Initial Screening Trials of Some Quaternary Ammonium Compounds and Amine Salts as Wood Preservatives

Nineteen quaternary ammonium compounds, one polymeric biocide, and salts of three tertiary amine compounds were screened for effectiveness in preventing decay of Pinus radiata sapwood by three basidiomycete fungi (Gloeo hyllum trabeum, Poria placenta, and Fomes gilvus). In general tertiary amine salts were more effective than quaternary ammonium salts. The chloride and formate salts of dimethyl lauryl amine prevented decay by all three test fungi when used at 0.25% a.i4 solution strength, indicating a toxic threshold below 1.6 kg/m (0.1 lb/cu ft). Alkyl trimethyl ammonium chlorides and dialkyl dimethyl ammonium chlorides and toxic thresholds in the order of 1.6 – 3.2 kg/m3 (0.1 -0.2 lb/cu ft). Most other quaternary ammonium compounds were effective at retentions of 3.2 – 6.4 kg/m3 (0.2 – 0.4 lb/cu ft). In general, toxicity of the quaternary ammonium compound was lost if the alkyl chain length was short (C2) or long (C18). Such compounds, together with the polymeric biocide, did not prevent decay when used at 2.0% a.i. solution strengths (wood retention of 12.8 kg/m3).

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