Good mechanical properties
Low compression set at elevated temperatures
Heat stable (indefinitely up to 180ºC)
Flexible at low temperatures (-40ºC)
High dielectric strength
Can be food grade compliant
Probably the single most important characteristic of silicone elastomers is their unique ability to retain their mechanical properties over a wide temperature range.
Construction: sealants, structural glazing
Moldmaking: prototyping, restoration, furniture, ornaments
Household: gaskets, o-rings
Automotive: cure-in-place gaskets, vibration dampers
Condensation Cure RTVs:
Probably the most widely used cure chemistry in RTVs is that of condensation cure. One of the key features of condensation cure is that of being hard to inhibit by most pollutants in the application environment.
These systems consist of one (RTV-1) or two (RTV-2) components. In the case of RTV-1, the product will cure upon exposure to moisture in the air as it is applied out of its package. In the case of RTV-2, the curable composition is formed by mixing two components during application.
RTV condensation cure systems are prepared from silanol-terminated PDMS, crosslinker and catalyst; reinforcing fillers and pigments are common additives.
There are four major cure systems in use related to the nature of the crosslinker: acetoxy, alkoxy, amine and oxime. The corresponding split products are acetic acid, alcohol, amine and oxime, respectively. Common catalysts are organotin and organotitanate.
As mentioned above, the reaction is carried out in the presence of moisture with evolution of the corresponding split product to form siloxane bonds in a tri-dimensional network.