One-pot preparation of hydrophobic lignin/SiO₂ nanoparticles and its reinforcing effect on HDPE

Nano silica (SiO₂) is usually used as a common reinforcing agent in polymer materials, in which the interfacial interaction greatly affects the mechanical properties of the composites. The reinforcement effect of silica on non-polar polymer is restricted due to their poor compatibility. In this work, amphipathic lignin modified by quaternization and alkylation was used as a modifier for silica to prepare hydrophobic lignin/SiO₂ nanoparticles by in-situ one-pot co-precipitation method. In alkaline solution, hydrophobic lignin and SiO₂ (from Na₂SiO₃) were self-assembled to form nanospheres through electrostatic and hydrophobic interactions. The results showed that the lignin/SiO₂ nanoparticles were highly hydrophobic nanospheres with macropores in the surface. When the lignin/SiO₂ nanoparticles (10 wt%) were added to reinforce high-density polyethylene (HDPE), the mechanical properties of HDPE were improved with the strength of 24.5 MPa and the elongation of 1096%, which were increased by 10.4% and 14.3% compared with the control HDPE, because of the good compatibility and large bonding area. This work puts forward a new solution for the application of lignin in reinforcement of non-polar polymers.