Bio-Based Polyurethane Foams from Kraft Lignin with Improved Fire Resistance

Effect of Liquid Glass-Modified Lignin Waste on the Flammability Properties of Biopolyurethane Foam Composites

Water-blown biopolyurethane (bioPUR) foams are flammable and emit toxic gases during combustion. Herein, a novel approach suggested by the current study is to use different amounts of lignin waste (LigW), which increases the thermal stability and delays the flame spread and sodium silicate (LG), which has foaming ability at high temperatures and acts as a protective layer during a fire. However, there have been no studies carried out to investigate the synergy between these two materials. Therefore, two different ratios, namely 1/1 and 1/2 of LigW/LG, were used to prepare bioPUR foam composites. The obtained bioPUR foam composites with a 1/2 ratio of LigW/LG exhibited inhibition of flame propagation during the ignitability test by 7 s, increased thermal stability at higher temperatures by 40 °C, reduced total smoke production by 17%, reduced carbon monoxide release by 22%, and increased compressive strength by a maximum of 123% and 36% and tensile strength by a maximum of 49% and 30% at 100 °C and 200 °C, respectively, compared to bioPUR foam composites with unmodified LigW. Additionally, thanks to the sufficient compatibility between the polymeric matrix and LigW/LG particles, bioPUR foam composites were characterised by unchanged or even improved physical and mechanical properties, as well as increased glass transition temperature by 16% compared to bioPUR foam composites with unmodified LigW particles, making them suitable for application as a thermal insulating layer in building envelopes.

Surface Treatment of Mongolian Scots Pine Using Phosphate Precipitation for Better Performance of Compressive Strength and Fire Resistance

Wood, as a naturally green and environmentally friendly material, has been widely used in the construction and decoration industries. However, the flammability of wood poses serious safety problems. To improve the fire resistance of wood, In this study, it is proposed to use calcium chloride (CaCl₂) and disodium hydrogen phosphate (Na₂HPO₄, DSP) to impregnate wood for multiple cycles. The experimental results show that phosphate mineral precipitation can be deposited on the surface of the wood. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) are used to analyze the micromorphology of mineral precipitation and use the MIP test to analyze the treated wood pore structure. The results show that with the increase in the number of cycles, the phosphate deposited on the surface of the wood increases, and the cumulative pore volume and water absorption rate of the wood after 10 cycles are 54.3% and 13.75% lower than that of untreated wood respectively. In addition, the cone calorimeter (CONE) confirmed that the total heat release (THR) and total smoke production (TSP) of wood treated in 10 cycles have decreased by 48.7% and 54.2% respectively compared with the untreated wood. Hence, this treatment method not only improves the mechanical properties of wood. It also improves fire resistance.