Acceleration of Moisture Migration in Larch Wood Through Microwave Pre-Treatments

Abstract

This study investigates the effects of microwave pre-treatments on moisture migration in larch wood. Two groups (high and low moisture contents) of specimens were treated in a microwave drier at a fixed output power of 0.8 kW for three different durations (1, 3, and 5 min). Changes of microscopic structure in larch wood after microwave treatments were then examined using scanning electron microscopy. The percentage of aspirated pits was estimated and water absorption was measured using a cylinder with a vacuum pump. In addition, drying rates after the treatments were also evaluated. The results show a significant reduction in the number of aspirated pits in larch wood and a sizable increase in water absorption and drying rate after a 3-min or 5-min microwave treatment. More ruptures and water absorption have been found in the group with lower moisture content. It is concluded that microwave pre-treatments can open some water pathways and accelerate moisture migration in larch wood.

Keywords:

• Aspirated pits
• Microwave treatment
• Water absorption
• Water pathways

ACKNOWLEDGMENTS

This work was financially supported by the National Natural Science Foundation of China (NSFC) through grant number 31070493 and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

Notes

All the specimens were equalized to 12% MC before the microscopic observation.

Groups with the same letters in each column indicate that there is no statistical difference (p < 0.05) between the samples according to the Duncan's multiple range test.

Values in parentheses are standard deviations.

All the specimens were equalized to 12% MC before the determination.

Groups with the same letters in each row indicate that there is no statistical difference (p < 0.05) between the samples according to the Duncan's multiple range test.

Values in parentheses are standard deviations.

All specimens were dried at dry/wet-bulb temp of 90/74°C with an air velocity of 4 m/s.

The same letters in the column of drying rate indicate that there is no statistical difference (p < 0.05) between the samples according to the Duncan's multiple range test.