RESUMO
Self-healing is achieved with a dual-microcapsule system utilizing epoxy-amine chemistry in a high temperature cured thermosetting epoxy polymer. One capsule contains a modified aliphatic polyamine prepared by vacuum infiltration of polyoxypropylenetriamine into hollow polymeric microcapsules. The second capsule contains a difunctional epoxide and reactive diluent. Healing efficiency is accessed through recovery of fracture toughness and excellent long-term stability at ambient conditions is demonstrated.
RESUMO
Double-walled polyurethane/poly(urea-formaldehyde) microcapsules (PU/UF) are prepared for use in self-healing materials. This modified encapsulation procedure combines two chemistries to form more robust capsule shell walls in a single operation. Robust capsules are formed by this procedure as long as the aromatic polyisocyanate prepolymer is soluble in the core liquid and the core liquid is compatible with isocyanates. Compared to a standard UF encapsulation, the modified procedure results in capsules with an increase in shell wall thickness from 200 to 675 nm as a function of the amount of PU added to the core liquid. Thermal stability of PU/UF microcapsules prepared with varying amounts of PU is compared to UF microcapsules. Mechanical properties of the PU/UF microcapsules are assessed from single-capsule compression testing.