Fig. 3 shows the morphological effect on thickness swelling and water absorption. The TS with whole powder was 16%, which could not meet the requirement for particleboard (JIS A5908, 2003) of 12%, whereas which met the requirement for MDF of 17% regard- less of the low IB (JIS A5905, 2014). In general, specimens showing better stability also showed high internal bonding strength because
good contact between particles could help to reduce moisture penetration into panel and particles (Boon et al., 2013). However, this study showed relatively low TS that did not be affected low IB. The WA of whole powder were higher than the requirement for Type- S20 of hardboard (JIS A5905, 2014). When TS was low and WA was high, the particles did not absorb water. Instead water entered cavities in the board. It seemed likely that something with high water resistance was present on the surface of the rice straw particles.