Dual Liquid Modified Silicone Gel Encapsulation Adhesive
Author: Lin Zhe Yong
Varieties of one component moisture-curing products (RTV1) available in the market are diverse, including commonly seen ones such as silicone and polyurethane (PU). The prominent advantages of these two adhesives in their strong bonding capabilities to various substrates, wide operating temperature range, and long-term weather resistance. Depending on the formulation designed by different manufacturers, when these products undergo moisture-curing reactions, silicone products may produce by products such as acetic acid, ketoxime, acetone, and alcohol elimination, while polyurethane (PU) products may contain isocyanate reaction components. Most of these chemical substances mentioned above often lead to issues like irritating odors, corrosion and degradation of substrates, and excessive volatile organic compounds (VOCs). Additionally, the core challenge faced by one component moisture-curing products (RTV1) is that they rely on external moisture for curing, thus requiring waiting time for gradual and increased gel curing depth. However, there is often a limit to the depth of curing, typically recommended not to exceed 1 centimeter. To overcome the aforementioned drawbacks, Everwide Chemical has developed the FS211 Series, which uses modified silicone (Silyl-modified polymer). This product addresses the issues of minimal odor, reduced corrosion, and low VOCs. It provides a 1:1 dual liquid adhesive that can cure deep within a short period of time.
As shown in Figure 1, using the dual-liquid developed product FS211 Series, a gel block with a Shore 00 hardness of 57 and a curing depth of 15mm can be achieved after 1 hour of room temperature standing. In contrast, the one component adhesive can only achieve a curing depth of 3.3mm after 24 hours at room temperature, and the Shore 00 hardness cannot be accurately measured. In Figure 2, after undergoing 85°C/85%RH environmental testing for 500 hours, it is observed that the Shore 00 hardness increases by 23% and the shear tensile strength improves by 50%. This phenomenon can be attributed to the adhesion between the adhesive resin and the substrate. During the environmental testing, temperature and UV light cause the compounds in the resin formulation to generate free radicals, which attack the resin and cause the material to become brittle and yellowing, leading to decreased cohesive strength. While this is a common and expected result, the temperature also provides an opportunity for molecular chains to reorganize. At higher temperatures, molecular chains are more mobile and can rearrange and stack more densely, similar to annealing. Subsequent testing after returning to room temperature enhances the cohesive strength. Therefore, a stable formulation within the permissible working temperature of the material promotes an increase in adhesion with higher temperatures. As shown in Figure 3, the adhesion strength declines in the 120°C high temperature environmental test but still maintains 92% of the initial adhesion strength, and in the 150°C high-temperature environmental test, the adhesion strength decreases but still maintains 85% of the initial adhesion strength. In Figure 4, even in environments where moisture is difficult to penetrate, such as between metal aluminum and aluminum bonding, using this dual liquid developed product can achieve 37% of full adhesion capability after 2 hours at room temperature and humidity and reach 70% of full adhesion capability after 24 hours. The final full curing time depends on the amount of adhesive, resulting in some variations in time, but the complete curing time will not exceed seven days.Finally, as shown in Figure 5. This adhesive overcomes the core issue faced by one component moisture-curing products (RTV1), where the curing depth typically does not exceed 1 centimeter. With this product, we can achieve a curing depth of 4 cm after 24 hours at room temperature. Moreover, we have developed various adhesives that meet customer process operation requirements, allowing adjustments in appearance, color, viscosity, anti-sagging properties, curing time, and high adhesion strength. For inquiries, please feel free to contact us.
Competitor's Grade：Sika:Sikaflex®-950、Henkel：Teroson® MS9399、SABA：Sabatack® Fast。
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