not as good as that of the hydrophobic silica gas with the same amount gel. It can be seen that hydrophobic silica aerogel as a reinforcing filler can greatly improve the tensile properties of silicone rubber. When the filler content is 10wt%, the tensile strength is the maximum value of 2.00MPa.

FIG. 4 is a performance diagram of the stress-strain curve of the samples obtained in each embodiment, and different icons in the figure correspond to different samples. It can be seen that the greater the filler content of the hydrophobic silica aerogel in the silicone rubber, the greater the required tensile stress under the same deformation. Only the silicone rubber composites with 6 wt % and 8 wt % of hydrophobic silica aerogel filler, when the tensile deformation is higher than 109%, the tensile stress of 6 wt % filler content is higher than that of 8 wt % filler content. Compared with the unmodified silica aerogel with 8wt% hydrophobic silica aerogel added, its tensile strength and deformation are better. Compared with pure silicone rubber, the composites with hydrophobic silica aerogel fillers increased in tensile strength and elongation at break, corresponding to the parameters in Table 1.

Figure 5 is a graph of the elongation at break properties of the samples obtained in each embodiment, the samples in the figure are SR, 2%M-SA/SR, 4%M-SA/SR, 6%M-SA/SR, 8%M -SA/SR, 8% SA/SR, 10% M-SA/SR. It can be seen that the addition of hydrophobic silica aerogel and unmodified silica aerogel both increased the elongation at break of the silicone rubber. However, under the same addition amount of 8 wt%, the elongation at break of the unmodified silica aerogel is 128.6%, which is significantly lower than that of the hydrophobic silica aerogel. When 2wt%, 4wt%, 6wt%, 8wt%, and 10wt% of trimethylsiloxy-modified silica aerogels were added, the elongation at break of the composites increased to 125.5%, 140.6%, and 152.7%, respectively. %, 195.2%, 152.9%. Compared with the elongation at break of pure silicone rubber of 67.1%, the corresponding increases were 87.0%, 109.5%, 127.6%, 190.9% and 127.9% respectively. The elongation at break increases first and then decreases with the increase of the hydrophobic silica aerogel filler content. When the filler content is 8wt%, the elongation at break of the silicone rubber is the largest, which is 195.2%, which is about 3 times that of the pure silicone rubber.

FIG. 6 is a thermal conductivity diagram of each sample obtained in each example. Compared with the thermal conductivity of pure silicone rubber of 0.216w/(m K), adding 2wt%, 4wt%, 6wt%, 8wt%, 10wt% of trimethylsiloxy modified silica aerogel, composite The thermal conductivity of the material is reduced to 0.208w/(m·K), 0.198w/(m·K), 0.192w/(m·K), 0.187w/(m·K), 0.176w/(m·K), respectively ), decreased by 3.70%, 8.33%, 11.1%, 13.4%, and 18.52%, respectively. Hydrophobic silica aerogel is used as a thermal insulation material. Its low thermal conductivity is related to its three-dimensional porous structure. The pore size of its micropores is less than 60nm, which is lower than the mean free path of air, and its thermal conductivity is also lower than that of air. coefficient. On the one hand, as a reinforcing filler, silica aerogel can improve the mechanical properties of silicone rubber. The modified hydrophobic silica aerogel is uniformly dispersed in the rubber, which can hinder the transfer of heat and improve the thermal insulation performance.

Table 1

It can be seen from Table 1 that while the mechanical properties of the silicone rubber with fillers are improved, with the increase of filler content, its hardness increases continuously. When the filler content is 10%, its hardness is the largest.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (5)

1. a hydrophobic silica aerogel nano-composite for modified silicone rubber, is characterized in that: the hydrophobic silica aerogel nano-composite is bonded on the surface of silica aerogel. The branch has trimethylsiloxy. 2. a preparation method of the described nanocomposite material of claim 1, is characterized in that: silica aerogel is added in toluene and ultrasonically dispersed uniformly, and obtaining concentration is the silica aerogel of 0.2g/mL Dispersion; Pour the silica aerogel dispersion and hexamethyldisilazane into a three-necked flask, add ammonia water dropwise to adjust the pH to 7-8, and then heat and stir in a water bath at 60°C under the condition of introducing nitrogen. First stir at 300-400r/min for 2h, and then at 700-800r/min for 2h; after stirring, set up a reflux device and conduct reflux reaction at 100°C for 5h, the obtained product is washed with toluene and acetone in turn, and then Vacuum freeze-drying to obtain hydrophobic silica aerogel nanocomposites. 3. The preparation method according to claim 2, wherein the mass ratio of the silica aerogel to the hexamethyldisilazane is 25:1. 4. an application of the hydrophobic silica aerogel nanocomposite material according to claim 1, is characterized in that: for use as reinforcing filler, the room temperature vulcanization methyl vinyl silicone rubber is modified, to improve Mechanical properties and thermal insulation properties of silicone rubber. 5. a method utilizing the hydrophobic silica aerogel nanocomposite material of claim 1 to carry out modification to silicone rubber, is characterized in that, comprises the steps: (1) Take 100 parts of liquid methyl vinyl silicone rubber, 5 parts of tetraethyl orthosilicate, 2 parts of dibutyltin dilaurate, 0.5 parts of triethylenetetramine and 2 to 10 parts of the hydrophobic described in claim 1 Silica aerogel nanocomposite material, mixed in a homogenizer at 2000r/min for 2min, and then mixed at 800r/min for 3-4min to obtain a silicone rubber composite material; (2) The silicone rubber composite material was evacuated for 5 minutes to remove air bubbles, then poured into a mold, cured at room temperature for 24 hours, and then placed in an oven at 100°C for 2 hours; after complete curing, cooled to room temperature to release the mold , that is, a hydrophobic silica aerogel nanocomposite modified methyl vinyl silicone rubber composite material is obtained.

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