Sub-micron spherical carbon particles with hollow cores from lignin-based hybrid precursors: preparation, characterization, and electrostatic dissipative application

Abstract

Novel sub-micron, spherical, bio-based carbon materials with hollow-core characteristics were synthesized from spherical lignin particle (SLP) hybrid precursors via thermo-stabilization and carbonization. Primarily, the mixture of bagasse lignin (BG-L) and palm kernel shell lignin (PKS-L) with an addition of dicumyl peroxide (DCP) at different BG-L:PKS-L:DCP ratios was utilized to prepare SLPs through anti solvent precipitation. Interestingly, as-prepared SLPs having a 250–331 nm diameter contained hollow cores of 41–223 nm inside the spherical particles. A mechanism of hollow-core formation was also proposed. Effects of BG-L:PKS-L:DCP ratio, heating rate (HR), oxygen flow rate (O2 FR), and stabilization time (SBT) on spherical shape retention of SLPs after thermo-stabilization were systematically investigated, and a cross-link pathway was suggested. The spherical aspect of SLPs having hollow cores was successfully maintained at optimal conditions of 250 °C for 1 h with a HR of 0.3 °C/min under O2 FR of 3 L/min using a BG-L:PKS-L:DCP ratio of 1:1:1 by wt. After carbonization at 900–1200 °C, spherical carbon particles (SCPs) with hollow cores were obtained, possessing a high carbon (C) element of ≅ 93–96%, a high specific surface area of ≅ 308–593 m2/g, and a high order of graphitic structure (ID/IG ratio ≅ 1). The average particle size of SCPs and hollow-core dimensions were ≅ 171–224 and 80–107 nm, respectively. The polylactic acid (PLA)/SCP composite films were prepared using SCPs at different carbonization temperatures and loadings via a solution casting technique. The composite film containing 20 wt% of SCPs carbonized at 900 °C (SCPs-900) provided a surface resistance of ≅ 3 × 105 Ω and a tribo-charge voltage of 0 V, appropriate for electrostatic dissipative (ED) applications. The Young's modulus and elongation at break of the PLA/SCP-900 (20 wt%) composite film were ≅ 3.4 MPa and 2.0%, respectively. These findings demonstrate a feasible and effective approach to utilize biomass-based lignin for producing carbon particles with unique features as renewable and sustainable conductive fillers in polymer composites.