Effect of grooving pretreatment on flame retardant vacuum-pressure impregnation performance of full-size timbers

We reported in a previous study that wood fiber orthogonal grooving improves flame retardant vacuum-pressure impregnation performance. However, it was limited to small sample sizes. We extended our previous study to investigate the effect of grooving on flame retardant impregnation in Japanese cedar (Cryptomeria japonica D. Don.) and Korean larch (Larix kaempferi (Lamb.) Carriere) full-size timber [2,400 mm(L) x 100 mm(W) x 22 mm(T)], which are widely used as a building interior lining. Japanese cedar had higher open-pore porosity and gas permeability than Korean larch. As a result, Japanese cedar had no significant difficulty impregnating the flame retardant, even without a grooving pretreatment process. The flame retardant's impregnating performance in Korean larch control was insignificant, but the impregnating ability was improved after fiber orthogonal grooving. In conclusion, Japanese cedar can meet the fire safety standards announced by the Ministry of Land, Infrastructure and Transport without groove processing before flame retardant impregnation. On the other hand, Korean larch had to be impregnated with a flame retardant after grooving processing in the orthogonal direction of the fiber to achieve fire safety performance. As a result, this grooving pretreatment is a simple and practical technique that can be used immediately on impervious commercial wood.