Comparative analysis of wettability with fire retardants of Poplar (Populus cv. euramericana I214) and Scots pine (Pinus sylvestris)

Abstract The research question of this study has been: does a good wetting with fire retardants mean a good fire retardancy of scots pine (Pinus sylvestris) and poplar (Populus cv. euramericana I 214) particles, used for CBPB. There are several FR's available, and the presumption has been made, that good wetting FR's offer good fire resistance. Wettability has been evaluated by contact angle measurement, with the FR's themselves: Borax (Na2B4O7), DSHP (Na2HPO4), DAHP ((NH2)4HPO4) and DW as reference. Fire performance was investigated with calorimeter test. High concentration of the FR resulted significant differences in the contact angle values of sanded, sawn and planed poplar surfaces, indicating that roughness has a strong influence when the concentration of the FR is high. With increasing concentration of the FR the wettability of poplar gets worse, whilst the wettability of scots pine remains unchanged. Increasing concentration of FR improves the fire resistance of poplar. This contradicts our original presumption. Good wetting FR, doesn't result good fire resistance. Contact angles of Poplar are significantly higher, irrelevant from machining type, relative to Scots Pine. The best fire resistance has been achieved on poplar, and in case of both species by high concentration DAHP and DSHP.