Evaluation of the effects of temperature and cooling rate on the freezing of water in wood using dielectric spectroscopy

Trees living in subfreezing environments for extended periods are susceptible to brittle fracture and freezing injury, which limits wood quality and final utilization. This study investigates the effects of temperature and cooling rate on the freezing of water in wood using dielectric spectroscopy. Dielectric parameters such as dielectric constant, loss factor, and relaxation strength were observed during cooling process of wood. The effects of subzero temperature and cooling rate on the dielectric parameters were found significant. The dielectric parameters at a slow-cooling rate were generally higher 12%∼143% than those at a fast-cooling rate. During the cooling process from 20°C dropped to − 80°C, the freezing process of water in wood was divided into four stages based on the dielectric parameter change and its impact on wood cell wall was characterized using SEM and DSC methods. The findings of this study provide the basis to explore the freezing behavior of water in wood and further to determine the cause of freezing injury in trees.