Properties and materials of window seals

What properties must gaskets have?

Window and door seals have different properties so that the entire window functions properly and no leaks occur:

  • Air tightness: Window seals prevent air from flowing from the outside to the inside or vice versa.
  • Watertightness: Window seals protect against rain and moisture. They seal the joints of the window elements.
  • Weather resistance: High-quality window seals made of TPE or silicone are highly resistant to UV radiation, ozone and temperature fluctuations.
  • Sound insulation: Hollow chamber seals in particular provide sound insulation thanks to their structure and shape.
  • Flexibility: Window seals are subject to many years of strong thermal and mechanical stresses, which is why a certain degree of elasticity must be present to compensate for window elements and gaps.
  • Durability: With the right care and maintenance, window seals have a long service life

Window gasket materials

Window and door seals are largely responsible for the function of building elements. The quality of the seals has been constantly improved in order to meet the high demands in terms of form and function, as well as a longer service life. Sealing material that has become hard or severely deformed has been a thing of the past for many years. New production methods and improved formulations are the reason for this. Here is a selection of different materials used in the manufacture of window and door seals:

TPE (thermoplastic elastomers)

TPE as a material is very popular and frequently used for window and door seals, as the material has good adhesion to many surfaces. The ratio of thermoplastics (plastic) and the softer elastomers (rubber) is adapted and can be easily processed. The material retains flexibility and elasticity even at very low temperatures, while EPDM can become brittle in cold temperatures. In addition to performance, environmental friendliness also plays a role, as the material can be recycled and reused*.

The seals are highly resistant to ageing, weathering, ozone and UV radiation. In addition, the seals are highly compatible with water-thinnable acrylic glazes and paints. Our gaskets in particular are free from additives and plasticizers and have a Shore A hardness of approx. 55° - 60°.

Temperature range: from - 40 °C to + 120 °C
Application: Windows, doors, gates, conservatories, furniture industry, glazing, automotive industry

Properties of TPE:
  • degrees of hardness from very soft to fairly hard can be achieved
  • excellent UV, ozone and weathering resistance
  • marked insensitivity to low temperatures (down to - 40 °C)
  • generally high thermal resistance
  • good electrical insulation
  • good sterilizability
  • insensitive to water
  • easy to color
  • easy to process

Silicone rubber

Silicone rubber is produced industrially. The material is characterized by its stable yet flexible form. Silicone seals offer long-lasting elasticity, are resistant to ageing, UV radiation, temperature and are compatible with water-dilutable and conventional paints. These gaskets are absolutely resilient and therefore provide a reliable seal in various applications*.

Silicone seals are characterized by their long-lasting elasticity and low compression set. This makes them particularly durable and reliable in their function. The high flexibility of silicone ensures that the seals retain their shape even under different pressure loads. This makes them ideal for applications where constant sealing and flexibility are required.

Temperature range: from -50 °C to + 250 °C
Application: Windows and doors of all kinds, conservatories

Properties of silicone window seals:
  • Silicone window seals require no maintenance or additional care
  • the very soft material guarantees minimal closing pressure on your windows
  • very high resistance to ageing in the temperature range of - 60° - + 250° Celsius.
  • the window seals do not stick to the window frame or sash


EPDM (ethylene propylene terpolymer) consists of a synthetic rubber material. EPDM seals are highly resistant to weathering and ozone, have good UV stability, are PVC-free and are compatible with water-thinnable acrylic glazes and paints. The color selection is limited to shades of grey and black. In contrast to TPE gaskets, EPDM has slightly poorer adhesion to surfaces and is less flexible at low temperatures.

Temperature range: from -30°C to + 100°C
Application: Front doors, windows, gates, conservatories, glazing

The quality of window and door seals explained:

Seals are crucial for the functionality of windows and doors. In addition to air and water tightness, protection from the weather and noise reduction, they also reduce noise pollution. High-quality materials such as TPE and silicone provide flexibility and durability, whereas older EPDM seals often became brittle and are not recyclable. Silicone seals are characterized by the particularly durable and long-lasting material and are well suited for retrofitting. The continuous development of materials and manufacturing processes ensures high quality and reliability.

Basically, the functionality of a window depends on the quality of the window seals. In the past, seals were made from APTK / EPDM. APTK stands for ethylene propylene terpolymer rubber and the English name of the sealing material is EPDM (ethylene propylene terpolymer).* This is a synthetic rubber. The properties of this material result from an admixture of carbon black particles in the manufacture of window seals. As a result, these black seals often became brittle, their shape changed considerably and they no longer functioned as window seals. This explains the black streaks in the cloth when cleaning the windows. These window seals made of APTK / EPDM are an elastomer, i.e. chemically reacted and cannot be recycled.

Today, window seals are made from thermoplastic elastomers (TPE). These can be welded, recycled and have a long service life in terms of form and function. It is the classic material for the production of seals for windows and doors.

Silicone window seals are rarely used in the manufacture of windows for cost reasons. They also cannot be welded. However, the advantages of silicone seals are their resistance to weather influences such as strong sunlight, ozone, light, atmospheric pollution and ageing. They remain elastic, colorfast and dimensionally stable in the long term. They also retain their shape when compressed or bent and therefore seal all surfaces perfectly. Silicone window seals are maintenance-free, have excellent temperature resistance and a very long service life. Silicone seals are therefore ideal for retrofitting defective window seals.






Silicone rubber: