Differences in simultaneous thermal analysis and time-to-ignition of wood materials treated with water glass flame retardants

The paper investigates efficiency of silicate flame retardants on wooden fibres (used for production of medium-density fibreboards) and spruce boards. A simultaneous thermal analysis and cone calorimetry are used for the assessment. Specimens are treated with three different types of silicate water glass: sodium silicate, potassium silicate and modified silicate. Along with these, one sample of untreated fibres is tested in order to provide a base sample. As a result of simultaneous thermal analysis, the ability of the treatments to increase the residual amount of biological char in samples during pyrolysis and ability of the flame retardant to penetrate these wood fibres is used to assess the efficiency of each flame retardant on the wood fibres. Modified silicate showed best results in binding to the wood fibres achieving 63.33 % of the mass of the residual biochar, however sodium silicate appeared to be the most efficient treatment acquiring 34.14 % of the former fibre mass of the sample in the residual biochar. All the treatments decreased the onset temperature of pyrolysisin fibres. Cone calorimeter tests showed decrease of the critical heat flux compared to untreated specimen from 11 kW/m² estimated for
untreated specimens to 9 kW/m2 for sodium silicate and 8 kW/m2 for modified silicate and potassium silicate. Accelerated carbonization in the treated spruce specimens was observed for high heat flux rates.