ADHESION BETWEEN PAINTS AND WOODEN SUBSTRATES - EFFECTS OF PRETREATMENTS AND WEATHERING OF WOOD

The effects on adhesion between paints and wooden substrates due to pr e-weathering (delay in painting), treatments of wood during pre-weathe ring and the moisture content of substrates were monitored. The adhesi on was studied by means of a torque test. Wooden panels were untreated , or treated with unpigmented, penetrating wood preservatives or treat ed with pigmented stain, and pre-weathered for various periods. The pa nels were then painted and subjected to further exposure. The adhesion of the paints was determined at two relative humidities. Pre-weatheri ng of 12 weeks impaired the adhesion significantly when emulsion paint s were used, and when the wood substrates were untreated or treated wi th the unpigmented treatments during the pre-weathering. When the subs trates were protected with a pigmented stain prior to painting, a long er. delay before painting could be accepted. Also, wood substrates wit h higher moisture contents reduced the adhesion of the emulsion paints .