The research work carried out to date by the Fraunhofer WKI and the Deutsches Textilforschungszentrum Nord-West (DTNW) has demonstrated that intumescent flame retardants have an efficient, flame-retardant effect on materials made from wood and cellulose.
Intumescent coatings expand in the event of a fire, thereby insulating the wood and, as a result, significantly slowing down or stopping the fire. One important functional component is phosphorus compounds. Due to the chemical versatility of phosphorus, these flame retardants can be efficiently synthesized for various applications.
Building on the knowledge already gained, in this project we are investigating the question as to whether it is possible to produce a fire-protection coating for exterior wood on the basis of water-soluble nitrogen-phosphorus silanes (N-P silanes) or cyclophosphazenes (CPZs).
Development goals
Improvement of fire behavior
- The coating is intended to upgrade wood and wood-based materials as far as building material class B (“flame-retardant”) in accordance with DIN EN 13501-1.
Appearance
- The coating should be transparent and not require a topcoat.
- The flame retardant should be permanently incorporated into the coating and not migrate to the surface, so ensuring that the appearance is not impaired.
Durability / Weathering stability:
- The flame retardant should not have a negative effect on hardness and abrasion resistance.
- The durability of the coating should be at least as good as that of commercially available coatings without flame-retardant effect - particularly with regard to the swelling and shrinkage of wood and wood-based materials in dependence on temperature and air humidity.
Processing:
- It should be possible to apply the coating using conventional technologies such as spray application (airless or air-mix), brushing or rolling.
- The application should be carried out in one to two coats.
Environment and health:
- The coating should be free of halogens, chlorine and bromine.
Further fields of application:
The N-P silanes and phosphazenes are to be further developed to such an extent that they can be used not only for wood façades but also in fire-protection coatings for the interior outfitting of buildings (e.g. upholstered furniture, cupboards) or in the transport sector (e.g. cars, trucks, trains, aircraft and ships).