No abstract

No abstract

Hydroxyl-terminated poly(ether ether ketone) with pendent tert-butyl groups (PEEKTOH) was synthesized by the nucleophilic substitution reaction of 4,4 0difluorobenzophenone with tert-butyl hydroquinone with potassium carbonate as a catalyst and N-methyl-2-pyrrolidone as a solvent. Diglycidyl ether of bisphenol A epoxy resin was toughened with PEEKTOHs having different molecular weights. The melt-mixed binary blends were homogeneous and showed a single composition-dependent glass-transition temperature (T g ). Kelley-Bueche and Gordon-Taylor equations gave good correlation with the experimental T g . Scanning electron microscopy studies of the cured blends revealed a two-phase morphology. A sea-island morphology in which the thermoplastic was dispersed in a continuous matrix of epoxy resin was observed. Phase separation occurred by a nucleation and growth mechanism. The dynamic mechanical spectrum of the blends gave two peaks corresponding to epoxy-rich and thermoplastic-rich phases. The T g of the epoxy-rich phase was lower than that of the unmodified epoxy resin, indicating the presence of dissolved PEEK-TOH in the epoxy matrix. There was an increase in the tensile strength with the addition of PEEKTOH. The fracture toughness increased by 135% with the addition of high-molecular-weight PEEKTOH. The improvement in the fracture toughness was dependent on the molecular weight and concentration of the oligomers present in the blend. Fracture mechanisms such as crack path deflection, ductile tearing of the thermoplastic, and local plastic deformation of the matrix occurred in the blends. The thermal stability of the blends was not affected by blending with PEEKTOH.

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.

No abstract