Development of a novel toughener for epoxy resins

BACKGROUND: Conventional tougheners for brittle epoxy resins form micrometre‐sized particles with ineffective interfaces, and meet toughening requirements with 10–20 wt% of toughener, which unfortunately causes deterioration of other desirable properties. RESULTS: We developed a novel polyurea toughener using a facile synthesis method from isophorone diisocyanate and polyoxyalkyleneamine. Polyurea forms thick‐interface particles, and creates an effective toughness improvement: 265% increase in fracture energy release rate. More importantly, polyurea causes no deterioration of other important properties. Different from conventional epoxy/rubber or epoxy/thermoplastic composites, the epoxy/polyurea composite shows Newtonian rheological behaviour, a convenient property for processing. CONCLUSION: This study describes a novel polyurea toughener. Its unique feature is that toughness can be significantly improved at low toughener content (5 wt%) without losing other desirable properties. The study illuminates the importance of the interface for toughening in polymer blends/composites.