In this paper, we report synthesis of DBU derivatives bearing various alkyl substituent (Alkyl DBU)s at 6-position and their catalytic effect in the thermal curing of bisphenol A diglycidyl ether (DGEBA). In the case of DBU, the curing process showed small exothermic peaks at 55 ºC and at 100 ºC. In contrast, in the case of Alkyl DBUs, the curing process exhibited their first exothermic peaks at 125 ºC, and second peaks at 200 ºC. All the cured epoxy resin prepared by DBU derivatives were insoluble, transparent, and hard solids. Compared to the epoxy resin cured by DBU, the resins cured by the alkylated DBUs showed higher gel fraction, volume shrinkage, and heat resistance. Therefore, Alkyl DBUs are expected to be useful compounds as thermally latent and highly active curing agents for epoxy resins.

Cresol formaldehyde novolac resins (Cre/Form) are used as photo-resist materials because they can be applied minutely onto hard silicon wafers, which are used in the process of making integrated semiconductor circuits. Resins with high hardness cannot be applied minutely onto flexible bases, such as polyimide films. To develop flexible novolac resins for photo-resists, bisphenol A (BisA), which has a bulky isopropylidene group, was incorporated into the molecular backbone chain of novolac resins as a phenolic (PhOH) component. Though BisA glutaraldehyde novolac resins (BisA/Glu) was inferior in drawing ability, they were much more flexible than cresol novolac resin. In this study, BisC/Glu, [BisA/BisC]/Glu and BisC/Form novolac resins ((BisC); 2,2-bis(4-hydroxy-3-methylphenyl)propane) were synthesized and investigated in expectation of improvement of the drawing ability. By increasing the crosslinker agent in the feed, it was observed that the dissolving ratio for alkaline aq. solution (DR) decreased with increasing M_w. To prepare cast films, resins meeting the condition of DR below 1100 Å/s and M_w over 1200 were chosen. Cast films of thickness 5 μm onto the polyimides, were prepared by spin-coating, heat-setting and then exposing to developer solution. The flexibility of the obtained resins was evaluated by observation of the bent parts with microscope. BisC/Glu and BisC/Form novolak resins were found to have high flexibility. Especially, BisC/Glu novolac resin exhibited extremely high flexibility comparable to that of BisA/Glu novolak resin. The lithographic performance of the novolac resins, coated with a thickness of 1.5 μm onto the silicon wafers was examined. The residual membrane thickness of BisC/Glu and BisC/Form novolac resins were high (>90%) and the resist pattern could draw up to 4 μm clearly. So, the BisC-type novolac resins were able to improve the drawing ability.

Phenoxy resin is an engineering plastic that is widely used as an insulating mold material, for example, in selfwelding insulating sheets that have superior moldability and low material costs. To improve the heat durability of phenoxy resin, the material can be doped with epoxy resin, which is a thermosetting material, and with an epoxy resin-phenolic resin mixture. We investigated the behavior of doped phenoxy resin in a heat-treatment process. We also investigated the heat durability, in terms of a thermal index (T_i), of these resins by using thermogravimetric analysis with the Ozawa－Flynn－Wall method. The thermally treated phenoxy resin doped with epoxy resin formed intermolecular-crosslinking, and its chemical heat durability improved compared with that of the phenoxy resin alone. On the other hand, phenoxy resin crosslinked by epoxy resin and phenolic resin closslinked by epoxy resin formed in the thermally treated phenoxy resin doped with the epoxy resin-phenolic resin mixture. By adding an appropriate amount of epoxy resin-phenolic resin mixture, its heat durability could be raised higher than that of phenoxy resin alone and of epoxy-resin-doped phenoxy resin.

Glass fiber reinforced plastic (GFRP) is widely used for various products even in the railway field because it has superior physical performance of electrical insulation. GFRP is used as the core parts of the circulating current prevention type pull-off arms and there were some examples of GFRP-breaking accidents. Most of the surface of the broken GFRP exhibited a smooth brittle fracture. In actual field, acid and water are considered to be the factors affecting the core conditions of pull-off arms. Therefore, in order to reproduce the actual condition, the authors developed and carried out the tests in which the solution (nitric acid and water) and mechanical stress were combined. As a result, the influence of nitric acid and water on GFRP was little when no mechanical stress was applied. However, when mechanical stress is applied, the influence of nitric acid is more significant. The mechanical strength of GFRP decreased dramatically and the surface of the broken GFRP exhibited a smooth brittle fracture.

Thermoplastic resins with benzoxazine rings in backbone have been studied in detail on their synthesis, reactivities and properties. These are carried out crosslinking reaction with ring opening by heating and formed networked structure containing phenolic hydroxyl and tertiary amino groups. These are also reported their advanced properties such as lower shrinkage, high heat resistance and flame retardance. Moreover, benzoxazine oligomers with ring structure in main chain have been developed and reported on their properties. In this article, outline of reactivities and post-cured properties of bifunctional benzoxazine (BXZ) and multifunctional benzoxazines oligomer in main chain (oBXZ) were explained.