A novel ceramized silicone rubber composite material, its preparation method and application

Abstract

The present invention provides a novel ceramized silicone rubber composite material, its preparation method and applications, belonging to the field of flame retardant materials. The present invention prepares a polyphosphazene-loaded silica nanosphere with a core-shell structure. By adding the nanospheres, inorganic fillers and other materials to the silicone rubber matrix, a ceramized silicone rubber composite material is obtained. The ceramized silicone rubber composite material is irradiated to obtain an irradiated crosslinked ceramized silicone rubber composite material. The composite material has high mechanical properties and can form a dense and hard ceramic layer after high-temperature ablation, effectively protecting the wire and cable. In addition, the polyphosphazene-loaded silica nanospheres obtained in the present invention improve the interfacial compatibility between the inorganic filler and the silicone rubber matrix.

Description

Technical Field:

[0001] The present invention belongs to the field of flame retardant materials, and particularly relates to a novel ceramizable silicone rubber composite material, a preparation method thereof and an application thereof. Background Art:

[0002] At present, the fireproof materials used in wire and cable need to have characteristics such as processability, flexibility, fire resistance, water resistance, heat insulation, corrosion resistance and aging resistance. As a novel polymer composite material, ceramizable silicone rubber is mainly used in the production of fireproof wire and cable. The produced fireproof wire and cable can ensure the smoothness of power and communication lines in case of fire and has reached the index requirements of national standards. However, the existing ceramizable silicone rubber has the following problems: First, the flame retardant performance is poor and it is difficult to form a hard and complete ceramized layer; Second, the ceramizable silicone rubber material uses silicone rubber as the matrix, and the compatibility between the ceramic filler and the silicone rubber matrix is poor, which affects the dispersion of the ceramic filler in the silicone rubber matrix, and further affects the denseness of the formed ceramized layer; Third, the ceramizable silicone rubber material also has the problem of difficult ceramization at low temperature, which seriously limits its application. Therefore, how to improve the flame retardancy and compatibility of ceramizable silicone rubber materials and form a hard and complete ceramized layer is a technical problem to be solved urgently at present. Summary of the Invention:

[0003] In order to solve the above technical problems, the present invention provides a novel ceramizable silicone rubber composite material, and its preparation method is as follows:

[0004] According to the mass ratio: 80-100 parts of silicone rubber, 5-20 parts of reinforcing agent, 20-50 parts of ceramic filler and 1-10 parts of structure control agent are kneaded at room temperature for 10-30 minutes to obtain kneaded rubber E; then 10-20 parts of melting aid, 5-20 parts of inorganic flame retardant and 10-20 parts of polyphosphazene supported silica are added, and kneaded for 10-30 minutes to obtain a silicone rubber composite material, and then irradiated and crosslinked to obtain a ceramizable silicone rubber composite material, wherein the irradiation dose is 20-160 kGy;

[0005] The silicone rubber is one or any combination of dimethyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber or fluorosilicone rubber;

[0006] The reinforcing agent is one or any combination of fumed silica or precipitated silica;

[0007] The structure control agent is one or any combination of hydroxyl silicone oil, high vinyl silicone oil;

[0008] The ceramic filler is one or any combination of mica, montmorillonite, wollastonite, aluminum hydroxide, calcium carbonate, kaolin;

[0009] The melting aid is one or any combination of low-melting glass powder, glass frit, zinc borate, and boron oxide; the inorganic flame retardant is one or any combination of magnesium hydroxide or aluminum hydroxide;

[0010] The polyphosphazene-supported silica described above has a preparation method including the following steps:

[0011] (1) At room temperature, NH3·H2O and deionized water are stirred at a volume ratio of 1:7 - 8 for 0.5 - 2 h to obtain a mixed solution A. Tetraethyl orthosilicate and absolute ethanol are quickly added to the mixed solution A at a volume ratio of 1:9 - 11. After stirring at room temperature for 2 - 5 h, it is centrifuged, filtered, and washed with absolute ethanol 3 - 6 times, and then vacuum dried at 60 - 70 °C for 16 - 24 h to obtain SiO2 nanoparticles with hydroxyl groups;

[0012] (2) The SiO2 nanoparticles with hydroxyl groups obtained in step (1) are ultrasonically stirred with acetonitrile for 1 - 2 h to obtain a suspension B. The concentration of the SiO2 nanoparticles in the acetonitrile solution is 1.0 - 2.0 mol / L. Then, hexachlorocyclotriphosphazene (HCCP) and 2 - 6 mL of triethylamine are added to the suspension B, and it is stirred at 40 - 60 °C for 1 - 5 h to obtain a suspension C. Then, bisphenol S is added to the suspension C to obtain a mixed solution D. The molar ratio of HCCP to bisphenol S is 1:6 - 1:3. After heating the mixed solution D to 60 - 80 °C and reacting for 8 - 10 h, it is centrifuged, filtered, and washed with deionized water and acetone 3 - 6 times respectively, and then vacuum dried at 60 - 80 °C for 24 - 48 h to obtain polyphosphazene-supported silica.

[0013] Further, the polyphosphazene-supported silica is a core-shell structured nanosphere with silica as the core and polyphosphazene as the shell; after the microsphere is ablated at high temperature, it can obtain a hard surface and has strong self-supporting ability.

[0014] Further, the radiation cross-linking is electron beam or γ-ray radiation cross-linking.

[0015] The present invention also provides an application of the novel ceramizable silicone rubber composite material in insulating materials, anti-shielding materials, or fireproof materials.

[0016] The effective effects of the present invention:

[0017] Compared with the silicone rubber composites prepared by the prior art (Xiaodong Guo, et al., Influence of Platinum-Loaded Polyphosphazene Microspheres on the Flame Retardancy and Ceramication Properties of Silicone Rubber Composites [J]. Polymer Materials Science and Engineering, 2019, 35(7): 82.), the ceramifiable silicone rubber composites obtained in the present invention can form a highly flame-retardant ceramified material at low temperatures. With organosilicone rubber as the matrix, the ceramic-forming filler has good compatibility with the organosilicone rubber matrix, and the ceramic-forming filler is well dispersed in the silicone rubber matrix, forming a relatively dense, hard and complete ceramification layer; it also has good mechanical properties and significantly improves the tensile strength. After the composite material is ablated at 700-1000 °C, the nitrogen, phosphorus and sulfur elements in the polyphosphazene-loaded silica nanospheres still appear in the ceramification layer and participate in the construction of the ceramification layer. The ceramification layer is relatively dense and hard, which can effectively protect the wire and cable, effectively solving the problems of ceramification and flame retardancy of the composite material. Compared with the expandable ceramifiable silicone rubber flame retardant material prepared by the prior art (Hongwei Zhu, Jianhua Li. Research on SR / frit composites: A novel low-temperature ceramifiable expandable flame-retardant material [J]. Materials, 2022, 15(9): 2961.), the limiting oxygen index of the ceramifiable silicone rubber composites obtained in the present invention is increased by 2%-4%; at the same time, the problem of interfacial compatibility is effectively solved. Description of the Drawings:

[0018] Figure 1 (a) SEM comparison diagrams of the ceramifiable silicone rubber composite prepared in Example 6 before ablation and (b) after ablation at 1000 °C;

[0019] Figure 2 Tensile strength comparison diagrams of the ceramifiable silicone rubber composites prepared in Examples 4-7;

[0020] Figure 3 Limiting oxygen index comparison diagrams of the ceramifiable silicone rubber composites prepared in Examples 4-7. Detailed Embodiments:

[0021] Example 1 Preparation of Polyphosphazene-Loaded Silica Nanospheres

[0022] (1) At room temperature, 4 mL of NH₃·H₂O (25 wt%) and 29.5 mL of deionized water were stirred for 0.5 h to obtain a mixed solution A1. After rapidly adding 4.5 mL of tetraethyl orthosilicate and 45.5 mL of absolute ethanol to the mixed solution A1, it was stirred at room temperature for 2 h. After centrifugal filtration and washing with absolute ethanol three times respectively, it was vacuum dried at 60 °C for 24 h to obtain SiO₂ nanoparticles B1 with hydroxyl groups;

[0023] (2) SiO₂ (1 g) and 100 mL of acetonitrile were ultrasonically treated for 1 h to obtain a suspension C1. 0.69 g of hexachlorocyclotriphosphazene (HCCP) and 2 mL of triethylamine were added to the suspension C1 and reacted in 40 mL of absolute acetonitrile, and continuously stirred at 40 °C for 1 h to obtain an HCCP-functionalized SiO₂ suspension D1. Then, 1.50 g of bisphenol S (BPS) was added to the suspension D1 to obtain a mixture E1. The mixture E1 was heated to 60 °C and reacted for 10 h, and centrifugally filtered and washed with deionized water and acetone 3 - 6 times respectively, and vacuum dried at 60 °C for 24 h to obtain polyphosphazene-loaded silica nanospheres F1.

[0024] Example 2 Preparation of polyphosphazene-loaded silica nanospheres

[0025] (1) At room temperature, 4 mL of NH₃·H₂O (25 wt%) and 28 mL of deionized water were stirred for 1 h to obtain a mixed solution A2. After rapidly adding 5 mL of tetraethyl orthosilicate and 45 mL of absolute ethanol to the mixed solution A2, it was stirred at room temperature for 3 h. After centrifugal filtration and washing with absolute ethanol three times respectively, it was vacuum dried at 60 °C for 24 h to obtain SiO₂ nanoparticles B2 with hydroxyl groups;

[0026] (2) SiO₂ (1 g) and 100 mL of acetonitrile were ultrasonically treated in an ultrasonic bath for 1.5 h to obtain a suspension B2. 0.69 g of hexachlorocyclotriphosphazene (HCCP) and 3 mL of triethylamine were added to the suspension C2 and reacted in 60 mL of absolute acetonitrile, and continuously stirred at 40 °C for 1 h to obtain an HCCP-functionalized SiO₂ suspension D2. Then, 3.60 g of bisphenol S (BPS) was added to the suspension D2 to obtain a mixture E2. The mixture E2 was heated to 50 °C and reacted for 12 h, and centrifugally filtered and washed with deionized water and acetone 3 - 6 times respectively, and vacuum dried at 60 °C for 24 h to obtain polyphosphazene-loaded silica nanospheres F2.

[0027] Example 3 Preparation of polyphosphazene-loaded silica nanospheres

[0028] (1) At room temperature, 4 mL of NH₃·H₂O (25 wt%) and 32 mL of deionized water were stirred for 2 h to obtain a mixed solution A3. After quickly adding 4 mL of tetraethyl orthosilicate and 44 mL of absolute ethanol to the mixed solution A3, it was stirred at room temperature for 2.5 h. After centrifugal filtration and washing with absolute ethanol three times respectively, it was vacuum dried at 60 °C for 24 h to obtain SiO₂ nanoparticles B3 with hydroxyl groups;

[0029] (2) SiO₂ (1.5 g) and 150 mL of acetonitrile were ultrasonically bathed for 1 h to obtain a suspension B3. 0.69 g of hexachlorocyclotriphosphazene (HCCP) and 3 mL of triethylamine were added to the suspension C3 and reacted in 50 mL of absolute acetonitrile, and continuously stirred at 40 °C for 1 h to obtain an HCCP-functionalized SiO₂ suspension D3. Then, 1.50 g of bisphenol S (BPS) was added to the suspension D3 to obtain a mixture E3. The mixture E3 was heated to 60 °C and reacted for 10 h, and centrifugally filtered and washed with deionized water and acetone 3 - 6 times respectively, and vacuum dried at 60 °C for 24 h to obtain polyphosphazene-loaded silica nanospheres F3.

[0030] Example 4 Preparation of ceramizable silicone rubber composite material 1

[0031] At room temperature, 1000 g of methyl vinyl silicone rubber was wrapped on a two-roll mill, and the roll gap was set to 2 - 3 mm. 150 g of fumed silica, 300 g of mica powder, and 25 g of hydroxyl silicone oil were added in sequence. After mixing for 10 minutes until evenly mixed, a mixed rubber G1 was obtained; then 180 g of low melting point glass powder, 95 g of magnesium hydroxide, and 100 g of the polyphosphazene-loaded silica nanospheres F1 obtained in Example 1 were added to the mixed rubber G1, the roll gap was adjusted to 1 - 2 mm, and mixing was continued for 10 minutes to obtain a silicone rubber material. The silicone rubber material was cold-pressed and formed with a flat vulcanizer, and irradiated with an electron beam with a radiation dose of 40 kGy to obtain an irradiated cross-linked ceramizable silicone rubber composite material 1.

[0032] Example 5 Preparation of ceramizable silicone rubber composite material 2

[0033] At room temperature, 800 g of methyl vinyl silicone rubber was wrapped on a two-roll mill, and the roll gap was set to 2 - 3 mm. 200 g of fumed silica, 250 g of mica powder, and 15 g of high vinyl silicone oil were added in sequence. After mixing for 10 minutes until evenly mixed, a mixed rubber G2 was obtained; then 200 g of glass frit, 100 g of aluminum hydroxide, and 150 g of the polyphosphazene-loaded silica nanospheres F2 obtained in Example 2 were added to the mixed rubber G2, the roll gap was adjusted to 1 - 2 mm, and mixing was continued for 10 minutes to obtain a silicone rubber material. The silicone rubber material was cold-pressed and formed with a flat vulcanizer, and further irradiated with an electron beam with a radiation dose of 80 kGy to obtain an irradiated cross-linked ceramizable silicone rubber composite material 2.

[0034] Preparation of Ceramed Silicon Rubber Composite Material 3 in Example 6

[0035] At room temperature, 900 g of dimethyl silicone rubber was wrapped on a two-roll mill, and the roll gap was set to 2 - 3 mm. 200 g of precipitated silica, 500 g of mica powder, and 50 g of hydroxy silicone oil were added in sequence. After kneading for 10 minutes until evenly kneaded, a kneaded rubber G3 was obtained; then 100 g of zinc borate, 150 g of magnesium hydroxide, and 150 g of the polyphosphazene-supported silica nanospheres F3 obtained in Example 3 were added to the kneaded rubber G3. The roll gap was adjusted to 1 - 2 mm, and kneading was continued for 10 minutes to obtain a silicone rubber material. The silicone rubber material was cold-pressed and formed with a flat vulcanizer, and further irradiated with an electron beam with an irradiation dose of 120 kGy to obtain the irradiated cross-linked ceramized silicone rubber composite material 3.

[0036] The ceramized silicone rubber composite material 3 obtained in Example 6 was burned at 700 °C - 1000 °C. Figure 1 Fig. is the morphology comparison diagram of the ceramized silicone rubber composite material 3 before ablation and after ablation at 1000 °C. It was observed that after high-temperature ablation, a dense ceramized layer was formed on the surface of the ceramized layer, which could effectively prevent the occurrence of fire. During the porcelain-forming process, the formation of SiO2 network structure, phosphates, nitrates, etc. participated in the construction of the ceramic layer. The flux melted at high temperature to form a flowing liquid, connecting the inorganic substances after ablation, and a hard, dense, complete, and continuous ceramized layer could be formed, which had a certain strength and self-supporting ability. The composite material had sufficient strength to support the weight of the residue after combustion. Compared with the prior art, it could better protect the cable material.

[0037] Preparation of Ceramed Silicon Rubber Composite Material 4 in Example 7

[0038] At room temperature, 1000 g of methylphenylvinyl silicone rubber was wrapped on a two-roll mill, and the roll gap was set to 2 - 3 mm. 200 g of precipitated silica, 400 g of mica powder, and 30 g of hydroxy silicone oil were added in sequence. After kneading for 10 minutes until evenly kneaded, a kneaded rubber G4 was obtained; then 200 g of zinc borate, 200 g of aluminum hydroxide, and 180 g of the polyphosphazene-supported silica nanospheres F3 in Example 3 were added to the kneaded rubber G4. The roll gap was adjusted to 1 - 2 mm, and kneading was continued for 10 minutes to obtain a silicone rubber material. The silicone rubber material was cold-pressed and formed with a flat vulcanizer, and further irradiated with an electron beam with an irradiation dose of 160 kGy to obtain the irradiated cross-linked ceramized silicone rubber composite material 4.

[0039] Attached Figure 2Shows the comparison chart of the tensile strength of the ceramized silicone rubber composites prepared in Examples 4-7. Among them, the tensile strength of the composite material in Example 6 is the highest. The content of polyphosphazene-loaded silica nanospheres or other components is not the highest in the examples, and the radiation dose is not the highest either. This shows that the most excellent tensile strength performance of the composite material is achieved by the synergistic effect of each component, component ratio and process.

[0040] Figure 3 Shows the comparison chart of the limiting oxygen index of the ceramized silicone rubber composites prepared in Specific Examples 4-7. Among them, the oxygen index of the composite material in Example 6 is the highest and the flame retardant performance is the best. The content of polyphosphazene-loaded silica nanospheres or other components is not the highest in the examples, and the radiation dose is not the highest either. This shows that the most excellent oxygen index performance of the composite material is achieved by the synergistic effect of each component, component ratio and process.

[0041] Comparative Example 1

[0042] The process of preparing the composite material in the literature (Guo Xiaodong, Liu Xiongrui, Zhang Yanzhao, etc. Influence of platinum-loaded polyphosphazene microspheres on the flame retardancy and ceramization properties of silicone rubber composites [J]. Polymer Materials Science and Engineering, 2019, 35(7): 82.) is as follows:

[0043] At room temperature, the mixing of the silicone rubber composite material is carried out on a two-roll open mill: First, 1000 g of methyl vinyl silicone rubber raw rubber is wrapped around the two rolls, 200 g of fumed silica is added, and the mixture is kneaded for 10 min to make kneaded rubber G6; then 300 g of mica powder, 250 g of glass powder, 175 g of magnesium hydroxide, 75 g of aluminum hydroxide and 0.1 g of Pt / PZS inorganic filler are added. After mixing evenly, continue to knead for 10 min, then add 50 g of KH-550 and 20 g of DBPMH as vulcanizing agents and continue to knead for 5 min. The kneaded rubber material is put into a mold and vulcanized at 150 °C and a pressure of 28 MPa for 15 min to form a refractory and flame-retardant silicone rubber composite material, and its tensile strength is 3.7 MPa.

[0044] Comparative Example 2

[0045] (Hongwei Zhu, Jianhua Li. Research on SR / frit composites: A novel low-temperature ceramifiable expandable flame-retardant material[J]. Materials, 2022, 15(9): 2961.) discloses mixing 1000 g of methyl vinyl silicone rubber raw material with 100 g of aluminum phosphate, 5 g of mica, 10 g of calcium carbonate, 20 g of silica and 10 g of glass frit using a two-roll mill. After mixing evenly, about 2.5 g of DCBP is added as a vulcanizing agent and mixing continues for 5 minutes to obtain an expandable ceramifiable silicone rubber flame retardant material, the tensile strength and limiting oxygen index of which are 3.9 MPa and 31.7% respectively.

[0046] Comparison of tensile strength and limiting oxygen index between Comparative Example 1 and Examples 4-7

[0047] Tensile strength Limiting oxygen index Comparative example 1 3.7 MPa — Comparative example 2 3.9 MPa 31.7％ Example 4 4.2 MPa 31.9％ Example 5 4.5 MPa 32.8％ Example 6 4.9 MPa 34.8％ Example 7 4.4 MPa 33.2％

[0048] Compared with the prior art, the ceramifiable silicone rubber composite material obtained in the present invention has the following advantages: First, it has good flame retardant performance and can form a hard and complete ceramified layer; second, with silicone rubber as the matrix, the compatibility between the ceramifying filler and the silicone rubber matrix is good, which increases the dispersion of the ceramifying filler in the silicone rubber matrix and improves the densification of the ceramified layer; third, the ceramifiable silicone rubber material can be ceramified at low temperature, expanding the application range of the material; simultaneously improving the flame retardancy, mechanical properties and compatibility of the ceramifiable silicone rubber material. Compared with Comparative Example 1, the ceramifiable silicone rubber composite material obtained in the present invention can form a high flame retardant ceramified material at low temperature. With silicone rubber as the matrix, the compatibility between the ceramifying filler and the silicone rubber matrix is good, and the ceramifying filler is well dispersed in the silicone rubber matrix, forming a dense, hard and complete ceramified layer; it also has good mechanical properties and significantly improves the tensile strength; after the composite material is ablated at 700-1000 °C, the nitrogen, phosphorus and sulfur elements in the polyphosphazene loaded silica nanospheres still appear in the ceramified layer and participate in the construction of the ceramified layer. The ceramified layer is relatively dense and hard, which can effectively protect the wire and cable and effectively solve the problems of ceramic formation and flame retardancy of the composite material. Compared with Comparative Example 2, (Hongwei Zhu, Jianhua Li. Research on SR / frit composites: A novel low-temperature ceramifiable expandable flame-retardant material[J]. Materials, 2022, 15(9): 2961.) the tensile strength and limiting oxygen index of the ceramifiable silicone rubber composite material obtained in the present invention are synchronously improved.

[0049] In all the embodiments of the present invention, the performance of the composite material obtained in Example 6 in terms of mechanics, flame retardancy and compatibility is the best among all the embodiments, but the proportion of each component is not the highest in the embodiments. In addition, the related processes are also different. In summary, the most excellent performance of the composite material obtained in the present invention is achieved by the synergistic effect of components, ratios and processes.

Claims

1. A ceramized silicone rubber composite material, characterized in that, The preparation method thereof is as follows: By mass ratio: 80 - 100 parts of silicone rubber, 5 - 20 parts of reinforcing agent, 20 - 50 parts of porcelain-forming filler, and 1 - 10 parts of structure control agent are kneaded at room temperature for 10 - 30 minutes to obtain kneaded rubber E; then 10 - 20 parts of melting aid, 5 - 20 parts of inorganic flame retardant, and 10 - 20 parts of polyphosphazene-supported silica are added, and after kneading for 10 - 30 minutes, a silicone rubber composite material is obtained, and then irradiated cross-linking is carried out to obtain a ceramized silicone rubber composite material, and the irradiation dose is 20 - 160 kGy; The silicone rubber is one or any combination of dimethyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber, or fluorosilicone rubber; The reinforcing agent is one or any combination of fumed silica or precipitated silica; The structure control agent is one or any combination of hydroxyl silicone oil or high vinyl silicone oil; The porcelain-forming filler is one or any combination of mica, montmorillonite, wollastonite, aluminum hydroxide, calcium carbonate, kaolin; the melting aid is one or any combination of low-melting glass powder, glass frit, zinc borate, boron oxide; The inorganic flame retardant is one or any combination of magnesium hydroxide or aluminum hydroxide; The preparation method of the polyphosphazene-supported silica includes the following steps: (1) At room temperature, NH3·H2O and deionized water are stirred at a volume ratio of 1:7 - 8 for 0.5 - 2 h to obtain a mixed solution A. Tetraethyl orthosilicate and absolute ethanol are quickly added to the mixed solution A at a volume ratio of 1:9 - 11, and stirred at room temperature for 2 - 5 h. After centrifugal filtration and washing with absolute ethanol for 3 - 6 times, it is vacuum dried at 60 - 70 °C for 16 - 24 h to obtain SiO2 nanoparticles with hydroxyl groups; (2) The SiO2 nanoparticles with hydroxyl groups obtained in step (1) are ultrasonically stirred with acetonitrile for 1 - 2 h to obtain a suspension B. The concentration of the SiO2 nanoparticles in the acetonitrile solution is 1.0 - 2.0 mol / L. Then, hexachlorocyclotriphosphazene HCCP and 2 - 6 mL of triethylamine are added to the suspension B, and stirred at 40 - 60 °C for 1 - 5 h to obtain a suspension C. Then, bisphenol S is added to the suspension C to obtain a mixed solution D. The molar ratio of HCCP to bisphenol S is 1:6 - 1:

3. After heating the mixed solution D to 60 - 80 °C and reacting for 8 - 10 h, it is centrifugally filtered and washed with deionized water and acetone for 3 - 6 times respectively, and vacuum dried at 60 - 80 °C for 24 - 48 h to obtain polyphosphazene-supported silica.

2. The ceramicized silicone rubber composite material according to claim 1, wherein The polyphosphazene-supported silica is a core-shell structured nano-microsphere with silica as the core and polyphosphazene as the shell; after the microsphere is ablated at high temperature, the surface becomes hard and has strong self-supporting ability.

3. A ceramized silicone rubber composite material according to claim 1, wherein, The irradiation cross-linking is electron beam or γ-ray irradiation cross-linking.

4. Application of the ceramized silicone rubber composite material according to any one of claims 1 - 3 in insulating materials, anti-shielding materials, or fireproof materials.

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