[en] The degradation behavior of composite materials due to each important environmental factor has been investigated for the purpose of establishing the techniques of environmental durability assessment for composite materials. The combined space environmental effect facility has been developed based on those systematic data on the evaluation of advanced composite materials such as carbon fiber-reinforced plastics (CFRP) using epoxy resin as the matrix in space environment. The facility was designed and assembled for simulating space environment, and it has the functions of thermal aging, heat cycle, far ultraviolet ray irradiation and electron beam irradiation being applicable in high vacuum and at high loading. Further it can analyze evaporated gas in situ with a gas mass analyzer. The facility houses a universal tensile testing machine so that the mechanical properties of composite materials can be measured directly in space environment. The examples of the results of measurement of CFRP with the gas mass analyzer, the change of mass number and temperature by aging time or electron beam irradiation in vacuum and so on are shown. (K.I.)

[en] C-13 NMR is one of the most powerful methods to study the microstructure of synthetic polymers. Particularly, the theoretical chemical shift calculation on the basis of both C-13 NMR gamma shielding effect and the characterization of polymer local conformation using the rotational isomeric state (R.I.S.) model is very useful for the purpose of the tacticity assignment for the C-13 NMR spectra of poly(1-olefin)s. On the other hand, 2D-double quantum coherence spectroscopy, so-called 2D-INADEQUATE NMR, gives information about the carbon-carbon connectivity of the molecular backbone via the neighboring C-13-C-13 spin-spin coupling. In this way, NMR technique is expected to be experimentally used for the tacticity assignment. In this paper, the C-13 NMR tacticity assignment of poly(1-pentene), poly(1-hexene), poly(1-heptene), poly(1-octene) and poly(1-nonene) is reported on the basis of both chemical shift calculation and the examination of the peak intensity using two-site polymerization model. The 2D-INADEQUATE spectra were recorded at 100degC with a JEOL GX-270 spectrometer operating at 67.8 MHz. The results are shown. (Kako, I.)

[en] The biosynthetic mechanism of silk fibroin in silkworms, Bombyx mori, is unique because this fibrous protein composed mainly of glycine, alanine and serine is produced very rapidly in large quantity in the posterior silk glands. It is very meaningful to investigate into the biosynthesis of silk protein under nondestructive condition by in vivo NMR and C-13 labeling techniques. The sugar metabolism related to the production of silk fibroin was analyzed by monitoring the change in the C-13 labeled peaks in the NMR spectra for silkworms. In this paper, the monitoring of the 2-(C-13) glycine metabolism in Bombyx mori by the C-13 NMR in vivo is reported. In particular, the in vivo transport of glycine from the midgut to the posterior silk gland was measured, and the rate constants were determined with the course of the peak intensity in the C-13 NMR spectra. It is possible to discuss quantitatively the in vivo production of silk fibroin with these rate constants. The experiment and the results are reported. The in vivo C-13 NMR spectra of a 5 day old, 5th instar larva of Bombyx mori after the oral administration of 2-(C-13) glycine are shown. The significant increase of the peak intensity occurred. (K.I.)

[en] This report deals with γ-ray-irradiation-induced changes in the phase transition and structure of a copolymer of VDF 52 mol% and TrFE 48 mol%, P(VDF₅₂/TrFE₄₈). The x-ray diffraction measurement and the thermal analysis are carried out and results obtained are discussed. x-ray observations show that a double peak resulting from the (110) and (200) reflections changes to a single peak while the peak position shifts towards the low angle side as the irradiation dose increases. Similar and reverse phenomena are seen in the heating and cooling process of an irradiated sample. The (110) and (200) spacings in irradiated samples gradually increase in the heating process while those in unirradiated samples change discontinuously at a certain temperature. When heating is repeated, samples with smaller exposure show the same behavior repeatedly while those with larger exposure give different curves in the spacing-temperature plot. Such bihaviors are also observed in the DSC heating curves of these samples. This indicates that a structural reorganization takes place due to annealing at elevated temperatures in the case of samples with larger irradiation dose. In addition to these measurements, changes in melting behavior caused by irradiation are also observed by the DSC technique. Some of the results obtained are outlined and discussed. (Nogami, K.)

[en] The posterior silkgland of Bombyx mori, silkworm larvae, produces abundant specific silk fibroin at about 80 μg/cell for one day. In this study, the continuous production of silk fibroin in the posterior silk-gland was monitored by circumfusion cultivation using both C-13 NMR and C-13 labeling techniques in order to quantitatively determined the production of silk fibroin in vitro. The experimental setup is shown. The posterior silkglands of four larvae were collected in a 10 mm NMR sample tube under sterile condition. The C-13 NMR spectra were observed in the culture medium. The time-dependence of the C-13 NMR spectra of the culture medium containing the posterior silkglands are shown. The peak intensity for silk fibroin increased with the lapse of time. Also the peak due to the Cα carbon of the serine residue of silk fibroin slightly increased, which indicates that there is a system which converts glycine to serine in the posterior silkglands. In order to discuss this silk production quantitatively, the relative intensity of the Cα peaks for silk fibroin and glycine in the cultivation medium was plotted. The ability of the posterior silk-glands to produce silk protein was still high in vitro when the circumfusion cultivation technique was used. (K.I.)

[en] Carbon fiber-reinforced plastic (CFRP) composites have been used as structural materials for space use because of their light weight, high strength and high rigidity. These materials are exposed to radiation such as gamma ray, high energy electrons and protons as well as severe temperature change. Therefore, the estimation of the endurance to radiation, heat cycle and heat shock is important for the long term durability. Since the interlaminar fracture is the weak point of FRP, the interlaminar fracture toughness should be evaluated in addition to the strength data for the proper understanding of radiation-induced degradation. Recently, toughened CFRP has been developed, but only a few papers have been published on the endurance of these materials. In this study, the effects of radiation and test temperature were evaluated and compared between both conventional and toughened epoxy matrix CFRPs on the interlaminar toughness and the dynamic viscoelastic properties. The materials used, the irradiation with 2 MeV electron beam generated with an accelerator, the method of interlaminar fracture test and the dynamic viscoelastic measurement are described. The results of fiber bridging, and the effects of radiation and test temperature are reported. (K.I.)