Data from: Cell wall microstructure, pore size distribution and absolute density of hemp shiv

This paper, for the first time, fully characterises the intrinsic physical
parameters of hemp shiv including cell wall microstructure, pore size
distribution and absolute density. Scanning Electron Microscopy revealed
microstructural features similar to hardwoods. Confocal Microscopy
revealed three major layers in the cell wall: middle lamella, primary cell
wall and secondary cell wall. Computed tomography improved the
visualisation of pore shape and pore connectivity in three dimensions.
Mercury intrusion porosimetry showed the average accessible porosity was
76.67 ± 2.03 % and pore size classes could be distinguished into
micropores (3-10 nm) and macropores (0.1-1 µm and 20-80 µm). The absolute
density was evaluated by helium pycnometry, mercury intrusion porosimetry
(MIP) and Archimedes’ methods. The results show that these methods can
lead to misinterpretation of absolute density. The MIP method showed a
realistic absolute density (1.45 g/cm3) consistent with the density of the
known constituents: including lignin, cellulose and hemi-cellulose.
However, helium pycnometry and Archimedes’ methods gave falsely low values
due to 10% of the volume being inaccessible pores, which require sample
pretreatment in order to be filled by liquid or gas. This indicates that
the determination of the cell wall density is strongly dependent on sample
geometry and preparation.