No. 1031 - Miljøstyrelsen

Curing of one-component RTV silicones starts
when the compounds are exposed to atmospheric
moisture during application. The crosslinking
agents are tri- or tetrafunctional silanes
containing hydrolyseable Si-O or Si-N bonds.
Depending on the used cross-linking agent different
compounds are formed as cleavage product
and will be released during the curing process
(see Table 1.1)
Well known is the smell of acetic acid, when silicone sealants with ethyltriacetoxysilane
as cross-linking agent are applied. The acetic acid is formed by
the curing process.
Table 1.1
Crosslinking agents and cleavage products for curing of silicone elastomers ( based
on Ullmann 2003)
Cross-linking agent Cleavage product
Alkoxysilanes Alcohols
Methyl- or ethyltriacetoxysilane Acetic acid
Tris(cyclohexylamino)methylsilane and others Amines
Methyl(tributanone oximo)silane Butanonoxime
Benzamide silanes N-butylbenzamide and ethanol
Silicone elastomers are characterised by excellent electrical insulating properties,
inertness, low toxicity and resistance to ozone, weathering, oil and moisture.
Some grades have the ability to perform at very low temperatures,
whereas others retain elastomeric properties at very high temperatures.
Unfilled silicone elastomers achieve only low mechanical strength when cured.
Adequate strength is obtained by incorporating reinforcing fillers. Smallparticle-size,
silicas are used almost exclusively for this purpose. Because of
the small particle size elastomers with high transparency can be produced.
The major application of silicone elastomers is as sealant, but they are also
widely used for other applications like electrical fittings, textile coating, paints
and rubbers for automotive, medical and dental purposes.
Silicone resins
Whereas silicone fluids and elastomers are based on cyclic or linear polymers,
silicone resins are highly branched polymers. Compared to the fluids and
elastomers, the market of silicone resins is limited.
The major market for silicone resins is surface coatings, mainly waterrepellant
coatings for masonry and high-performance paints. For these purposes
the silicone resin is often reacted with other polymers to form copolymers.
Silicone/alkyd and silicone/polyester are the most frequently used.
1.2 International market
Ethyltriacetoxysilane
C CH3
Globally the consumption of siloxanes totals about 0.85 million tonnes (Will
et al 2003). The main producer countries are the USA, Germany, Japan,
France and the UK. The American producer DOW Corning Corporation is
O
H5C2
O
Si
O
O C CH3
O C CH3
O
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