Reaction-to-Fire Performance of Steam-Exploded and Suberinic Acids-Bonded Particleboards for Building Façade Applications

Fully bio-based high-density particleboards were produced from wheat straw (WS), grey alder (GA), and softwood (SW) using two manufacturing approaches: steam-explosion-based (SE) binder-less processing and suberinic acid (SA) bonding. The boards were additionally modified with SA-, chitosan-, and earth-pigment-based surface treatments. We evaluated their reaction-to-fire behavior by cone calorimetry at an external heat flux of 50 kWm−2 and by the ISO 11925-2:2020 single-flame source test, using commercial MDF, OSB, and flame-retardant-treated particleboard (PB) as references. Raw material, manufacturing approach, and surface treatment affected different aspects of fire behavior. WS boards generally exhibited the lowest heat-release intensity, whereas SW boards showed the highest peak heat release rates (HRR) and most pronounced secondary HRR maxima. The manufacturing approach most clearly influenced smoke production, with SE boards exhibiting substantially lower total smoke release than SA-bonded boards. Surface treatments affected ignition behavior but produced no consistent changes in total or peak heat release or smoke production. During cone-calorimeter testing, specimen deformation and subsequent flaming of the exposed lower surface were visually observed. They coincided with secondary HRR development, although a causal relationship could not be established. All investigated materials met the applied single-flame source test criteria; only the commercial OSB exhibited sustained flaming after removal of the ignition source. Overall, these material-level results support the further development of fully bio-based high-density particleboards for potential façade applications. However, the fire performance of complete façade systems remains to be evaluated.