XMC® F40 All-Season Polyurethane Foam for Doors and Windows

Window and Door PU Foam: a Little Less Expansion Pressure Keeps the Frame Straight

The worst outcome when installing a window is not an under-filled gap — it is a sash that no longer closes properly. The frame bows out slightly, the locking points no longer line up, and a slider starts to drag. Take it apart and the culprit is rarely the hardware: it is the expansion pressure generated while the foam cures, pushing the frame away from its set position.

The root cause is the wrong material. Standard high-expansion foams are designed to fill large cavities; they produce a lot of foam and a lot of curing pressure. Used around a thin-walled, long-span component like a window frame, that pressure has nowhere to go except into the frame itself.

Low-Pressure Curing: Windows That Still Open and Close

The TDS describes the behaviour as slight expansion without rebound: the foaming volume is precisely controlled and pressure during curing is kept low, which safeguards smooth operation of doors and windows.

For an installation crew this means two things. First, the frame does not need extra temporary bracing to resist foam pressure, which simplifies the sequence. Second, dimensional stability after installation is better — the "straight on day one, off on day two" problem becomes rare.

That matters most on narrow frames, large windows and sliding doors, where frame straightness is critical.

Elastic After Curing: It Moves with the Building

Buildings move constantly. Facades warm in the sun and cool at night, concrete and masonry shrink as they dry, and tall buildings sway under wind load. A completely rigid filler will crack at the joint as these movements repeat.

F40 cures to a soft or semi-rigid state, able to expand and contract with the building's thermal movements and minor vibrations, which makes it resistant to cracking. The TDS lists high elasticity and weather resistance together as product advantages — and they belong together: elasticity is what keeps a seal sealed through the seasons.

At a window opening this translates directly into service life: the joint does not widen with use, and callbacks go down.

Closed-Cell Structure: Insulation, Sound and Water in One Pass

F40 uses a closed-cell foam structure. Because the cells are discrete, a group of related properties follows:

• Thermal insulation: the closed-cell structure effectively blocks heat transfer, improving the energy performance of the opening and reducing cold bridging around the frame.
• Acoustic insulation: the foam layer reduces external noise transmission — a real benefit on streetside residential and office projects.
• Moisture and water resistance: rainwater is prevented from seeping indoors through window and door gaps, lowering the risk of mould around the frame.

At a window opening all three are required at once. Solving them with one material saves process steps compared with separate insulation, sealing and waterproofing — and leaves fewer interfaces where something can go wrong.

Where It Is Used

Application areas listed in the TDS:

• Around window and door frames: fills the rough opening gap between the wall and a wood, vinyl or metal frame, blocking draughts.
• Sealing the gap between frame and wall: the perimeter seal after the unit is installed.
• Penetrations and junctions: seals spaces around electrical wires, plumbing pipes, base plates and similar points where air leaks occur.

Typical Physical Properties

Density to FEICA TM1019:2014, expansion ratio to FEICA TM1003:2013, shear strength to ISO 844:2021. Values are typical figures obtained under the conditions specified in the TDS and may vary with substrate, application method and site conditions.

Three Application Steps

1. Prepare the surface: remove dust, greasy dirt and standing water with cotton yarn. Where rust peels away easily, remove it with a metal brush first, and wipe with an organic solvent such as acetone where necessary.
2. Fit the nozzle: cut the nozzle to the required size, screw it onto the canister, and apply with a manual or compressed-air gun.
3. Tool immediately: the surface should be tooled right after application. Where appearance matters, apply masking tape along both sides first and remove it after tooling for a cleaner finish.

Packaging, Transport and Storage

F40 is supplied in 300 ml, 500 ml and 750 ml canisters, so the format can be matched to opening size and per-window consumption.

Keep packaging sealed during transport and protect it from moisture, direct sunlight, high temperature and impact. Store in a dry place below 25 °C, avoiding heat and humidity. Shelf life is 15 months; first-in first-out rotation is recommended.

Application conditions per the TDS: ambient 5–35 °C, optimal 18–25 °C, canister above 5 °C before use, and minimum relative humidity ≥45%, since dry conditions will affect moisture curing.

About XMC

Shanghai XMC New Material Technology Co., Ltd. was founded in 2004 and specializes in the research, development and manufacturing of sealants and adhesive products for construction and industrial applications. With more than two decades of industry experience, XMC has built a modern production system integrating product development, manufacturing and international trade, with a plant area of approximately 80,000 m², annual output of approximately 60,000 t, and more than 500 containers shipped per year.

XMC's product portfolio covers silicone sealants, hybrid sealants, MS sealants, liquid nails, polyurethane foam, automotive sealants and various industrial bonding materials. The company serves global distributors, building material suppliers and project customers with stable products and customized services, backed by 20 years of OEM/ODM experience and more than 1,000 custom colours.

For more information about XMC products and cooperation opportunities, please visit: https://www.xmcsil.com