Method for improving bonding strength of RTV566 silica gel

Abstract

The invention relates to the technical field of adhesives, in particular to a method for improving the bonding strength of RTV566 silica gel. The method comprises the following steps: uniformly mixing RTV566 silica gel with acetone and / or water, and then bonding a sample to be bonded; the RTV566 silica gel comprises the following components: a base material and a coupling agent. According to the invention, acetone and / or water in a certain proportion are / is added into RTV566 silica gel (RTV566 silica gel comprises the base material and the coupling agent), so that not only is the bonding strength of the RTV566 silica gel improved, but also the curing time of the RTV566 silica gel is shortened.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and more specifically to a method for improving the bonding strength of RTV566 silicone adhesive. Background Technology

[0002] RTV566, a two-component room temperature vulcanizing adhesive, is commonly used for bonding components in precision opto-mechanical products. Component A is called the base material, and component B is the coupling agent. After curing, RTV566 exhibits a low elastic modulus, effectively preventing damage to precision components such as opto-mechanical lenses. However, RTV566 silicone has relatively low bond strength, limiting its application in situations requiring high bond strength; furthermore, its long curing time impacts production efficiency. Existing RTV566 silicone offers limited performance characteristics, making it difficult to meet the demands of diverse application scenarios.

[0003] Currently, there are many methods to improve adhesive strength. For example, adding fillers can improve the adhesive strength of silicone. However, since silicone generally has a high viscosity, mixing the filler with silicone is extremely difficult. Furthermore, increasing the amount of filler can also increase the brittleness of silicone, reducing its toughness. Alternatively, changing the crosslinking agent or coupling agent can also improve the adhesive strength of silicone and increase the interaction between silicone and the bonded materials, but this may affect other properties, such as the elastic modulus, and is costly and complex to implement.

[0004] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0005] The purpose of this invention is to provide a method for improving the adhesive strength of RTV566 silicone, so as to solve or improve the problems of low adhesive strength of RTV566 silicone and the adverse effects of existing methods for improving adhesive strength on other properties.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for improving the bonding strength of RTV566 silicone, comprising the following steps: mixing RTV566 silicone with acetone evenly and then using it for bonding samples to be bonded; or, mixing RTV566 silicone with acetone and water evenly and then using it for bonding samples to be bonded; wherein the components of the RTV566 silicone include a base material and a coupling agent.

[0007] In this invention, the addition of acetone dilutes the RTV566 silicone, reducing its viscosity and allowing it to fully penetrate the tiny gaps at the bonding interface of the samples to be bonded (e.g., glass and Invar), increasing the microscopic contact area between the adhesive and the interface and forming a sufficient mechanical interlocking effect. Furthermore, acetone evaporates quickly and completely, leaving almost no impurities. The addition of water promotes rapid curing of the RTV566 silicone, saving curing time, and does not adversely affect the bonding strength of the RTV566 silicone (if acetone is omitted and only water is added to the RTV566 silicone, the silicone becomes viscous, causing a decrease in strength).

[0008] In a preferred embodiment, the mass ratio of acetone to the base material is (1-6):20 (e.g., 1:20, 2:20, 3:20, 4:20, 5:20, or 6:20). However, if the amount of acetone added is inappropriate, a large number of air bubbles and voids will be generated in the silicone during the acetone evaporation process, and the shrinkage rate of the silicone during curing will increase significantly, severely affecting the bonding strength.

[0009] In a preferred embodiment, the mass ratio of water to the base material of the RTV566 silicone is (0.01-1):100 (e.g., 0.01:100, 0.03:100, 0.05:100, 0.08:100, 0.1:100, 0.3:100, 0.5:100, 0.8:100, or 1:100). In the prior art, water is typically not added to RTV566 silicone; this is because adding an inappropriate amount of water may cause the silicone to react violently in a short time, instantly generating a large amount of byproduct gas. This can easily form numerous tiny bubbles in the cross-linked network of the silicone, thereby affecting the bonding strength.

[0010] In a preferred embodiment, the mass ratio of water to the base material of the RTV566 silicone is (0.01-0.1):100 (e.g., 0.01:100, 0.02:100, 0.04:100, 0.06:100, 0.09:100 or 0.1:100).

[0011] In a preferred embodiment, the mass ratio of the base material to the coupling agent is 100:0.2.

[0012] In a preferred embodiment, after uniform mixing, the mixture further includes a degassing step. This degassing step helps remove air bubbles generated during the mixing process.

[0013] Degassing is achieved by centrifugation under vacuum conditions; the centrifugation speed is 1600-1800 r / min (e.g., 1600 r / min, 1650 r / min, 1700 r / min, 1750 r / min, 1800 r / min), and the centrifugation time is 8-10 min (e.g., 8 min, 9 min, 10 min); the vacuum degree is 0.1-0.15 MPa (e.g., 0.1 MPa, 0.11 MPa, 0.12 MPa, 0.13 MPa, 0.14 MPa, 0.15 MPa).

[0014] In a preferred embodiment, before bonding, the bonding area of ​​the sample to be bonded is further polished.

[0015] In a preferred embodiment, the sample to be bonded is Invar alloy steel 4J36 and ULE optical glass.

[0016] In a more preferred embodiment, the roughness of the bonding area of ​​the Invar alloy steel 4J36 is 0.03-0.05 μm (e.g., 0.03 μm, 0.04 μm, 0.05 μm), and the roughness of the bonding area of ​​the ULE optical glass is 0.15-0.20 μm (e.g., 0.15 μm, 0.16 μm, 0.17 μm, 0.18 μm, 0.19 μm, 0.20 μm).

[0017] The present invention has the following advantages:

[0018] This invention, by adding a certain proportion of acetone and / or water to RTV566 silicone (the components of RTV566 silicone include a base material and a coupling agent), not only helps to improve the bonding strength of RTV566 silicone, but also helps to shorten the curing time of RTV566 silicone.

[0019] Furthermore, the method of the present invention also helps to maintain the elastic modulus of the original RTV566 silicone, and increase its maximum stress and strain.

[0020] The method for improving the bonding strength of RTV566 silicone in this invention helps overcome the limitations of existing methods (e.g., difficulty in balancing strength and toughness, complex operation, and high cost), and has broad application prospects. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a single lap joint.

[0022] Figure 2 This shows the dimensions and a picture of the dumbbell-shaped rubber strip.

[0023] Figure 3 It is a tooling for curing single-joint components.

[0024] Figure 4 The figures show a comparison of viscosity and adhesive strength with different proportions of acetone added; where (a) is a viscosity comparison figure and (b) is an adhesive strength comparison figure.

[0025] Figure 5 The graphs show the changes in bond strength with curing time after adding different proportions of water and the comparison of bond strength after 4 days of curing. Among them, (a) is the comparison of bond strength at different curing times, and (b) is the comparison of bond strength after 4 days of curing with different proportions of water.

[0026] Figure 6 The results are shown in the dumbbell-shaped rubber strip test; (a) is the stress-strain curve, and (b) is the comparison diagram of average Young's modulus. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art should understand that the embodiments described below are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0029] In the following embodiment:

[0030] A schematic diagram of a single lap joint tension member is shown below. Figure 1 As shown, the single-lap joint curing fixture is as follows: Figure 3 As shown in Tables 1 and 2, Invar alloy steel 4J36 (YB / T 5241-1993) and ULE optical glass (Corning 7972) both have extremely low coefficients of thermal expansion. The Invar steel dimensions are 72mm × 25mm × 5mm, and the ULE optical glass dimensions are 36mm × 25mm × 4mm. The length and width of the bonding area are 25mm and 12mm respectively, and the length from the center of the pin hole to the edge of the adhesive layer is 50mm. Standard thickness sheets are placed on the platforms on both sides of the bonding area groove to control the adhesive layer thickness. The bonding surfaces of the Invar steel and ULE optical glass were polished with 1000-grit sandpaper, resulting in a surface roughness of 0.04μm for the Invar steel and 0.15μm for the ULE optical glass. Then, the Invar steel specimen and ULE optical glass were ultrasonically cleaned with acetone for 10 minutes to remove surface oil and impurities.

[0031] Table 1 Mechanical properties of Invar steel

[0032]

[0033] Table 2 Mechanical Properties of ULE Optical Glass

[0034]

[0035] The manufacturing standard for the silicone strips follows the method described in GB / T 528-1998. Pour the prepared silicone into a 100mm × 100mm × 3mm rectangular mold according to the specified ratio. After curing for one week, remove the silicone from the mold and then cut it using the Type II standard dumbbell cutter from GB / T 528-1998. The cut silicone strips are shown in the figure. Figure 2 The image shows the shape and actual product of the Type II dumbbell rubber strip. The experimental area measures 20mm × 4mm × 3mm, and the curing mold for the rubber strip measures 100mm × 100mm × 3mm.

[0036] Example 1

[0037] The method for improving the adhesive strength of RTV566 silicone in this embodiment includes the following steps:

[0038] (1) Preparation of adhesive: Each time the adhesive is prepared, the base material (component A; 10g), coupling agent (component B), acetone and water of the two-component room temperature vulcanizing silicone rubber RTV566 (Momentive RTV566) are mixed in a weight ratio of 100:0.2:10:0.1 to obtain a mixture.

[0039] (2) Stirring and mixing: Stir the mixture with a glass rod for about 5 minutes to ensure that all components in the mixture are fully and evenly mixed.

[0040] (3) Degassing treatment: Place the mixed adhesive in a vacuum centrifuge and centrifuge for 10 minutes at a pressure of 0.1 MPa and a speed of 1600 r / min to remove the bubbles generated during the stirring process.

[0041] (4) Curing: Apply the degassed adhesive to the surface of the materials to be bonded. The bonding surface needs to be coated with primer SS4415 (coupling agent, 3-hydroxy-4H-pyran-4-one, also known as pyrocoagulant, purchased from Hubei Shishun Biotechnology Co., Ltd.; dosage is 5-10 microliters) 2 hours in advance to ensure that the primer is completely dry. When making the overlapping parts, use a spatula to take a small amount of silicone and apply it evenly to the bonding area, and then place the Invar substrate, ULE optical glass and standard thickness sheet in sequence. Figure 3 The tooling shown is fixed and pressed in place. The fabricated single overlap and adhesive strip are then placed at room temperature and 65% humidity for four days to cure.

[0042] Example 2

[0043] The only difference between this embodiment and Example 1 is that in step (1), the weight ratio of the base material (component A; 10g), coupling agent (component B), acetone and water of the two-component room temperature vulcanizing silicone rubber RTV566 is 100:0.2:10:0.01; the rest are consistent with Example 1.

[0044] Example 3

[0045] The only difference between this embodiment and Example 1 is that in step (1), the weight ratio of the base material (component A; 10g), coupling agent (component B), acetone and water of the two-component room temperature vulcanizing silicone rubber RTV566 is 100:0.2:10:1; the rest are consistent with Example 1.

[0046] Example 4

[0047] The only difference between this embodiment and embodiment 1 is that the step of adding water is omitted in step (1); the rest is consistent with embodiment 1.

[0048] Example 5

[0049] The only difference between this embodiment and Example 4 is that the weight ratio of the base material (component A; 10g), coupling agent (component B), and acetone in the two-component room temperature vulcanizing silicone rubber RTV566 is 100:0.2:5; all other aspects are consistent with Example 1.

[0050] Example 6

[0051] The only difference between this embodiment and Example 4 is that the weight ratio of the base material (component A; 10g), coupling agent (component B), and acetone in the two-component room temperature vulcanizing silicone rubber RTV566 is 100:0.2:15; all other aspects are consistent with Example 1.

[0052] Example 7

[0053] The only difference between this embodiment and Example 4 is that the weight ratio of the base material (component A; 10g), coupling agent (component B), and acetone in the two-component room temperature vulcanizing silicone rubber RTV566 is 100:0.2:20; all other aspects are consistent with Example 1.

[0054] Example 8

[0055] The only difference between this embodiment and Example 4 is that the weight ratio of the base material (component A; 10g), coupling agent (component B), and acetone in the two-component room temperature vulcanizing silicone rubber RTV566 is 100:0.2:25; all other aspects are consistent with Example 1.

[0056] Example 9

[0057] The only difference between this embodiment and Example 4 is that the weight ratio of the base material (component A; 10g), coupling agent (component B), and acetone in the two-component room temperature vulcanizing silicone rubber RTV566 is 100:0.2:20; all other aspects are consistent with Example 1.

[0058] Comparative Example 1

[0059] The only difference between this comparative example and Example 1 is that the step of adding water and acetone is omitted in step (1); the rest is the same as Example 1.

[0060] Experimental Example

[0061] 1. The viscosity and adhesive strength of two-component RTV566 silicone after adding different proportions of acetone (Examples 4-9) are as follows: Figure 4 As shown. The viscosity of silica gel with different acetone addition ratios was tested using a rotational viscometer, as shown. Figure 4 As shown in (a), the viscosity of silica gel without the addition of acetone (Comparative Example 1) was 124.33 Pa·s. When acetone was added in a ratio of 20:1 (Example 5), the viscosity decreased to 63.06 Pa·s, a decrease of 49.3%. As the ratio of acetone added increased, the viscosity continued to decrease. When the ratio of acetone added reached 20:6 (Example 9), the viscosity of silica gel was only 8.25 Pa·s.

[0062] To investigate the effect of acetone on the performance of RTV566 silicone adhesive, six adhesives with different acetone addition ratios (20:1 to 20:6) were prepared (Examples 4-9), and the bonding strength of their single lap joints was tested. The results are as follows: Figure 4 As shown in (b), the results indicate that adding a small amount of acetone (20:1; Example 5) significantly improves the bond strength compared to the adhesive without acetone (Comparative Example 1), increasing the shear strength from 1.28 MPa to 3.17 MPa, a 1.47-fold increase. With increasing acetone ratio, the shear strength did not change significantly, stabilizing at approximately 3.20 MPa. When the acetone ratio reached 20:6 (Example 9), the shear strength decreased to 2.91 MPa. This demonstrates that acetone can enhance the bond strength of RTV566 silicone and is a very simple and effective method, but excessive acetone can reduce this effect. It can be concluded that adding acetone effectively reduces the viscosity of silicone. Acetone is an organic solvent with strong polarity, and silicone easily dissolves in it, reducing its viscosity. The diluted silicone can be applied more evenly to the Invar surface and the adhesive layer thickness can be more accurately controlled.

[0063] 2. Water was added at a ratio of 100:0.1 to the optimal acetone ratio (20:2) (Example 1) to prepare single-lap joints, and the bond strength of the single-lap joints at different curing times was measured. Figure 5 As shown in (a), after 3 days of curing, the shear strength reached 2.46 MPa, close to the shear strength after 7 days of curing without water. After 4 days of curing, the shear strength reached 3.02 MPa, which meets the engineering requirements (above 3 MPa). With increasing curing time, the shear strength remained around 3 MPa, within the allowable error range. This indicates that with the addition of water, the silicone can meet the engineering requirements after 4 days of curing. After curing time exceeding 3 days, the displacement when the silicone breaks is not affected by the curing time. It can be concluded that adding a small amount of water can significantly accelerate the curing efficiency of RTV566 silicone, shortening the curing time from 7 days to 4 days.

[0064] To further explore the effect of water addition on bond strength Figure 5 (b) Bond strength of single-lap joints under different water addition ratios (cured for 4 days). It can be seen that compared to silicone without water (Example 4), the shear strength decreases slightly after adding water, but the strength is still within the error range and can be ignored. When the water addition ratio is 100:10:1 (Example 3), the bond strength decreases to 2.28 MPa. This indicates that excessive water has an adverse effect on the bond strength of RTV566.

[0065] 3. Dumbbell-shaped adhesive strips with added water and acetone (Example 2) and the original dumbbell-shaped adhesive strip (Comparative Example 1) were prepared and cured for four days to investigate the effect of water on the mechanical properties of silicone. Figure 6 (a) shows the stress-strain curve of the silicone strip. Compared with the original silicone, when acetone and water are added to the silicone, the maximum stress reaches 5.02 MPa, and the strain increases to 2.43 MPa, with both stress and strain increasing by more than 20%. The slopes of the two stress-strain curves are consistent, and the calculated Young's modulus is 2.11 and 2.12, respectively. Figure 6 As shown in (b), this indicates that the addition of acetone and water does not affect the Young's modulus of silicone. It can be concluded that the addition of acetone and water can significantly improve the mechanical properties of silicone.

[0066] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for improving the adhesive strength of RTV566 silicone, characterized in that, The process includes the following steps: mixing RTV566 silicone with acetone until homogeneous before using it for bonding the samples to be bonded; or mixing RTV566 silicone with acetone and water until homogeneous before using it for bonding the samples to be bonded. The RTV566 silicone rubber comprises a base material and a coupling agent.

2. The method as described in claim 1, characterized in that, The mass ratio of acetone to the base material is (1-6):

20.

3. The method as described in claim 2, characterized in that, The mass ratio of water to the base material of the RTV566 silicone is (0.01-1):

100.

4. The method as described in claim 3, characterized in that, The mass ratio of water to the base material of the RTV566 silicone is (0.01-0.1):

100.

5. The method as described in claim 1, characterized in that, The mass ratio of the base material to the coupling agent is 100:0.

2.

6. The method according to any one of claims 1-5, characterized in that, After the mixture is thoroughly mixed, the process also includes a step of degassing the resulting mixture.

7. The method as described in claim 6, characterized in that, Degassing was achieved by centrifugation under vacuum conditions; the centrifugation speed was 1600 r / min, the centrifugation time was 10 min, and the vacuum degree was 0.1 MPa.

8. The method as described in claim 1, characterized in that, Before bonding, the bonding area of ​​the sample to be bonded is also polished.

9. The method as described in claim 1, characterized in that, The samples to be bonded are Invar alloy steel 4J36 and ULE optical glass; The roughness of the bonding area of ​​the Invar alloy steel 4J36 is 0.04 μm, and the roughness of the bonding area of ​​the ULE optical glass is 0.15 μm.

Images