Technology for Wood and Natural Fiber-Based Materials

Research Project

Flame Retardants for WPC

There have recently been many enquiries as to whether wood-plastic composites (WPC) can be equipped with a flame retardant. Many construction applications are already subject to legal restrictions pertaining to fire safety. Common flame retardants are detrimental to WPC’s mechanical properties and have to be applied in large quantities to be effective. The aim of this project is to develop new kinds of flame retardants which perform better.

There are legal requirements pertaining to fire safety for flame-proofed floor coverings in the hallways of places such as hotels and shops, places of public assembly, and in publicly-accessible hospital corridors. In terms of quantity, significantly more interesting fields of application are the facades of buildings with more than three storeys and all aspects of trade fair construction. These fields are also subject to legal demands for flame-retardant materials. 

Wood-based materials are classed as “normally flammable” according to DIN 4102-1 (Fire Safety Class B2). The same can also be achieved for WPC terrace deck planks. An improvement of the building material class is desirable in order to expand the range of uses of WPC. Flame retardants which have been used so far are generally detrimental to WPC’s mechanical properties due to the unfavorable interactions the bonding agent (normally maleic anhydride-grafted polyolefin). Another disadvantage of the currently used flame retardants is the very high proportion (up to 40% of the total mass) which is required to achieve the desired flame-retardant effect.

The aim of the research project is to develop flame retardants for WPC which have little or no interaction with the bonding agent and which can be applied in smaller quantities than the current products. Achieving this goal should involve applying the flame retardant to a highly porous base material. Such modified flame retardants can then be applied to the wood particles and/or be mixed into the resin matrix. 

© Fraunhofer WKI
Compounds with flame retardants
© Fraunhofer WKI
Test set-up to ascertain the rate of combustion
© Fraunhofer WKI
Manufacturing flame-resistant compounds
© Fraunhofer WKI
WPC profile extrusion
© Fraunhofer WKI
Combustion shaft test


Official project title:
Verbundvorhaben: Entwicklung von flammgeschützten WPC; Teilvorhaben 1: Biobasierte Polymere, Verbundkoordinierung 

Funding body: German Federal Ministry of Food and Agriculture (BMEL)

Funding reference: 22010212

Project management: Fachagentur Nachwachsende Rohstoffe e. V.

Duration: 01.09.2014 to 28.02.2017

Funded by the Federal Ministry of Food and Agriculture by decision of the German Parliament
Fachagentur Nachwachsende Rohstoffe e. V. (Agency for Renewable Resources)