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－　　－3Published PaperEvaluation of Mechanical Properties for CFRTP Using In Situ Polymerizable Thermoplastic Urethane ResinRecent research on carbon fiber reinforced thermoplastic (CFRTP) resin has been actively pursuing its application to automobile parts to reduce the weight of automobiles. However, since thermoplastic resin is provided as a polymer, its melt viscosity is high and it is difficult to impregnate into continuous fiber. This is the reason for the development of in situ polymerizing thermoplastic resin that has a low viscosity before curing and polymerizes linearly after impregnation into continuous fibers. In addition, in situ polymerizing thermoplastic urethane resin has a high glass transition tem-perature (Tg). By using this resin, it is expected that CFRTP having excellent impregnating property and heat resistance can be produced. In this study, CFRTP using the newly developed in situ polymerizing thermoplastic urethane resin was prepared and compared with CFRTP using representative in situ polymerizing thermoplastic resin and CFRP using thermosetting resin. The mechanical properties of CFRTP were evaluated by a static three-point bending test, dynamic three-point bending test, creep test, DCB test, and dynamic viscoelasticity test. Based on the test results, the following conclusions were obtained.1) The CFRTP prototype using the field-polymerized urethane resin did not have any voids and was in a good impreg-nation state.2) It exhibited a higher static and dynamic bending strength than that of the CFRTP using in situ polymerized thermo-plastic resin and CFRP using thermosetting resin developed so far.3) It showed excellent impact energy absorption until breakage.4) The glass transition temperature evaluated from the decrease in the storage elastic modulus and the peak of the loss tangent (tan δ) was about 160°C, showing excellent heat resistance.5) There was little decrease in the bending strength even in a high-temperature environment, showing excellent heat re-sistance.6) There was no increase in creep strain even after about 30 h, the creep strain rate was almost 0, and the creep resis-tance was excellent.Keywords: In situ polymerizable, Thermoplastic, CFRTP, Mechanical property, Urethane resin現場重合型熱可塑性ウレタン樹脂をマトリックスとするCFRTPの機械的特性の 評価　本研究では，ガラス転移温度（Tg）の高い現場重合型の熱可塑性ウレタン樹脂を新規に開発し，炭素繊維強化熱可塑性樹脂（CFRTP）を試作してその機械的特性を評価した．機械的特性は，静的3点曲げ試験，動的3点曲げ試験，クリープ試験，DCB試験および動的粘弾性試験により評価し，これまでに開発されてきた現場重合型の熱可塑性樹脂をマトリックスとするFRTPと比較して，その優位性について考察した．これらの評価試験結果から得られた主な結論は以下のとおりであり，すべての評価試験においてこれまでに開発されたFRTPや熱硬化性樹脂を使用したCFRPよりも優れた機械的特性を示した．1）現場重合ウレタン樹脂を用いて試作したCFRTPにはボイドがなく含浸状態が良好である．2）これまで開発されたCFRTPやCFRPよりも高い静的および動的曲げ強度を有している．3）高い破壊靭性値を有しており，破断までの衝撃エネルギー吸収性に優れている．4）損失接線（tan δ）のピークから評価したTgは約160℃であり，貯蔵弾性率の低下はほとんどみられない．5）高温環境下でも曲げ強度の低下が少なく，優れた耐熱性を有している．6）長期間の荷重環境下においてクリープひずみ速度はほぼ0であり，耐クリープ性・耐久性に優れている．キーワード：現場重合，熱可塑性樹脂，CFRTP，機械的特性，ウレタン樹脂Journal（掲載誌）Journal of the Japan Reinforced Plastics Society, Vol.66, No.11, 519-526, 2020.Norio HIRAYAMA, Hirofumi NISHIDA, Tsuyoshi SUGITA, Kiyoshi UZAWA, Yoshinori YAMADA and Tadashi TAKEKAWA