Is polyurethane basically plastic?

Yes, polyurethane is basically plastic, as it is a synthetic polymer made from petrochemicals that falls under the broad category of plastics. Chemically, plastics are defined as synthetic materials made from polymers that can be molded and hardened, and polyurethane fits that definition perfectly because it is made by reacting diisocyanates with polyols to form long polymer chains. It is classified as a thermoset or thermoplastic polymer depending on formulation. In everyday life, polyurethane appears as many forms of plastic, including rigid foam insulation, flexible foam in mattresses, hard coatings for wood floors, faux leather, wheels, and adhesives. While it can feel like rubber when soft and like hard varnish when cured, its chemical family is plastic, not natural rubber or wood. It shares characteristics with other plastics like being durable, not biodegradable, and potentially breaking down into microplastics over time. So when people say polyurethane finish is a plastic coating, that is accurate, it forms a thin plastic film that protects wood. In industry, polyurethane is listed alongside polyethylene, polypropylene, and PVC as a major plastic type, albeit one that can be engineered to be elastic.