Polyurethane paint

polyurethane paint

Extreme durability and gloss from PU paint

Sometimes it is difficult to find the coating, that provides protection, extreme durability and brilliant looks. One of the few paints that offer all those properties is polyurethane paint (PU coating). In general, it provides an extremely durable, hard and glossy finish; it is however, possible to modify the coatings to make them fit the purpose perfectly.

In this article we will answer questions like; what is a PU coating, where is it applied and how much does it costs.

But what is the use of polyurethane coating?

It could be almost anything. Polyurethanes exist as industrial and architectural coatings and they are often applied as finish coats over primer and/ or intermediate coats. However, some PU coatings are also applicable as base coats especially on wood. Other suitable substrates for PU coating include for example steel work, cladding and concrete.

“Industrial polyurethane coatings are used in almost every industry, due to their many advantages, which we’ll soon come back to.”

A PU coat can be an ideal solution when the substrate needs protection from:

  • Chemicals
  • Mechanical abrasion
  • Corrosion (metal surfaces)
  • Water 

Polyurethane coating in technical terms

You may have heard about polyurethane coatings but still be wondering what they exactly are. PU coatings are usually two component systems which have many protective and decorative purposes. They have a plastic-like structure and they cure into extremely hard wearing glossy layers.

But what is a polyurethane paint made of?

The coating system results from a reaction between the two components being:

  • Polyol resin (base, part A); 
  • Polyisocyanate curing agent (hardener. part B).

Fun fact: polyurethanes were first made in Germany in 1937 by Otto Bayer.

The two component are usually separately packed and mixed prior to application. The pot life of PU coatings is unfortunately, rather short, meaning that you should always mix only the necessary amount of the parts to avoid waste. Luckily, to improve user friendliness, one pot PU coating also exists.

The short pot life of 2K systems is one of the very few disadvantages of polyurethane coatings.

But let’s look at the advantages… 

PU paint advantages

Polyurethane coats typically exhibit at least the following features and advantages:

  • Waterproof;
  • Tough and abrasion resistant;
  • Resistant to weathering, UV radiation and heat up to 110 °C;
  • Chemical (also solvent) resistant.

It is also possible to further modify the coatings to give them a specific function. For example fluorinated polyurethanes contain fluorine carbon bonds, the strongest chemical bonds, which provide the coating with properties such as:

  • UV resistance
  • Improved corrosion protection
  • Shield from fungi and other microorganisms
  • Extreme chemical resistance including alkali, solvents, salts and acids. 

“PU coatings are thus, also suitable for substrates where graffiti may appear; neither the graffiti paint nor the cleaning chemicals affect the PU coat.”

 And when it comes to the colour and gloss…

Compared to other paint solutions PU coating retains the glossy surface longer; the gloss level, in general, is higher than in other paints. Thus, the colour of PU coatings also remain brighter for longer.

Types and suppliers of PU coating UK

A PU coating usually consists of thermosetting polymers which do not melt in presence of heat. These coatings are usually heat resistant up to 110°C. Nevertheless, there are also thermoplastic based PU paints, which do react on heat by melting. These coatings naturally are not heat resistant; but little damage on them can easily be repaired by melting the coating.

Both of these types of PU coating are available as liquid paint and dry powder.

The consumer products however, are mainly liquid paints which can be divided into three groups as the table below presents. Here you can additionally find general guidelines for applying those paints and an example of such a product. More product and price information will follow later on.

PU paint Description Application Product example
Waterborne
The best choice for projects where no exposure to heat or cleaning products is present.

  • clear finish for new surfaces
  • fast drying yet more expensive than oil based
  • clear coat for interior; spar urethane for exterior
Use a synthetic-filament brush or buy the aerosol spray to apply 3 coats of either clear polyurethane or spar urethane. Clear polyurethane takes 2 hours to dry between coats, while spar urethane takes 4 hours. Rust-Oleum 6711 System water based clear PU concrete sealer
Oil based
Cheaper and more durable than its waterborne alternative and suitable for projects you expect to come into contact with heat or chemicals.

  • contains 15 to 20 percent more polyurethane solids than water-based polyurethane
  • leaves a yellowish tint behind.
  • interior wipe-on, stain-and-poly combo, high-build and fast-drying
  • exterior spar urethane.
Wipe-on: apply 3coats with a lint-free cloth. Each coat needs 2 to 3 hours to dry.
Stain-&-poly combo, high-build or fast-drying polyurethane: use a natural bristle brush to apply 2 coats.Wait 4 to 6 hours between coats.
Spar urethane: apply with a synthetic-filament brush or purcahse as aerosol. It takes 4 hours to dry between coats.
Olympic Polyurethane, oil based finish for interiors
Waterborne, oil modified
A hybrid mix of oil- and water-based polyurethane.

  • more durable than regular water-based polyurethane
  • comes in a brush-on and a wipe-on forms
Wipe on: Apply 3 coats using a lint-free cloth. These coats take 2 to 3 hours to dry each.
Brush-on form apply 3 coats using a synthetic filament brush or spray. Each coat takes 2 hours to dry.
Minwax water based oil modified polyurethane

Environment and safety

There is a lot  of talk about PU coating being durable, but is polyurethane paint environmentally friendly, actually.

preparing for applying PU varnish

Getting ready for applying PU paint wearing protective clothing

Most polyurethane paints contain isocyanate, which is indeed, harmful for the environment and health. However, it does not need to be an issue, if the coating is applied, and the paint rests disposed appropriately.

“Whenever you apply PU coatings, wear protective clothing such as mask, coveralls and goggles. Additionally, study the manufacturer’s advice on protection and proper application, and stick with it. ” 

There is also a difference in using PU powders and liquid paints; inhaling solvent fumes of liquid paint does not present as great hazard as powder particles ending up in the respiration channels. Therefore, when applying powders, wearing a mask in crucial.

Nevertheless, powders are more environmentally friendly when it comes to disposing paint rests. Most of the times the excess powder can be collected and preserved for later use.

Therefore, polyurethane coatings are commonly used also in industrial applications and applied in factory environment. For example the metal industry is a large client of the PU coating market.

Industrial polyurethane coating in the metal industry

Applying polyurethane coatings for metal surfaces is common due to the fact that it also has anti corrosive properties.

Polyurethanes are used for example in the following:

PU paint

Aerospace / aviation industry

polyurethane paint

On- & offshore structural steel

Automotive interiors and exteriors

pu coating

Commercial transport

polyurethane paint

Floors

polyurethane paint

Tunnels & bridges

polyurethane paint

Pipe externals


Nice to know: the first polyurethane coatings were applied on metal surfaces namely on few aircrafts during the Second World War.

Applying PU coating on metal surfaces such as worktops, desks and garden furniture is also common. This is mainly due to the ideal combination of protection and decoration, polyurethane paint provides.

The PU metal coatings are often more industrial than consumer products. However, polyurethane coating for wood is applicable also at home.

Let’s dig deeper into the coatings for wood!

Increasing wood durability

The applications on wood include for example furniture and worktops. Polyurethane coatings for wood exist as different products. For example:

  • Clear & pigmented basecoats
  • Clear & opaque topcoats (matt and glossy)
  • Waxy topcoats
  • Metallic and pearl effect topcoats
  • Wood sealers & melamine paper foils
  • Acrylic base & top coats
  • Varnish 

Creating decorative and durable floors

poring PU coating on floor

Applying PU coating on floor

If asked what the best floor coating is, the answer is polyurethane and epoxy. These two coatings are hard wearing and resistant to most of the hazards a floor might encounter. In general an epoxy floor might be more durable and suitable for heavy industrial locations where the floor must endure heavy mechanical loads and abrasion. PU floor is however, cheaper.

But, what is PU floor good for?

Polyurethane floors are the most common in office buildings, schools and apartments. They are however, also applicable on garage floors. Polyurethanes can be applied as the complete flooring system or as a decorative topcoat on top of an epoxy layer.

What does a polyurethane do for a floor?

Simple; polyurethane coating on floor protects and provides the wished look. It additionally, makes the floor resistant to chemicals and abrasion meaning that PU coating is ideal for example for laboratories.


Polyurethane products and prices

Now, it’s time to introduce some products and create an idea about PU paint price. 

Note that these prices are merely indications and the products may not be offered at the same price by all polyurethane paint suppliers. PU coating is also available as PU foam for sealing and insulation.

Brand Product Price (MSRP) Packaging
 Rust-Oleum  9600 Rust-o-Thane polyurethane  £190.02  5 L
 Blackfriar  Polyurethane floor paint  £52.66  5 L
 Sadolin  Polyurethane varnish for floors  £48.54  2.5 L
 Teamac  P101 2 Pack Polyurethane topcoat  £36.74  1 Kg
Coo-Var  Polyurethane varnish  £19.70  1 L
 Sika  Sikafloor 400 N Elastic  £293.82  18 Kg

 


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