Haruka Ogawa

YELLOWING OF THE RECONSTITUTED STONE AND THE OUTBREAK FACTORS

高 橋 晃一郎 小 川 晴 果 Yellowing of Reconstituted Stone and Outbreak Factors Koichiro Takahashi Haruka Ogawa Abstract Organic reconstituted stone is used to make kitchen tops in countries outside Japan, it is often used for the flooring and inner walls of buildings. As organic reconstituted stone contains polymer resin, it may discolor to a yellowish hue because of external factors such as ultra-violet light and heat. At some construction sites, organic reconstituted stone became yellow. We conducted tests to investigate the causes of yellowing, prevention methods, and possibilities of further yellowing by replicating the process and performing chemical analysis. We found that long-term exposure to water and heat changes the chemical components and leads to the formation of chromophores having a conjugated double bond and auxochromes having a hydroxyl radical. We also found that yellowing was limited to depths of less than 100 μm from the surface grinding and polishing may remove and prevent further yellowing.

New Construction Materials for the Preservation of Tropical Rain Forest

In Japan, plywood made of hard wood from tropical rain forests used in concrete forms for construction. About 3 million m3 raw logs are used per year for this purpose. This amount represents only 0.2% of the whole worlds tropical logging, but it was judged that we must reduce consumption. Accordingly, we investigated materials which were capable of replacing the usual plywood forms were found to be good potential materials.