displays the FTIR spectra of SKL at different acetylation
levels; spectra were normalized with respect to the peak
at 856 cm1
, which is attributed to C–H bending on aromatic
rings. As the amount of Ac2O decreased from 15 to 0.66 ml/g
SKL, intensity of the hydroxyl peak at 3400 cm1 increased
significantly. Also, the weight gain of lignin after reaction with
Ac2O moderated from 18% to 5%. Larger content of hydroxyl
group retained by these reaction conditions led to increased
reactivity/crosslinking of the precursor during subsequent
thermo-oxidation step. This enhanced crosslinking enabled
the stabilized fibers to retain the original fiber shape and size
without becoming tacky. At the same time, Ace-SKL obtained
from limited acetylation could be fully dissolved in acetone.