Self-Expanding Adhesive: How to Use Polyurethane Foam to Fill Gaps
2026-08-25
When sprayed from the can, it emerges as a soft, fluffy foam that slowly expands upon contact with air and eventually hardens, filling the gap tightly.
How Does It “Expand”?
Polyurethane foam is a single-component product; the prepolymer inside the can is dispensed by a propellant. Once sprayed, it absorbs moisture from the air, undergoes a cross-linking reaction, and releases gas, causing it to gradually expand. During this expansion, the foam fills every corner of the gap, even penetrating irregular voids. After curing, the foam becomes a semi-rigid or rigid closed-cell structure that provides thermal insulation, soundproofing, and structural support.
Where Can It Be Used?
It is commonly used to fill gaps between door and window frames and walls during installation. It can also be used to seal pipe penetrations through walls, air conditioning openings, cold storage insulation, and gaps in partition walls. It has good adhesion and can bond to a variety of substrates, including concrete, brick walls, wood, and metal.
Steps for Applying the Foam
Clean the gap: Remove dust, grease, and loose debris. Spray a little water to moisten the surface, which helps the foam expand.
Shake the can: Shake it up and down to mix the contents thoroughly.
Apply the sealant: Insert the nozzle into the gap and squeeze the sealant out at a steady rate from the inside out. Fill the gap to about one-third of its volume, leaving room for expansion.
Wait for expansion: After application, the sealant will expand on its own; do not touch it immediately.
Trim: Once cured, use a knife to trim off the excess, then apply sealant or paint.
Previous:
More Products
The products cover silicone, acrylic, epoxy, MS, PU foam, Nail-free, etc. Products are widely used in construction, photovoltaic, electric power, automotive, industrial sealing and other fields.
