Scalable solution for high dispersibility and low heterogeneity of nuclear-shielding high inorganic filler/polymer composites: a vitrimer via reactive extrusion & mechanochemical intercalation†

Many are pursuing high-performance polymer composites with ultra-high inorganic fillers, focusing on improving inorganic particle dispersion. However, few studies have explored how to address the heterogeneity introduced by inorganic particles after meeting dispersion requirements. This work proposed that resolving the heterogeneity in polymer composites with high inorganic particle content relies on utilizing the movement of polymer chains for self-adaptation. We employed ultra-high-filled tungsten powder (W)/high-density polyethylene (HDPE) composites as the basic model. A vitrimer was introduced to enhance the intensity of mutual diffusion of HDPE chains during static hot pressing. The vitrimer-modified W/HDPE composites (W/HDPE-v) not only ensured the high dispersion of W but also facilitated intense mutual diffusion of the chains through the bond exchange of the vitrimer under thermal action. This process led to the ordered stacking of the C–C main chains and increased the crystallinity of the composites. Through the chains’ mutual diffusion, fluctuations in the modulus of the HDPE matrix were reduced, and the interfacial layer between the HDPE and W underwent continuous dynamic reorganization. This dynamic reorganization achieved heterogeneity reduction. The introduction of the vitrimer also generated regions within the polymer chains that exhibited different steric hindrances, which were significantly influenced by factors such as the crosslinking agent content and external forces. This resulted in a directional bond exchange of the vitrimer and traction on the polymer chains, promoting the self-aggregation of polymer chains and the rejection of inorganic particles. The final composites exhibited good mechanical properties and gamma-ray shielding effects.