SWELLING OF WOOD .2. SWELLING IN ORGANIC LIQUIDS

The rate and maximum swelling of several North American wood species in 40 organic liquids have been obtained with a computer interface linear variable displacement transformer. Since wood swells very fast in some organic liquids, even at room temperature, this apparatus made it possible to obtain accurate rate data on the swelling of wood in organic liquids. It was found that many similarities existed between wood and cellulose maximum swelling within various solvent chemical classes. Hence, it appears that cellulose is the primary wood polymer responsible for the major amount of swelling of wood. In general, all the liquids, with a molar volume greater than 100cc or with a small hydrogen bonding parameter, caused very little equilibrium swelling. The logrithm of the rate of wood swelling (lnk) in the liquids was inversely correlated with the solvent molecular weight as well as with the molar volume of the solvent, that is, the larger the solvent molecular size, the slower the rate of swelling. The lnk also was strongly correlated with the maxmium tangential swelling of wood. The maximum tangential swelling for all wood species was linearly correlated with the solvent basicity (donor number). Other solvent properties such as solubility parameter, dipole moment, dielectric constant, and surface tension showed very weak correlations with the maximum tangential swelling of wood in organic liquids.