Both epoxy and urethane are considered to be “topical sealers.” When applied to a material's surface, they leave a protective coating over the top.
These materials are readily available to the general public and can be purchased in many home improvement stores such as Lowe's. Solvent-based as well as water-based epoxies and urethanes are available.
Both materials, especially epoxy, needs to be applied and smoothed quickly as it dries quickly. Epoxy and urethane are often used together to seal concrete garage floors. The urethane is applied over the epoxy to create a hard, durable surface.
Urethanes are more heat- and scratch-resistant than epoxies, which are likely to scratch and scuff. Epoxy and urethane leave a glossy finish on surfaces.
Unlike epoxy, which can fade and degrade if overexposed to ultraviolet light, urethane is quite resistant to the negative effects associated with ultraviolet light.