Method for measuring viscoelastic properties of wood under high temperature and high pressure steam conditions

A method for measuring the viscoelastic properties of wood under high temperature and high pressure steam was developed using a testing machine with a built-in autoclave. A newly developed load cell capable of resisting a steam pressure of 16 kgf/cm(2) and a temperature of 200 degrees C was installed in the autoclave. This load cell could be used to determine precisely the loads while steaming at temperatures from 100 degrees C to 200 degrees C, In addition to load-detection problems, it was necessary to avoid the nonuniform thermal degradation of wood during the measurement process under steaming at high temperatures. This nonuniform degradation could be minimized by shortening the time required for the wood to attain thermal equilibrium using specimens conditioned to the fiber saturation point. According to this method, a stress relaxation curve for sugi (Cryptomeria japonica D. Don) wood being compressed while steaming at 180 degrees C was obtained. The stress was seen to decrease rapidly with time, reaching almost zero at 3000 s.