Thermal mending in immiscible poly(ε-caprolactone)/epoxy blends

Abstract

Blends of commercial epoxy monomer with a 4,4′-diaminodiphenylsulfone hardener and poly(ε-caprolactone) (PCL) were evaluated for their potential as a self-healing matrix for fiber-reinforced composites, based on their room temperature toughness and stiffness and their capacity for healing when subjected to a moderate heating cycle. Analysis of the microstructure and thermal properties of the blends indicated three types of morphology to result from polymerization-induced phase separation during cure, depending on the PCL content, including an interconnected particulate epoxy phase and a co-continuous PCL phase above 23vol% PCL. While the mechanical performance diminished with increasing PCL content, toughness recovery after healing at 150°C for 30min strongly increased. Blends with 25vol% PCL showed a healing efficiency in excess of 70%, while retaining suitable room-temperature mechanical properties (a tensile modulus of 1.5GPa and a tensile strength of about 20MPa), and were concluded to be promising candidates for self-healing composites.