Silicone systems for extreme usage conditions

FERMASIL® is our brand name for 2-component silicone systems for the production of silicone foam seals and soft elastic silicone elastomers, used for the potting and gluing of components.

FERMASIL® is applied using FIPFG dispensing technology (Formed In-Place Foam Gasket) (Formed In-Place Foam Gasket) directly to the part and cures there at room temperature.

Chemical constituents

FERMASIL® silicone systems consist of an A-component and a cross-linking B-component, which are processed in a given mixing ratio in the mixing chamber of the dispensing head. Most FERMASIL® systems react at room temperature of their own accord after the mixing of the components and create, according to the recipe, flexible silicone foam seals or permanently elastic silicone elastomers.

FERMASIL® systems are processed using 2-component low pressure mixing and dispensing systems. Both dynamic mixing systems and static mixers are suitable for the mixing. Sonderhoff recommends dynamic mixing systems for material-friendly processing.

Physical and chemical Properties*
Appearance white, grey or black, other colours upon request (also transparent)
Hardness gel-like up to 80 Shore A possible
Compression load deflection (25% compression) 20 to 150 kPa
Density from 0,3 g/cm³ to 2 g/cm³
Temperature resistance from -60° C to +180° C (short time up to +350° C)
Tensile strength up to 4,5 MPa [N/cm²]
Elongation at break up to 600 %
Compression set (DVR) > 97 % depending on test conditions
Water absorption < 1 %
Flame retardancy up to UL-94 HF-1 possible
Viscosity of the A component: from 1.000 mPa·s (liquid) to 500.000 mPa·s (highly pasty)

UL50 conformity, UV resistant, low fogging, good chemical resistance, if requested IP 69K ingress protection class and NEMA 4-6p protection class are possible. Customized developments can be agreed any time on request.

Broad spectrum of characteristics of FERMASIL® systems

Depending on customer requirements, FERMASIL® systems can express many different characteristics. Different part applications are protected effectively in extreme surroundings. Numerous FERMASIL® product family recipes are available for this..

High temperatures

The different softness grades and flexibilities of FERMASIL® silicone systems are maintained even at long-term temperatures of -60 to +180°C, in special cases to 250°C, and for short periods even to +350°C.

Very low water absorption (<1%)

Because of the closed-celled structure of silicone foams, they are tropicalised and wet room safe; infiltration protection to IP 69K and NEMA 4-6p are possible.

High chemical resistance

FERMASIL® silicone systems are resistant to many chemicals (e.g. Common cleaning materials, alcohols, dilute acids and alkalis, brake fluids, oils and lubricants, coolants) and are low-fogging.


Ease of flow, reactivity and colour can be multifariously varied.

Curing at room temperature

FERMASIL® silicone foams cure on the component at room temperature in a time range from approx. 20 minutes to around 12 hours, becoming a soft foam seal. The part can then be sent on to further processing.

Crystal clear or translucent silicone potting

Temperature stable to 180°C, very high tear resistance and flexural strength (example extension at break 600%), UV-stable

Flame protection in accordance with UL 94 HF-1

FERMASIL® silicone systems can be equipped with UL 94 HF-1 flame protection; any flame after this is extinguished within 10 seconds, with max. 30 seconds’ afterglow.

ATEX approval

For FERMASIL® silicone foam seals, an ATEX approval for component applications in explosive environments e.g. mining, oil drilling is possible.

FERMASIL® – the technology

FERMASIL® sealing foams can be efficiently and accurately piped onto 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.

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 ensure truly secure sealing of industrial components for the most varied uses against damp, dust and other environmental influences is achieved.

FERMASIL® – the reaction process

The reaction of FERMASIL® sealing foams is begun by the mixing of the A and B components. The reaction progresses evenly from this point at room temperature. The applied mass thus foams up into an even, closed-cell soft foam seal.

reaction process
FERMASIL® – The foaming process
Mixing time: Time period in which the A and B components are mixed.
Reaction time: Time period in which the FERMASIL® foam system begins to react (after approx. 15 - 60 seconds *)
Rise time: Time period in which the FERMASIL® foam system expands to form the seal body (after approx. 60 - 180 seconds *)
Tack-free time: Time after which the seal surface of FERMASIL® foam systems is tack free at room temperature and can be touched without causing damage (after approx. 2 - 30 minutes *)
Assembly time:

Time point after which FERMASIL® foam systems can bear loads or the sealed components can be assembled (after approx. 20 minutes - 12 hours *)

* depends on the temperature conditions

FERMASIL® – The great application diversity

The FERMASIL® pallet offers effective component protection for the most diverse requirements for sealing, gluing and potting. In the table you will find a selection of different silicone systems for various industries, from lighting to control cabinet and automotive construction, to electronics, packaging and white goods.

Shore 00
Other properties

2C addition curing

FERMASIL® 1809-1


Distance sensors

(Shore 00)
0,70Slightly foamed, liquid silicone system, particularly suitable for ultrasonic sensores – good ratio between resonance and absorption behaviour


Drive belt covers

> 100.00070
(Shore 00)

Highly viscous, stable, medium hardness, curing possible without heat treatment

FERMASIL® 5020-1


Linear luminaires, e-boxes, packaging, electric enclosures

approx. 15.00050
(Shore 00)
0,30Liquid, good fl ow, curing possible without heat
treatment, lights with Atex approval


Potting of electronics, battery packs, potting of sensors, potting of PC boards

(Shore A)
1,00very good dielectric properties, good fl ow rating, color and reactivity are adaptable to costumers’ wishes, by changing the mixing ratio also able to process gel-like.


Packaging covers in contact with
food, Food-Boxen

> 10.00020
(Shore A)
1,10Soft elastomer seal with good mechanical properties
A-9160-FERMASIL® 5515E-1-G


Food-Boxes, packaging
covers in contact with

approx. 10.00025-55
(Shore A)
1,25Use in contact with food is possible, fast curing, good mechanical properties
FERMASIL® 6505-1

Electric enclosures

E-boxes, electric enclosures,
ultrasonic sensors

approx. 10.00060
(Shore 00)
0,40Liquid, PTB approved in electric enclosure applications
FERMASIL® 60C0-1Electric enclosures> 100.00060
(Shore 00)
0,35Thixotropic, stable, standard material with medium hardness, UL50E listed
FERMASIL® 6590-1-G

Electric enclosures

Electric enclosures with
ATEX approva

> 100.00060
(Shore 00)
0,35UL50E listed, thixotropic, stable, curing possible without heat treatment

2C condensation curing


Household ,

ceramic glass sealings,
splash guard in the engine

> 60.00025
(Shore 00)
0,45alkoxy cross linking, no corrosive fi ssion products while curing, very soft foam seal
* 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 FERMASIL® *

  • FERMASIL® systems can be used by a constant temperature up to +180°C (special types up to 250°C) and temporary up to +350°C.

  • FERMASIL® systems are closed-cell and therefore do not absorb water.

  • FERMASIL® systems are highly resistant to many chemicals.

  • FERMASIL® systems are hydrolysis stable and therefore suitable for the use in tropic or damp rooms.

  • FERMASIL® systems keep greatest possible flexibility even down to -60°C.

  • FERMASIL® systems are tack free in 2 - 30 minutes which depends on the thermal condition. An oven can reduce the reaction time considerably, but it is not a necessity in all cases.

  • FERMASIL® systems are processed using two component metering units and can be adapted anytime flexibly and quickly to other components to be sealed.

  • FERMASIL® systems develop a cross-linked structure which is extremely resistant to environmental effects such as humidity, dust and temperature.

  • FERMASIL® systems possess exceptional long-term behaviour and have almost 100% resetting ability, even after many years of continual use.

  • FERMASIL® systems are suitable for direct contact with food in some cases.