A. Bjorkman et L. Salmen, Studies on solid wood. II. The influence of chemical modifications on viscoelastic properties, CELL CHEM T, 34(1-2), 2000, pp. 7-20
The relation between the properties of wood polymers and those of the compo
site material of wood is a subject that has been of interest for a long tim
e. In order to increase oar knowledge in this matter, changes of wood prope
rties have been studied on samples of spruce and birch, subjected to variou
s chemical treatments. Three properties were measured on completely dry sam
ples: stiffness, creep and axial compression strength, using previously dev
eloped methods, tailored to slim axial samples, which allow complete impreg
nation with liquids. On native and treated samples, fully saturated with wa
ter, the glass transition was measured by applying sinusoidal vibrations wi
th frequencies of 0.05-20 Hz, giving a transition for each frequency and an
apparent activation energy of frequency changes. In wet wood, these quanti
ties characterise the influence of a certain treatment on the properties of
lignin. The treatments chosen were immersion in liquid ammonia and aqueous
delignification and hydrolysis, acetylation (with anhydride), succinylatio
n (with anhydride) and carbanylation (with phenylisocyanate:). Measurements
of mechanical and theological alterations demonstrate conclusive effects o
f the treatments, though it is difficult to relate these effects to wood ul
trastructure.