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Polyurethane sealant: Tough, and then some

It’s strong and it’s tough! Discover how you can benefit from the many great attributes of polyurethane sealant, the professional’s choice.

Polyurethane sealant: An introduction

A professional grade sealant, polyurethane sealant (sometimes called polyurethane caulk) is regarded as one of the strongest sealers available on the market. It is highly regarded for fantastic abrasion and tear resistance, its suitability for a wide range of joint sizes and its compatibility with many different materials, including wood, metal and stone.

Due to this broad range of positive attributes, polyurethane sealant is most commonly used in the building and construction trades for a number of different purposes. These include sealing joints in floors, roofs, walls and, due to its toughness and waterproof characteristics, drainpipes and gutters. Polyurethane sealer dries to form a strong and elastic-type seal that can make it resistant to any movement in the joint.

Not every flexible polyurethane caulk is created equal – some may have a smaller range of joint movement resistance than others, so be sure to check the label or ask an in-store expert before purchasing.

The difference between polyurethane sealant and silicone sealant

The biggest difference between silicone and polyurethane sealants is chemical composition. Simply put, polyurethane is polymer composed of organic units, while silicone is inorganic. Because of its organic nature, the attributes of a polyurethane sealant can be enhanced – its adhesiveness, elasticity and UV resistance, for example, can all be boosted.

However, silicone, while generally more expensive, does have its advantages – for a start, because it is inorganic it is naturally more resistant to UV radiation and more weatherproof in general. This pays off in terms of lifespan. While a polyurethane sealant will typically last from five to 10 years, its silicone equivalent will be good for over 20 years.

How to use polyurethane sealant

  1. Prepare. In addition to your tube of polyurethane sealant, you’ll need
    • a sharp knife or scissors, 
    • a caulk gun and
    • a smoothing agent compatible with the sealant.
  2. Prime. This will depend on the material you’re working with. In general, all materials should be cleaned of dust and dirt. Concrete must be roughened with a wire brush, while metal has to be rust-free. Check the instructions on your sealant to see what it requires.
  3. Cut. Use a sharp knife of scissors to cut the tip of the application syringe on the sealant tube at a 45-degree angle to create an aperture equivalent to the joint you are sealing. If the bead size is too small when you begin, you can always make it larger.
  4. Apply. Attach the caulk gun to the tube and carefully apply the polyurethane sealant from one end of the joint to the other, slowly squeezing the trigger as you go along. 
  5. Smooth. To create the best finish, apply the smoothing agent to the bead you’ve just completed, as per the smoothing agent’s instructions.