Patent ID: 8597741

Claim:
An insulated glass unit comprising at least two spaced-apart sheets of glass in spaced relationship to each other, a low thermal conductivity gas therebetween and a gas sealant element including a two-part curable sealant composition wherein Part 1 comprises (a) at least one first diorganopolysiloxane exhibiting a permeability to a gas or a mixture of gases wherein each end of the polymer chain of each of the first diorganopolysiloxanes is silanol terminated, wherein the viscosity of the silanol terminated first diorganopolysiloxanes can be from about 1,000 to 200,000 cps at 25 degrees C., and (b) a polymer exhibiting permeability to the gas or mixture of gases that is less than the permeability of the silanol terminated first diorganopolysiloxane (a); and, Part 2 comprises (c) at least one second diorganopolysiloxane wherein each end of the polymer chain of each of the second diorganopolysiloxane is trialkylsilyl terminated, (d) an alkylsilicate crosslinker, and (e) a crosslinking catalyst; wherein said two-part curable sealant composition when cured has a permeability to argon of no more than about 900 barrer units at 25 degrees C. and under 100 psi pressure.