PU Foam Manufacturer — Polyurethane Foam Sealant from China

What Is PU Foam Sealant?

PU foam (polyurethane foam sealant) is a one-component, moisture-curing expanding foam dispensed from a pressurized aerosol can. When the foam exits the can, it reacts with atmospheric moisture and expands to fill gaps, cavities, and joints in building structures. The foam cures into a rigid or semi-rigid cellular structure that provides sealing against air infiltration, water penetration, and sound transmission, while also delivering meaningful thermal insulation value. PU foam has become an indispensable product on construction sites worldwide — from residential door and window installation to commercial building envelope sealing.

The chemistry behind PU foam is straightforward: a prepolymer based on MDI (methylene diphenyl diisocyanate) reacts with moisture in the air to form polyurethane polymer chains. This reaction generates carbon dioxide gas, which creates the foam's cellular structure and causes expansion. A propellant gas (typically HFO or DME, both CFC-free) provides the pressure to expel the foam from the can. The combination of chemical expansion and propellant pressure determines the foam's expansion ratio, cell structure, and final density — all of which are carefully formulated for different applications.

PU Foam Types and Formulations

General-Purpose Expanding PU Foam

Standard PU foam is designed for general gap filling and insulation tasks. It expands 2-3 times its dispensed volume, adheres to most construction substrates (concrete, brick, wood, metal, PVC), and cures to a semi-rigid foam with good insulation and sealing properties. Available in straw-type cans (with a plastic application tube) for consumer and light-commercial use, and gun-type cans that attach to professional PU foam applicator guns for precise dispensing and volume control. General-purpose foam is the workhorse product for construction contractors, handling everything from pipe penetration sealing to irregular cavity filling.

Door and Window PU Foam (Low Expansion)

Door and window foam is specifically formulated with controlled low expansion (approximately 1.5x volume) and carefully calibrated post-expansion pressure. Standard expanding foam can generate enough pressure during expansion to warp or bow window and door frames — a common complaint from installers using inappropriate foam products. Low-expansion door and window foam solves this problem by expanding gently to fill the gap between the frame and the rough opening without exerting damaging force on the frame. This formulation is essential for professional window and door installation, where frame alignment and smooth operation of opening hardware must be preserved.

Fire-Rated PU Foam (B1 Classification)

Fire-rated PU foam incorporates flame-retardant additives that prevent the foam from sustaining combustion and limit smoke generation. Meeting B1 fire classification (DIN 4102-1) or equivalent standards, fire-rated foam is required by building codes for applications in fire-rated walls, fire-stops around pipe and cable penetrations, and joint sealing in fire compartment boundaries. When exposed to flame, the foam intumesces (swells) to form an insulating char layer that blocks the passage of fire and hot gases through sealed joints. ChinaGluePro's fire-rated PU foam is tested and certified to B1 classification with documented test reports available for building code compliance.

Primary Construction Applications

• — Door and window installation: Filling and insulating the gap between door/window frames and the surrounding wall structure. This is the single largest application for PU foam globally. Proper foam application provides thermal insulation, air sealing, and structural support for the installed frame.
• — Gap filling and cavity sealing: Sealing irregular openings, gaps around pipes and conduits, spaces behind electrical boxes, and joints between structural elements. The expanding nature of PU foam allows it to fill complex geometries that rigid sealants cannot reach.
• — Thermal insulation: PU foam's closed-cell structure provides thermal conductivity of approximately 0.035-0.040 W/mK, making it an effective insulating material for small-area applications. It fills thermal bridge gaps in wall assemblies and insulates penetrations through the building envelope.
• — Sound insulation: PU foam dampens airborne noise transmission through gaps and joints. While not a substitute for dedicated acoustic materials, foam sealing of air leaks significantly reduces sound flanking paths in wall and floor assemblies.
• — Adhesive bonding: PU foam also functions as a bonding adhesive for lightweight insulation panels, fixing decorative elements, and securing conduit runs. The expanding foam fills uneven surfaces and creates a strong mechanical bond after curing.

ChinaGluePro PU Foam Production

Our PU foam production facility in Guangzhou features high-speed aerosol filling lines with capacity exceeding 80,000 cans per day. The production process includes prepolymer synthesis, propellant charging, and quality verification at every stage. Each production batch is tested for expansion ratio, density, adhesion to standard substrates, dimensional stability, and fire performance (for fire-rated grades). We manufacture PU foam in 300ml, 500ml, and 750ml can sizes, in both straw-type and gun-type applicator formats. Full OEM and private label services include custom can design, label printing, valve and actuator selection, and branded outer carton packaging. Our PU foam is exported to construction markets across Southeast Asia, Africa, the Middle East, and Latin America, where our formulations are optimized for tropical and high-humidity curing conditions.