Sealing and bonding of panel filter frames


The reference material presented has been used by leading manufacturers of HVAC systems and air filters for many years, and is tried and tested. We also offer FERMAPOR K31 2-component polyurethane sealing foams to seal filter frames and FERMADUR adhesive sealants to bond filter packs into filter frames.

Whenever possible, we can also customize our material systems to meet your specific requirements. The influencing factors for sealing foams include pot life until start of foaming, curing time, the viscosity, hardness and adhesion properties.

Thanks to the mixed-cell foam structure, the closing forces when installing the foam gasket are low. When installing the air filter in the air conditioning system, the tongue-and-groove design ensures that the foam gasket of the filter frame is firmly bonded to its counterpart.

The gasket therefore prevents unfiltered outside air from being drawn past the filter.

The very good resetting ability of the FERMAPOR K31 polyurethane foam gasket allows repeated installation and removal of the air filter for maintenance purposes and renewed compression of the foam structure while maintaining a consistent sealing effect (tested according to DIN EN ISO 1856­).

Besides the compact material systems, we also offer foamed filter adhesives with a lower density from the FERMADUR product family to bond the filter packs into the filter frames.


Bespoke system solutions to seal and bond filter frames

We carry out developments individually for your specific requirements

The lower weight ensures lighter – and therefore easier – handling of the parts. It also leads to a marked reduction in the amount of adhesive used per filter and therefore saves costs. The requirements for high-quality filter bonding are still satisfied.

The good flow properties of FERMADUR adhesive sealants ensure they are applied to the entire surface on the inside of the filter frame and the filter pack. The filter pack positioned in the filter frame is therefore optimally bonded and sealed on all sides.

The foam and adhesive are cured at room temperature. This saves the expense of an annealing oven, which has to be used for other processes.


The different reaction phases of the sealing foam in the chronological sequence


Reference material

    Sealing of filter frames Bonding of filter frames
    FERMAPOR K31-A-3030-1-MX        FERMADUR A-45D05-1-W-CT

Mixing ratio

  6 : 1 4.5:1
Pot life time   35 sec. 27 sec.
Tack-free time   5 min. 1.5 min.

Viscosity of the A component

  33,000 mPas 5,500 mPas
Density of the foam   0.20 g/cm³ 1.38 g/cm³
Hardness   26 (Shore 00) 40 (Shore A)
Temperature resistance   from -40 to + 80 °C from -40 to + 80 °C

In addition to the reference products, we develop material systems according to your individual requirements. Influencing factors include pot life until start of foaming, curing time, and the viscosity, hardness and adhesion properties.


Repeated installation and removal of the air filter for maintenance purposes

The very good resetting ability of the FERMAPOR K31 polyurethane foam gasket allows repeated installation and removal of the air filter for maintenance purposes without the seal tightness decreasing.

The video shows the polyurethane foam seal FERMAPOR K31 in cross section - first in the uncompressed state, then 50% compressed, so that the sealing function of the seal is given.

Cross-section of a polyurethane foam bead – unpressed


Cross-section of a polyurethane foam bead with 50 % compression

DM 503 mixing and dosing system with 3-axis linear robot for the sealing and bonding of filter frames

Flexible and fully automatic –
fully in line with your requirements

The reference configuration shown here for sealing filter frames with polyurethane foam and bonding filter packs into filter frames using adhesive sealant consists of the DM 503 mixing and dosing system with a 3-axis linear robot and the WT 1-LEVEL shuttle table. Parts are picked up and processed in continuous shuttle mode in one plane. Alternatively, we can offer the WT 2-LEVEL shuttle table with pick-up plates operating in shuttle mode, one above the other in two planes.

The highly dynamic LR-HD 3-axis linear robot used or, alternatively, the highly efficient LR-HE plus ensures that the MK 800 PRO precision mixing head is repeatedly guided accurately over the component. In this process, the FERMAPOR K31 sealing foams are precisely applied to the pre-programmed contour of the filter frame fully automatically and with high dosing accuracy.

After the dosing cycle, the coupling point of the foam gasket closes seamlessly and is therefore almost invisible. The applied material foams, expanding for operating the dosing system to several times its original volume, and forms an elastic soft foam gasket with the desired foam hardness at room temperature.

The 2-component FERMADUR adhesive sealants are applied by the mixing head to the inside surfaces of the filter frame in a process reliable manner. In addition, the good flow properties of FERMADUR ensure that the adhesive is applied to the entire surface. This ensures that the filter pack is optimally bonded and sealed within the frame on all sides.

Our fail-safe mixing and dosing systems can be operated easily and intuitively without the need for extensive training. Thanks to the automatic logging of dosing program data, all process data can be traced and evaluated by the machine operator via the CONTROL 2 operating panel while production is running.

In all solutions, our main focus is on extremely reliable plant engineering, minimized maintenance times and consistent dosing quality. As process experts, we support you with tailored advice for the automation of your manufacturing processes.