A seal assembly, for use within a hot melt adhesive or other thermoplastic material dispensing valve assembly, comprises a sealing cartridge comprising a first primary seal, a secondary seal, and a viscous incompressible silicone grease disposed internally within the sealing cartridge. The viscous silicone grease effectively distributes the pressure forces such that internal pressure forces within the silicone grease are substantially equal to the external pressure forces of the hot melt adhesive whereby a pressure differential across the primary seal member is effectively eliminated thereby effectively eliminating the tendency for leakage of the hot melt adhesive or other thermoplastic materials.
