Physical, thermal, chemical and rheological characterization of cellulosic microfibrils and microparticles produced from soybean hulls

• SMF and SMP were isolated from soybean hulls, characterized and compared to MNFC.
• Hemicellulose content was higher for MNFC compared to SMF and SMP.
• Compared to MNFC, SMF and SMP display higher crystallinity and thermal stability.
• SMF and SMP properties make them attractive to reinforce thermoplastic composites.
• SMF and SMP dispersions are of interest in rheology modification, coating and films.

Soybean hulls were used to isolate cellulosic microfibrils (SMF) and brick-like microparticles (SMP) by combining chemical and mechanical pretreatments. The key physical and chemical features of SMF and SMP were compared with those of micro and nanofibrillated cellulose (MNFC) obtained from fully bleached wood fibers. SMF and SMP chemical composition includes residual polysaccharides and lignin that endow such biologically-derived materials with properties typical of nanocellulosics. Compared to MNFC, SMF and SMP exhibit enhanced crystallinity (∼ > 10% higher) and thermal stability (onset degradation temperature >295 °C and maximum degradation at 361 and 355 °C). Such observations make SMF and SMP suitable for reinforcement in thermoplastic composites. A strong shear thinning behavior was observed for aqueous dispersions of SMF and SMP, revealing that these cellulose microstructures are of interest for rheology modification, coatings and films. Overall, the availability and low cost of biomass from residual soybean hulls constitutes a viable option for their use as a feedstock for the production and development of novel materials from SMF and SMP.

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