| abstract |
A two part moisture cure organosiloxane composition that may be used as a sealant in insulation systems in building facades or the like and which exhibits low thermal conductivity. The two part moisture curing composition has a Part A and a Part B in which, Part A comprises either 1) A siloxane polymer (I) having at least two terminal hydroxyl or hydrolysable groups having a viscosity of from 20000 to 40000 mPa.s at 25°C; or 2) A mixture of polymer (i) and polymer (ii), wherein • Polymer (i) is a siloxane polymer having at least two terminal hydroxyl or hydrolysable groups and a viscosity ≥ 25,000 mPa.s at 25°C and • Polymer (ii), a siloxane polymer having at least two terminal hydroxyl or hydrolysable groups and a viscosity of between 1,000 and 20,000 mPa.s at 25°C, together with a reinforcing filler and a low density filler, with the total filler content being between 30 and 45 % in volume of the total formulation; and Part B comprises a moisture curing agent formulation comprising a suitable amount of a tin based catalyst and one or more crosslinkers. Part A and/or the composition of Part A + Part B after mixing has a thermal conductivity ≤ 0.20 W/mK. |