Effects of glycol on leachability and efficacy of boron wood preservatives

Although boron has many advantages as a wood preservative, this chemical pe rforms poorly in leaching exposures. In this study, we investigated the pot ential for decreasing the leachability of boron preservatives with polyethy lene glycol (PEG). Southern pine (Pinus spp.) test samples impregnated with combinations of sodium berate or boric acid and PEG were subjected to both leaching and decay tests. Samples treated sequentially with sodium borate or boric acid and then with PEG-400 or PEG-600 showed a significantly incre ased resistance to boron leaching. However. decay tests indicated that bloc ks treated with sodium berate or boric acid and PEG experienced slightly hi gher weight losses at nearly all retention levels, possibly as a result of PEG depletion. Thus, although the results suggest that bulking agents may e nhance the resistance of boron to leaching, the enhanced leach resistance m ay be a temporary effect.