Dimensional Stabilization of Wood. Part III. Butylation

The dimensional stabilization of wood was studied by the etherification of balsam fir wafers measuring, 1 to 1-1/2 inches longitudinally and 1-1/2 inches in diameter, with pyridine as the swelling agent and catalyst, and n-butyl chloride and t-butyl chloride as the alkylating agents. The influence of the following factors on Weight Increase (W.I.) and Antishrink Efficiency (A.E.) were: 1) For treating time the relationship with weight increase was linear for both types of butylation with the slope being five times greater for n-butylation than for t-butylation. A.E.’s increased curvilinearly to apparent maximums at the maximum time with n-butylation being more rapid than t-butylation. 2) For reaction temperature, values of W.I. and A.E. indicated that the preferred reaction temperature is the reflux temperature of the solution. 3) For composition of the treating solution, maximum W.I. and A.E. s were obtained at about 20 mole percent of the alkyl chloride with the A.E. values spread over a somewhat greater range. 4) For number of repeated n-butlation treatments the maximum W.I. and A.E. were obtained for two treatments. This study indicates that dimensional stabilization by butylation methods is affected by two factors: a) the bulking effect of a pyridinum alkyl chloride salt, and b) the deposition of a hygroscopic salt within the wood structure. The bulking effect is shown by the tangential swelling of butylated samples at different moisture contents. At low moisture contents, the percent swell is about the same, for all samples. At about 10-15 Percent M.C. , the curves for those samples with high levels of butyl content ( percent) level off, while those of lower content continue to show swelling with increased moisture content. For wafers of different butyl content the moisture content increased curvalinearly with increasing relative humidity, with a sharp increase at 57 percent R.H. (the equilibrium relative vapor pressure of a saturated solution of pyridinium salt of n-butyl chloride). The samples with the greater content absorbed the greater amount of moisture as would be expected due to the deposition of the hygroscopic salt within the wood structure. Both methods of butylation studied impart stability to the dimensions of wood on a temporary basis only. The stabilization mechanism places the two methods of butylation in the same class as the procedures used for chemical seasoning which employed sugars and salts. Although the alkylating agents used are relatively inexpensive petrochemicals, butylation seems to be of little value for chemical seasoning.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member