Fixation and Creep of Compressed Wood of Chinese Fir Irradiated with Gamma Rays

In order to discuss the mechanisms of permanent fixation of wood compression set, compressed wood of Chinese fir (Cunninghamia lanceolata)was irradiated by gamma rays from ⁶⁰Co.The irradiation doses were 0 (for match specimens), 10³, 5×10³, 10⁴, 5×10⁴, 10⁵, 5×10⁵, 10⁶, 5×10⁶ Gy, respectively. Then the weight loss, the equilibrium moisture content (EMC), the recovery of wood compression set after adsorption (RSA) and the recovery after immersion in water (RSW), as well as the creep behaviour under a dry specimen condition and under an adsorption and subsequent desorption condition were measured and discussed.This research proves that the doses of gamma irradiation have great effect on weight loss, EMC, RSA, RSW of irradiated compressed wood of Chinese fir.The weight loss and the EMC increase, the RSA and the RSW fall drastically when the irradiation doses exceed 106 Gy. Both the instantaneous compliance and the creep compliance of the irradiated specimens under the two measurement conditions show the general trend of increase with the increase of gamma irradiation doses.It can be deduced that decomposition or decrystallization reactions happen in the wood cell wall at high gamma irradiation doses, especially at doses of around 5×10⁶ Gy.In addition, this research proves that decomposition of main components of cell wall of compressed wood will lead to fixation of compression set of wood to a certain degree.