Well-dispersed silica nanoparticle-reinforced epoxy vitrimer composites prepared by dynamic crosslinking

Realizing nano-filler well dispersed in epoxy matrix is essential for the fabrication of high-performance epoxy composites. However, the aggregation of untreated nano-filler in epoxy resin during static curing greatly reduces the material performance. Herein, we report an effective and facile approach to fabricate well-dispersed silica nanoparticle (SiNP)-reinforced epoxy composites through dynamic crosslinking depending on vitrimer chemistry. The epoxy vitrimer synthesized by dynamic crosslinking method was named as EVD, and the epoxy vitrimer synthesized by static curing method was named as EVS. EVD/SiO 2 nanocomposites were prepared by dynamic crosslinking technology with unmodified nano-SiO 2 as a reinforcement filler, sebacic acid as a curing agent, diglycidyl ether of bisphenol A (DGEBA) as an epoxy monomer, zinc acetylacetonate as a transesterification catalyst, and a torque rheometer (internal mixer) as a dynamic crosslinking equipment, and EVS/SiO 2 nanocomposites were prepared by traditional static curing method as counterparts. The structure, properties, and stress relaxation of the EVD/SiO 2 and EVS/SiO 2 were comparatively investigated in detail. When the loading amount of SiO 2 was 5 wt%, EVD/SiO 2 -5 indicated 2.38 times tensile strength and 2.06 times elongation at break of EVS/SiO 2 -5. The Young's modulus of EVD/SiO 2 -5 (6.76 ± 1.07 MPa) was slightly higher than that of EVS/SiO 2 -5 (5.81 ± 1.06 MPa), which was attributed to more well-dispersed SiNP in EVD/SiO 2 -5. Moreover, the amount of SiO 2 can be filled up to 40 wt% in epoxy vitrimer to obtain high-modulus (1001 times of pure vitrimer) composite. We believe that this study provides a new idea for the preparation of other vitrimer composites with desired properties. Graphical abstract