Mineralization of wood by soluble carbonate based compounds for improved essential properties Z4-9298
Due to its unique properties wood is considered an important sustainable material. Unfortunately, it is flammable and susceptible to degradation by a wide variety of microorganisms, water and ultraviolet radiation. To improve wood’s reaction to fire, many approaches have been proposed so far, including addition of fire-retardants, deposition of flame retardant coatings or the development of wood composites. When burning some fire retardants release toxic and carcinogenic substances. Therefore their use is progressively restricted and prohibited which opens new opportunities for development of non-toxic and "eco-friendly" alternatives. A promising direction is mineralization of wood by incorporation of metal carbonates or hydroxides. Upon their endothermic decomposition non-flammable gases, CO2 and H2O, are released, which leads to dilution and cooling of flammable combustion products. Recently two promising procedures for incorporation of CaCO3 into the wood structure have been proposed. The first is based on a solid-exchange process by alternating solution-exchange cycles with CaCl2 in ethanol and NaHCO3 in water and second on alkaline hydrolysis of dimethyl carbonate in the presence of calcium ions inside the cell wall structure. The main disadvantage of both methods is that they are time consuming and involve formation of harmful by-products, such as NaCl and methanol. The former causes corrosion of metal objects, which are often incorporated in wood, while the latter is harmful to the environment.

In the present project we will develop a new method for integrating carbonates (CaCO3, MgCO3 and SrCO3) and hydroxide (Al(OH)3) into the wood structure based on deep impregnation with soluble organic compounds in order to improve wood’s reaction to fire and durability. The principle is based on the decomposition of soluble organic compounds in the wood structure in the presence of water into carbonate/s or hydroxide with no harmful by-products. The proposed method signifies a simple, ecologically friendly and more effective mineralization of wood in a comparison to the traditional incorporation of carbonates. The main objective of the project is to obtain and deepen the knowledge about wood mineralization procedures. In particular we will evaluate the effect of proposed mineralization process on essential properties of wood, mainly its reaction to fire and determine the mechanisms of action of incorporated carbonates and hydroxides. A combination of vacuum and pressure will be used for wood impregnation. For selected wood species, i.e. spruce and beech, we will determine: (i) the optimal impregnation parameters for deep penetration and high retention of impregnation solution, (ii) optimal drying mode of impregnated wood samples and (iii) the optimal impregnation formulation. The evaluation of suitability of proposed impregnation formulation/s regarding efficiency and toxicity will be evaluated as well. For evaluation of the wood mineralization advanced research equipment will be used, such as TG/DTA coupled with GC-MS, SEM, FE-SEM, µCT, FTIR, XRD, gas sorption, cone calorimetry, etc.

Post-doc research project
Financing: Slovenian Research Agency, SRA
2018 0,5 FTE (B), 2019 1 FTE (B), 2020 0,5 FTE (B)

Link to SICRIS
2018/07/01 - 2020/06/30