Phenol-formaldehyde-resin treatment of Scots pine sapwood for the reduction of resin exudation through coatings

ABSTRACT

Brown discolouration caused by resin exudation from knots is a problem for a range of light-coloured painted pines, and will negatively affect the appearance of the finish. To solve this problem, a hot-and-cold bath impregnation process of wood prior to painting was tested. Sawn timber, 18 × 120 mm in cross-section dimension, were heated in an oven and then immediately immersed in a cold liquid containing a phenol-formaldehyde-based solution, filling a 1–5 mm thick layer beneath the surface with phenol-formaldehyde. After curing, the timbers were painted with a white coloured coating system intended for exterior use, and tested in artificial weathering test (QUV). The phenol-formaldehyde treatment greatly reduced the discolouration of the coating compared to non-impregnated wood.

KEYWORDS:

• Wood
• resin exudation
• phenol-formaldedye resin
• coatings

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Support from CT WOOD – a centre of excellence at Luleå University of Technology supported by the Swedish wood industry – is also acknowledged, along with additional support through the project “Advanced research supporting the forestry and wood-processing sector’s adaptation to global change and the 4th industrial revolution”, OP RDE [grant number CZ.02.1.01/0.0/0.0/16_019/0000803].