Kenzo Fukumori

A novel morphological model for carbon nanotube/polymer composites having high thermal conductivity and electrical insulation

Carbon nanotubes (CNTs), owing to their extremely high thermal conductivity (∼3000 W m−1 K−1), have recently attracted attention as notable nanofiller candidates to improve the thermal conductivity of polymers. However, CNTs cannot practically be used for highly electrically insulating polymers because even a few CNTs impart a high electrical conductivity to the polymers. Here, we design and fabricate CNT/polymer composites having a novel morphology, which achieves both enhanced thermal conductivity and high electrical insulation. This morphology comprises a matrix polymer and a CNT-localizing domain polymer encapsulated by a shell-forming component, which contributes to the selective localization of the CNTs into the dispersed domains. Such a controlled morphology is formed by the self-organization of the CNTs and the constituent polymers. A tailor-made morphology of CNT/polymer composite in accordance with our proposed model represents a promising route to a wide variety of applications of CNTs in materials requiring high electrical insulation.

Study of chemical gelation dynamics of acrylamide in water by real‐time pulsed nuclear magnetic resonance measurement

Chemical gelation process of acrylamide monomers in water has been studied by a real‐time pulsed nuclear magnetic resonance (NMR) measurement. The temporal change of molecular mobility has been detected by a real‐time observation of the spin–spin relaxation time T2. The influence of the concentration of crosslinker and acrylamide on gelation dynamics has been studied, and it becomes clear that these factors have strong effects on the gelation dynamics. The effects of linear polymerization and network formation on the motional state of water have been studied. The formation of three‐dimensional cages drastically reduces the mobility of water. In low acrylamide concentration, the results of NMR measurement mainly reflect the state of water. In high acrylamide concentration, on the other hand, they reflect both polymer network and water, and furthermore, in high crosslinker concentration the spatial heterogeneity of gels is observed. In this paper, we demonstrate that a real‐time NMR measurement is a useful ...

Swelling behaviour of rubber vulcanizates: 1. Real-time pulsed nuclear magnetic resonance measurements

Abstract Swelling behaviour of acrylonitrile-butadiene copolymer rubber vulcanizates immersed in a nonprotonic solvent was studied by real-time pulsed nuclear magnetic resonance (n.m.r.) measurements. The temporal change of the proton spin-spin relaxation time, T 2 , during the swelling process was obtained. The T 2 signal for the rubber vulcanizates was resolved into two exponentially decaying components (short T 2 and long T 2 ). The short T 2 component is assigned to the constrained regions in the rubber matrix, which may be mainly located around the crosslinks, and the long T 2 component to the regions lying outside the constraints. It was suggested that the decreased change of the fraction of the short T 2 component by swelling is closely connected with the enhanced molecular mobility of the network chains between the adjacent crosslinks through the diffusion of the solvent. The restricted swelling behaviour of the carbon black-filled rubber vulcanizates was interpreted mainly in terms of the constrained molecular motions of the network chains through the rubber-filler interactions and spatial effects of the filler particles. It becomes clear that the real-time pulsed n.m.r. measurements complement the results of the macroscopic swelling measurements for the rubber vulcanizates with more detailed information on the molecular interactions between the rubber and solvent molecules.

Pulsed NMR Study of Motional Heterogeneity in Acrylonitrile-Butadiene/Poly(Vinyl Chloride) Blends

Abstract Motional heterogeneity in blends of NBR (AN = 38%) and PVC was studied by 1H pulsed NMR. It was estimated from NMR relaxation measurements that the PVC molecules in the NBR phase form phase domains of the order of less than 10 nm, consistent with the microheterogeneous structure observed by TEM. Furthermore, by spin diffusion experiments using the Goldman-Shen pulse sequence, the size of the PVC phase domains was semiquantitatively evaluated to be 4.2 nm in the case of the cylindrical domains and to be 5.1 nm in the case of the spherical domains. It becomes clear that pulsed NMR complements the results of other analytical methods with more detailed information on the state of the molecular mixing in the blends.

New Surface Treatment of Polymers by Simultaneous Exposure to Vacuum Ultra-Violet Light and Nanometer-Sized Particles

By focusing the strong vacuum ultra-violet absorption of carbon atoms, polymer surfaces were simultaneously exposed to vacuum ultra-violet light (VUV) and nanometer-sized particles. As a result, the adhesive properties of polymer surfaces were improved. The improvement of the polymer surface is caused by the creation of the bonds between nanometer-sized particles and carbon atoms of the polymer surfaces, which is supported by the theoretical calculation of core electron bonding energy. Despite the other UV treatment, the polymers themselves were not damaged or maintained their surface activations for more than one month. This result should expand new applications of polymers, and apply to almost all polymers scientifically and industrially.

Swelling behaviour of rubber vulcanizates: 2. Effects of tensile strain on swelling

Abstract The effects of tensile strain on the swelling behaviour of acrylonitrile-butadiene copolymer rubber vulcanizates were studied by real-time pulsed nuclear magnetic resonance (n.m.r.) measurements and volume swelling measurements at equilibrium. It was shown that tensile strain causes an increase of the initial swelling rate evaluated by n.m.r. measurements and of the swelling ratio of the rubber matrix at equilibrium. This behaviour was discussed qualitatively in terms of the molecular mobility of the network chains on the basis of Treloars theory for swelling under deformation. It was suggested that the presence of reinforcing fillers in the rubber matrix exerts two noticeable effects on swelling under deformation: (1) a transient effect through some oriented structure induced by stretching, which restricts the increase of the swelling rate; (2) a strain amplification effect, which causes the increase of the average local strain in the rubber matrix and enhances the swelling ratio more remarkably proportional to the filler concentration as compared with that of the unfilled system.

Deformation behaviors of nitrile rubber vulcanizates as studied by pulsed NMR: Effects of carbon black fillers.

伸長状態下でのスピンースピン緩和時間(T2)の測定を行い, 一定伸長下の応力緩和特性と対応づけて, ニトリルゴム(NBR)の変形に伴うゴム網目鎖の分子運動性と不均質性の変化を調べた. NBR系のT2信号は, 2成分(Short, Long)に分離できた. Short T2成分は分子運動が拘束された架橋点近傍のゴム網目鎖の領域に対応し, ゴム網目鎖の変形挙動を直接特徴づけていることがわかった. Short T2成分の成分量は変形とともに徐々に増加し, 架橋点による拘束領域の広がりを反映していると考えられる. カーボン配合系では, 粒子充てん量の増加とともにその増加挙動はむしろ抑制され, ゴム-粒子間の相互作用を通じた種々の応力緩和機構に伴うエネルギー損失挙動と対応していると推定された. 更に, カーボン配合系のゴム網目鎖の分子運動性と巨視的な変形との関係において, ひずみ増幅作用の仮定が有用な近似であることが明らかになった.

A New Material Recycling Technology for Automobile Rubber Waste

A new material recycling technology for crosslinked rubber was developed using the continuous reactive processing method. In this process of producing reclaimed rubber, breakage of crosslinking points in the crosslinked rubber occurs selectively under the controls of shear stress, reaction temperature, and internal pressure in a modular screw type reactor. Deodorization during the process has also become possible by a newly developed method. The reclaimed rubber obtained from rubber waste generated from both automobile manufacturing products and post-consumer products shows excellent mechanical properties applicable to new rubber compounds. Furthermore, an enhanced rubber recycling process for producing thermoplastic elastomer (TPE) based on rubber waste has been established. The obtained TPE exhibits highly recoverable rubber elasticity and mechanical properties comparable to commercial TPE. It is expected that the rubber recycling technology developed and presented in this study will contribute to protecting the environment and also saving of resources. (A) For the covering abstract see ITRD E121867.

Polyamide 6 and high molecular weight phenol novolac blend having excellent mechanical properties in humid conditions

Polymer blends of polyamide 6 (PA6) and phenol novolac (PN) were prepared by melt mixing. Up to 30 wt% of high molecular weight PN (HPN) or low molecular weight PN (LPN) was blended with PA6, and the physical and mechanical properties were examined. The water absorption of PA6 is inhibited by PN, and this effect is independent of the molecular weight of PN. PA6 and PN are miscible, and their blends show a single glass transition temperature (T g) that is higher than that of PA6. HPN can enhance the T g of PA6 more efficiently than LPN because of its high T g. PA6 and the PA6/LPN blend after immersion in water had lower-than-room-temperature T gs transitioning to rubbery states. In contrast, the PA6/HPN blend after immersion in water had a higher-than-room-temperature T g. The PA6/HPN blend in water has excellent mechanical properties in its glassy state compared to those of PA6 in the dry state. Thus, the PA6/HPN blend can be used to broaden the applications of PA6, especially in humid conditions.

Molecular Dynamics Simulation of Thermal Motion and Elasticity of a Polymer Chain.

高分子鎖の熱運動とそれに基づく弾性を分子動力学シミュレーションにより解析し, ガウス鎖モデルを用いた統計的な理論と比較した. モデル作成と計算にはPOLYGRAFを使用し, 重合度50のシスポリブタジエンを用いて, 両端を拘束しない自由高分子鎖および両末端間距離を拘束したものについて計算を行った. その結果, 自由高分子鎖の回転半径と温度との関係には屈曲点が現れ, その温度はシスポリブタジエンのガラス転移温度171Kにほぼ一致した. 拘束高分子鎖について, 高分子鎖の自由エネルギー変化から計算した拘束力は, 両末端に働く力を直接に計算した拘束力に一致した. 拘束力は, 高分子鎖が伸びきり状態になる少し前まではガウス鎖モデルとほぼ同じ大きさであるが, そこから急激に立ち上がった. 一方, 両末端間距離の小さいランダムコイル状の場合には, 非結合原子間の相互作用によりエネルギー弾性的な力が働いていることが分かった.