Study on some alkoxysilanes used for hydrophobation and protection of wood against decay

Two types of silanes, namely aklylalkoxysilanes and arylalkoxysilanes, were used for wood impregnation aiming at hydrophobisation of the ligno-cellulose material. The suggested mixture of alkyltriethoxysilanes and dialkyldiethoxysilanes improved water repellence when compared to conventionally used silanes. An attempt to immobilise boric acid with the siloxane matrix was also done. Decay resistance of the treated samples was tested by soil-jar test using the brown rot fungus Postia placenta. Features of the impregnated wood such as moisture content, swelling, anti-swelling efficacy and weight percentage gain were not significantly related to the mass loss of samples caused by the fungus. Samples impregnated with EtPhSi(OEt)(2) silanes showed improved durability (3.5-11.5% mass loss). Addition of boric acid to two of the silanols showed the best result for durability of wood, i.e. the lowest mass loss of 2.3 and 1.1%. These treatments upgraded the wood to "very durable", a significant improvement from its natural status, i.e. slightly durable. The studied alkoxysilanes have moderate ability to penetrate the wood cell wall and hence to improve its hydrophobicity. These silanes are promising although more research should be carried out on the degree of oligomer polymerisation in the wood cell wall. (C) 2009 Elsevier Ltd. All rights reserved.