How to Use Polyurethane Sealant

How to Use Polyurethane Sealant

Loading and Cutting the Nozzle:

Load the sealant tube or barrel into the gun.

Use a nozzle cutter to create an opening at approximately a 45-degree angle (or a flat cut for wide seams) at the tip of the nozzle, depending on the desired width of the sealant bead. The opening should be slightly smaller than the seam width to ensure the sealant bead is fully pressed into the seam. After cutting the nozzle, check for a clear opening.

Extrusion Test:

Test a small amount of sealant onto scrap cardboard or lint-free cloth to ensure an even distribution of sealant, free of bubbles, and no skinning. If any problems are found, replace or repair the nozzle/gun.

Applying Glue:

Place the nozzle at approximately a 45-degree angle against the bottom of the seam.

Move the gun at a steady, continuous speed, ensuring that the sealant completely fills the seam, with a slight overspill. Maintain a consistent speed to avoid excessively fast movements that create bubbles or excessively slow movements that cause accumulation.

Keep the nozzle tip submerged in the squeezed sealant to prevent air bubbles from being trapped.

Ensure full contact between the sealant and the substrate on both sides of the joint.

Scraping and Finishing:

Before the sealant dries (usually within 5-20 minutes after application, depending on the product instructions and temperature and humidity conditions), immediately use a scraper or tongue depressor dipped in a small amount of soapy water (or a dedicated primer) to smooth and compact the sealant.

Hold the scraper at a roughly 45-degree angle to the substrate surface and apply even pressure in a single pass. This will ensure a smooth, flat surface, a tight, seamless bond, and a desired concave or flat surface.

Purpose: Ensure the sealant fully penetrates the substrate surface, eliminates any air bubbles, and achieves a good appearance and bond.

Removing Anti-fouling Tape:

Before the sealant has dried and reached sufficient strength (but immediately after scraping), carefully remove the anti-fouling tape on both sides. Pull outward at an angle to avoid damaging the sealant edges.