Moisture in untreated, a cetylated, and furfurylated Norway spruce studied during drying using time domain NMR
Using time domain NMR, the moisture in Norway spruce (Picea abies (L.) Karst.) sapwood subjected to four different treatments (never-dried, dried and remoistened, acetylated, and furfurylated) was studied during drying at 40°C, at sample average moisture contents above fiber saturation. Spin-spin relaxation time distributions were derived from CPMG relaxation curves using multiexponential fitting (CONTIN), and the resulting water populations were assigned according to the literature and their behavior during drying. It was found that both acetylation and furfurylation increased the average spinspin relaxation time of the lumen water in earlywood tracheids from about 80–100 ms to 200 and 300 ms, respectively. The average spin-spin relaxation time of the cell wall water was reduced from about 1.4 to 0.65 ms by furfurylation, while acetylation had less effect on this water. The relaxation times of both the earlywood lumen water and of the cell wall water were slightly longer for the never-dried samples than for the dried and remoistened samples.