Rapid Prototyping involved creating a working model of various parts of the system at a very early stage, after a relatively short investigation. The method used in building it is usually quite informal, the most important factor being the speed with which the model is provided.
There are water-and solvent-based -- also called oil-based -- polyurethane varnishes. Water-based polyurethanes are more environmentally friendly and safer to use than solvent-based, but they are not as resistant to wear and tear as solvent-based products.
Definition - What does Urethane mean? Urethane is a type of polymer containing organic chains united by carbamate links. It is formed by the reaction of polyol and isocyanate. Both of these are utilized to produce polyurethanes that contain at least two of several functional groups in every molecule. Urethane is mainly used as an ingredient in: