Control of inclusion size and toughness by reactivity of multiblock copolymer in epoxy composites

• Inclusions size was controlled from nanometer to micrometer by simply adjusting the reactivitiy of block copolymer.
• Significant toughness improvement was observed for reactive block copolymer modified DGEBA/DDM epoxy thermosets.
• Toughening efficiency varied by fracture speed, while sub-micron inclusions was optimized for both SENB and impact tests.

In this paper, the strategy to achieve high fracture toughness and impact strength of epoxy blends by introducing a new family of reactive block copolymer (RBCP), poly[styrene-alt-(maleic anhydride)]-block-polystyrene-block-poly(n-butyl acrylate)-block-polystyrene, with different reactivity is reported. Inclusions size of RBCP in cured blends was controlled from nanometer to micrometer by simply adjusting the fraction of reactive block in RBCP. The systematical study on the structure–property relationship revealed that the thermal and mechanical properties of modified blends strongly depend on inclusion size. The results suggested that blends containing nano inclusions of RBCP were more sensitive to test rates. And blends containing sub-micron inclusions showed substantially increased toughness in SENB measurements and IZOD impact tests without loss in Tg. The findings of this work provide an insight on developing toughened epoxy thermosets utilized for both high and low fracture rates via innovative reactive blending.

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