Effect of compound coupling agent treatment on mechanical property and water absorption of hollow glass microspheres/epoxy composite

Hollow glass microspheres (HGMs), as a reinforcing material to prepare lightweight high-performance composites, have excellent mechanical properties. However, the composites prepared by simply mixing hollow glass microspheres with polymer resin have poor performance. In this study, compound coupling agent-modified HGM/EP composites were prepared by casting process with two silane coupling agents as compound coupling agents. Scanning electron microscopy and infrared (IR) spectroscopy were used to characterize the treated HGM. Meanwhile density, water absorption behavior, and mechanical properties of the modified HGM-filled epoxy composites were examined. It is found that the compound coupling agent could effectively improve the interfacial bonding between HGM and the matrix resin. A new chemical bond was formed between HGM and EP, which was confirmed by IR spectroscopy. Compared with their untreated counterparts, the composites treated with the complex coupling agent exhibited excellent mechanical properties, along with lower density and lower water absorption. Graphical abstract The composites prepared by treating hollow glass microspheres with mixed coupling agents showed improved properties in all the cases. The mechanical properties of the composites prepared using No. HGM-1 reached the maximum with tensile strength of 36.38 MPa, tensile modulus of 2.383 GPa, flexural strength of 49.82 MPa, flexural modulus of 1.558 GPa, and compressive strength of 98.14 MPa. Our strategy opens a new way to fabricate composites with enhanced mechanical performances.