One-part silicone adhesives

One-part silicone adhesives are generally polysiloxanes, i.e. a silicon-oxygen chain to which organic groups are bonded such as methyl groups.

One-part silicone adhesive is available in a number of forms which cure in different ways, to form a rubbery elastomer:

• At ambient humidity; these products are referred to as RTV (Room Temperature Vulcanisation) adhesives
• At high temperatures; these products are referred to as HTV (High Temperature Vulcanisation) adhesives

RTV silicone adhesive is cross-linked (or vulcanised) by polycondensation at room temperature (as a result of absorbing moisture from the ambient air).

At normal temperatures and humidity levels (25°C and 50%), silicone polymerises slowly (3 mm of depth/24 h) however, the cross-linking process can be accelerated by changing these parameters.

HTV silicon adhesive (also known as high-temperature silicone adhesive) cross-links by polyaddition after exposure to high temperature (approximately 150°C). Unlike RTV adhesives, these adhesives do not require moisture in the ambient air to cross-link, and for this reason they can be used in places where the availability of air is limited. This type of adhesive cures very quickly.

We classify RTV silicone adhesives into three main families, based on the type of product released during cross-linking:

• Acetic silicones;
• Neutral alkoxy silicones;
• Neutral oxime silicones.

One-part silicone adhesives are available in a wide range of viscosities to suit their intended application.