岸 肇

One of the conventional methods to develop biodegradable plastics at a reasonable cost is manufacturing the blend of expensive polycaprolactone (PCL) and lower-priced starch. However, past studies have shown that the amount of starch blended with plastics is relatively small and the dynamic properties are not sufficiently improved. This study focuses on the improvement of physical properties of starch, including thermal plasticity, compatibility with PCL and dynamic properties. Starch was blended with glycerine and water to achieve thermal plasticity and improve compatibility with PCL. Addition of maleic anhydride to PCL improved compatibility, which resulted in improved dynamic properties. Addition of clay results in dispersed thermo plastic starch, which improves compatibility with PCL. In addition, it was clarified that addition of clay accelerates the positive effect of electron irradiation on the blend. Copyright (c) 2006 John Wiley & Sons, Ltd.

Wood-based epoxy resins were synthesized from resorcinol-liquefied wood. Wood was first liquefied in the presence of resorcinol with or without a sulfuric acid catalyst at high temperature. Because of the hydroxyl groups, the resorcinol-liquefied wood was considered as a precursor for synthesizing wood-based epoxy resin. Namely, the phenolic OH groups of the liquefied wood reacted with epichlorohydrin under alkali condition. By the glycidyl etherification, epoxy functionality was introduced to the liquefied wood. The epoxy functionality of the resins was controlled by the concentration of phenolic OH groups in the liquefied wood, which would be a dominant factor for crosslink density and properties of the cured epoxy resins. The flexural strength (150-180 MPa) and the modulus of elasticity (3.2 GPa) of the highly crosslinked wood-based epoxy resin were equivalent to those of the commercially available epoxy resin, diglycidyl ether of bisphenol A (DGEBA). Also, the shear adhesive strength of the wood-based epoxy resin was higher than that of DGEBA when plywood was used as the adhesive substrates. The mechanical and adhesive properties suggested that the wood-based epoxy resins would be well suited for matrix resins of natural plant-fiber reinforced composites. (c) 2006 Wiley Periodicals, Inc.

Carboxyl-terminated butadiene acrylonitrile (CTBN) liquid rubber/ epoxy (dialycidyl ether of bisphenol-A: DGEBA) / diamino diphenyl methane (DDM) resins, in which CTBN was the major component, were formulated to evaluate the damping and adhesive properties. In case that acrylonitrile (AN) in CTBN copolymer were 10 similar to 18 mol%, the blend resins including 60wt% CTBN showed micro-phase separated morphologies with rubber-rich continuous phases and epoxy-rich dispersed phases. The composite loss factors (eta) for steel laminates, which consisted of two steel plates with the resin layer in between, depended highly on the environmental temperature and the resonant frequencies. On the other hand, in case that AN in CTBN was 26 mol%, the cured resin did not show clear micro-phase separation in nano-scale, which means the components have excellent miscibility. This polymer alloy had broad glass-transition temperature range, which resulted in the high loss factor (eta > 0.1) for the steel laminates in broad temperature range and at several resonant frequencies. Also the resin indicated high adhesive strengths to aluminum substrates under both shear and peel stress mode. The high adhesive strengths of the CTBN / DGEBA / DDM alloy originated in the high strength and energy absorbability of the bulk resin.

The damping properties and the adhesive properties of carboxyl-terminated butadiene acrylonitrile rubber (CTBN)/epoxy (diglycidyl ether of bisphenol-A: DGEBA) polymer blends, including 60 wt% CTBN, were evaluated. In cases when the acrylonitrile (AN) contents in CTBN were 10-18 mol%, the blend resins showed micro-phase separated morphologies with rubber-rich continuous phases and epoxy-rich dispersed phases. The composite loss factors (eta) for steel laminates, which consisted of two steel plates with the resin layer in between, depended strongly on the environmental temperature and the resonant frequencies. Moreover, in the case that the acrylonitrile (AN) content in CTBN was 26 mol%, the compatibility in the blend was enhanced and the resin did not indicate clear micro-phase separation in nanoscale. The temperature dependence of the tan delta of the resin was small, which resulted in the high loss factor (eta > 0.1) for the steel laminate over a broad temperature range, with several resonant frequencies. The resin also indicated high adhesive strength values in both shear mode and peel mode. The temperature dependence of eta and the order of eta among resin formulations could be explained according to the mode proposed by Ross, Unger, and Kerwin.

FRP用塗料等に用いられるゲルコートの主成分である不飽和ポリエステル樹脂表面に紫外線照射した際の形態変化について顕微鏡的評価を行った.具体的には, イソ系不飽和ポリエステル樹脂とオルソ系不飽和ポリエステル樹脂とを比較し, 表面近傍について紫外線照射時間ごとの形態観察を行い, 表面粗さや樹脂厚みを測定することにより, オルソ系樹脂よりイソ系樹脂の表面劣化が少ないことを定量的に把握した.両者はエステル結合位置以外には化学構造に違いがなく, 動的粘弾性から知られる平均架橋密度も同等であったが, 紫外線照射により性じた表面凹凸やバルク樹脂破断面の凹凸はオルソ系樹脂の方が大きいことが知られた.

耐熱接着性と加熱解体性を兼備する構造用エポキシ樹脂接着剤の組成設計を試みた。イミド骨格を有する高極性単官能エポキシ（グリシジルフタルイミド: GPI) をビスフェノールA型エポキシ樹脂に配合することにより，他の単官能エポキシ添加系と比較して硬化樹脂の Tg 低下を抑制しつつ Tg を越えた温度域での軟化が大きくなり，ゴム平坦域弾性率を効果的に低下させうることを見出した。また，同エポキシ組成であっても硬化剤種によって熱軟化挙動は異なり，潜在性硬化触媒ジシアンジアミド／ジクロロフェニルジメチルウレアは，Tg 低下抑制効果と熱軟化効果のバランスに優れた硬化物を与えた。これらの知見を基に，80℃以上の Tg，3GPa以上のガラス領域樹脂弾性率を保ちつつ，ゴム状平坦域弾性率を約 2MPa にまで低下させ得る GPI 25%含有エポキシ樹脂組成物を得た。さらに，上記樹脂組成物に膨張黒鉛を 10%添加することにより，80℃せん断接着強さが 20MPa という構造材適用レベルの耐熱接着性を有し，かつ，膨張黒鉛の熱膨張により加熱解体する解体性接着剤組成を見出した。

木材とレゾルシノールとの加溶媒分解反応により得られる液化木材を前駆体として合成した木材エポキシ樹脂の接着性能を評価した。鋼板を被着体とした場合，木材エポキシ樹脂の引張せん断接着強さはビスフェノールA型エポキシ樹脂に及ばないが，木材単板を被着体とした場合は逆に，木材エポキシ樹脂はビスフェノールA型エポキシ樹脂の約2倍の引張せん断接着強さを発現した。破壊モード観察の結果，被着体木材内での破壊が主に生じており，木材エポキシ樹脂が木質バイオマスとの良好な接着性を有することがわかった。このバイオマス接着性の応用展開として，木材エポキシ樹脂をマトリックス材とし亜麻繊維を強化材とするバイオマス複合材を調製した。その破断面からも，木材エポキシ樹脂特有の植物繊維への高接着性が認められ，高性能バイオマス複合材創出への糸口を見いだした。

カルボキシル基末端ブタジエンニトリルゴム(CTBN)をエポキシ樹脂に反応ブレンドしたポリマアロイ樹脂により金属板を接着し，制振特性および接着強さを評価し，物性発現機構をアロイ樹脂の動的粘弾性，力学特性や相分離構造と関連づけ考察した。CTBN/ジグリセロールポリグリシジルエーテルアロイ樹脂(CTBN添加量30wt%)には，ゴムリッチ相が連続相，エポキシリッチ相が分散相となるミクロ相分離構造が硬化中に形成された。硬化樹脂の低強度・低伸度を反映し接着強さは低く，また拘束型制振鋼板の損失係数（η）の温度・周波数依存性は大きいものであった。一方，CTBN/ビスフェノールAジグリシジルエーテルアロイ樹脂硬化物(CTBN添加量60wt%)には明確な相分離構造は認められず，両成分がナノレベルにまで相溶化が進んだと考えられる。硬化樹脂の広温度範囲における高損失正接(tanσ)を反映し，広い温度・周波数領域にて拘束型制振鋼板のηが0.1以上となる高制振性を発現した。ηの温度依存性や樹脂組成間の序列は，硬化樹脂のtanσ,せん断弾性率および制振鋼板の形状因子をパラメータとしたRoss-Unger-Kerwin式により概ね説明できる。また，CTBN／ビスフェノールAジグリシジルエーテルアロイ樹脂の高せん断・はく離接着強さは，バルク樹脂の高エネルギー吸収能力とアルミ板への高界面接着性によりもたらされたと考えられる。

単官能エポキシを添加した数種のエポキシ接着剤組成について，アルミニウム被着体へのせん断接着強さを評価し，その接着強さ発現機構を添加剤の極性や接着層の残留内部応力との関連にて考察した。イミド骨格を有する高極性単官能エポキシ（グリシジルフタルイミド:GPI)の添加により，ビスフェノールA型エポキシ樹脂／アルミニウム被着体の引張りせん断接着強さが向上した。別の単官能エポキシであるt－ブチルフェニルグリシジルエーテルを添加した系では同様の効果は認められず，単官能骨格導入による残留内部応力の低下のみではこの現象を説明できない。FT-IR解析を行ったところ，GPI添加系の場合，イミド骨格（カルボニル基）が接着界面近傍に高濃度に存在することが知られた。高極性を有するGPIは高極性表面を持つ金属被着体との親和性が高く，被着体表面近傍に硬化中に引きよせられ，両者の引力的相互作用により接着強さ向上をもたらしたと考えられる。

種々の化学構造を有するイオン含有ポリマーを新規に合成し，それを硬化触媒として用いたエポキシ樹脂硬化物の動的粘弾性測定におけるTgレス化挙動を観察することにより，Tgレス化を引き起こすための化学構造上の必要条件に関し，検討を行なった。その結果，Tgレス化させるイオン含有ポリマーとしては，エポキシ基をアニオン重合させることのできる求核性を有するアルカリ金属のカチオンと共役塩基とのイオン対，及びイオン含有ポリマーの凝集を抑える脂溶性連鎖を備える必要があるが，主鎖骨格の化学構造及び酸基の種類には依存しないことが分った。また，エポキシ樹脂を効果的にTgレス化させるためのイオン含有ポリマーの添加量には最適値が存在し，K+を含有するポリマーの場合，その添加量は概ねエポキシ基1モルに対しK+0.02～0.03モルであった。

A novel type matrix resin using clay-nanocomposite based on epoxy/acrylate interpenetrating polymer network (IPN) was prepared by in situ polymerization technique. Three types of organophilic montmollironite as a nano-filler which treated with alkyl, ω-calboxyl alkyl, or dihydroxyl alkyl ammonium salt were dispersed into the base IPN resin. The cured products were evaluated by X-ray diffraction, dynamic mechanical analysis and fracture toughness test. And the developed matrix resin was attempted to design the glass fiber reinforced plastic (GFRP). Properties of GFRP were investigated by dynamic mechanical analysis and fracture toughness test.

種々のカルボン酸のアルカリ金属塩をアニオン重合触媒として用い, モノエポキシドを重合させた場合の分子鎖成長を追跡することにより, それらカルボン酸塩のアニオン重合触媒としての活性を評価した。更にそれらをビスフェノールA型エポキシ樹脂の硬化触媒とした場合の硬化物の動的粘弾性測定を行なうことにより, T_gレス化を検討した。その結果, カルボン酸のアルカリ金属塩はイミダゾ-ル等の従来のアニオン重合触媒に比較してエポキシドを極めて短時間で高重合体にまで重合させることが分った。また, 硬化触媒のアニオン重合性が高い方がより顕著にエポキシ樹脂をT_gレス化させる傾向があった。これらの結果を基に, T_gレス化のメカニズムを推定した。

The aim of this study was to characterize the adhesive properties of epoxy resins toughened with pre-formed polyamide-12 particles in comparison to the conventional approach using core-shell rubber particles. Dicyandiamide-cured diglycidyl ether of bisphenol-A was used as the base epoxy resin. The T-peel adhesive strength of the toughened resin containing 20 phr polyamide-12 particles was about 3-times higher than that of the unmodified resin. In the case of rubber toughening, the improvement in adhesive strength tended to reach a plateau, even after improvement in the resin toughness itself. Besides, the polyamide particle toughening utilizes the bulk resin toughness for the peel adhesive strength, even in a thin adhesive layer between the substrates. The polyamide particles embedded in epoxy resin matrix were fractured after bridging cracks and stretching in the peel process. The crack-bridging mechanism by the pre-formed thermoplastic polymer particles was operative behind the crack-tip and would, therefore, experience a relatively small constraint by the presence of rigid metal substrate, in comparison to conventional rubber toughening. The requirements for the polymer particles to work as a modifier using the bridging mechanism would be good adhesion to the epoxy matrix, high toughness and a relatively lower modulus of elasticity than that of matrix resin.

粘着剤は粘着テープを中心に幅広く利用されているが，タック性だけでなく他の機能も注目され始めている。本研究では，粘着剤の衝撃吸収性に着目し，プラスチックとの積層による耐衝撃性の改善を試みた。4種類のプラスチック，ポリカーボネート，ポリアミド，ポリアセタール，ポリメチルメタアクリレートと粘着剤を積層した試料の貫通衝撃試験を行い，粘着剤が衝撃特性に及ぼす影響について検討を行った。プラスチック単層板と粘着剤を貼り合せた試料では，プラスチックの種類によってその効果は異なり，ポリアセタールにおいて衝撃吸収エネルギーが約4倍まで上昇した。プラスチック板3枚を粘着剤で貼り合せた試料では，すべての材料で粘着剤貼付による吸収エネルギーの増加がみられたが，特にポリアミド6，6，ポリアセタールで大きなエネルギー増となった。粘着剤との貼り合わせにより衝撃エネルギーが大きく増加した試料はすべて，衝撃速度が低下するにつれて吸収エネルギーが増加する傾向があり，その増加の原因はひずみ速度の低下が主要因であると結論づけられた。

木材とフェノール類との加溶媒分解反応により得られる木材液化物を前駆体とし，フェノール性水酸基をグリシジルエーテル化する反応経路により，木質バイオマスを主原料とする液状エポキシ系樹脂を合成した。反応溶媒にフェノールを用いた液化木材を前駆体として合成した木材エポキシ樹脂からは，充分な架橋構造を有する樹脂硬化物を得ることはできなかった。一方，フェノール性水酸基を2個有するレゾルシノールとの反応で得た液化木材を前駆体に合成した木材エポキシ樹脂からは，市販ビスフェノールA型エポキシ樹脂と同等以上の室温曲げ弾性率 (3.2GPa)，曲げ強度 (150～180MPa)を発現する高強度硬化樹脂を得ることができた。液化木材中の水酸基含有量は原料組成が同一の場合でも液化条件（温度・時間）により変化する。液化木材中のフェノール性水酸基の確保は，それを前駆体に合成される木材エポキシ樹脂のエポキシ基含有量を支配し，結果としての樹脂硬化物の架橋密度や力学特性を決定する重要因子であることがわかった。

Recently, carbon-nanotubes (CNT) have become a main focus in the polymer nanocomposites field. In a previous study, polymer composites with good CNT dispersion were obtained using a twin-screw extruder. There was a close correlation among the following three parameters: the total shear strain [γ·t] responsible for the dispersion in the extruder, the area ratio of agglomerate CNT in the composite and the conductivity of the polymer composite. [Ar] indicates the degree of dispersion and is obtained through microscopic observations. Lower [Ar] corresponds to better dispersion, while higher values correspond to poor dispersion. In the high [Ar] region, the composite conductivity increases with a decrease in [Ar], while in the low [Ar] region, the conductivity decreases with a decrease in [Ar]. This indicates that an optimum value of [Ar] exists to obtain the best (highest) conductivity (minimum value of resistivity).<br>This report will describe attempts to obtain better dispersion than those in the previous study by modifying the screw profile with a high shear rate segment. Volume resistivity dependence on [Ar] obtained in this study was in good agreement with previous resistivity results.<br>Uniform dispersibility was proposed as a new parameter. We investigated the relationship between CNT length and uniform dispersibility in the matrix and the behavior of the resistivity curve.<br>We can conclude that a CNT composite shows the best conductivity when it has an optimum balance of CNT length and uniform dispersibility.

The aim of this study is to characterize the damping properties of carbon fiber-reinforced interleaved epoxy composites. Several types of thermoplastic-elastomer films, such as polyurethane elastomers, polyethylene-based ionomers and polyamide elastomers were used as the interleaving materials. The damping properties of the composite laminates with/without the interleaf films were evaluated by the mechanical impedance method. Also, the effects of the lay-up arrangements of the carbon-fiber prepregs on the damping properties of the interleaved laminates were examined. The viscoelastic properties of interleaved polymer films were reflected in the damping properties of the corresponding interleaved laminates. The loss tangent of the interleaf films at the test temperature played an important roll in the loss factor of the interleaved laminates. Also, the stiffness of the films at the resonant frequency of the laminates was another important parameter that controlled the loss factor of the interleaved laminates. (C) 2004 Elsevier Ltd. All rights reserved.

A series of newly developed HAP (Hydroxyapataito) fiber reinforced bone cement composite ranging from 5-25%, by weight fraction have consequently been developed and investigated for use in orthopedic surgery. The resulting HAP fiber reinforced bone cement was characterized by measurement made of tensile strength, fracture mechanics parameter including fatigue crack propagation (FCP), creep resistance, polymerization features and degree of monomer release. It is demonstrated that HAP reinforcement provides an increase in fracture toughness, FCP resistance and creep resistance with reductions in exthothermic temperature and in monomer release ratio. This study offers considerable potential for addressing the major problem in current orthopedic practice. (C) 2003 Published by Elsevier Ltd.

Clay nanocomposites of amorphous polymers with ester groups were prepared by twin screw extrusion and injection molding. Although, in general, an organophilic clay is required to form good nanocomposites, we succeeded in preparing nanocomposites with good clay dispersion by using natural clay without organophilic agents. In this study, PETG, an amorphous polymer with excellent clarity, was used as the matrix polymer. The resultant nanocomposites retained high transparency and clarity despite the 5% clay content. Flammability properties were measured using a cone-calorimeter. The heat release rate decreased 54% for the PETG/clay nanocomposites compared to the neat PETG resin and the phenomenon of molten droplets (dripping) does not appear during the combustion. Therefore, high flame retardancy has been achieved. Furthermore, the tensile modulus of the nanocomposites increased by 50% over the neat PETG modulus. The evaluation of WAXD patterns and TEM observations indicated that the silicate layers of the clay were not intercalated nor individually exfoliated. Partial exfoliation and a decrease in the number of layers were, however, indicated.

構造用接着剤への要求特性のうち，剥離接着強さと耐熱性はトレードオフの関係になりやすく，これらを両立する接着剤の研究開発は重要課題である。本研究では，ポリアミド系微粒子添加エポキシ樹脂を調製し，樹脂特性と接着特性との関係および物性発現メカニズムを検討した。ポリアミド12微粒子添加樹脂は既存のコアシェルゴム微粒子添加樹脂に比較し，樹脂靭性向上が剥離接着強さ向上に結びつく効果が高いことがわかった。ポリアミド微粒子添加系では進展クラック先端より後方側に粒子ブリッヂングが生じ，粒子の塑性変形にてエネルギーを吸収するため，樹脂の塑性変形に依存するゴム添加系より被着体による変形拘束の影響が小さく，剥離接着強さ向上が顕著になると考察した。樹脂との界面接着性良好な高靭性熱可塑性樹脂微粒子による接着剤改質は，ゴム添加に比較して耐熱性を損なわずに剥離接着強さを向上させる有効技術と考えられる。

Newly developed self-adhesive type honeycomb co-curable carbon fiber prepreg system, "TORAYCA T700GC / 3680": reduces fabrication cost and weight of honeycomb sandwich structures. Excellent adhesive property of the 3680 toughened epoxy resin allows the elimination of cost-added adhesive films in prepregs / honeycomb co-curing sandwich structures, which also leads to weight reduction of aircraft composite parts. Good fiber-spreading capability of T700GC-12K fabric combines very well with the flow-controlled 3680 resin. This combination minimizes internal porosity and surface pitting of honeycomb sandwich skins. Good tackiness and excellent formability of prepreg expedite the fabrication of complex contoured parts. Additionally the higher tensile strain of T700GC fabric compared to the conventional T300-3K fabric gives the higher impact-penetration resistance of honeycomb sandwich skins.

Newly developed self-adhesive type honeycomb co-curable carbon fiber prepreg system, "TORAYCA T700GC / 3680", reduces fabrication cost and weight of honeycomb sandwich structures. Excellent adhesive property of the 3680 toughened epoxy resin allows the elimination of cost-added adhesive films in prepregs / honeycomb co-curing sandwich structures, which also leads to weight reduction of aircraft composite parts. Good fiber-spreading capability of T700GC-12K fabric combines very well with the flow-controlled 3680 resin. This combination minimizes internal porosity and surface pitting of honeycomb sandwich skins. Good tackiness and excellent formability of prepreg expedite the fabrication of complex contoured parts. Additionally, the higher tensile strain of T700GC fabric compared to the conventional T300-3K fabric gives the higher impact-penetration resistance of honeycomb sandwich skins.

The local strains in unmodified and rubber-modified epoxies under multiaxial stress states were examined. Matrix ductility was varied by using epoxide resins of different epoxide monomer molecular weights. The stress state was altered from a pi a ne strain case to a plane stress case by varying the thickness of the test specimens. It was confirmed that, in the case of unmodified resins, the thinner specimens which experienced nearly uniaxial tensile stress exhibited much higher local strains at failure than the thicker counterparts which experienced highly triaxial tensile stress. Also, the cross-link density was reduced as monomer molecular weight increased, thus the increase in local plastic strain due to the stress state change also became greater. Furthermore, it was found that rubber modification markedly increased the plastic strain to failure, irrespective of the specimen dimensions, and that the extent of this plastic strain increased as cross-link density was lowered. These results are consistent with the concept that the cavitation of rubber particles relieves the initial multiaxial constraint in a thick specimen, induces a stress state closer to plane stress throughout the specimen, and consequently enables the matrix to deform to a larger extent. The results also show clearly that the toughenability of a matrix resin is not independent of the stress state and the matrix ductility. (C) 1998 Kluwer Academic Publishers.

The objective of the present study was to determine whether the ductility and toughenability of a highly cross-linked epoxy resin, which has a high glass transition temperature, Tg, can be enhanced by the incorporation of a ductile thermoplastic resin. Diglycidyl ether of bisphenol-A (DGEBA) cured by diamino diphenyl sulphone (DDS) was used as the base resin. Polyethersulphone (PES) was used as the thermoplastic modifier. Fracture toughness and shear ductility tests were performed to characterize the materials. The fracture toughness of the DDS-cured epoxy was not enhanced by simply adding PES. However, in the presence of rubber particles as a third component, the toughness of the PES-rubber-modified epoxy was found to improve with increasing PES content. The toughening mechanisms were determined to be rubber cavitation, followed by plastic deformation of the matrix resin. It was also determined, through uniaxial compression tests, that the shear ductility of the DDS-cured epoxy was enhanced by the incorporation of PES. These results imply that the intrinsic ductility, which had been enhanced by the PES addition, was only activated under the stress state change due to the cavitation of the rubber particles. The availability of increasing matrix ductility seems to be responsible for the increase in toughness.

The structure of prepregs (TORAYCA Prepreg P2302) for aircraft primary structure materials consists of TORAYCA T800H, high-strength carbon fibers, and 3900-2, high toughness resin and the improvement of impact resistance was achieved while maintaining superior heat resistance of epoxy matrices. The TORAYCA Prepreg 2302 satisfies environment resistance and durability necessary as a structural material and has been accepted as an industrial material because of its superiority in prepreg handling properties which are important for actual fabrication. The P2302 is used for empenage and floor beams of the B777 by Boeing and also contributes to light-weight of primary structural materials for aircraft.

イミドオリゴマーアロイによって高靱性となったエポキシ樹脂について, 靱性向上機構および相分離構造形成機構について考察し, 硬化条件と靱性およびモルフォロジーとの関係を検討した。<BR>UCST型の相図を持つ本系は, 硬化過程においてスピノーダル分解型の相分離をし, マイナー成分 (30wt%) であるオリゴマーリッチ相が連続相を形成する。破壊時には, 高靱性相であるイミドオリゴマーリッチ連続相の延性的破壊, および本来は脆性相であるエポキシリッチ分散相の大変形が生じていることが電子顕微鏡観察でわかった。これらが靱性向上につながる主たるエネルギー吸収機構であると考えられる。硬化条件の影響を検討したところ, より低温で相分離およびゲル化を行った場合の方が相分離構造周期が小さくなり, より高靱性となることがわかった。構造周期が小さくなることにより上記の高靱性化機構がより効果的に働き, エネルギー吸収量を増大させたと考えられる。

エポキシ樹脂の靭性改質剤としてアミノ基末端ポリイミドオリゴマーを合成検討し, 3種のエポキシ可溶性イミドオリゴマーを見出した。オリゴマーをエポキシ樹脂に溶解し相図を作成したところ, オリゴマーPI-Aを混合した系は二相分離領域のない均一相溶型相図を有するが, このオリゴマーにジメチルシロキサンをブロック共重合したオリゴマーPI-Siを混合した系は上限臨界共溶温度 (UCST) 型相図を有することがわかった。またビス (アミノフェノキシフェニル) ヘキサフルオロプロパンを共重合成分として含むPI-F添加系もUCST型相図を持つことがわかった。<BR>オリゴマーを30wt%添加した系について破壊靭性値G_ICを測定し, 電子顕微鏡によるモルフォロジー観察を行った。均一相溶構造であるPI-A系の靭性値G_ICは改質前の2倍程度に留まり, 樹脂破断面は平滑である。それに対し, UCST型相図を有するオリゴマーPI-Si系およびPI-F系の靭性は, 改質前の8～9倍程度にまで向上した。オリゴマーPI-Si系は両相連続構造, オリゴマーPI-F系は, 海相がオリゴマーリッチである逆海/島構造を形成するといった相分離形態の違いはあるが, どちらもマイナー成分であるイミドオリゴマーリッチ相が連続相を形成し, 破断面が複雑化し, 高靭性を発現している。