Bio-based flame-retardant coatings for furniture and interior construction using wood and wood-based materials

InnFla – Project start / June 01, 2021

Furniture and construction elements made from wood and wood-based materials are environmentally friendly and extremely popular. Until now, however, there have been no sustainable flame-retardant solutions for wooden surfaces in indoor areas. In collaboration with our project partners, we are developing transparent and colored flame-retardant coatings with a durable fire-protection effect on the basis of renewable raw materials. In doing so, we are expanding the possibilities for interior construction with wood whilst complying with stricter environmental and fire-protection regulations - for example in schools, theaters and airports or in trade-fair construction.

Last modified: June 01, 2021

The photo shows a metallic apparatus in which a piece of spruce plywood is clamped. The piece of wood is being directly flamed by means of a gas flame which is positioned in front of it. On the wood, an oval dark brown patch (charring) is forming in the area of the flame. — © Fraunhofer WKI | Manuela Lingnau
The flame-retardant effect of the new wood coating is tested in the fire laboratory of the Fraunhofer WKI by means of a single-flame test in accordance with EN-ISO 11925-2 - here using the example of spruce plywood which has been treated with a water-based, transparent coating.

Customary flame-retardant solutions are based on intumescent coatings on the basis of melamine-formaldehyde resins. These, however, must be critically evaluated in indoor areas as a result of the potentially carcinogenic formaldehyde emissions. Furthermore, some of the solutions currently in use cause unsightly efflorescence, loss of the durability of the fire-protection effect and, in the worst case, loss of strength due to wood degradation as a result of released acids. Moreover, conventional flame-retardant coatings are based on petrochemical raw materials.

We develop transparent and colored flame-retardant coatings for solid wood, veneer-based materials (molded parts, laminated veneer lumber, plywood) and other wood-based materials which are utilized in interior construction. Both the binder and the flame retardant should have a renewable raw-material content of at least 50 percent. In addition, they should not contain any saline additives. Our aim is to make furniture and construction products made from wood “flame retardant” through the application of our flame-retardant coating.

As the starting materials for the new binder, both established and new bio-based monomers are utilized, such as saccharides. Using these binders, we produce formulations with a fire-retardant effect. The group of substances containing alkoxyamines and alkoxyimides is already being successfully applied as flame retardants for plastics. We are investigating their applicability in wood coatings and are conducting research to determine whether these substances can be synthesized from bio-based building blocks. A further advantage: The utilization of alkoxyamines and alkoxyimides requires smaller quantities of flame retardants than intumescent coatings and other conventional solutions.

The flame-retardant coating should not contain a formaldehyde source or have any other negative effects on indoor-air quality. In terms of resistance to chemicals, abrasion and scratching, it should be able to compete with commercially available products for furniture and interior construction.

We are testing the new flame-retardant coating on traditionally widely-used softwoods such as spruce, pine and larch, as well as on hardwoods such as beech and poplar as these will play a greater role in the future due to climate-related forest restructuring.

Furniture and construction elements made from wood can contribute towards reducing the consumption of finite and climate-damaging raw materials. In interior design, a trend towards visible wood surfaces is emerging. Fire-protection issues are therefore playing a greater role - for example, when a drywall structure is to be planked with wood panels or plywood boards instead of gypsum board or fiber-cement panels. In the case of ceiling elements, doors, and trade-fair and event construction, sustainable materials could also be increasingly utilized if they are flame-retardant.

Products which are used in indoor areas should be low-emission or emission-free. And: Particularly in the case of products made from wood, it is desirable – from the point of view of both users and manufacturers – that the coating is also bio-based. Formaldehyde-free wood coatings on the basis of renewable raw materials are already available on the market – thanks in part to our research. Until now, however, they have not been available with a flame-retardant effect.

Economic advantages

Architectural offices, the construction industry, the furniture industry and trade-fair construction companies can benefit from the expanded design possibilities.

For manufacturers of wooden furniture, new marketing opportunities are being opened up under stricter environmental and fire-protection requirements.

Manufacturers of bio-based monomers as well as paint manufacturers can enhance their product portfolio.

The increasing potential utilization of wood, in particular hardwood, for furniture construction and interior outfitting can provide benefits for the wood-based materials industry and the forestry sector in Germany.

The photo shows an apparatus made from glass, connected to which are an agitator and several hoses. A white mass can be seen in the glass vessel. — © Fraunhofer WKI | Manuela Lingnau
For the production of the new binder, various experiments are conducted in the chemistry laboratory of the Fraunhofer WKI (shown here: emulsion polymerization in the double-wall reactor).

The photo shows a laboratory jar containing a white powder. — © Fraunhofer WKI | Manuela Lingnau
As the starting materials for the new binder, both established and new bio-based monomers are utilized, such as saccharides.

The photo shows a paint can with a whitish-transparent liquid in which a stirring rod is immersed. — © Fraunhofer WKI | Manuela Lingnau
The bio-based binder is intended to enable the formulation of sustainable flame-retardant coatings for wood and wood-based materials (shown here: dispersion of the coating in the dissolver).

Project partners

Research institutes:

Fraunhofer Institut for Wood Research, Wilhelm-Klauditz-Institut WKI (overall coordination)
Fraunhofer Institute for Structural Durability and System Reliability LBF

Industry partners: