Miscibility, phase morphology, thermomechanical, viscoelastic and surface properties of poly(ϵ-caprolactone) modified epoxy systems: effect of curing agents

In this paper, we report on the effect of curing agents on the miscibility, morphology, thermomechanical properties, and surface hydrophobicity of diglycidyl ether of bisphenol A (DGEBA)/poly(ϵ-caprolactone) (PCL) blends. Two curing agents, 4,4′-diamino diphenylsulfone (DDS) and 4,4′-diamino diphenylmethane (DDM), were used. Studies revealed that the epoxy/PCL/DDM system was completely miscible due to the intermolecular hydrogen bonding interactions between carbonyl groups of PCL and hydroxyl groups of epoxy resin. On the other hand, the epoxy/PCL/DDS system exhibited phase separated matrix/droplet type morphology, primarily due to the intramolecular hydrogen bonding interactions within the epoxy phase between sulfonyl groups of DDS and hydroxyl groups generated during epoxy-DDS reaction. The storage modulus of the epoxy/PCL/DDM system was greater than that of the epoxy/PCL/DDS system, and the dependence of modulus on PCL content was more pronounced in the former. Moreover, the epoxy/PCL/DDM system exhibited better tensile properties and thermal stability.