A Technique for Reducing the Outgassing of Silicone Compounds

A technique was developed to heat silicone resins in vacuum and thereby remove the low molecular weight molecules which contribute to the high outgassing of the untreated resins. The technique was successfully applied to two silicone resins. Heating the monomer to a temperature about 398 K (125 C) in a vacuum of about 0.0001 N/sq m removes about 10% of the resin weight, and the resultant resin when catalyzed can meet the outgassing requirements when tested according to ASTM E-595. The physical properties of RTV-615 when devolatilized at 398 K (125 C) or at 423 K (150 C) were measured.