Urethane

One named urethane product shows how a maker describes the chemistry in its own guide.

Seal 'n Lock's Super-Wet-Look is a two-part, water based pure urethane sealer, and the maker says it penetrates into the pavers. That is the maker's claim for its own formulation. ICPI's description of the chemistry, a high gloss and enhanced color, belongs to urethanes as a group rather than to any one brand. What the carrier does, solvent or water, and how a sealer behaves as it wears, is set out in the section on sealer carriers and renewal.

ICPI's two lines about urethane sit close together, and the second one changes what happens to a worn coat.

The institute writes that polyurethanes produce a high gloss and enhance the color of pavers, the gloss a wet-look product name trades on. It then separates them from acrylics: urethanes cannot be rejuvenated simply by re-coating, where worn acrylics can be easily cleaned and resealed. Whether a different product can go over an old urethane at all is its own question, answered at can new sealer go over an old sealer of a different kind.

Two more ICPI lines about urethane are easy to misread: what removing it takes, and what its UV language is about.

If urethane sealers must be removed, ICPI says methylene chloride or sand blasting is often necessary. It calls methylene chloride a hazardous chemical that is not acceptable for flushing into storm drains and should not be allowed to soak into the soil, and concludes that urethane removal is best handled by professionals, ICPI's word for that trade. The removal process has its own entry at stripping.

ICPI's UV wording about urethane concerns the coating's own yellowing, not protection of the paver from the sun. Whether a paver sealer yellows, and whether any sealer guards a paver against fading, are separate questions answered at does paver sealer turn yellow and at does paver sealer protect against sun fading.