Phase separation, porous structure, and cure kinetics in aliphatic epoxy resin containing hyperbranched polyester

Abstract

Thermosetting blends of an aliphatic epoxy resin and a hydroxyl‐functionalized hyperbranched polymer (HBP), aliphatic hyperbranched polyester Boltorn H40, were prepared using 4,4′‐diaminodiphenylmethane (DDM) as the curing agent. The phase behavior and morphology of the DDM‐cured epoxy/HBP blends with HBP content up to 40 wt % were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The cured epoxy/HBP blends are immiscible and exhibit two separate glass transitions, as revealed by DMA. The SEM observation showed that there exist two phases in the cured blends, which is an epoxy‐rich phase and an HBP‐rich phase, which is responsible for the two separate glass transitions. The phase morphology was observed to be dependent on the blend composition. For the blends with HBP content up to 10 wt %, discrete HBP domains are dispersed in the continuous cured epoxy matrix, whereas the cured blend with 40 wt % HBP exhibits a combined morphology of connected globules and bicontinuous phase structure. Porous epoxy thermosets with continuous open structures on the order of 100–300 nm were formed after the HBP‐rich phase was extracted with solvent from the cured blend with 40 wt % HBP. The DSC study showed that the curing rate is not obviously affected in the epoxy/HBP blends with HBP content up to 40 wt %. The activation energy values obtained are not remarkably changed in the blends; the addition of HBP to epoxy resin thus does not change the mechanism of cure reaction of epoxy resin with DDM. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 889–899, 2006

Amphiphatic Piperazine, Pyrazine, and Pyridine Derivaties as the Thermal Latency for Epoxy-Phenolic Resins

“…Due to the intramolecular or intermolecular acid-base neutralization, the reactivity of piperazine, pyrazine, and pyridine moieties was reduced in the curing epoxy resins to provide the good latent properties. Based on the studies of the viscosity and E a measurement, the activity order of the thermally latent catalytic systems was estimated to be piperazine-2-carboxylic acid (6) > 3-aminopyrazine-2-carboxylic acid (4) > 3-piperazin-1-yl-propionic acid (7) > 2-pyrazinecarboxylic acid (2) > picolinic acid (5) > 2,3-pyrazinedicarboxylic acid (3).…”

“…[1][2][3][4][5][6] Although the biphenyl type epoxy resins are of great advantage as highly reliable electronic molding compounds (EMC) with good adhesion and high toughness, and used as high filter loadings, their epoxy resin system has low storage stability at room temperature. As a result, latent catalysts were developed to improve the pot life at room temperature for biphenyl type epoxy resins.…”

Nanostructure Formation in Thermoset/Block Copolymer and Thermoset/Hyperbranched Polymer Blends

“…Guo et al [75] discovered that for the blend with a G4 hydroxyl functionalized HBP content up to 10 wt%, discrete HBP domains are dispersed in the continuous cured epoxy matrix. Guo et al [75] discovered that for the blend with a G4 hydroxyl functionalized HBP content up to 10 wt%, discrete HBP domains are dispersed in the continuous cured epoxy matrix.…”

Synthesis and characterization of APTMS/melamine cured hyperbranched polyester-epoxy hybrid coatings

“…Hybrid material containing Boltorn H20 and SiO 2 -TiO 2 networks have been successfully prepared for toughening DGEBA epoxy resin, which can form ternary cured networks of DGEBA via a sol-gel process leading to an epoxy resin with a high modulus, impact strength and T g [19]. Q Guo et al [20] have studied the phase separation, porous structure, and cure kinetics thermosetting blends of an aliphatic epoxy resin and a hydroxyl-functionalized hyperbranched polymer (HBP). Based on detailed literature review the hybrid coatings prepared by using different alkoxysilane precursors and sol-gel techniques result in brittle coating films, however, the incorporation of alkoxysilane precursors in the polymer network through in situ methods and/or modification of reactive polymers with inorganic precursors are becoming increasingly important for the development of tough and flexible coatings.…”