Abstract
In order to protect wooden boards from weather and wear, to mask their defects and to improve their paintability, studies on the effect on wooden boards of overlaying them with phenolic resin impregnated paper (Phenolic resin sheets) have been carried out by many workers. This paper is a review of the previous papers which have been reported by the author on the phenolic resin sheet overlaid on plywoods.
The phenolic resin sheets, or the kraft paper (Base paper) varying in thickness and in resin content, were overlaid on both sides of lauan plywoods either on the strength of their own resinousness or with the use of film glue. The plywoods thus overlaid with the phenolic resin sheets and other plywoods as they were both left exposed outdoors for six years in Tokyo facing south, inclined at 45 degrees to the land surface. The weathered plywoods were respectively examined after the six years' exposure in respect of their water absorbing property, mechanical properties and adhesion strength.
From the results it is concluded that by overlaying wood with phenolic resin sheets the two factors mentioned below give the wood effective weather resistance power.
(1) Ninty grams per square meter or more solid resin in the overlaying material.
(2) Sixteen kilograms per 15 millimeters wide or stronger tensile strength of the cured resin sheet, including the strength of the film glue when it is used, in the cross-grain direction of the face veneer.
