Epoxidation of agricultural byproduct konjac fly powder and utilization in toughening and strengthening epoxy resin

•A novel bio-based epoxidized resin derived from konjac processing by-products.•Epoxidized konjac fly powder was used as a green toughener for epoxy resins.•The toughness and strength of epoxy thermosets were simultaneously enhanced.•Increased free volume through the incorporation of epoxidized konjac fly powder.•Reduced internal stress by the use of epoxidized konjac fly powder.