The method for preparing monodisperse spherical polyimide particles by heating polyamic acid in aprotic polar solvents was examined. The copolymer consisting of a soluble polyimide and an insoluble polyimide were found to form the monodisperse spherical polyimide particles by heating it for imidization. This may be due to the dispersion effect, in which the soluble polyimide chains form a stable layer on the particle surface in the process of polyimide particle formation. However, monodisperse spherical particles were not obtained by the copolymerization of the polyimide that formed formless particles with the soluble polyimide. Moreover, monodisperse spherical particles with amino groups were also prepared by this method. The amino groups introduced on the particles were allowed to react with an acid chloride.

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High molecular weight o-cresol resins and the acetylated resins (Ac-oCR) were prepared. The dilute solution properties of Ac-oCR were determined to elucidate the nature of high molecular weight phenolic resins. The intrinsic viscosity [η] of Ac-oCR was determined in THF (good solvent) and THF/cyclohexane mixed solvent (θ-solvent). The exponent in MHS Eq. for Ac-oCR was 0.43 in THF and 0.28 in θ-solvent, respectively. Each value was much smaller than that for polystyrene. However, the values of expansion factor α_η³= [η] / [η] _θ for Ac-oCR in THF were equal to that for polystyrene in toluene, indicating that Ac-oCR showed the excluded volume effect and behaved like a linear polymer in good solvent.
On the other hand, the molecular weight dependence of mean-square radius of gyration <S²> for Ac-oCR agreed with that for polystyrene in both good and θ-solvent. The values of <S²>₀/X_w were constant for higher molecular weight Ac-oCR samples with x_w >500. This means that Ac-oCR behaves like a Gaussian chain, which is an ideal chain for linear polymer. We concluded that Ac-oCR with higher molecular weight showed linear polymeric properties such as polystyrene in solution.

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Network polymers are used for various corrosion protection applications because of their excellent corrosion resistance. Although there are many resins actually used for corrosion protection, their characteristics differ significantly. Therefore, it is essential to determine in detail the corresponding corrosion factors under the applied environment in order to choose the most suitable resin and the appropriate construction method. For example, the corrosion degradation of concrete structures by the generation of sulfuric acid poses a problem in sewer environment, and therefore, resin linings have been used as anti-corrosive protection. In this study, an actual long-term in-situ examination was performed using about 15 kinds of commercial resins, and a comparative test was also performed through weight and intensity measurements to establish an ultimate analysis of their corrosion degradation behavior under sulfuric acid environment. The obtained results indicated that even though the corrosion behavior varies with the kind of resins applied, it can be roughly classified into three types. For the epoxy resin, in which high permeation of sulfuric acid proceeds more readily than that of water, the permeation of sulfuric acid into the resin was found to proceed stepwise, and it was also clearly shown that over the long period, the penetration depth increased in proportion to the square root of time. Using this method, the life prediction of a lining system can be attained.

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In enhanced and horizontal recycling of Fiber Reinforced Plastics (FRP), which are very difficult to be recycled, optimization of sub-critical water hydrolysis using potassium hydrate and sodium hydrate, demonstration test of styrene-fumaric acid copolymer (SFC), separation by actual centrifugal separator, trial for SFC modification method using anhydride exchange reaction with acetic anhydride, and evaluation test of anhydrated SFC were conducted. The optimum concentrations of KOH and NaOH at 230°C for 4h were 0.38mol/l and 0.78mol/l, respectively. The optimum temperature was 230°C for the above both cases. SFC separation demonstration test was successfully demonstrated with water content of 67% after separation. The water content remaining in SFC after separation was decreased to approximately one fifth comparing to ordinary method as filter press. Anhydrated SFC was obtained from anhydride exchange reaction at 20°C for 8h with sulfuric acid and acetic anhydride. FRP board samples were produced and tested using anhydrated SFC with commercial low profile additive (LPA). At 50% of anhydrated SFC mixing ratio, anhydrated SFC showed almost equivalent performance to the commercial LPA, which is more expensive than styrene monomer as raw material. The 5 to 10 times enhanced recycling of the SFC was verified.

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Epoxy resins have high solvent resistance and high creep resistance in consequence with the network structure. However, the network structure may be the source of the brittleness. In order to improve the fracture toughness of the epoxy resins, several types of modifications have been applied. Initially in this review, reaction-induced phase separation method and particle-addition type toughening technology are compared from viewpoints of industrial application. Then, the mechanisms of particle-addition type toughening technology (ex. rubber particles, glass particles and thermoplastic particles) are individually discussed, which followed by the discussions on the role of the particulate modifiers and the epoxy resins as matrix in the toughening mechanisms.

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Radical polymerization of vinyl monomers can proceed independently of the non-radical curing reaction of thermosetting resins. Therefore, vinyl polymer modifiers for such thermosetting resins are expected to be prepared in situ during the curing procedure. In this review, we describe toughening of the thermosetting resins using the modifiers prepared in situ by radical polymerization. Utilization of in situ polymerized modifiers is advantageous due to not only its simplified processes and decreased viscosity of the uncured resins but also the achievement of large increase in fracture toughness without sacrificing other properties such as strength and modulus. The in situ prepared alternating copolymer of styrene with N-phenylmaleimide (PMS) modified with polyoxyethylene (POE) was found to be effective for toughening of acid-anhydride-cured epoxy resin with reducing decrease in flexural strength. The modification of cyanate ester resin with the in situ generated PMS grafted with POE and crosslinked by divinylbenzene showed 2.35 times higher fracture toughness than the unmodified resin with keeping flexural strength, flexural modulus and Tg of the original resin. In situ generated crosslinked poly (benzyl methacrylate) toughened amine-cured epoxy resin, to which toughening by in situ generated PMS polymers could not be applied due to the inhibition of the alternating copolymerization by the amine used as a curing agent.

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