Back to search

BIONÆR-Bionæringsprogram

FireCellCoat - Bio-inspired fire retardant wood coatings based on microfibrillated cellulose

Alternative title: Bioinspirerte brannbeskyttende overflatebehandlinger basert på mikrofibrillert cellulose

Awarded: NOK 3.5 mill.

Wood has recently experienced a renaissance as construction material in Europe, but its usage in medium and high-rise buildings being typical for urban areas is still low. One reason for this is wood’s deficiency regarding fire safety. Although novel construction methods and fire safety designs have widened the field of applications of wood during the last years, architects and engineers still face challenges. Protection measures like fire stops, sprinklers, or smoke detectors can aid to reduce the spread of fire; yet, such means alone are often not sufficient or cannot be fully utilized in a building project, which makes a fire-retardant treatment of wood necessary. Fire-retardant treatments facilitate considerable improvements of the fire properties of wood-based products, and the highest fire classification for combustible products can be obtained. However, a significant drawback of most fire retardants is their low humidity resistance, tendency to leaching and environmental and toxic profile. The main objective of the FireCellCoat project is to develop fire-retardant coatings based on functionalized microfibrillated cellulose (MFC) using high consistency enzymatic fibrillation (HefCel) from the project partner VTT. The project is inspired by the architecture and chemistry of Canary pine bark, which efficiently protects the trees against forest fires. FireCellCoat’s bionic approach is to construct a similar macro-scaled multi-layer structure like that of Canary pine bark. This coating is meant to be used for interior applications as the MFC-based multi-layer structure may allow to obtain a high water vapor permeability, which in turn would maintain wood’s positive characteristic to buffer relative humidity and thereby improve indoor air quality. Two other approaches are to either use phosphorylated MFC as additive in acrylic coatings or to bind it to the binder by polymerization. Especially polymerization is promising as it may counteract leaching of fire-retardant actives in exterior applications like façades. During the first to years, different methods of functionalizing MFC with phosphor have been investigated. This included both, modification directly in the production process of MFC (in-situ modification) and subsequent modification (post-treatment modification). The stepwise approach turned out to be most promising, resulting in a notably high yield (solid content of 25%) and low energy consumption (0.6 MWh/t). Initial investigations showed that phosphorylation of MFC reduces coating adhesion. Fluidization combined with a bi-layer structure consisting of MFC and phosphorylated MFC was eventually found to decrease flaking of the coating. The fire-retardant properties of phosphorylated MFC coated spruce were improved compared to uncoated references. The coated wood showed self-extinguishing behavior during ?ammability tests and did not ignite as quickly when subjected to the cone calorimeter heat ?ux. The coatings were also found to delay the heat release. Best results were obtained in combination with inorganic plates in the multi-layer structure. However, the MFC-based coating for interior applications does not perform as well as commerical fire retardant coatings and ,thus, needs further optimization. Experiments on moisture-related properties confirmed our hypothesis that MFC-based coatings maintain wood’s positive property of moderating humidity variations in indoor air. In addition, exterior coatings have been developed with the aim to incorporate high amounts of phosphorylated MFC in acrylic coatings. The application of mini-emulsion polymerization allowed to increase the amount to 15%. Preliminary results after 9 months of natural weathering in Norway and Germany indicate good resistance of the developed exterior coating. However, different fire tests have shown that the amount of phosphor must be considerably increased to obtain fire retardancy. During the remaining project time, the moisture-related properties of the new coatings will be studied in detail. Another focus will be to further increase the amount of phosphorylated MFC in the products and to improve the adhesion properties of the interior product. In additon, environmental and economic assessments of wood treated with the newly developed systems are in progress. FireCellCoat can be followed on the project website (www.firecellcoat.com) and accounts on Twitter, Facebook and LinkedIn.

-

Wood has recently experienced a renaissance as construction material in Europe, but its usage in medium and high-rise buildings typical in urban areas is still low, which in particular is restricted by wood’s deficiencies regarding fire safety, but also due to biodegradation and color stability issues. Although novel construction methods and fire safety designs have widened the field of applications of wood during the last years, architects and engineers still face challenges. Protection measures like fire stops, sprinklers, or smoke detectors can aid to reduce the spread of fire; however, such means alone are often not sufficient or cannot be fully utilized in a building project, which makes a flame-retardant treatment of wood necessary. Flame retardant treatments facilitate considerable improvements of the fire properties of wood-based products and the highest fire classification for combustible products can be obtained. However, a significant drawback of most fire retardants is their low humidity resistance, tendency to leaching and their environmental and toxic profile. The FireCellCoat project will solve these challenges through using modified cellulose as non-leachable fire retardant component for wooden surfaces. The project is inspired by the architecture and chemistry of Canary pine bark - nature’s outstanding solution against fire. Our approach is to construct a similar macro-scaled multi-layer structure, which is able to delay ignition and fire propagation. Micro-fibrillated cellulose (MFC) will be used in combination with inorganic components. This will be complemented by a chemical approach involving co-polymerization techniques to protect the fire-retardant material against leaching from the coatings.

Funding scheme:

BIONÆR-Bionæringsprogram