Particle boards are currently prepared by treating the particles (e.g. wood chips) with a binder comprising an organic polyisocyanate and an internal release agent and then subjecting the treated particles to a forming process involving heat and pressure. While the resulting particle board will generally release well from the caul plates of the press after forming, due to the effect of the internal release agent, it has been found that the ease of release is enhanced by precoating the surfaces of the caul plates or platens which come into contact with the particle board with a layer of polytetrafluoroethylene which layer optionally contains an internal release agent.