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What are the common problems with silicone adhesive sealants?


Silicone adhesive sealant, also known as room temperature vulcanized silicone rubber sealant, also known as RTV, is a silicone adhesive that can be hardened in a greenhouse. In an open environment, a cross-linking reaction occurs under the action of water to form a rubber elastomer. According to the type of small molecules released, it is divided into dealcoholization type, deacetonization type, deacidification type and deketone type. In a closed environment, ketone fat products will corrode copper and hard PC (making copper rust and PC crack), so you should pay attention when choosing and using them.

The following takes the ketone oxime type product as an example to illustrate the common problems of one-component bonding sealant.

1. How do single-component silicone adhesive sealant products achieve curing performance?

One-component condensation curing silicone rubber products are cured using moisture in the air. When curing, from the outside to the inside, usually under the conditions of 25℃ and 50%RH, the one-component adhesive sealant can cure 3mm in 24h; it usually takes 7 days to achieve the inherent physical properties.

2. Why do silicone adhesive sealants have different surface drying times in winter and summer?

The surface dryness and curing speed of single-component condensation cured silicone rubber products are closely related to the ambient temperature. In winter, when the humidity and temperature are low, the glue will be surface dry and the curing speed is slow. In summer, when the humidity is high and the temperature is high, the glue will be surface dry and solidify quickly.

3. What is the temperature resistance of silicone adhesive sealant?

Generally, the temperature range of silicone is -40°C to 20O0C, and the long-term use temperature does not exceed 150°C. The use temperature range of special high-temperature resistant red silicone is -40C to 250°C, and the long-term use temperature does not exceed 180°C. Temperature resistance is closely related to whether the colloid is completely cured. If the colloid is not completely cured, heating will cause bubbles, cracking, smoke and other undesirable phenomena.

4. Why does white silicone adhesive sealant easily turn yellow?

The ketoxime cross-linking agent, aminosilane tackifier and catalyst contained in the deketoneized fatty silica gel may surface due to the oxidation of the amino group or some chemical reactions of the catalyst under long-term UV irradiation or in a high temperature environment above 8OC. Yellowing occurs. To improve the yellowing phenomenon, a special formula is required. For example, solar silica gel has good anti-yellowing properties. When the dealcoholized silica gel is not completely cured, the titanate catalyst that did not participate in the reaction will show up under heating conditions due to its yellow color, causing the colloid to turn yellow.

5. Why does the viscosity of silicone adhesive sealant differ in winter and summer?

The viscosity of the glue will change with temperature changes. In summer, the viscosity will decrease when the temperature is high. In winter, it is just the opposite, but it will be within the acceptable range.

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