Tailor-made chemistry for growing requirements.

FERMAPOR® K31 is Sonderhoff Chemicals’ brand name for the 2-component polyurethane systems used for the production of mixed-cell, flexible foam seals.

They are directly foamed onto the part with the aid of mixing and dispensing systems and FIPFG sealing technology (Formed-In-Place Foam Gasket).

Chemical constituents

FERMAPOR® K31 systems consist of a basic resin (A-component) and a hardener (B-component) which are mixed to a prescribed ratio and react together in the dispensing head’s mixing chamber. After application to the part a soft foam seal forms in a few minutes with an even distribution. The flow behaviour, reactivity and colour of the components of FERMAPOR® K31 seals are freely adjustable depending on the intended use. Depending on the recipe, FERMAPOR® K31 foam seals can take from approx. 20 minutes up to about 12 hours to cure fully at room temperature on the part. After this, construction can continue.

The sealing function is reached with a compression of approximately 30-60% of the cured seal. In this way the part is protected from damp, dust and the influence of the weather.

Broad range of properties

Mixed-cell FERMAPOR® K31 polyurethane foam seals have a broad profile of properties, combining the positive sealing qualities of closed-cell systems, e.g. low water uptake, with the low construction forces of open-cell systems. Polyurethane foam seals are used mostly in a temperature range from -40°C to about +100°C, though in the short term temperatures up to +160°C are possible.

Numerous product properties in the FERMAPOR® K31 family

Depending on customer requirements, FERMAPOR® K31 can cover many different characteristics. For this, many different Fermapor® K31 family recipes are available; combinations of disparate characteristics within a single recipe are rather exceptional.

Physical and chemical Properties*
Property FERMAPOR K31
Appearance black or grey, other colours upon request
Hardness from 5 Shore 00 to 40 Shore A possible
Compression load deflection (25% compression) 5 kPa to 200 kPa
Density from 0,1 g/cm³ to 0,6 g/cm³
Temperature resistance from – 40 °C to + 100 °C (short time up to + 160 °C)
Tensile strength up to 2 MPa [N/cm²]
Elongation at break up to 400 %
Compression set (DVR) > 97 % depending on test conditions
Water absorption from < 3,5 %, hydrophobic versions available
Flame retardancy up to UL-94 HF-1 possible

E.g. antimicrobial finish, lubricated, suitable for food packaging, up to IP68 protection class, up to NEMA 12 protection class, low fogging, special foam systems with outer elastic protective layer possible

Special properties for special requirements

Sonderhoff has access to the experience of more than 1000 FERMAPOR® K31 recipes, the result of catering to many diverse customer specifications.

We offer you a wide spectrum of different product properties suited to the varying usage conditions and quality requirements of your components. The FERMAPOR® K31 foam sealing systems are characterised by a very broad profile of properties for the most varied part applications.


Reliability through FIPFG dispensing technology application

The FERMAPOR® K31 sealing foams can be efficiently and accurately piped on to parts from the most varied of branches of industry using the FIPFG (Formed-In-Place Foam Gasket) technology and mixing and dispensing systems by Sonderhoff. Depending on the viscosity, they are either freely applied to the surface of the part as a paste or poured in fluid form into a groove.

Only with the exact interplay of the most variable set-up parameters and additional functions of the mixing and dispensing machines, the exact calibration of the part and FERMAPOR® K31 foam seal within the complete construction and the right material choice, can a truly secure seal of industrial components for the most varied uses against damp, dust and other environmental influences be achieved.

FERMAPOR® K31 – the reaction process

FERMAPOR® K31 polyurethane-based sealing foams consist of a fluid-to-paste-like A-component (polyol) and a hardener, the B-component (MDI, isocyanate). The reaction is begun with the mixing together of A and B, resulting in the uniform progress of a chemical reaction at room temperature. Thereby, the applied mass foams up into an even, mixed-cell soft foam seal.


FERMAPOR® K31 – the reaction process
Mixing time: Time period in which the A and B components are mixed.
Reaction time: tTime period in which the FERMAPOR® K31 foam system begins to react (after approx. 15 – 60 seconds).
Rise time: Time period in which the FERMAPOR® K31 foam system expands to form the seal body (after approx. 15 – 180 seconds).
Tack-free time: Time after which the seal surface of FERMAPOR® K31 foaming systems is tack free at room temperature and can be touched without causing damage (after approx. 2 – 20 minutes).
Assembly time: The time point after which FERMAPOR® K31 foaming systems can bear loads or the sealed components can be assembled (after approx. 20 minutes – 12 hours).

FERMAPOR® K31 – The great application diversity

The FERMAPOR® K31 pallet offers effective seal protection for a wide range of application areas and requirements. In the table you will find a selection of foam sealing systems for various industries, from lighting to switch cabinet and automotive construction, to filters, packaging and the household appliance industry.

Fermapor® K31
Application area* Viscosity
Shore 00
Other properties
A-9854-7 Lighting 900 - 1.200 30 - 45 0,30 - 0,40 self-levelling, high tightness, very good compression set
A-9652-11-VP2 Lighting 1.000 - 1.600 30 - 45 0,20 - 0,40 spec. product for moisture-proof luminaires, good levelling
A-9020-5 Enclosures 45.000 - 65.000 45 - 55 0,25 - 0,30 UL-50 listed and good adhesion to paint
A-9021-2-VP1 Enclosures 37.000 - 52.000 35 - 50 0,25 - 0,35 UL-50 and UL-94 HBF listed
A-9230-2-VP Enclosures 40.000 - 50.000 55 - 65 0,30 - 0,40 UL-50 listed, hydrophobic, good compression set / adhesion to paint
A-9160-VP3 Enclsures 18.000 - 22.000 43 - 53 0,20 - 0,30 high mech. strength, low friction, optimized against shear stress
A-9025-2-VP2 Enclosures 38.000 - 50.000 25 - 40 0,20 - 0,30 ultra soft, UL-50 listed, good adhesion to paint
A-9550-VP2 Enclosures 2.000 - 4.000 40 - 50 0,22 - 0,40 special product for high-pressure dispensing machines
A-9020-15-F Filters 50.000 - 65.000 50 - 60 0,20 - 0,30 antimicrobial, qualified for air conditioning plants
A-9020-VP299-1 Filters 58.000 - 68.000 45 - 57 0,25 - 0,40 or inverse height/width ratio
A-9808 Filters 800 - 2.000 40 - 50 0,20 - 0,35 for smallest groove applications (2 mm)
A-9675-2-VP Automotive 1.000 - 2.500 35 - 75 0,25 - 0,50 high tightness, hydrophobic, extremly good compression set
A-9260-2 Automotive 40.000 - 60.000 20 - 30 0,15 - 0,30 very soft, low assembly force
A-9308-5-VP5 Automotive 130.000 - 200.000 35 - 45 0,25 - 0,40 product for upside-down application, high mech. strength, hydrophobic
A-9675-20-VP3 Automotive 1.500 - 2.500 44 - 55 0,35 - 0,60 special product for high-pressure dispensing machines
A-9212-3-VP Automotive 53.000 - 65.000 50 - 65 0,35 - 0,50 high tightness, hydrophobic, extremly good compression set
A-9199-29-VP3 Automotive 45.000 - 60.000 20 - 35 0,20 - 0,30 high tightness, low assembly force and high mechanical strength
A-9199-28-VP4 Automotive 35.000 - 45.000 40 - 70 0,30 - 0,50 good adhesion to galvanized surfaces, hydrophobic
A-9575-3 Automotive 1.000 - 1.500 40 - 70 0,30 - 0,50 special component for automotive lighting products
A-9575-3LE Automotive 1.000 - 1.500 60 - 70 0,35 - 0,50 low emission, approved according to VW50180, VDA277 / DIN75201-B
A-9828-1 Packaging 1.800 - 2.700 60 - 75 0,30 - 0,40 highly elastic, for highest tightness requirements, good compression set
A-9843-8-VP2 Packaging 7.000 - 15.000 55 - 75 0,30 - 0,40 good cost performance ratio, good compression set
A-9762 Packaging 5.000 - 8.000 60 - 75 0,25 - 0,40 approved for food packaging
A-9370-VP5 Appliances 60.000 - 80.000 7 - 30 0,15 - 0,35 hypersoft, for use at ceramic stove tops

* The description of the possible fields of use of our products as well as the technical data and values only have a general character and do not mean that a certain product can be used under all conditions in the respective field of use. In this respect, the stated field of use is not a binding specification or usage provision. Due to the great number of environment variables and their influences (e.g. temperature, test specimens, size, interaction with substrates, influence of machines, or the like) you as our customer must check whether the product is suitable for your specific field of use. We will be pleased to assist and advise you in this respect.


Good reasons for using FERMAPOR® K31 *


  • FERMAPOR® K31 systems are the most suitable for sealing industrial parts
  • The use of FERMAPOR® K31 systems is possible for almost every shape and seal geometry
  • FERMAPOR® K31 systems achieve particularly good adhesion to parts due to the chemical reaction of the two components on the carrier material
  • FERMAPOR® K31 systems possess exceptional long-term behaviour and display almost 100% resetting ability, even after many years of continual use
  • FERMAPOR® K31 systems will become tack-free at room temperature in 2 – 20 minutes and an oven can reduce the reaction time considerably, but it is not a necessity
  • With FERMAPOR® K31 systems even large part tolerances can easily be compensated for
  • The FERMAPOR® K31 systems develop a cross-linked structure which is extremely resistant to environmental effects such as humidity, dust and temperature
  • With FERMAPOR® K31 systems also sealing foams with ultra softness are possible
  • FERMAPOR® K31systems are processed using two component metering units and can be adapted flexibly and quickly to other parts at any time
  • By using FERMAPOR® K31 systems even small product series become profitable