Micromechanical Characterization of Particle-Particle Bond in Biomass Assemblies Formed at Different Applied Pressure and Temperature

Abstract

During biomass pelletization, the presence of activated natural binders is thought to promote the formation of solid bridges in a biomass assembly. To examine this hypothesis, bonded particles were extracted from the switchgrass compacts formed at different pressure and temperature. This study investigated the influence of these two factors on the resistance to dislocation of the particle-particle bond. The generated force-bond dislocation curves were used to calculate the slope from no load to failure from the assemblies formed at the treatments A (60 MPa and 75 °C), B (100 MPa at 75 °C), C (60 MPa and 90 °C), and D (100 MPa at 90 °C). Assemblies from the treatment B had the highest diametral tensile strength (60.9 ± 7.1 kPa) and densities (653.2 kg m -3 ), whereas, assemblies formed from the treatment C had the lowest diametral strength (7.2 ± 1.4 kPa). The resistance to dislocation of particle-particle bonds at microscale was linearly correlated to the strength (R 2 =0.838) and density (R 2 =0.981) of the densified assemblies. High pressures are documented to form stronger compacts. However, the presence of sufficient moisture at low temperature can significantly improve the densified assembly properties by lowering the glass transition temperature of lignin to form stronger bonds.