Effect of fire retardants on internal bond strength and bond durability of structural fiberboard

This study evaluated the effect of a number of chemicals on the internal bond (IB) strength and bond durability of phenolic-bonded structural fiberboard (medium density fiberboard) panels. Borax (BX), boric acid (BA), monoammonium phosphate (MAP), diammonium phosphate (DAP), and phosphoric acid (PA) were sprayed onto the fibers made from 50% pine (Pinus nigra Arnold var. pallasiana) and 50% beech (Fagus orientalis Lipsky) woods at 2%, 4%, and 6% retention levels based on oven-dry fiber weight. The panels were tested for unaged IB strength (dry), and IB strength (aged), after cyclic-accelerated aging, according to the procedures defined by European Norm (DIN EN) 321 (1999). Unaged IB and aged IB values of all the treated specimens at three retention levels were significantly decreased when compared to untreated control values. The IB strength and bond durability of all the treated panels decreased with increasing chemical content. BX-treated specimens had the best IB strength and bond durability, followed by DAP-, MAP-, BA-, and PA-treated specimens, respectively.