Two-component addition type low-density liquid foaming silicone rubber and preparation method thereof

Abstract

The invention discloses two-component addition type low-density liquid foaming silicone rubber and a preparation method thereof, and belongs to the technical field of silicone rubber preparation. Comprising a component A and a component B, the component A is prepared from the following components in parts by weight: 50 to 70 parts of vinyl terminated polysiloxane, 10 to 20 parts of vinyl hydroxyl silicone oil, 0.5 to 2 parts of platinum catalyst, 15 to 25 parts of HGM (at) PN-rGO / APP and 3 to 8 parts of methyl vinyl MQ resin; the component B is prepared from the following components in parts by weight: 50 to 60 parts of vinyl-terminated polysiloxane, 8 to 15 parts of hydrogen-terminated hydrogen-containing silicone oil, 10 to 20 parts of methyl-terminated hydrogen-containing silicone oil, 5 to 10 parts of hydroxyl-terminated silicone oil, 0.002 to 0.01 part of an inhibitor, 10 to 20 parts of fumed silica and 1 to 3 parts of a tackifier. The synergistic components in the HGM-coated PN-rGO / APP can greatly improve the flame retardant property of the silicone rubber, improve the compression strength and reduce the heat release rate at the same time.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of silicone rubber preparation, and particularly relates to a two-component addition type low-density liquid foaming silicone rubber and a preparation method thereof. BACKGROUND

[0002] The addition type liquid silicone rubber is an organosilicon material formed by a three-dimensional network elastomer through a silicon hydrogen addition reaction under the action of a platinum catalyst, with vinyl silicone oil and hydrogen-containing silicone oil as raw materials. Its advantages include high and low temperature resistance, good electrical insulation, no by-product in curing, low thermal expansion coefficient, non-toxicity, environmental protection, etc., and is widely used in the fields of automobiles, electronics, aviation, etc. However, the material has poor adhesion to substrates such as fabrics due to low surface energy, is easy to fall off; at the same time, the fracture toughness and elongation are insufficient, and it is easy to break under external force, which seriously restricts its application in flexible scenarios such as belt coating.

[0003] Patent application with publication number CN 118931488 A discloses a self-adhesive type low-density sealing two-component liquid silicone rubber formed by on-site dispensing molding, and a preparation method and application thereof, which comprises the following raw materials: vinyl-terminated dimethyl silicone oil, methyl-terminated hydrogen-containing silicone oil, hydrogen-terminated hydrogen-containing silicone oil, hydroxyl-terminated silicone oil, white carbon black, hexamethyl disilazane, tetramethyl divinyl disilazane, distilled water, tackifier, inhibitor, catalyst; wherein the inhibitor is a combination of tetramethyl divinyl disiloxane and ethynyl cyclohexanol or a combination of tetramethyl divinyl disiloxane and methyl butynol, but it is sensitive to humidity (foaming rate is too fast when relative humidity is >80%), and the construction environment needs to be strictly controlled; and the high-strength scenario is limited, with a tensile strength of only 0.8-1.2 MPa, which is not suitable for structural load-bearing parts; patent application with publication number CN 108219671 A discloses a two-component addition type liquid silicone rubber and a preparation method thereof, which blends end-vinyl silicone oil with end-vinyl side chain vinyl silicone oil (vinyl content 0.5%-5%), kneads in the presence of a silicon-nitrogen treatment agent with fumed white carbon black to form a networked pre-polymer, and pre-hydrolyzes γ-aminopropyl triethoxysilane under acidic conditions to improve the wettability of nylon and polyester, with an adhesion strength of 4.0 N / mm (150% higher than traditional products), but the foaming function is not optimized, with a density >0.9 g / cm³, which cannot meet the lightweight and high-mechanical and flame-retardant requirements; and the platinum catalyst is easy to be poisoned by fabric dyes. Therefore, it is necessary to prepare a two-component foaming silicone rubber to improve the compression strength and flame-retardant performance of the addition type silicone rubber. SUMMARY

[0004] The present application aims to provide a two-component addition type low-density liquid foaming silicone rubber and a preparation method thereof, to improve the compression strength and flame-retardant performance of the addition type silicone rubber.

[0005] The object of the present application can be achieved by the following technical solutions: Two-component addition type low-density liquid foaming silicone rubber, comprising A component and B component; The A component comprises 50-70 parts of vinyl-terminated polysiloxane, 10-20 parts of vinyl hydroxy silicone oil, 0.5-2 parts of platinum catalyst, 15-25 parts of HGM@PN-rGO / APP and 3-8 parts of methyl vinyl MQ resin by weight; The B component comprises 50-60 parts of vinyl-terminated polysiloxane, 8-15 parts of hydrogen-terminated hydrogen-containing silicone oil, 10-20 parts of methyl-terminated hydrogen-containing silicone oil, 5-10 parts of hydroxyl-terminated silicone oil, 0.002-0.01 parts of inhibitor, 10-20 parts of fumed white carbon black and 1-3 parts of tackifier.

[0006] Further, the HGM@PN-rGO / APP is prepared by the following steps: (1) Disperse HGM in ethanol, add silane coupling agent, reflux at 75-85°C, centrifugal washing, vacuum drying, and obtain pretreated HGM; (2) Disperse GO in deionized water to obtain GO dispersion liquid; stir and dissolve H3PO4, urea and deionized water to obtain doping liquid; add the doping liquid to the GO dispersion liquid, add PVP, adjust pH to 9-10, add pretreated HGM, and react at 180-190°C for 12-16h; centrifugal collection after cooling, washing and drying to obtain HGM@PN-rGO; (3) Dissolve APP in deionized water and add to HGM@PN-rGO, ultrasonic dispersion, react at 120-130°C for 4-8h, centrifugal collection, drying to obtain HGM@PN-rGO / APP.

[0007] Further, the weight ratio of HGM and silane coupling agent is (25-35):(2-4).

[0008] Further, the weight ratio of GO, H3PO4, urea and APP is (4-6):(3-4):(6-8):(50-60).

[0009] Further, the tackifier is prepared by the following steps: Mix 3-(2,3-epoxypropoxy) propyl trimethoxysilane, vinyl trimethoxysilane, hydroxyl-terminated silicone oil and acetic acid aqueous solution, reflux at 80-85°C for 3-4h, vacuum distillation after cooling to obtain tackifier.

[0010] Further, the weight ratio of 3-(2,3-epoxypropoxy) propyl trimethoxysilane, vinyl trimethoxysilane, hydroxyl-terminated silicone oil and acetic acid aqueous solution is (12-18):(8-12):(45-60):(4-6).

[0011] Further, the vinyl-terminated polysiloxane has a viscosity of 20000±100 mPa·s and a vinyl content of 0.07-0.09 mol%.

[0012] Further, the vinyl-hydroxyl silicone oil has a hydroxyl content of 6%-8% and a molecular weight of 3000-5000.

[0013] Further, the hydrogen-terminated hydrogen-containing silicone oil has a hydrogen content of 0.05%-0.5% and a viscosity of 500±50 mPa·s.

[0014] Further, the methyl-terminated hydrogen-containing silicone oil has a hydrogen content of 0.5%-1.65% and a viscosity of 1000±50 mPa·s.

[0015] Further, the hydroxyl-terminated silicone oil has a hydroxyl content of 8%-10% and a molecular weight of 1500-3000.

[0016] Further, the inhibitor is composed of tetramethyl divinyl disiloxane (TMDVS) and ethynyl cyclohexanol (ECH) in a molar ratio of (5-9):1.

[0017] The application discloses a preparation method of a two-component addition type low-density liquid foaming silicone rubber. S1, mixing the vinyl-terminated polysiloxane, HGM@PN-rGO / APP and methyl vinyl MQ resin, adding the vinyl-hydroxyl silicone oil, mixing at 50-60 DEG C for 40-60 min; after cooling, adding the platinum gold catalyst, mixing, defoaming, and obtaining component A; S2, treating the fumed white carbon black with hexamethyl disilazane at 50-60 DEG C for 2-3 h to obtain pretreated white carbon black; uniformly mixing the vinyl-terminated polysiloxane, the hydroxyl-terminated silicone oil, the methyl-terminated hydrogen-containing silicone oil and the hydrogen-terminated hydrogen-containing silicone oil; adding the pretreated white carbon black, the tackifier and the inhibitor, and filtering to obtain component B; S3, mixing and extruding components A and B to obtain a mixed glue solution; point coating the mixed glue solution on a substrate and freely foaming in an environment at 25-40 DEG C; after pre-curing at 40-45 DEG C for 60-70 min, secondarily vulcanizing at 75-80 DEG C for 120-140 min, and performing plasma treatment on the foam surface, a two-component addition type low-density liquid foaming silicone rubber is obtained.

[0018] Further, the power of the plasma treatment is 95-110 W, and the treatment time is 5-10 min.

[0019] The application has the following beneficial effects: (1) The HGM@PN-rGO / APP used in this invention is synthesized through gradient hydrothermal synthesis. Combined with the interfacial reinforcement effect of silane coupling agent-modified hollow glass microspheres (HGM) and nitrogen-phosphorus doped graphene (PN-rGO), a synergistic effect of physical barrier and chemical catalytic flame retardancy is achieved. The low density of HGM can reduce the overall density of the material. The phosphorus and nitrogen of PN-rGO catalyze carbonization, and its layered structure delays the diffusion of pyrolysis gas through intercalation effect. Combined with the expansion flame retardancy of APP, it improves the flame retardancy of silicone rubber foam. The lightweight of hollow glass microspheres (HGM) and the mechanical reinforcement of rGO work together to improve the compressive strength of the material. The thermally conductive network of rGO and the thermal insulation properties of HGM work together to improve the thermal stability of the foam. The three factors work together to significantly improve the flame retardancy of silicone rubber, increase the compressive strength and reduce the heat release rate.

[0020] (2) The cascade effect of the epoxy-vinyl bifunctional tackifier and plasma surface treatment used in this invention: the epoxy groups in the tackifier undergo a ring-opening reaction with the epoxy coating on the metal substrate, and the vinyl groups participate in hydrosilylation, thereby improving the bonding strength of the substrate; in addition, the tackifier network toughened by the terminal hydroxyl silicone oil inhibits interfacial embrittlement, realizes chemical bonding between silicone rubber and the metal substrate, and maintains high strength after damp heat aging. Plasma treatment introduces carboxyl / hydroxyl groups on the foam surface, improves wettability with the coating substrate, and further enhances the peel strength. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0022] Example 1

[0023] This embodiment provides a two-component addition-curing low-density liquid foamed silicone rubber, which is prepared through the following steps: S1. Disperse 30 parts of HGM (hollow glass microspheres) in 100 parts of anhydrous ethanol and sonicate for 30 min; add 3 parts of silane coupling agent KH-550, reflux at 80℃ for 2 h, centrifuge, wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ to obtain pretreated HGM. Five parts of GO (graphene oxide) and 250 parts of deionized water were sonicated for 1 hour to obtain a GO dispersion. 3.5 parts of H3PO4 (phosphoric acid), 7 parts of urea, and 50 parts of deionized water were stirred to dissolve the GO and obtain a dopant solution. The dopant solution was added to the GO dispersion, followed by 1.5 parts of PVP (polyvinylpyrrolidone). The pH was adjusted to 9.5 with ammonia, and pretreated HGM was added. The mixture was magnetically stirred for 30 minutes. The mixture was then transferred to a high-pressure reactor and reacted at 180°C for 12 hours. After cooling, the mixture was centrifuged, washed alternately with water and ethanol, and vacuum dried at 60°C to obtain HGM@PN-rGO. Dissolve 55 parts of APP (ammonium polyphosphate) and 150 parts of deionized water at 60℃; add HGM@PN-rGO, sonicate for 30 min, transfer to a reaction vessel, and react at 120℃ for 4 h; collect by centrifugation, and dry at 60℃ for 12 h to obtain HGM@PN-rGO / APP; S2. In a three-necked flask equipped with a condenser, add 15 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 10 parts of vinyltrimethoxysilane, 50 parts of hydroxyl-terminated silicone oil (hydroxyl content 8%), and 5 parts of acetic acid aqueous solution (10%), and reflux at 85°C for 3 hours. After cooling to 50°C, remove small molecules by vacuum distillation at -0.09 MPa to obtain the thickener; S3. Add 60 parts of vinyl-terminated polysiloxane (20000 mPa·s, vinyl content 0.08 mol%) to a kneader, heat to 60°C, slowly add 20 parts of HGM@PN-rGO / APP and 5 parts of methyl vinyl MQ resin, mix at a low speed of 30 rpm for 20 min; then increase the speed to 80 rpm, add 15 parts of vinyl hydroxyl silicone oil (hydroxyl content 7%, molecular weight 4000), maintain the temperature at 60°C, and continue to mix for 40 min until the filler is completely wetted; after cooling to 40°C, add 1.5 parts of platinum catalyst, mix at a low speed of 20 rpm for 15 min; transfer the compound to a vacuum planetary mixer, degas at -0.1 MPa and 25°C for 30 min to obtain component A; Pretreated silica was obtained by treating 15 parts of fumed silica and 5 parts of hexamethyldisilazane at 60°C for 2 hours in a high-speed mixer. 40 parts of vinyl-terminated polysiloxane (20000 mPa·s), 8 parts of hydroxyl-terminated silicone oil (10% hydroxyl content), 12 parts of methyl-terminated hydrogen-containing silicone oil (1.2% hydrogen content, 1000 mPa·s viscosity), and 10 parts of hydrogen-terminated hydrogen-containing silicone oil (0.3% hydrogen content, 500 mPa·s viscosity) were added to a planetary mixer and mixed thoroughly at 500 rpm. Pretreated silica, 2 parts of tackifier, and 0.006 parts of inhibitor (TMDVS:ECH=7:1) were added, and the mixing speed was increased to 800 rpm. The mixture was then mixed for 40 minutes under a vacuum of -0.08 MPa. The mixture was filtered through a 200-mesh filter to obtain component B. Components A and B are loaded into a two-component dispensing device at a 1:1 mass ratio and extruded under a pressure of 0.3 MPa. The static mixer rotates at 300 rpm and the mixing time is 30 s to obtain a mixed adhesive. The mixed adhesive is then applied to a substrate and allowed to foam freely at 35°C. After pre-curing at 40°C for 60 min, it is then vulcanized again at 80°C for 120 min. The foam surface is then subjected to plasma treatment (air atmosphere, 100W, 5 min) to obtain a two-component addition-curing low-density liquid foamed silicone rubber.

[0024] Example 2

[0025] Compared with Example 1, this embodiment differs in that the amount of HGM@PN-rGO / APP is reduced, and the remaining components are adjusted accordingly. The specific implementation steps of S3 are as follows: S3. Add 60 parts of vinyl-terminated polysiloxane (20000 mPa·s, vinyl content 0.08 mol%) to a kneader, heat to 60°C, slowly add 15 parts of HGM@PN-rGO / APP and 7 parts of methyl vinyl MQ resin, mix at a low speed of 30 rpm for 20 min; then increase the speed to 80 rpm, add 17 parts of vinyl hydroxyl silicone oil (hydroxyl content 7%, molecular weight 4000), maintain the temperature at 60°C, and continue to mix for 40 min until the filler is completely wetted; after cooling to 40°C, add 1.5 parts of platinum catalyst, mix at a low speed of 20 rpm for 15 min; transfer the compound to a vacuum planetary mixer, degas at -0.1 MPa and 25°C for 30 min to obtain component A; Pretreated silica was obtained by treating 15 parts of fumed silica and 5 parts of hexamethyldisilazane at 60°C for 2 hours in a high-speed mixer. 40 parts of vinyl-terminated polysiloxane (20000 mPa·s), 8 parts of hydroxyl-terminated silicone oil (10% hydroxyl content), 12 parts of methyl-terminated hydrogen-containing silicone oil (1.2% hydrogen content, 1000 mPa·s viscosity), and 10 parts of hydrogen-terminated hydrogen-containing silicone oil (0.3% hydrogen content, 500 mPa·s viscosity) were added to a planetary mixer and mixed thoroughly at 500 rpm. Pretreated silica, 2 parts of tackifier, and 0.006 parts of inhibitor (TMDVS:ECH=7:1) were added, and the mixing speed was increased to 800 rpm. The mixture was then mixed for 40 minutes under a vacuum of -0.08 MPa. The mixture was filtered through a 200-mesh filter to obtain component B. Components A and B are loaded into a two-component dispensing device at a 1:1 mass ratio and extruded under a pressure of 0.3 MPa. The static mixer rotates at 300 rpm and the mixing time is 30 s to obtain a mixed adhesive. The mixed adhesive is then applied to a substrate and allowed to foam freely at 35°C. After pre-curing at 40°C for 60 min, it is then vulcanized again at 80°C for 120 min. The foam surface is then subjected to plasma treatment (air atmosphere, 100W, 5 min) to obtain a two-component addition-curing low-density liquid foamed silicone rubber.

[0026] The remaining raw materials and preparation process are the same as in Example 1.

[0027] Example 3

[0028] Compared with Example 1, this embodiment differs in that the amount of HGM@PN-rGO / APP is increased, and the remaining components are adjusted accordingly. The specific implementation steps of S3 are as follows: S3. Add 60 parts of vinyl-terminated polysiloxane (20000 mPa·s, vinyl content 0.08 mol%) to a kneader, heat to 60°C, slowly add 25 parts of HGM@PN-rGO / APP and 4 parts of methyl vinyl MQ resin, mix at a low speed of 30 rpm for 20 min; then increase the speed to 80 rpm, add 13 parts of vinyl hydroxyl silicone oil (hydroxyl content 7%, molecular weight 4000), maintain the temperature at 60°C, and continue to mix for 40 min until the filler is completely wetted; after cooling to 40°C, add 1 part of platinum catalyst, mix at a low speed of 20 rpm for 15 min; transfer the compound to a vacuum planetary mixer, degas at -0.1 MPa and 25°C for 30 min to obtain component A; Pretreated silica was obtained by treating 15 parts of fumed silica and 5 parts of hexamethyldisilazane at 60°C for 2 hours in a high-speed mixer. 40 parts of vinyl-terminated polysiloxane (20000 mPa·s), 8 parts of hydroxyl-terminated silicone oil (10% hydroxyl content), 12 parts of methyl-terminated hydrogen-containing silicone oil (1.2% hydrogen content, 1000 mPa·s viscosity), and 10 parts of hydrogen-terminated hydrogen-containing silicone oil (0.3% hydrogen content, 500 mPa·s viscosity) were added to a planetary mixer and mixed thoroughly at 500 rpm. Pretreated silica, 2 parts of tackifier, and 0.006 parts of inhibitor (TMDVS:ECH=7:1) were added, and the mixing speed was increased to 800 rpm. The mixture was then mixed for 40 minutes under a vacuum of -0.08 MPa. The mixture was filtered through a 200-mesh filter to obtain component B. Components A and B are loaded into a two-component dispensing device at a 1:1 mass ratio and extruded under a pressure of 0.3 MPa. The static mixer rotates at 300 rpm and the mixing time is 30 s to obtain a mixed adhesive. The mixed adhesive is then applied to a substrate and allowed to foam freely at 35°C. After pre-curing at 40°C for 60 min, it is then vulcanized again at 80°C for 120 min. The foam surface is then subjected to plasma treatment (air atmosphere, 100W, 5 min) to obtain a two-component addition-curing low-density liquid foamed silicone rubber.

[0029] The remaining raw materials and preparation process are the same as in Example 1.

[0030] Example 4

[0031] Compared with Example 1, the difference in this embodiment is that the amount of tackifier is reduced, and the other components are adjusted accordingly. The specific implementation steps of S3 are as follows: S3. Add 60 parts of vinyl-terminated polysiloxane (20000 mPa·s, vinyl content 0.08 mol%) to a kneader, heat to 60°C, slowly add 20 parts of HGM@PN-rGO / APP and 5 parts of methyl vinyl MQ resin, mix at a low speed of 30 rpm for 20 min; then increase the speed to 80 rpm, add 15 parts of vinyl hydroxyl silicone oil (hydroxyl content 7%, molecular weight 4000), maintain the temperature at 60°C, and continue to mix for 40 min until the filler is completely wetted; after cooling to 40°C, add 1.5 parts of platinum catalyst, mix at a low speed of 20 rpm for 15 min; transfer the compound to a vacuum planetary mixer, degas at -0.1 MPa and 25°C for 30 min to obtain component A; Pretreated silica was obtained by treating 15 parts of fumed silica and 5 parts of hexamethyldisilazane at 60°C for 2 hours in a high-speed mixer. 40 parts of vinyl-terminated polysiloxane (20000 mPa·s), 8 parts of hydroxyl-terminated silicone oil (10% hydroxyl content), 12 parts of methyl-terminated hydrogen-containing silicone oil (1.2% hydrogen content, 1000 mPa·s viscosity), and 10 parts of hydrogen-terminated hydrogen-containing silicone oil (0.3% hydrogen content, 500 mPa·s viscosity) were added to a planetary mixer and mixed thoroughly at 500 rpm. Pretreated silica, 1 part of thickener, and 0.007 parts of inhibitor (TMDVS:ECH=7:1) were added, and the mixing speed was increased to 800 rpm. The mixture was then mixed for 40 minutes under a vacuum of -0.08 MPa. The mixture was filtered through a 200-mesh filter to obtain component B. Components A and B are loaded into a two-component dispensing device at a 1:1 mass ratio and extruded under a pressure of 0.3 MPa. The static mixer rotates at 300 rpm and the mixing time is 30 s to obtain a mixed adhesive. The mixed adhesive is then applied to a substrate and allowed to foam freely at 35°C. After pre-curing at 40°C for 60 min, it is then vulcanized again at 80°C for 120 min. The foam surface is then subjected to plasma treatment (air atmosphere, 100W, 5 min) to obtain a two-component addition-curing low-density liquid foamed silicone rubber.

[0032] The remaining raw materials and preparation process are the same as in Example 1.

[0033] Example 5

[0034] Compared with Example 1, the difference in this embodiment is that the amount of thickener is increased, and the other components are adjusted accordingly. The specific implementation steps of S3 are as follows: S3. Add 60 parts of vinyl-terminated polysiloxane (20000 mPa·s, vinyl content 0.08 mol%) to a kneader, heat to 60°C, slowly add 20 parts of HGM@PN-rGO / APP and 5 parts of methyl vinyl MQ resin, mix at a low speed of 30 rpm for 20 min; then increase the speed to 80 rpm, add 15 parts of vinyl hydroxyl silicone oil (hydroxyl content 7%, molecular weight 4000), maintain the temperature at 60°C, and continue to mix for 40 min until the filler is completely wetted; after cooling to 40°C, add 1.5 parts of platinum catalyst, mix at a low speed of 20 rpm for 15 min; transfer the compound to a vacuum planetary mixer, degas at -0.1 MPa and 25°C for 30 min to obtain component A; Pretreated silica was obtained by treating 15 parts of fumed silica and 5 parts of hexamethyldisilazane at 60°C for 2 hours in a high-speed mixer. 40 parts of vinyl-terminated polysiloxane (20000 mPa·s), 8 parts of hydroxyl-terminated silicone oil (10% hydroxyl content), 12 parts of methyl-terminated hydrogen-containing silicone oil (1.2% hydrogen content, 1000 mPa·s viscosity), and 10 parts of hydrogen-terminated hydrogen-containing silicone oil (0.3% hydrogen content, 500 mPa·s viscosity) were added to a planetary mixer and mixed thoroughly at 500 rpm. Pretreated silica, 3 parts of tackifier, and 0.005 parts of inhibitor (TMDVS:ECH=7:1) were added, and the mixing speed was increased to 800 rpm. The mixture was then mixed for 40 minutes under a vacuum of -0.08 MPa. The mixture was filtered through a 200-mesh filter to obtain component B. Components A and B are loaded into a two-component dispensing device at a 1:1 mass ratio and extruded under a pressure of 0.3 MPa. The static mixer rotates at 300 rpm and the mixing time is 30 s to obtain a mixed adhesive. The mixed adhesive is then applied to a substrate and allowed to foam freely at 35°C. After pre-curing at 40°C for 60 min, it is then vulcanized again at 80°C for 120 min. The foam surface is then subjected to plasma treatment (air atmosphere, 100W, 5 min) to obtain a two-component addition-curing low-density liquid foamed silicone rubber.

[0035] The remaining raw materials and preparation process are the same as in Example 1.

[0036] Example 6

[0037] Compared with Example 1, the difference in this embodiment is that the amount of APP is reduced and the other components are adjusted accordingly. The specific implementation steps of S1 are as follows: S1. Disperse 30 parts of HGM (hollow glass microspheres) in 100 parts of anhydrous ethanol and sonicate for 30 min; add 3 parts of silane coupling agent KH-550, reflux at 80℃ for 2 h, centrifuge, wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ to obtain pretreated HGM. Five parts of GO (graphene oxide) and 250 parts of deionized water were sonicated for 1 hour to obtain a GO dispersion. 3.5 parts of H3PO4 (phosphoric acid), 7 parts of urea, and 50 parts of deionized water were stirred to dissolve the GO and obtain a dopant solution. The dopant solution was added to the GO dispersion, followed by 1.5 parts of PVP (polyvinylpyrrolidone). The pH was adjusted to 9.5 with ammonia, and pretreated HGM was added. The mixture was magnetically stirred for 30 minutes. The mixture was then transferred to a high-pressure reactor and reacted at 180°C for 12 hours. After cooling, the mixture was centrifuged, washed alternately with water and ethanol, and vacuum dried at 60°C to obtain HGM@PN-rGO. 51 parts of APP (ammonium polyphosphate) and 150 parts of deionized water were dissolved at 60℃; HGM@PN-rGO was added, ultrasonically dispersed for 30 min, transferred to a reaction vessel, and reacted at 120℃ for 4 h; collected by centrifugation, and dried at 60℃ for 12 h to obtain HGM@PN-rGO / APP; The remaining raw materials and preparation process are the same as in Example 1.

[0038] Example 7

[0039] Compared with Example 1, the difference in this embodiment is that the amount of APP is increased, and the other components are adjusted accordingly. The specific implementation steps of S1 are as follows: S1. Disperse 30 parts of HGM (hollow glass microspheres) in 100 parts of anhydrous ethanol and sonicate for 30 min; add 3 parts of silane coupling agent KH-550, reflux at 80℃ for 2 h, centrifuge, wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ to obtain pretreated HGM. Five parts of GO (graphene oxide) and 250 parts of deionized water were sonicated for 1 hour to obtain a GO dispersion. 3.5 parts of H3PO4 (phosphoric acid), 7 parts of urea, and 50 parts of deionized water were stirred to dissolve the GO and obtain a dopant solution. The dopant solution was added to the GO dispersion, followed by 1.5 parts of PVP (polyvinylpyrrolidone). The pH was adjusted to 9.5 with ammonia, and pretreated HGM was added. The mixture was magnetically stirred for 30 minutes. The mixture was then transferred to a high-pressure reactor and reacted at 180°C for 12 hours. After cooling, the mixture was centrifuged, washed alternately with water and ethanol, and vacuum dried at 60°C to obtain HGM@PN-rGO. Dissolve 60 parts of APP (ammonium polyphosphate) and 170 parts of deionized water at 60℃; add HGM@PN-rGO, sonicate for 30 min, transfer to a reaction vessel, and react at 120℃ for 4 h; collect by centrifugation, and dry at 60℃ for 12 h to obtain HGM@PN-rGO / APP; The remaining raw materials and preparation process are the same as in Example 1.

[0040] Comparative Example 1

[0041] The difference between this comparative example and Example 1 is that the foam surface is not subjected to plasma treatment in S3. The specific implementation steps of S3 are as follows: S3. Add 60 parts of vinyl-terminated polysiloxane (20000 mPa·s, vinyl content 0.08 mol%) to a kneader, heat to 60°C, slowly add 20 parts of HGM@PN-rGO / APP and 5 parts of methyl vinyl MQ resin, mix at a low speed of 30 rpm for 20 min; then increase the speed to 80 rpm, add 15 parts of vinyl hydroxyl silicone oil (hydroxyl content 7%, molecular weight 4000), maintain the temperature at 60°C, and continue to mix for 40 min until the filler is completely wetted; after cooling to 40°C, add 1.5 parts of platinum catalyst, mix at a low speed of 20 rpm for 15 min; transfer the compound to a vacuum planetary mixer, degas at -0.1 MPa and 25°C for 30 min to obtain component A; Pretreated silica was obtained by treating 15 parts of fumed silica and 5 parts of hexamethyldisilazane at 60°C for 2 hours in a high-speed mixer. 40 parts of vinyl-terminated polysiloxane (20000 mPa·s), 8 parts of hydroxyl-terminated silicone oil (10% hydroxyl content), 12 parts of methyl-terminated hydrogen-containing silicone oil (1.2% hydrogen content, 1000 mPa·s viscosity), and 10 parts of hydrogen-terminated hydrogen-containing silicone oil (0.3% hydrogen content, 500 mPa·s viscosity) were added to a planetary mixer and mixed thoroughly at 500 rpm. Pretreated silica, 2 parts of tackifier, and 0.006 parts of inhibitor (TMDVS:ECH=7:1) were added, and the mixing speed was increased to 800 rpm. The mixture was then mixed for 40 minutes under a vacuum of -0.08 MPa. The mixture was filtered through a 200-mesh filter to obtain component B. Components A and B are loaded into a two-component dispensing device at a 1:1 mass ratio and extruded under a pressure of 0.3 MPa. The static mixer rotates at 300 rpm and the mixing time is 30 s to obtain a mixed adhesive. The mixed adhesive is then applied to a substrate and allowed to foam freely at 35°C. After pre-curing at 40°C for 60 min, it is then vulcanized again at 80°C for 120 min to obtain a two-component addition-type low-density liquid foamed silicone rubber.

[0042] The remaining raw materials and preparation process are the same as in Example 1.

[0043] Comparative Example 2

[0044] The difference between this comparative example and Example 1 is that the graphene oxide in S1 is not nitrogen-phosphorus hybridized. The specific implementation steps of S1 are as follows: S1. Disperse 30 parts of HGM (hollow glass microspheres) in 100 parts of anhydrous ethanol and sonicate for 30 min; add 3 parts of silane coupling agent KH-550, reflux at 80℃ for 2 h, centrifuge, wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ to obtain pretreated HGM. Five parts of GO (graphene oxide) and 250 parts of deionized water were sonicated for 1 hour to obtain a GO dispersion. Pretreated HGM was added to the GO dispersion and magnetically stirred for 30 minutes. The mixture was then transferred to a high-pressure reactor and reacted at 180°C for 12 hours. After cooling, the mixture was centrifuged, washed alternately with water and ethanol, and vacuum dried at 60°C to obtain HGM@PN-rGO. Dissolve 55 parts of APP (ammonium polyphosphate) and 150 parts of deionized water at 60℃; add HGM@PN-rGO, sonicate for 30 min, transfer to a reaction vessel, and react at 120℃ for 4 h; collect by centrifugation, and dry at 60℃ for 12 h to obtain HGM@PN-rGO / APP; The remaining raw materials and preparation process are the same as in Example 1.

[0045] Comparative Example 3

[0046] The difference between this comparative example and Example 1 is that PN-rGO is not added in S1. The specific implementation steps of S1 are as follows: S1. Disperse 30 parts of HGM (hollow glass microspheres) in 100 parts of anhydrous ethanol and sonicate for 30 min; add 3 parts of silane coupling agent KH-550, reflux at 80℃ for 2 h, centrifuge, wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ to obtain pretreated HGM. Dissolve 55 parts of APP (ammonium polyphosphate) and 150 parts of deionized water at 60℃; add pretreated HGM, sonicate for 30 min, transfer to a reaction vessel, and react at 120℃ for 4 h; collect by centrifugation, and dry at 60℃ for 12 h to obtain HGM / APP; In subsequent steps, HGM@PN-rGO / APP should be replaced with HGM / APP; The remaining raw materials and preparation process are the same as in Example 1.

[0047] Comparative Example 4

[0048] The difference between this comparative example and Example 1 is that no APP is added in S1. The specific implementation steps of S1 are as follows: S1. Disperse 30 parts of HGM (hollow glass microspheres) in 100 parts of anhydrous ethanol and sonicate for 30 min; add 3 parts of silane coupling agent KH-550, reflux at 80℃ for 2 h, centrifuge, wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ to obtain pretreated HGM. Five parts of GO (graphene oxide) and 250 parts of deionized water were sonicated for 1 hour to obtain a GO dispersion. 3.5 parts of H3PO4 (phosphoric acid), 7 parts of urea, and 50 parts of deionized water were stirred to dissolve the GO and obtain a dopant solution. The dopant solution was added to the GO dispersion, followed by 1.5 parts of PVP (polyvinylpyrrolidone). The pH was adjusted to 9.5 with ammonia, and pretreated HGM was added. The mixture was magnetically stirred for 30 minutes. The mixture was then transferred to a high-pressure reactor and reacted at 180°C for 12 hours. After cooling, the mixture was centrifuged, washed alternately with water and ethanol, and vacuum dried at 60°C to obtain HGM@PN-rGO. Dissolve 55 parts of APP (ammonium polyphosphate) and 150 parts of deionized water at 60℃; add HGM@PN-rGO, sonicate for 30 min, transfer to a reaction vessel, and react at 120℃ for 4 h; collect by centrifugation, and dry at 60℃ for 12 h to obtain HGM@PN-rGO; In subsequent steps, HGM@PN-rGO / APP should be replaced with HGM@PN-rGO; The remaining raw materials and preparation process are the same as in Example 1.

[0049] Comparative Example 5

[0050] The difference between this comparative example and Example 1 is that neither APP nor PN-rGO is added. The specific implementation steps are as follows: S1. Disperse 30 parts of HGM (hollow glass microspheres) in 100 parts of anhydrous ethanol and sonicate for 30 min; add 3 parts of silane coupling agent KH-550, reflux at 80℃ for 2 h, centrifuge, wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ to obtain pretreated HGM. In subsequent steps, HGM@PN-rGO / APP is replaced with preprocessed HGM; The remaining raw materials and preparation process are the same as in Example 1.

[0051] Performance testing

[0052] Compressive strength (KPa): The compressive strength of the two-component addition-type low-density liquid foamed silicone rubber obtained in the various embodiments and comparative examples of this application was tested according to GB / T 8813-2020 "Determination of compressive properties of rigid foamed plastics". Thermal conductivity (W / m·K): According to GB / T 10297-2015 "Determination of thermal conductivity of non-metallic solid materials by hot wire method", the thermal conductivity of the two-component addition-type low-density liquid foamed silicone rubber obtained in various embodiments and comparative examples of this application was tested. Flame retardancy rating: The flame retardancy performance of the two-component addition-curing low-density liquid foamed silicone rubbers obtained in various embodiments and comparative examples of this application was tested according to the UL94-V0 flame retardancy rating test. Substrate bond strength (MPa): According to GB / T7124-2008 "Determination of tensile shear strength of adhesives", the bond strength of the two-component addition-type low-density liquid foamed silicone rubber obtained in various embodiments and comparative examples of this application was tested. The results are shown in Table 1: Table 1

[0053] As shown in Table 1, compared with Example 1, Comparative Example 3 lacks nitrogen and phosphorus doped graphene, resulting in the loss of the sheet reinforcement effect of PN-rGO, leading to a decrease in char residue, flame retardancy downgrade, and compressive strength. Compared with Example 1, Comparative Example 4 lacks the expanded char layer of APP, resulting in an increase in thermal conductivity and a simultaneous decrease in flame retardancy. In Comparative Example 5, after removing PN-rGO and APP, the lightweight and heat insulation functions of HGM are lost, the flame retardancy level decreases significantly, and the heat release rate increases, verifying the synergistic effect of PN-rGO's catalytic char formation and APP's expansion flame retardancy.

[0054] A comparison of Examples 1, Comparative Example 1, and Examples 4-5 shows that the lack of plasma treatment in Comparative Example 1 leads to a decrease in adhesive strength, proving that the introduction of surface carboxyl / hydroxyl groups can improve wettability; in Examples 4-5, the adhesive strength fluctuates by only 7.4% with the amount of ingredients increased or decreased, verifying the stability of the hydroxyl-terminated silicone oil toughening network and preventing interface brittleness.

[0055] Compared with Example 1, Examples 2-3 and 6-7 differ only in the rational increase or decrease of component dosage. The silicone rubbers prepared in these examples all have excellent properties, indicating that the silicone rubber of the present invention can withstand a certain degree of formulation fluctuation and has good process robustness.

[0056] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A two-component addition-cured low-density liquid foamed silicone rubber, characterized in that, Includes component A and component B; Component A, by weight, comprises 50-70 parts vinyl-terminated polysiloxane, 10-20 parts vinyl hydroxyl silicone oil, 0.5-2 parts platinum catalyst, 15-25 parts HGM@PN-rGO / APP and 3-8 parts methyl vinyl MQ resin. Component B, by weight, comprises 50-60 parts vinyl-terminated polysiloxane, 8-15 parts hydrogen-terminated hydrosilicone oil, 10-20 parts methyl-terminated hydrosilicone oil, 5-10 parts hydroxyl-terminated silicone oil, 0.002-0.01 parts inhibitor, 10-20 parts fumed silica, and 1-3 parts tackifier.

2. The two-component addition-curing low-density liquid foamed silicone rubber according to claim 1, characterized in that, The HGM@PN-rGO / APP is prepared by the following steps: (1) Disperse HGM in ethanol, add silane coupling agent, reflux at 75-85℃, centrifuge and wash, and vacuum dry to obtain pretreated HGM; (2) Disperse GO in deionized water to obtain GO dispersion; stir and dissolve H3PO4, urea and deionized water to obtain doping solution; add doping solution to GO dispersion, add PVP, adjust pH to 9-10, add pretreated HGM, react at 180-190℃ for 12-16h; collect by centrifugation after cooling, wash and dry to obtain HGM@PN-rGO; (3) After dissolving APP in deionized water, add HGM@PN-rGO, disperse by ultrasonication, react at 120-130℃ for 4-8h, collect by centrifugation, and dry to obtain HGM@PN-rGO / APP.

3. The two-component addition-curing low-density liquid foamed silicone rubber according to claim 2, characterized in that, The weight ratio of HGM to silane coupling agent is (25-35):(2-4); the weight ratio of GO, H3PO4, urea and APP is (4-6):(3-4):(6-8):(50-60).

4. The two-component addition-curing low-density liquid foamed silicone rubber according to claim 1, characterized in that, The thickener is prepared by the following steps: Mix 3-(2,3-epoxypropoxy)propyltrimethoxysilane, vinyltrimethoxysilane, hydroxyl-terminated silicone oil and aqueous acetic acid, reflux at 80-85℃ for 3-4 hours, cool and then distill under reduced pressure to obtain the thickener.

5. The two-component addition-curing low-density liquid foamed silicone rubber according to claim 4, characterized in that, The weight ratio of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, vinyltrimethoxysilane, hydroxyl-terminated silicone oil and aqueous acetic acid is (12-18):(8-12):(45-60):(4-6).

6. The two-component addition-curing low-density liquid foamed silicone rubber according to claim 1, characterized in that, The vinyl-terminated polysiloxane has a viscosity of 20000±100 mPa·s and a vinyl content of 0.07-0.09 mol%; the vinyl hydroxyl silicone oil has a hydroxyl content of 6%-8% and a molecular weight of 3000-5000.

7. The two-component addition-cured low-density liquid foamed silicone rubber according to claim 1, characterized in that, The hydrogen-capped hydrogen-containing silicone oil has a hydrogen content of 0.05% to 0.5% and a viscosity of 500±50 mPa·s; the methyl-capped hydrogen-containing silicone oil has a hydrogen content of 0.5% to 1.65% and a viscosity of 1000±50 mPa·s; the hydroxyl-terminated silicone oil has a hydroxyl content of 8% to 10% and a molecular weight of 1500-3000.

8. The two-component addition-curing low-density liquid foamed silicone rubber according to claim 1, characterized in that, The inhibitor is composed of tetramethyldivinyldisiloxane and ethynylcyclohexanol in a molar ratio of (5-9):

1.

9. A method for preparing a two-component addition-type low-density liquid foamed silicone rubber as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Mix vinyl-terminated polysiloxane, HGM@PN-rGO / APP and methyl vinyl MQ resin, add vinyl hydroxyl silicone oil, and knead at 50-60℃ for 40-60 min; after cooling, add platinum catalyst and mix, then degas to obtain component A. S2. Treat fumed silica with hexamethyldisilazane at 50-60℃ for 2-3 hours to obtain pretreated silica; mix vinyl-terminated polysiloxane, hydroxyl-terminated silicone oil, methyl-terminated hydrogen-containing silicone oil and hydrogen-terminated hydrogen-containing silicone oil evenly. Add pretreated silica, thickener, and inhibitor, mix; filter to obtain component B; S3. Mix and extrude components A and B to obtain a mixed adhesive; apply the mixed adhesive to the substrate and allow it to foam freely in an environment of 25-40℃; pre-cur at 40-45℃ for 60-70 minutes, then vulcanize again at 75-80℃ for 120-140 minutes, and perform plasma treatment on the foam surface to obtain a two-component addition-type low-density liquid foamed silicone rubber.

10. The method for preparing two-component addition-type low-density liquid foamed silicone rubber according to claim 9, characterized in that, The plasma treatment has a power of 95-110W and a treatment time of 5-10 minutes.

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