Silicone adhesive is a powerful and flexible bonding material that has an extremely high temperature resistance. It creates a permanent seal on most surfaces, including wood, glass, paper, plastic, metals, ceramic and concrete. Besides bonding two surfaces together, silicone is also used as an effective, watertight sealant to fill holes, level surfaces and seal off gaps.
Silicone adhesive performs in temperatures up to 600º F and is therefore used in many high heat exposure applications within the automotive and manufacturing industries. However, it lacks the strength of other epoxies or acrylic resins. Silicone adhesives are available in a number of different ways. Some are two-part formulas, which must be mixed right before use.
This makes the application process more complicated since timing is everything in the prep and application. It is also available as a pressure sensitive adhesive, or PSA, that is applied to surfaces with the help of a paper or foam backing. They are less common than other types of adhesives and sealants, but have found their niche within high temperature applications. They are often used in automobile engine applications like gasket sealing.
Silicone adhesives are also popular in hobbies and crafts that require gluing objects together. Aquariums and fish bowl corners are sealed off with silicone, and construction companies use it to join materials that face exposure to sunlight, low temperatures or water, and are commonly used outdoors.
Adhesives made of silicone are cured in a number of different ways. Some adhesives can moisture cure, which is when the adhesive reacts with moisture in the air or a bonding substrate to start curing. This gives off acid fumes and vapors and is called room temperature vulcanizing. Another type of curing, called ultraviolet or radiation curing is prompted by ultraviolet light, visible light or electron beam irradiation. No excessive heat is needed.
A disadvantage of this process is that one of the substrates must be transparent. Other silicone adhesives start curing with the application of heat and are called thermoset adhesives. This type, however, can’t be softened a second time with heat. Once it has cured, thermoset silicone adhesive remains cured. Pressure sensitive silicone adhesives have permanent tackiness and will easily adhere with pressure from a finger or hand. They never lose their stickiness, and can be removed or repositioned without damaging the surface, as needed.