the invention relates to an isocyanate - terminated polysiloxane material that can preferably be used as a curing agent , hardener or co - reactant in coatings . the invention further relates to a method of manufacturing the isocyanate - terminated polysiloxane material by partially hydrolyzing a methoxy - functional polysiloxane such as a methyl phenyl polysiloxane , and reacting it with a polyisocyanate to yield the isocyanate - terminated polysiloxane hardener . the hardener can preferably be used with any isocyanate - reactive functional group of another component to form coating systems , including acrylics , polyesters , epoxies and urethanes .