Abstract: Disclosed is a high-penetration two-component polyurethane adhesive for separation apparatus, such as thin film composite reverse osmosis filtration membranes. The polyisocyanate reactive side of the two-component adhesive comprises hydrogenated castor oil or derivative thereof to increase the viscosity and provide a thixotropic property. Surprisingly, these high-viscosity polyisocyanate reactive components provide a two-component polyurethane adhesive exhibiting excellent penetration of the membranes used in such separation apparatus. Also disclosed is a method of using these two component polyurethane adhesives to bond these membranes to one or more other components of a separation apparatus.