Abstract: This study demonstrated a method for toughening a highly crosslinked anhydride cured DGEBA epoxy using rubbery block copolymer grafted SiO2 nanoparticles. The particles were synthesized by a sequential reversible addition-fragmentation chain transfer (RAFT) polymerization. The inner rubbery block poly(n-hexyl methacrylate) (PHMA) had a glass transition temperature below room temperature. The outer block poly(glycidyl methacrylate) (PGMA) was matrix compatible. A rubbery interlayer thickness of 100% and 200% of the particle core radius was achieved by grafting a 20 kg/mol and a 40 kg/mol PHMA at a graft density of 0.7 chains/nm2 from the SiO2 surface. The 20 kg/mol rubbery interlayer transferred load more efficiently to the SiO2 cores than the 40 kg/mol rubbery interlayer and maintained the epoxy modulus up to a loading of 10 vol% of the rubbery interlayer. Both systems enabled cavitation or plastic dilatation. Improvement of the strain-to-break and the tensile toughness was found in both systems. We hypothesize that plastic void growth in the matrix is the primary mechanism causing the improvement of the ductility.
Keywords: toughened epoxy; rubbery interlayer; nanocomposites; RAFT polymerization
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Gao, J.; Li, J.; Benicewicz, B.C.; Zhao, S.; Hillborg, H.; Schadler, L.S. The Mechanical Properties of Epoxy Composites Filled with Rubbery Copolymer Grafted SiO2. Polymers 2012, 4, 187-210.
Gao J, Li J, Benicewicz BC, Zhao S, Hillborg H, Schadler LS. The Mechanical Properties of Epoxy Composites Filled with Rubbery Copolymer Grafted SiO2. Polymers. 2012; 4(1):187-210.
Gao, Jianing; Li, Junting; Benicewicz, Brian C.; Zhao, Su; Hillborg, Henrik; Schadler, Linda S. 2012. "The Mechanical Properties of Epoxy Composites Filled with Rubbery Copolymer Grafted SiO2." Polymers 4, no. 1: 187-210.