Constructing ‘bayberry shape’ structure on HGMs surface using CNTs to enhance the mechanical properties of HGMs/epoxy composites

The lightweight composites, composed of epoxy resin (EP) and hollow glass microspheres (HGMs), have been widely applied in marine buoyancy materials, insulation for marine pipelines, and aerospace. However, achieving lower density often requires a significant addition of HGMs, leading to a compromise in mechanical properties. To address this problem, this paper proposes a method to enhance the mechanical properties of HGMs/EP composites without altering the HGMs content. Here, the ‘bayberry shape’ structure of HGMs was achieved by chemically grafting carbon nanotubes (CNTs) onto their surface through an esterification reaction. Subsequently, a lightweight CNTs-HGMs/EP composite with improved strength was fabricated using these ‘bayberry’ HGMs as fillers and EP as the matrix. The effect of different grafted-CNTs content on HGMs' surface on the mechanical properties of CNTs-HGMs/EP composites, along with the enhancement mechanism, were systematically analyzed. The tensile strength, flexural strength and compressive strength of CNTs-HGMs/EP composites demonstrated remarkable increases of 39.14%, 21.78% and 17.87%, respectively, compared to pure HGMs/EP composites. Our results demonstrate that surface modification of HGMs could significantly improved the mechanical properties of HGMs/EP composites without affecting their density. Moreover, this method was characterized by its simplicity in operation and batch preparation, which holds great significance for the efficient production of lightweight composites.