Rethinking fire protection for wood-based materials
Riku Salomäki of Kiilto discusses the development of a biobased, intumescent flame retardant chemistry for cellulose-based materials
Softwood plywood manufacturers face a practical challenge when selecting flame retardants( FRs): treatments must deliver fire performance without creating processing issues. Existing FR systems for plywood could leave a sticky surface after drying, creating handling and processing issues.
At the same time, manufacturers are seeking improved performance-to-cost ratios while maintaining the fire- safety characteristics required for demanding applications. To address this, Kiilto launched a three-year development programme of R & D involving hundreds of formulations, laboratory testing, production trials and continuous collaboration between sales, R & D and industrial partners.
Moving beyond legacy formulations
One of the most significant moments in the project came when the team decided to stop attempting incremental improvements to an existing product and focus fully on a new chemical approach. However, making that decision required a growing understanding of how the new chemistry functioned.
Although related concepts had appeared in patents and scientific literature, the underlying mechanisms remained largely unexplained. As a result, the development team had to build its understanding from first principles through experimentation. Many experiments led to dead ends, but accumulated knowledge gradually revealed the direction forward.
The initial inspiration began with reports describing university students who had developed a biobased FR molecule. Having already experimented extensively with biobased materials, there seemed to be potential to build upon similar concepts and pursue new possibilities. That curiosity ultimately produced test results that significantly exceeded the fire performance of Kiilto’ s previous products, providing the confidence to continue development.
A different mechanism
The resulting product family differs from conventional FR systems in several important respects. First, the chemistry can be produced using abundant biobased and mineralbased raw materials, rather than relying predominantly on conventional feedstocks. Second, the system is intumescent, meaning it forms a protective char layer when exposed to fire. During this process, only water and
CO 2 are released. Importantly, the chemistry operates through a different mechanism from the acid-catalysed dehydration reactions that drive many traditional FRs. This distinction illustrates a broader trend within speciality chemicals towards exploring alternative pathways that can achieve fire protection while reducing reliance on established chemistries and materials.
Optimising multiple requirements
Flame retardancy alone is rarely sufficient for commercial adoption. Products must also meet the practical requirements of manufacturing and enduse performance.
In plywood applications, penetration behaviour, drying characteristics and processability can all influence whether a formulation is commercially viable. Thus here are always trade-offs to be accepted. In this case, however, Kiilto was able to optimise penetration, drying performance and fire performance close to their fullest potential.
76 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981