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A mesogenic epoxy resin (DGETAM) was cured with a series of curing agents having different lengths of long alkyl chain (nBAB, n = 4, 8, 12). Properties of the curings were compared with those of the DGEBA cured with the same curing agents revealing the achievement of a balance between certain levels of thermal properties and excellent mechanical properties. Moreover, some curing systems were prepared with twin mesogenic type epoxy resins (DGEnMA, n = 4, 6, 8, 10, 12) having different lengths of alkyl chain as a flexible spacer and the same curing agents (n′BABs). Combinations of the same concentrations of chemical structures in the basic units of the network structure were applied, and the thermal and mechanical properties of their curing systems were investigated. The fracture energy of each system increased considerably with the increase of the alkyl chain length that adjoins the two mesogenic groups in the epoxy resins. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44244.

The bisphenol-F type flexible epoxy resin, having a good flexibility, was combined with an organo- and slurry-clay. The clay dispersions in the obtained epoxy/clay systems are significantly different depending on the type of clay. Particularly, the epoxy/slurry-clay system showed a high clay dispersibility into the epoxy matrix and was transparent in spite of the addition of 10 wt % clay. This result means that the swelling of the clay with formamide is effective for the expansion of the basal spacing of the clay. The slurry-clay nanocomposite (clay content: 5 wt %) showed a 4 times higher fracture energy than the neat epoxy system in the tensile test, though the organo-clay system (clay content: 5 wt %) was 1.5 times higher. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Polyglycidyloxypropyl silsesquioxane, which has an excellent heat resistance, was combined with sheet-like and spherical titanate as nano-fillers. The burning property of the composites was related to the shape of the dispersed titanate. A burning test was carried out according to the UL-94 test method. As a result, though the test specimen burned from one end to the other in the spherical titanate filled composite system, a fire extinguishing property was observed in the sheet-like titanate filled composite system. The extinguishing time of the latter system classified V-0 in the specification test. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Poly-(glycidyloxypropyl) phenyl silsesquioxane (PGPSQ) was combined with an organo-layered titanate filler. The phase structure of the obtained composite was evaluated by XRD and TEM observations. Moreover, a burning test was carried out according to the UL-94 test method. The extinguishing time of the nanocomposites was classified V-0 even for the 1 wt % layered titanate content. Based on the results, it was clarified that the frame retardancy of the PGPSQ/organo-layered titanate system was superior to the poly-(glycidyloxypropyl) silsesquioxane (PGSQ)/organo-layered titanate system, which was reported in a previous paper. In addition, the layered titanate as a filler also improved the ductility of the PGPSQ. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

When tensile stress was applied to epoxy resin filled with silica particles, we expected that the stress concentration would occur in the epoxy matrix near the interface between the matrix and the silica particles. We investigated the plastic deformation of the network chains near the interface, which was quantitatively evaluated using a polarized microscope FTIR technique. A biphenol-type epoxy resin, which has a mesogenic group in the backbone moiety, was used as the matrix resin. As a result, reorientation of the network chains along the direction of the tensile stress near the interface with the silica particles was observed. Especially when the silica/matrix interface has good bonding properties, the reorientation of the network chains was observed at a larger area around the silica particles. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 787–794, 2003

A novel terphenyl liquid crystalline (LC) epoxy resin was synthesized and characterized by 1H-NMR, Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), and polarizing optical microscopy. Depending on the curing temperature, the synthesized resin formed both smectic and nematic LC phases. A time-temperature-transformation diagram was constructed to optimize the curing process, which helped in the preparation of LC and isotropic system. The terphenyl epoxy resin obtained exhibited higher acid resistance than a comparable Schiff-base epoxy resin, and also displayed excellent fracture toughness. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41296.

Reactive copolymers with flexible alkyl side chains were used as modifiers to improve the toughness of a cycloaliphatic epoxy resin. In this study, we used three types of copolymers with different alkyl chain length (C4H9, C6H13, and C10H21). As a result, the system with an added copolymer having the longest alkyl chain length (C10H21) formed a phase separation structure. The addition of this copolymer (C10H21) led to a 50% increase in the fracture toughness (KIC) of the cured resin at the slight expense of its glass transition temperature. Scanning electron microscope observations in the vicinity of a crack tip after a compact tension test showed that cavitation of the dispersed phase occurred. The crack growth was inhibited and thus the toughness was improved due to the plastic deformation of the epoxy matrix followed by cavitation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011