Coating performance on glutaraldehyde-modified wood

Scots pine (Pinus sylvestris L.) panels were modified with glutaraldehyde (GA) to various weight percent gains and subsequently coated with several commercial coatings. The drying rate and adhesion of the coatings on the modified wood were measured; the coated/modified woods were exposed outdoors to analyze how the wood modifications influence the coating deterioration. The results showed that GA modification caused an increase in the drying rate of the waterborne coatings, but had no influence on drying of tested solvent-borne coatings. GA-modification did not change the dry adhesion but reduced the wood strength in a pull-off test. Wet adhesion of waterborne coatings was improved, while that of the solvent-borne coatings tended to be somewhat reduced. During 22months of outdoor weathering, the coated/modified samples exhibited lower moisture content than the coated/unmodified samples, but GA modification didn't contribute a substantially synergistic effect with surface coatings on resistance to weathering.