Two-component low-hardness silicone rubber based on vinyl silicone oil / silicon dioxide composite material and preparation process thereof

Abstract

The invention provides two-component low-hardness silicone rubber based on a vinyl silicone oil / silicon dioxide composite material and a preparation process of the two-component low-hardness silicone rubber. By introducing modified silicon dioxide, a photoinitiator and a platinum catalyst and combining a dual cross-linking mechanism of ultraviolet curing and thermocuring, rapid curing and uniform deep cross-linking of the silicone rubber are realized. And the modified silicon dioxide adopts a core-shell structure design, so that the compatibility of the filler and a matrix is improved, and the mechanical property and long-term stability of the material are effectively improved. The prepared silicone rubber has low hardness, high tensile strength, excellent high temperature resistance and self-repairing capability, and is suitable for the fields of electronic packaging, medical instruments, automobile parts and the like. The process is simple and convenient, the curing speed is high, the product performance is excellent, and the industrial application value is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone rubber, and in particular to a two-component low-hardness silicone rubber based on vinyl silicone oil / silica composite material and its preparation process. Background Art

[0002] As a polymer material with excellent properties, silicone rubber materials are widely used in the fields of electronics, medicine, automobiles, etc. in modern industry. Its unique thermal stability, anti-aging property and low-temperature elasticity depend on the traditional composite material system with vinyl silicone oil and silica (SiO 2 ) as the core. In this system, vinyl silicone oil forms a three-dimensional network structure with silica filler through thermal initiation or addition cross-linking reaction. The active hydroxyl groups (-OH) on the surface of silica enhance the interfacial bonding between the filler and the matrix through hydrogen bonding, thereby endowing the material with high mechanical strength and elasticity. However, with the upgrading of the industrial requirements for the performance of silicone rubber, especially the comprehensive requirements for low hardness, deep curing uniformity and high temperature / ultraviolet environmental stability, the limitations of the traditional system are becoming increasingly prominent.

[0003] In the preparation of low-hardness silicone rubber, although the traditional thermal curing process can control the surface hardness by adjusting the cross-linking density, the interfacial stability between the silica filler and the silicone oil matrix becomes the key limiting factor for deep curing uniformity. Research shows that when the quality of vinyl silicone oil is low or it is decomposed by moisture, it may contain trace amounts of Si-OH. In a high-temperature environment, the hydroxyl groups on the surface of silica are prone to condensation reaction with the silicon hydroxyl groups in the silicone oil (Si-OH + HO-Si → Si-O-Si + H 2 O), resulting in filler agglomeration and interfacial stress concentration, which not only weakens the mechanical properties of the material, but also causes microcracks in the cross-linking network, exacerbating the aging and embrittlement phenomenon. Summary of the Invention

[0004] When the quality of vinyl silicone oil is low or it is decomposed by moisture, it may contain trace amounts of Si-OH. In a high-temperature environment, the hydroxyl groups on the surface of silica are prone to condensation reaction with the silicon hydroxyl groups in the silicone oil (Si-OH + HO-Si → Si-O-Si + H 2 O), resulting in filler agglomeration and interfacial stress concentration, which not only weakens the mechanical properties of the material, but also causes microcracks in the cross-linking network, exacerbating the aging and embrittlement phenomenon.

[0005] This application provides a preparation process for a two-component low-hardness silicone rubber based on a vinyl silicone oil / silica composite material, including the following technical steps: Step S1. The vinyl silicone oil and the photoinitiator are mixed evenly under light-shielded conditions, and the modified silica is slowly added. A planetary mixer is used to disperse the modified silica evenly to form Phase A; Step S2. The platinum catalyst and the delayed inhibitor are added to the hydrogen-containing silicone oil, and ultrasonic dispersion is carried out under light-shielded conditions to form Phase B; Step S3. After Phase A and Phase B are mixed at a mass ratio of 10:1, they are mechanically stirred evenly and injected into a transparent mold; Step S4. Use a 365 nm, 10 mW / cm 2 ultraviolet lamp with an irradiation time of 60 - 120 seconds, and transfer the sample to an oven at 50 °C and keep it for 1 - 2 hours.

[0006] It should be noted that in Step S1, the vinyl silicone oil and the photoinitiator are mixed under light-shielded conditions, and the modified silica is slowly added. The planetary mixer is used to fully disperse the filler, improving the compatibility between the silicone oil and the filler. Through the "core-shell synergy" mechanism, while maintaining the reinforcing effect of silica, the modified silica solves the problem of performance deterioration caused by the incompatibility at the filler-matrix interface. Polystyrene forms a dense hydrophobic shell layer, completely covering the Si-OH groups on the surface of the silica core and isolating their direct contact with the Si-OH in the silicone oil; in Step S2, the addition of the platinum catalyst and the delayed inhibitor not only helps the uniform progress of the hydrosilylation reaction, but also reduces the possibility of catalyst agglomeration through ultrasonic dispersion, thus avoiding the risk of cracks caused by too high local crosslinking degree. Subsequently, in Step S3, Phase A and Phase B are uniformly mixed at a mass ratio of 10:1 and then injected into a transparent mold. In Step S4, first, a 365 nm wavelength ultraviolet lamp is used for short-time irradiation to achieve rapid surface curing and initially form a stable crosslinked network. The free radicals generated by the decomposition of the photoinitiator may attack the tertiary carbon sites of the PS shell layer, initiating the graft copolymerization of the C=C bond of the vinyl silicone oil and the PS chain to form a chemical bond (C-Si-O bond). Under thermal or mechanical stress, some C-Si-O bonds are reversibly broken and recombined to release the interfacial stress and avoid the propagation of microcracks. And then, by keeping it in an oven at 50 °C for 1 - 2 hours, the deep curing is slowly advanced. Finally, the mechanical strength and thermal stability of the product are improved, and the hardness uniformity and long-term service performance of thick-walled or complex geometric structure products are ensured.

[0007] As a preferred technical solution of a preparation process for a two-component low-hardness silicone rubber based on a vinyl silicone oil / silica composite material, the platinum catalyst is 0.01% to 0.05% of the mass of the hydrogen-containing silicone oil.

[0008] It should be noted that the role of the platinum catalyst is to promote the addition of Si-H and vinyl to form a crosslinked network.

[0009] As a preferred technical solution for the preparation process of a two-component low-hardness silicone rubber based on vinyl silicone oil / silica composite material, the preparation steps of the modified silica include: First, disperse the pretreated silica particles in ethanol, with the concentration of silica in ethanol being 5 mg / mL. Add the monomer of polystyrene and the initiator of benzoyl peroxide, and at 70 - 80 °C, form a polystyrene shell on the surface of silica by the polystyrene molecules. After the reaction is completed, remove the excess monomer and solvent through precipitation, washing, and drying to obtain the composite nanoparticles with a silica core / polystyrene shell.

[0010] It should be noted that the dispersion of silica (SiO 2 ) in ethanol depends on the hydrogen bond interaction between its surface hydroxyl groups (Si-OH) and ethanol molecules, keeping the particles stable. Styrene monomer (St) and benzoyl peroxide (BPO) initiator are added to the system. BPO decomposes at 70 - 80 °C to generate benzoyloxy radicals (PhCOO·), initiating the free radical polymerization of styrene to form a polystyrene coating layer. After the reaction is completed, remove the unreacted monomer and low-molecular-weight polymers through precipitation and washing, and finally obtain the stable SiO 2 @PS core-shell structured composite nanoparticles.

[0011] As a preferred technical solution for the preparation process of a two-component low-hardness silicone rubber based on vinyl silicone oil / silica composite material, the treatment steps of the pretreated silica include: Vacuum-dry the nano-silica at 120 °C for 2 hours to remove the adsorbed moisture.

[0012] It should be noted that the main purpose of vacuum-drying silica (SiO2) at 120 °C for 2 hours is to remove the surface-adsorbed moisture and improve its reaction stability in the subsequent polystyrene polymerization process.

[0013] As a preferred technical solution for the preparation process of a two-component low-hardness silicone rubber based on vinyl silicone oil / silica composite material, the delayed inhibitor is ethynylcyclohexanol, and the ethynylcyclohexanol accounts for 0.05% to 3% of the mass of the hydrogen-containing silicone oil.

[0014] It should be noted that as a delayed inhibitor, the action mechanism of ethynylcyclohexanol (ACH) mainly depends on the reversible coordination between its ethynyl group (C≡C) and the platinum catalyst. At room temperature, the ethynyl group of ACH can coordinate with the platinum catalyst, temporarily reducing the activity of platinum, thereby delaying the occurrence of the hydrosilylation reaction. This coordination is reversible. When the temperature rises, the binding between ACH and platinum will be disrupted, and the platinum catalyst is reactivated, enabling the curing reaction to proceed smoothly.

[0015] As an optimized technical solution for the preparation process of a two-component low-hardness silicone rubber based on vinyl silicone oil / silica composite materials, the mass ratio of the modified silica to the vinyl silicone oil is (1 to 3):10.

[0016] It should be noted that through the optimization of this ratio, the composite material can balance the reinforcement effect and processability, enabling the final product to reach the optimal state in terms of mechanical properties, stability, and operability.

[0017] The present invention realizes the efficient preparation of a two-component low-hardness silicone rubber by introducing modified silica, photoinitiator, and an optimized crosslinking system. Compared with traditional silicone rubber materials, it has significant beneficial effects. First of all, this material has excellent mechanical properties, with a tensile strength of up to 8.7 MPa and an elongation at break exceeding 870%, which is significantly higher than that of the unmodified system, enhancing the durability and stability of the material. Secondly, the use of core-shell structured modified silica fillers improves the interfacial compatibility of the silicone rubber, reduces filler agglomeration and microcrack propagation, thereby enhancing the long-term use performance of the material. In addition, the process scheme combining ultraviolet curing and thermal curing ensures the rapid curing and deep and uniform curing of the material, improves the processing efficiency, and is applicable to the manufacture of complex-structured products. Through the induction of free radical polymerization by the photoinitiator and the introduction of a dynamic crosslinking network, this silicone rubber exhibits good self-healing ability and can partially recover its mechanical properties through heat treatment after being damaged, extending its service life. Description of the Drawings

[0018] Figure 1 Infrared spectrum of the product prepared in Example 1; (a) is the infrared spectrum without ultraviolet lamp irradiation, and (b) is the spectrum after ultraviolet lamp irradiation; Detailed Embodiments

[0019] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given in conjunction with the embodiments of the specification.

[0020] In the following description, many specific details are set forth to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0021] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that can be included in at least one implementation manner of the present invention. The appearances of "in one embodiment" in different places in this specification do not all refer to the same embodiment, nor are they separate or selectively exclusive embodiments from other embodiments.

[0022] Preparation Example

[0023] Preparation Example 1

[0024] The preparation steps of the modified silica include: First, vacuum-dry the nano-silica at 120 °C for 2 hours to remove the adsorbed moisture. Disperse the pretreated silica particles in ethanol, with the concentration of silica in ethanol being 5 mg / mL. Add the monomer of polystyrene and the initiator benzoyl peroxide, and form a polystyrene shell on the surface of the silica at 70 - 80 °C. After the reaction is completed, remove the excess monomer and solvent by precipitation, washing, and drying to obtain the composite nano-particles of silica core / polystyrene shell.

[0025] Example

[0026] Example 1

[0027] Example 1 provides a preparation process of a two-component low-hardness silicone rubber based on vinyl silicone oil / silica composite material, including the following technical steps:

[0028] Step S1. Mix 100 parts of vinyl silicone oil with 0.5 part of photoinitiator (2,2-dimethoxy-2-phenylacetophenone) in the dark, slowly add 30 parts of modified silica (Preparation Example 1), and use a planetary stirrer to disperse the modified silica evenly to form Phase A;

[0029] Step S2. Add 0.03 part of platinum catalyst and 0.05 part of delayed inhibitor (ethynylcyclohexanol) to 100 parts of hydrogen-containing silicone oil, and disperse them ultrasonically in the dark to form Phase B;

[0030] Step S3. After mixing Phase A and Phase B in a mass ratio of 10:1, stir them evenly mechanically and inject them into a transparent mold;

[0031] Step S4. Use a UV lamp with a wavelength of 365 nm and an intensity of 10 mW / cm 2 to irradiate for 120 seconds, and transfer the sample to an oven at 50 °C and keep it for 1 hour.

[0032] Example 2

[0033] Example 2 provides a preparation process of a two-component low-hardness silicone rubber based on vinyl silicone oil / silica composite material, including the following technical steps:

[0034] Step S1. Mix 100 parts of vinyl silicone oil with 1.0 part of photoinitiator (2,2-dimethoxy-2-phenylacetophenone) in the dark, slowly add 10 parts of modified silica (Preparation Example 1), and use a planetary stirrer to disperse the modified silica evenly to form Phase A;

[0035] Step S2. Add 0.05 parts of platinum catalyst and 1.0 part of delayed inhibitor (ethynylcyclohexanol) to 100 parts of hydrogen-containing silicone oil, and disperse under ultrasonic irradiation in the dark to form Phase B;

[0036] Step S3. After mixing Phase A and Phase B in a mass ratio of 10:1, stir evenly by mechanical stirring and inject into a transparent mold;

[0037] Step S4. Use a UV lamp with a wavelength of 365 nm and an intensity of 10 mW / cm 2 to irradiate for 60 seconds, and transfer the sample to an oven at 50 °C and keep it for 2 hours.

[0038] Example 3

[0039] Example 3 provides a preparation process for a two-component low-hardness silicone rubber based on vinyl silicone oil / silica composite material, including the following technical steps:

[0040] Step S1. Mix 100 parts of vinyl silicone oil and 3.0 parts of photoinitiator (2,2-dimethoxy-2-phenylacetophenone) evenly under dark conditions, slowly add 20 parts of modified silica (Preparation Example 1), and use a planetary stirrer to disperse the modified silica evenly to form Phase A;

[0041] Step S2. Add 0.01 part of platinum catalyst and 3.0 parts of delayed inhibitor (ethynylcyclohexanol) to 100 parts of hydrogen-containing silicone oil, and disperse under ultrasonic irradiation in the dark to form Phase B;

[0042] Step S3. After mixing Phase A and Phase B in a mass ratio of 10:1, stir evenly by mechanical stirring and inject into a transparent mold;

[0043] Step S4. Use a UV lamp with a wavelength of 365 nm and an intensity of 10 mW / cm 2 to irradiate for 100 seconds, and transfer the sample to an oven at 50 °C and keep it for 1.5 hours.

[0044] Example 4

[0045] Example 4 provides a preparation process for a two-component low-hardness silicone rubber based on vinyl silicone oil / silica composite material, including the following technical steps:

[0046] Step S1. Mix 100 parts of vinyl silicone oil and 3.0 parts of photoinitiator (2,2-dimethoxy-2-phenylacetophenone) evenly under dark conditions, slowly add 25 parts of modified silica (Preparation Example 1), and use a planetary stirrer to disperse the modified silica evenly to form Phase A;

[0047] Step S2. Add 0.02 part of platinum catalyst and 3.0 parts of delayed inhibitor (ethynylcyclohexanol) to 100 parts of hydrogen-containing silicone oil, and disperse under ultrasonic irradiation in the dark to form Phase B;

[0048] In step S3, phase A and phase B are mixed at a mass ratio of 10:1, mechanically stirred evenly, and then injected into a transparent mold.

[0049] In step S4, a UV lamp with a wavelength of 365 nm and an intensity of 10 mW / cm 2 is used to irradiate for 120 seconds, and then the sample is transferred to an oven at 50 °C and kept for 2 hours.

[0050] Control example

[0051] Control example 1

[0052] The difference between this control example 1 and example 1 is that the unmodified silica material is replaced with an equal amount of modified silica material.

[0053] Control example 2

[0054] The difference between this control example 2 and example 1 is that in step S4, it is directly thermally cured without using UV lamp irradiation for curing.

[0055] Table 1

[0056]

[0057] Note: A is vinyl silicone oil, B is photoinitiator, C is modified silica (unmodified silica is used in the control example); D is platinum catalyst; E is hydrogen-containing silicone oil; F is delayed inhibitor;

[0058] Performance detection test

[0059] 1. Hardness test: The hardness of the cured rubber material is tested according to GB / T531-2008 "Test method for indentation hardness of vulcanized rubber or thermoplastic rubber - Part 1: Shore hardness tester method".

[0060] 2. Tensile strength test: The tensile strength of the cured silicone rubber is detected according to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets".

[0061] Table 2

[0062]

[0063] Combined with example 1 and Figure 1 It can be seen that according to the provided infrared spectrum (wavenumber range 500 - 4000 cm -1 ), 1600 cm -1The intensity of the absorption peak (attributed to the C═C skeletal vibration of the aromatic ring of polystyrene PS) at [specific position] decreases significantly, indicating that the chemical environment of the PS shell has changed, which may be related to the radical attack on the tertiary carbon site and the perturbation of the aromatic ring electron cloud caused by the grafting reaction. 1000 cm -1 The intensity of the broad peak (Si-O-Si asymmetric stretching vibration) near [specific value] increases and the peak shape broadens, indicating that C-Si-O bonds or a silicone cross-linked network may have formed in the system. 800 cm -1 (Si-CH 2 rocking vibration) and the weak peak at 1250 cm -1 (Si-CH 2 stretching vibration) broadens, which may be related to the dynamic interfacial bonding behavior of the silicone chain segments.

[0064] Combined with Examples 1 to 4 and Table 2, it can be seen that the Shore hardness, tensile strength, and elongation at break of the silicone rubber material prepared by this application are 20 to 24 degrees, 8.1 to 8.7 MPa, and 835% to 872% respectively.

[0065] Combined with Example 1, Comparative Example 1, and Table 2, it can be seen that the tensile strength of Comparative Example 1 relative to Example 1 increased from 4.5 MPa to 7.8 MPa, and the elongation at break increased from 564 to 835. This is mainly because the modified silica, through the "core-shell synergy" mechanism, while maintaining the reinforcing effect of silica, solves the problem of performance deterioration caused by the incompatibility between the filler and the matrix interface. The polystyrene forms a dense hydrophobic shell layer that completely covers the Si-OH groups on the surface of the silica core, isolating their direct contact with the Si-OH in the silicone oil, improving the mechanical properties of the material, and avoiding the initiation of microcracks in the cross-linked network and exacerbating the aging and embrittlement phenomenon.

[0066] Combined with Example 2, Control Example 2, and Table 2, it can be seen that the tensile strength of Comparative Example 2 relative to Example 1 increased from 4.2 MPa to 7.8 MPa, and the elongation at break increased from 543 to 835. This is mainly because the free radicals generated by the decomposition of the photoinitiator may attack the tertiary carbon sites of the PS shell, initiating the graft copolymerization of the C═C bonds of vinyl silicone oil and the PS chain to form chemical bonds (C-Si-O bonds). Under thermal or mechanical stress, some of the C-Si-O bonds break reversibly and recombine, releasing the interfacial stress and preventing the propagation of microcracks.

[0067] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A process for preparing a two-component low-hardness silicone rubber based on a vinyl silicone oil / silicon dioxide composite material, characterized in that: The technical steps include: Step S1. Vinyl silicone oil and photoinitiator are mixed under light-proof conditions, and modified silica is slowly added, and the modified silica is evenly dispersed using a planetary mixer to form phase A; Step S2. Adding a platinum catalyst and a delayed inhibitor to hydrogen-containing silicone oil, dispersing the mixture under ultrasonication in the dark to form a phase B; Step S3. After mixing phase A and phase B at a mass ratio of 10:1, mechanically stir them to make them uniform, and inject them into a transparent mold; Step S4: Use 365nm, 10mW / cm 2 The sample was placed in an oven at 50 °C for 1-2 hours.

2. The process for preparing a two-component low-hardness silicone rubber based on a vinyl silicone oil / silicon dioxide composite material according to claim 1, characterized in that: The photoinitiator is 2,2-dimethoxy-2-phenylacetophenone, and the 2,2-dimethoxy-2-phenylacetophenone accounts for 0.5% to 3.0% of the mass of the vinyl silicone oil.

3. The process for preparing a two-component low-hardness silicone rubber based on a vinyl silicone oil / silicon dioxide composite material according to claim 1, characterized in that: The platinum catalyst accounts for 0.01% to 0.05% of the mass of the hydrogen-containing silicone oil.

4. The process for preparing a two-component low-hardness silicone rubber based on a vinyl silicone oil / silicon dioxide composite material according to claim 1, characterized in that: The preparation steps of modified silica include: first, dispersing pretreated silica particles in ethanol, wherein the concentration of silica in ethanol is 5 mg / mL, adding polystyrene monomer and benzoyl peroxide initiator, and allowing polystyrene molecules to form a polystyrene shell on the surface of silica at 70-80° C., and after the reaction is completed, removing excess monomer and solvent by precipitation, washing and drying to obtain composite nanoparticles of silica core / polystyrene shell.

5. The process for preparing a two-component low-hardness silicone rubber based on a vinyl silicone oil / silicon dioxide composite material according to claim 4, characterized in that: The pre-treated silicon dioxide treatment step includes: vacuum drying the nano silicon dioxide at 120° C. for 2 hours to remove adsorbed moisture.

6. The process for preparing a two-component low-hardness silicone rubber based on a vinyl silicone oil / silicon dioxide composite material according to claim 1, characterized in that: The delayed type inhibitor is ethynyl cyclohexanol, and the ethynyl cyclohexanol accounts for 0.05% to 3% of the mass of the hydrogen-containing silicone oil.

7. The process for preparing a two-component low-hardness silicone rubber based on a vinyl silicone oil / silicon dioxide composite material according to claim 1, characterized in that: The mass ratio of the modified silica to the vinyl silicone oil is (1 to 3):

10.

8. A silicone rubber material prepared based on the preparation process described in claim 1.

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