2003 Volume 52 Issue 3 Pages 301-308
Effect of pit destruction and boric compounds on flame retardancy of woods was studied using “Obi” Japanese cedar which grew in Miyazaki prefecture. As woods has a lot of cells which are independent and isolated each other by blockade of the pit at the end of the life, woods was pretreated and destroy the pit under several conditions so as to be blended with flame retardants. The rate of the destruction depended on the pretreated temperature and about 70% to the whole pit could be destroyed at 120°C. After boronic compounds were impregnated, combustion tests and thermal degradation experiments have been achieved. The heat release rate observed by a cone calorimeter decreased with increasing boron contents in wood. Namely, the peak value of no-treated cedar was 200kW/m2 and the total amount of the heat release was twice as much as that of treated cedar. The difference was recognized between heartwoods and sapwood. It was caused by the location of both woods. Thermal degradation and elemental analysis of residue at higher temperature were also measured and discussed on relation to flame retardancy and structural changes in wood during combustion and degradation. In particular, the decomposition rate of untreated woods at 350-550°C was twice as much as that of the treated woods. It means the total heat releases were proportional to the decomposition rate because fuels by which materials can continue to burn was supplied by the decomposition.