# Enhancing Fire Resistance and Mechanical Properties of Wood Strand Boards by Impregnation with Sodium Bicarbonate and Sodium Borate

## TL;DR

This study shows that treating wood panels with sodium bicarbonate and sodium borate improves fire resistance and maintains mechanical strength, offering a safer and more sustainable option for wood-based materials.

## Contribution

The novel contribution is demonstrating a synergistic halogen-free treatment combining sodium bicarbonate and sodium borate to enhance fire resistance and mechanical properties of wood panels.

## Key findings

- Treatment reduced mass loss by 38% and flame spread speed by over 50% in fire tests.
- Thermal stability improved with char residue increasing from 16.9% to 31.5%.
- Internal bond strength increased by 16%, while modulus of rupture and elasticity were slightly affected.

## Abstract

The development of halogen-free flame-retardant formulations for wood-based panels is a promising strategy to improve both fire safety and environmental performance. In this study, oriented strand boards (OSB) were impregnated with aqueous solutions of sodium borate (SBo) and sodium bicarbonate (SBi) to evaluate their combined effects on fire resistance and mechanical properties. Fire performance was assessed using the ASTM D3806 small-scale tunnel test, while mechanical and physical properties were measured according to ASTM D1037. Significant improvements in fire performance were observed: mass loss (ML) during flammability testing decreased by 38% (from 6.9% to 4.3%), flame spread speed (FSS) was reduced by more than 50% (from 6.8 to 3.3 mm/s), and after-flame times (AFT) dropped from 17.2 s to 0 s. Thermogravimetric analysis (TGA) further confirmed enhanced thermal stability, with increased char residue (from 16.9% in untreated boards to 31.5% in treated ones). Mechanical testing revealed a 16% increase in internal bond (IB) strength (from 0.44 to 0.51 MPa), while modulus of rupture (MOR) and modulus of elasticity (MOE) were only slightly affected (decreased by up to 4.2% and 3.6%, respectively). Interestingly, the two additives exerted contrasting effects: SBo reduced strength and bonding performance, whereas SBi improved internal bond strength and dimensional stability. The optimal balance was obtained with treatment P250-50 (250 g SBi and 50 g SBo), which combined enhanced fire resistance with acceptable mechanical integrity. Overall, the results demonstrate that the synergistic use of SBo and SBi offers an effective halogen-free approach to simultaneously enhance the fire resistance and mechanical performance of OSB panels, highlighting its potential for industrial applications.