RTV Silicone
RTV (Room Temperature Vulcanizing) silicones are a type of silicone sealant that has a one-part system and cures at room temperature. These silicones have a wide range of viscosities and consist of a combination of organic and inorganic materials, making them one of the most stable adhesive products on the market. They are resistant to high temperatures and are much more flexible compared to other industrial adhesives.
RTV silicones use water and a curing agent to form adhesion or a coating. When these materials combine during the crosslinking process, a chemical reaction occurs. Depending on the curing agent used, this chemical process may produce acetic acid (acetoxy), amine (base), or neutral compounds such as methyl and ethyl (alkoxy) or oxime. The curing agent will determine the final characteristics of your adhesive. Relative humidity and ambient temperature directly influence the drying rate; generally, RTV silicone dries within 72 hours, although the adhesive may continue to gain strength for up to two weeks after curing.
These adhesives have several properties; their only limitation is that they cannot be painted with water-based paints. They are highly flexible (depending on temperature) and have a wide operational temperature range. They are resistant to harsh weather conditions, humidity, mold, and mildew, and also exhibit excellent electrical properties. RTV silicone has a lifespan of 40 years and possesses high tensile strength; these adhesives maintain high UV resistance and excellent thermal stability even at low temperatures.
Fillers such as citric acid can provide fast drying times, while oxides and nitrides can offer better thermal conductivity.
Typically, RTVs include acetoxy-cured silicone and neutral-cured (oxime) silicone. Acetoxy silicone has a relatively fast drying speed and a short tack-free time, resulting in good quality adhesion, although it is corrosive to metals. This type of RTV silicone releases acid and emits a vinegar-like smell.
On the other hand, oxime or neutral-cured silicone is non-corrosive and possesses excellent oil resistance and temperature tolerance. This type of silicone produces a neutral product that requires more time to cure and has a longer tack-free period.
