Polyurethane Coatings

Polyurethane polymers are most commonly formed by reacting a di- or tri poly-isocyanate with a polyol. Both the isocyanates and polyols used to make Polyurethanes contain, on average, two or more functional groups per molecule. So the polymer is composed of organic units joined by urethane links.

A Polyurethane coating can be glossy or matt and can be opaque or transparent, with most being thermosetting polymers that do not melt when heated.

Polyurethane coatings adhere very well to a wide variety of base materials, often without a primer. They usually require no additional processing after application, using moisture in the air to cure. They have a range of cure times and can be applied and cured in a broad range of temperatures. Application is usually by spray or roller.

The properties of a Polyurethane are greatly influenced by the types of isocyanates and polyols used to make it. A soft elastic coating will be achieved by having long, flexible units whereas highly crosslinked short units will result in tough or rigid polymers. The crosslinking present in Polyurethanes gives a polymer that consists of a three dimensional network. The molecular weight is also very high.

Polyurethanes are effective because of their outstanding life expectancy and performance. They are generally resistant to corrosive environments, have high abrasion and impact resistance, and often can be built to high film builds.

Their fast application, strong adhesion, range of colours and zero or near zero VOC’s mean they are very popular. Their inertness and ability to be machined if chilled opens up many applications.

As a coating Polyurethanes are often found where a tough and resilient surface is required. The industries that use these coatings is diverse, from quarrying through printing to automotive and aerospace.