Expandable graphite is produced by embedding defined compounds in the layer structure of natural graphite. The most outstanding property of expandable graphite is its expansion in heat: At high temperatures, expandable graphite expands to a maximum of 300 times its original volume, depending on the embedded compounds.
The use of expandable graphite for flame-proofing takes advantage of this expansibility.
Triggered by the flame temperature, the expandable graphite used in the product expands and creates an insulating layer between the fire load and the fire.
Additionally, the large surface of the expandable graphite uses the surrounding oxygen through its chemical reaction with CO₂, thus creating an additional inert gas shield for the fire load.   

Previously, this solution offered great advantages, but also problems regarding its use in latex:

• The addition of dry expandable graphite to the latex compound created a dust burden, while the homogeneous dispersion of the particles in the compound posed an additional problem due to the insufficient wetting behaviour.
• Expandable graphite often has low pH values, which can promote coagulation.
• If the expandable graphite is predispersed in water, the necessary dosages lead to excessive water induction into the compound with the corresponding shrinkage of the finished product and an energy-intensive drying process.

Emtex® L 7709-1  –  easier to process, lower dosage

The new Emtex® L 7709-1 based on expandable graphite is a coated powder, which eliminates the problems stated above and makes it highly suitable as a flame-proofing component in latex foam products:

• The use of a special neutralized raw material achieves a pH value within the specific range of latex compounds. The influence on processing characteristics such as gelling time, gelling behaviour and vulcanisation is minimal.
• The high content of >90% expandable graphite in Emtex® L 7709-1 allows for a low dosage with little water induction into the compound.
• The surface modification causes very good dispersion behaviour with a low dust burden during the compounding process.
• Due to the careful selection of the raw material, the finished product contains only a low dosage of expandable graphite, resulting in a minimal influence of the “filler” on the mechanical properties of the latex foam.

Do you have any questions or suggestions regarding our Emtex® L 7709-1?
Please contact us!

Weserland – Join The Success             07/2008