A new networked polymer bearing urethane linkages and hydroxyl groups was synthesized by the polyaddition reaction of a bifunctional 5-membered cyclic carbonate and a triamine. The bifunctional cyclic carbonate used herein was synthesized from bisphenol A diglycidyl ether through its reaction with CO₂ that was catalyzed by lithium bromide efficiently and thus proceeded under atmospheric pressure. Upon heating the networked polymer, it underwent several chemical transformations involving the intramolecular nucleophilic attack of the hydroxyl group to the urethane linkage that permitted the regeneration of the 5-membered cyclic carbonate moiety.

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Toughening of cycloaliphatic epoxy resin with polyvinyl formal resins (PVF) that have good compatibility with the epoxy resin was investigated. The fracture energy in tensile tests and K_IC in fracture toughness tests of the cured resin modified with 10wt% of PVF are three times and 1.3 times higher than those of the unmodified cured resins, respectively. In addition, the modified epoxy resins maintain high glass transition temperature (T_g>200℃) and high transparency even after the addition of PVF. The fractured surfaces of the unmodified and PVF-modified resins were observed with Atomic Force Microscope (AFM). It was clearly shown that the diameter of microgel increased considerably and its boundary became to be indistinct with the addition of PVF. These mean that the coexistence of PVF molecules in the gelation process of the epoxy resin suppressed the formation of the microgel. Such a suppression of the formation of microgel results in the increase in the toughness of the cured resins. SynopsisToughening of cycloaliphatic epoxy resin with polyvinyl formal resins (PVF) that have good compatibility with the epoxy resin was investigated. The fracture energy in tensile tests and K_IC in fracture toughness tests of the cured resin modified with 10wt% of PVF are three times and 1.3 times higher than those of the unmodified cured resins, respectively. In addition, the modified epoxy resins maintain high glass transition temperature (T_g>200℃) and high transparency even after the addition of PVF. The fractured surfaces of the unmodified and PVF-modified resins were observed with Atomic Force Microscope (AFM). It was clearly shown that the diameter of microgel increased considerably and its boundary became to be indistinct with the addition of PVF. These mean that the coexistence of PVF molecules in the gelation process of the epoxy resin suppressed the formation of the microgel. Such a suppression of the formation of microgel results in the increase in the toughness of the cured resins.

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With phenol, formaldehyde, and a catalyst, the layered silicate compound was added and novolac was synthesized. Montmorillonite and organized montmorillonite were used as a layered silicate compound. Next, the phenolic composites were produced using these novolac, and the dispersion state of the silicate compound under the composite was examined. As a result, the dispersion state of the layered silicate compound under phenolic composite was excellent in the composite produced from the novolac which used organized montmorillonite. Next, the structure and physical properties of phenolic composite which produced from molding compound prepared from conventional novolac and organized montmorillonite by the hot-roll kneading were examined. As a result, although the flexural strength and heat resistance of the phenolic composite produced from the synthesized modified novolac with organized montmorillonite were inferior to phenolic resin with no filler, the coefficient of linear expansion of the phenolic composite became small to about 60% of phenol resin with no filler. On the other hand, the flexural strength and heat resistance of phenolic composite which produced from molding compound by the hot-roll kneading were superior to those of phenolic resin with no filler. However, although the coefficient of linear expansion of the phenolic composite was smaller than phenol resin with no filler, the extent was only about 86% of phenol resin with no filler. Namely, the dimensional stability of the phenolic composite produced from the synthesized modified novolac with organized montmorillonite was superior to those of phenolic composite produced by the hot-roll kneading.

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The gelation mechanism and cross-link inhomogeneity of phenolic resins prepared via polycondensation of phenol and formaldehyde under acidic conditions were studied by using small-angle X-ray scattering. The structural analysis of the gelation process indicated the presence of different mechanisms of the formation and growth of the inhomogeneity that depend on the cross-linker concentration.

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