| POLYMERS Vol.68 No.10 |
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COVER STORY
Curing and Molding of Polymers |
| COVER STORY: Highlight Reviews |
| Inhomogeneity of Thermosetting Resins | Toshio NAKAO, Atsushi IZUMI |
| <Abstract> Thermosetting resins are high strength and high heat resistant polymers, which are widely used in applications requiring reliability. One of the most important factors of the reliability is the inhomogeneity of the cross-linked structure, but the content has not been sufficiently elucidated. In this review, we introduce recent analysis methods and show the obtained findings from them, using phenol resin and epoxy resin as an example. Phenolic resin was difficult to analyze by scattering methods because the density contrast cannot be obtained. However, quantitative evaluation of the cured product became possible by high power quantum beam and solvent swelling techniques. Regarding the epoxy resins, interesting results have been obtained by the analysis of inhomogeneity as free volume. A persistent homology is effectively used in the analysis of inhomogeneity. It is suggested that the design of the precursor is momentous since the basis of inhomogeneity is determined by the sol-gel phase transition. And further elucidation of the co-continuous structure is expected. Keywords: Thermosetting Resins / Cross-Linked Structure / Inhomogeneity / Scattering Analysis / Free Volume / Persistent Homology |
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| Molecular Designs of Rigid Monomers for High-Performance Networked Polymers | Atsushi SUDO |
| <Abstract> High-performance network polymers exhibiting high thermal stability and mechanical strength are indispensable to the current electronics and aerospace fields. Such network polymers can be synthesized by the polymerization of multifunctional monomers. Among various factors that affect the physical properties of network polymers, rigidity of core structures of monomers is a dominant one. Various epoxides, benzoxazines, and cyanates with highly rigid cores have been developed and their reactions have afforded network polymers with excellent heat resistance, which exhibit high glass transition temperatures of ＞300℃ in some cases. So far, such rigid cores have been constructed from synthetic phenolic compounds as starting materials. Moreover, naturally occurring phenolic compounds and sugar derivatives have recently gained attention as sources of rigid cores of multifunctional monomers. The increase in variation of the monomer structure and the relevantly accumulated information about the physical properties of the corresponding network polymers will help in establishing a correlation between them, thereby guiding the future development of network polymers. Keywords: Network Polymer / High-Performance / Multifunctional Monomer / Rigidity / Epoxide / Benzoxazine / Cyanate |
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| COVER STORY: Topics and Products |
| Curing Reactions by Using Photobase Generators | Kanji SUYAMA |
| <Abstract> For the purpose of curing, photobase generators (PBGs) are attractive functional molecules. So far, carmbamates, O-acyloximes, aromatic amides and aldehydes, ortho-hydroxy-trans-cinnamamides, piperidines spiro-linked with azobenzene unit, α-aminoketones, amineimides and transition metal complexes have been proposed as PBGs that release amines mainly. Other families such as ammonium salts, reduced form of amidines, metallocenes, triphenylmethane derivatives, and nifedipines can release basic materials other than amines. Generated bases can work as nucleophiles to form covalent bonds or activate bond-formation reactions. Also, the bases are able to abstract protons from acidic molecules. Especially, strong bases abstract protons from acidic molecules such as alcohols, thiols, diketones, ketoesters, which form covalent bonds with acrylates, isocyanates, thiocyanates, epoxides, and thiiranes. These bond formations are highly useful for polymerization of monomers containing multi-functional monomers or cross-linking of polymers bearing such functional groups. Keywords: Photobase Generaor / Curing / Photopolymerization / Photo-Induced Cross-Linking / Nucleophile / Brönstead Base |
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| Photocuring of Epoxy Resins: Amplification of Photoreactions | Koji ARIMITSU |
| <Abstract> A system that amplifies the first stage of a photochemical reaction by connecting several thermochemical reactions is called cascade-type chemistry. Cascade-type chemistry will enable us to create highly sensitive photopolymers, such as photoresists and UV curing materials. We have developed compounds that generate organic acids and bases autocatalytically, denoted as either acid amplifiers or base amplifiers, because the number of acid or base molecules can be boosted in a nonlinear manner as a result of the autocatalytic decomposition of the amplifier. Our effort has been focused on the development of these amplifiers, and on how to combine these acid or base amplifiers with photoacid or photobase generator systems, because a small concentration of photogenerated acidic or basic species may be amplified. This results in a marked enhancement of the subsequent acid- or base-catalyzed curing reactions of epoxy compounds. Surprisingly, these systems enable us to cure opaque epoxy resins by UV irradiation and subsequent heating. Keywords: UV Curing / Epoxy Resin / Acid Amplifier / Base Amplifier / Photoacid Generator / Photobase Generator / Photochemical Reaction / Cascade-Type Chemistry |
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| Development of Processing Technology for CFRTP | Wataru OKUMURA |
| <Abstract> Several processing technologies of Carbon Fiber Reinforced Thermoplastic (CFRTP) are featured in the topic. First, the Double Belt Press (DBP) process is reported. The method is able to produce a board of CFRTP continuously. Second, the press molding process of CFRTP is reported. Some CFRTP products formed by this method are introduced. And some attention points in the procedure are explained. Finally, two welding processes of CFRTP are reported. A vibration welding process is welded by frictional heat at vibration. As an applied example of the process, a CFRTP honeycomb core sandwich, which we have developed, is reported. A laser welding process is a new method that we developed recently. The features of the laser welding process is reported. Keywords: Carbon Fiber Reinforced Thermoplastic (CFRTP) / Processing Technologies |
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| Functional CFRP Using Conductive Polymers | Tomohiro YOKOZEKI |
| <Abstract> The effectiveness of lightning damage suppression by a carbon-fiber-reinforced polymer (CFRP) laminate with a newly developed polyaniline (PANI)-based conductive thermosetting resin is introduced. We developed the PANI-based conductive thermosetting resin using dodecylbenzenesulfonic acid (DBSA) as a dopant and divinylbenzene (DVB) as a crosslinking agent, which improved the electrical conductivity and homogeneity of the resin. The develped PANI-based composite, when subjected to simulated lightning currents of 40 kA, showed dramatic improvements in lightning damage resistance compared to the conventional CF/epoxy composite. Keywords: Conductive Polymer / CFRP / Lighnig Damage Suppression / Electrical Properties / Mechanical Properties |
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| Polymer Science and I: A Personal Account |
| My Curiosity about Soft Matter | Yoshihiro MORISHITA |
| <Abstract> Although a lot of problems remain unsolved for soft matters, we can find various industrial products made of soft matter, such as tires. I’m interested in the topic of soft matter and try now to satisfy my curiosity through the investigation of industrial rubber products. Keywords: Soft Matter / Rubber Composite / Crack Growth |
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| Front-Line Polymer Science |
| Dynamics Imaging of Biological/Synthetic Polymers with High-Speed Atomic Force Microscopy | Takayuki UCHIHASHI |
| <Abstract> Atomic force microscopy (AFM) is a powerful tool to visualize the material surface at nm resolution even under liquid condition and thus has been applied to a wide variety of specimens so far. One of the most coveted new functions of AFM is “fast recording” because it should allow us to directly visualize dynamic processes that occur at solid/liquid interfaces. We have been challenging to break this limitation over 15 years and established high-speed AFM that enables to capture successive images with temporal resolution less than 100 ms. Further, the interaction force between the tip and the sample, which significantly influences the measurement on soft materials, is greatly reduced without deterioration of the scanning performance. This review first gives an overview of key techniques to realize fast AFM imaging. Then recent applications on single protein dynamics, supramolecular assembly/manipulation and structural dynamics of hydrogel particles are demonstrated. Keywords: High-Speed Atomic Force Microscopy / Visualization / Single-Molecule Dynamics / Supramolecular Assembly / Structural Manipulation / Thermosensitive Hydrogel Particle |
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