Recyclable carbon fiber‐reinforced plastics (CFRP) containing degradable acetal linkages: Synthesis,properties, and chemical recycling

Two epoxy resins containing degradable acetal linkages were synthesized by the reaction of cresol novolak‐type phenolic resin (CN) with vinyl ethers containing a glycidyl group [cyclohexane dimethanol vinyl glycidyl ether (CHDMVG) and 4‐vinyloxybutyl glycidyl ether (VBGE). Carbon fiber‐reinforced plastics (CFRPs) were prepared by heating laminated prepreg sheets with CN‐CHDMVG resin (derived from CN and CHDMVG) and CN‐VBGE resin (derived from CN and VBGE), in which carbon fibers are impregnated with epoxy resins containing curing agents [dicyandiamide (DICY)] and curing accelerator [3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU)]. CN‐CHDMVG‐based CFRPs and CN‐VBGE‐based CFRPs exhibited almost the same tensile strength as the conventional bisphenol‐A‐based CFRPs. CN‐CHDMVG‐based CFRPs and CN‐VBGE‐based CFRPs underwent smooth breakdown with the treatment of hydrochloric acid in tetrahydrofuran at room temperature for 24 h to regenerate strands of carbon fibers. The surface conditions of the recovered carbon fibers had little changes during degradation and recovery processes on the basis of scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The recovered carbon fibers exhibited almost the same tensile strength as virgin carbon fibers and hence would be reused for the production of CFRPs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1052–1059     

Mode-mode coupling theory of itinerant electron antiferromagnetism in superconducting state

It has been considered since the first discovery of a high-T(c) cuprate that an antiferromagnetic (AF) state and a superconducting (SC) state are separated in it. However, it is very intriguing that the coexistence of the AF and SC states has recently been observed in HgBa(2)Ca(4)Cu(5)O(12+) (Hg-1245). Moreover, it is very novel that this coexistence of these two states appears if the SC-transition temperature T(c) is higher than the AF-transition temperature T(N). The mode-mode coupling theory can provide a clear elucidation of this novel phenomenon. A key point of this theory is that the AF susceptibility consists of the random-phase-approximation (RPA) term and the mode-mode coupling one. The RPA term works to make a positive contribution to the emergence of the antiferromagnetic critical point (AF-CP). In contrast, the mode-mode coupling term works to make a negative contribution to the emergence of the AF-CP. However, the growth of the SC-gap function in the d(x(2)-y(2))-wave SC state works to suppress the negative contribution of the mode-mode coupling term to the emergence of the AF-CP. Moreover, the effect of SC fluctuations near the SC-transition temperature T(c) suppresses the mode-mode coupling term of the AF susceptibility that works to hinder the AF ordering. For these two reasons, there is a possibility that the d(x(2)-y(2))-wave SC state is likely to promote the emergence of the AF-CP. Namely, the appearance of the above-mentioned novel coexistence of the AF and SC states observed in Hg-1245 can be explained qualitatively on the basis of this idea.     

Distribution patterns of gamma radiation dose rate in the high background radiation area of Odisha,India

Journal of Radioanalytical and Nuclear Chemistry - Absorbed dose rates in air for 20 residential areas in Odisha were measured using a vehicle-mounted NaI(Tl) scintillation spectrometer. The...     

A SYNTHETIC ROUTE TO 3-METHYLTHIO-2-ALKANONES STARTING FROM 3-ALKYL-2,4-PENTANEDIONES

Abstract

An efficient preparation of a 3-methylthio-2-alkanone (1) has been realized by the reaction of a 3-alkyl-2,4-pentanedione (8) with one mol-equiv of S-methyl methanethiosulfonate (4) in the presence of excess EtONa in EtOH. Furthermore, treatment of 8 with 4 and K₂CO₃ in refluxing acetone, followed by addition of MeOH and heating the resulting mixture, gave 1 in a high yield. These methods were applied to synthesis of pseudoionone.     

Investigation of radon and thoron concentrations in a landmark skyscraper in Tokyo

The temporal variation of the radon concentration, and the radon and thoron concentrations every 3 months for a year were measured using two types of devices in a landmark skyscraper, the Tokyo Metropolitan Government Daiichi Building. In the measurement of temporal variation of the radon concentration using a pulse type ionization chamber, the average radon concentration was 21 ± 13 Bq m^?3 (2–68 Bq m^?3). The measured indoor radon concentration had a strong relationship with the operation of the mechanical ventilation system and the activities of the office workers. The radon concentration also increased together with temperature. Other environmental parameters, such as air pressure and relative humidity, were not related to the radon concentration. In the long-term measurements using a passive radon and thoron discriminative monitor, no seasonal variation was observed. The annual average concentrations of radon and thoron were 16 ± 8 and 16 ± 7 Bq m^?3, respectively. There was also no relationship between the two concentrations. The annual average effective dose for office workers in this skyscraper was estimated to be 0.08 mSv y^?1 for 2000 working hours per year. When considering the indoor radon exposure received from their residential dwellings using the annual mean radon concentration indoors in Japan (15.5 Bq m^?3), the annual average effective dose was estimated to be 0.37 mSv y^?1. This value was 31 % of the worldwide average annual effective dose.     

Fluorescence properties of novel 6-butyl-2,3-dicyano-7-methyl-6H-1,4-diazepine styryl dyes containing ethyleneglycol units

The fluorescence properties of novel 6-butyl-2,3-dicyano-7-methyl-6H-1,4-diazepine styryl dyes having mono-, di-, tri-, and tetra(ethyleneglycol) units were examined. The mono(ethylenglycol) derivative was solid at room temperature, whereas the di-, tri-, and tetra(ethylenglycol) derivatives were oily. The monoethyleneglycol derivative showed weak aggregation-induced emission enhancement with fluorescence maximum at 649 nm, which comes from J-aggregates. The fluorescence of oily di-, tri-, and tetra(ethyleneglycol) derivatives in neat form was very weak. No aggregation-induced emission enhancement was observed for the oily derivatives.     

Synthesis and characterization of transparent silica-based aerogels using methyltrimethoxysilane precursor

Silica-based aerogels with high transparency and high bending strength were prepared using methyltrimethoxysilane and non-ionic surfactant under supercritical drying condition of CO₂. Non-ionic surfactant, ethylene oxide/propylene oxide block copolymer, was appropriate to form the three dimensional-connected thinner fibers of silica skeletons, which was extruded by soaking the wet gel in hot water at 50 °C, resulting in the formation of porous materials having small pores with narrow size distribution. The transparency of aerogels increased with decreasing the pore size, reaching to higher than 65 and 88% at 400 and 600 nm wavelength, respectively, for 10 mm thickness of sample. The formation of fiber skeletons were discussed using small angle X-ray scattering experiments.