[en] A process for preparing polytetrafluoroethylene resin waxes is provided. It comprises irradiating commercial polytetrafluoroethylene resins with ionizing radiations (10³ to 10⁶ Rad/hr) in the presence of gaseous hydrogen and oxygen at an elevated temperature (200 to 400⁰C). The gaseous hydrogen accelerates the depolymerization so that a high molecular weight polytetrafluoroethylene can be converted into a wax speedily with a low radiation dose. In one example, 10 g of a powdery commercial polytetrafluoroethylene (mp ca. 327⁰C, DP ca. 10,000) was placed in an glass ampoule and irradiated with Co-60 gamma rays (dose rate 5 x 10⁴ Rad/hr) for 50 hrs at 350⁰C, while a 1:1 (by vol.) gaseous mixture of oxygen and hydrogen was introduced into the ampoule. After irradiation, 9.8 g of polymer was recovered. Melting point was 321⁰C, degree of polymerization 180. In the control experiment carried out in the presence of hydrogen-free air, depression of the polymer melting point was not observed. (Kaichi, S.)

[en] Acrylic monomers useful in the production of films, coatings, moldings and the like are cross-linked in polymerization by a process which comprises irradiating acrylic acids, methacrylic acids and esters thereof with radiation in the presence of 10^-2 to 5.0 mole percent of acetylene derivatives substituted by hydrogen radicals of aliphatic or aromatic hydrocarbons leaving one of the two hydrogen atoms to bind to carbon atoms of acetylene. The products have superior mechanical properties, heat resistance and corrosion resistance to chemicals. Cross-linking polymerization has been discovered between acrylic acids and derivatives thereof in the presence of a small amount of acetylene. This method is provided by using acetylene derivatives in the form of a liquid at room temperature and pressure. Further, the polymerization can be carried out by efficiently by irradiating with ionizing radiations or ultraviolet radiations at a high dose rate, generally 10 to 10⁶ roentgen per second. In one of the examples, 2 cc of methyl methacrylate and 70 g of azobisisobuthyl nitrile were sealed in an ampoule together with 24.7 mg of propine-1 and kept at 40⁰C for 16 hrs. A clear solid was produced with no soluble methyl methacrylate detected, and a gel content of 100%. In another example, 2 cc of methacrylate and 24.7 mg of propine-1 were polymerized with ultraviolet radiations from a 250W mercury arc lamp for 5 hrs with similar results. (Iwakiri, K.)

[en] A chlorine-containing resin is modified by cross-linking with methyl methacrylate to improve the mechanical properties of the resin and to make the forming and molding operation easier. The method comprises polymerizing the chlorine-containing resin so as to form a cross-link with methyl methacrylate in the presence of acetylene or acetylene derivatives in which one of the two hydrogen atoms bonding a carbon atom remains in the acetylene. This method of modification can be applied to a wide range of chlorine-containing resins. The chlorine-containing resins may be the individual or mutual polymers or copolymers of ethylene, butadiene, acrylonitrile, etc.. This method of modification builds up the three dimensional network construction that gives the resin a very strong surface layer while maintaining its internal elasticity. The chlorine-containing resin may be the polymers of vinyl chloride, vinilidene chloride, or the like, and may be the copolymers of these monomers with other vinyl monomers. The amount of acetylene added is 10^-2 to 5.0 mo%, based on methyl methacrylate. In an embodiment, after the surface of chlorine-containing resin moldings are coated with methyl methacrylate, they are polymerized by irradiation with ionizing radiations or ultraviolet radiations in the presence of an initiator with a dose of 10 to 10⁶ r. at a dose rate of 10⁶ to 10⁷ r/sec. The temperature may be -50⁰ to 200⁰C, preferably 0⁰ to 100⁰C. (Iwakiri, K.)

[en] A process for modifying poly-α-olefins is provided. The process comprises mixing 0.5 to 5 parts of a cross-linking agent XYsub(m) (X is saturated or unsaturated alkyl, aryl or aralkyl; Y is a group having at least one -CN; and m is an integer equal to or greater than 1) with 100 parts of a poly-α-olefin, followed by shaping the resulting mixture, and irradiating it with ionizing radiations (10⁴ to 10⁸ R) to give a homogeneously cross-linked poly-α-olefin. The process can proceed even in the presence of air and is characterized by its inexpensiveness. In one example, a powdered polyethylene (MWsub(n) 35,000) was mixed with dipropargyl terephthalate (mp ca. 100⁰C), pressed into a sheet of 1 mm in thickness, and irradiated with Co 60 gamma rays (1 x 10⁵ R/hr) for 16 hrs at room temperature. Quantity of the dipropargyl terephthalate (% by weight), gel fraction (%) after irradiation in vacuum and gel fraction (%) after irradiation in the air were: 0, 0, 0; 1.0, 19.0, 21.3; 5.0, 17.0, 18.9 (Kaichi, S.)

[en] Ethylene and vinyl acetate are copolymerized by adding tetrafluoroethylene to improve the copolymerization reaction velocity with ionizing radiations. In the process of copolymerization, chlorofluorohydrocarbon is employed as a solvent, tetrafluoroethylene is added to a mixture of ethylene and vinyl chloride, and they are irradiated with ionizing radiations under pressure. In embodiments, pressure may preferably be 100 to 2,000 kg/cm³. The temperature may be -50⁰ to 200⁰C. The content of chlorofluorohydrocarbon may be 20 to 80% by volume of the monomers. The dose rate of the ionizing radiations may generally be 100 to 100 x 10⁴ r/hr. In one example, 6.7 g of dichlorofluoroethane, 3.7 g of vinyl acetate, 5.0 g of tetrafluoroethylene and 26.6 g of ethylene were mixed and exposed to gamma rays from a Cs-137 source under a pressure of 400 kg/cm³ at a temperature of 30⁰ for 20 hrs. The weight of the thus produced copolymer was 6.6 g. The melting point of the crystal was 125⁰C. In another example, 5.5 g of dichlorotetrafluoroethane, 14.5 g of vinyl acetate and 4.5 g of tetrafluoroethylene were mixed, and thereafter 22.1 g of ethylene were added thereto under pressure. Irradiation was conducted with gamma rays from a Co-60 at a dose rate of 100,000 r/hr under 400 kg/cm³ at 30⁰C for 1 hr. The yield of copolymer was 4.0 g. (Iwakiri, K.)

No abstract available

[en] The radiation disintegration of polymers and the acceleration of disintegration by the addition of a third substance are reviewed. This report is divided into three main parts, namely 1) the radiation disintegration of polymers, 2) the effects of adding third substances on the disintegration, and 3) the effective use of disintegrated polymers. The first part deals with 1-1) the classification of vinyl polymers, 1-2) elemental reactions and their energy characteristics in the disintegration, and 1-3) the disintegration and cross-linking of vinyl polymers. The vinyl polymers can be classified into disintegration type vinylidene and cross-linking type vinyl. The relationships between the heat of polymerization and the recovery rate of monomers are discussed. The second part deals with 2-1) the addition effects of oxygen, and 2-2) the design of chain disintegration reaction. The presence of oxygen makes the decomposition into chain reaction. The addition of methane substituted by halogen promotes the disintegration reaction. The third part deals with 3-1) the reuse of polytetrafluorethylene (PTFE) wastes as fine-powder wax, 3-2) the adjustment of molecular weight of polyethylene oxide, and 3-3) the others. About 1,200 tons of PTFE are produced in Japan annually. Their 10 - 15% are recoverable. The reuse of PTFE for lubricants, paint additives, etc. is now under research. The wide variety of the viscosity of solutions and the concentration of polymers are desired. To this end, the arbitrary change of the molecular weight of polymers is desired. (Iwakiri, K.)

[en] On the cables used for nuclear power stations, in particular those ranked as IE class, flame retardation test, simulated LOCA environment test, radiation resistance test and so on are imposed. The results of the evaluation of performance by these tests largely depend on the insulating materials mainly made of polymers. Ethylene propylene copolymer rubber has been widely used as cable insulator because of its electrical characteristics, workability, economy and relatively good radiation resistance, but it is combustible, therefore, in the practical use, it is necessary to make it fire resistant. The author et al. have advanced the research on the molecular design of new fire retarding materials, and successfully developed acenaphthylene bromide condensate, which is not only fire resistant but also effective for improving radiation resistance. The condition of flame retardant, radiation resistant auxiliary agents is explained, and there are additive type and reaction type in fire retarding materials. The synthesis of acenaphthylene bromide condensate and its effect of giving flame retardant and radiation resistant properties are reported. The characteristics of the cables insulated with the flame retardant ethylene propylene rubber containing acenaphthylene bromide condensate were tested, and the results are shown. (Kako, I.)

[en] The Takasaki Radiation Chemistry Research Establishment (TRCRE) of Japan Atomic Energy Research Institute (JAERI) was founded in 1963 as the center for the research and development of radiation chemistry in Japan. Using its extensive facilities for irradiation by gamma rays from a Cobalt 60 source and electron beams from accelerators, the TRCRE has contributed to R and D on technology for the industrial application of radiation chemistry. In 1987, the TRCRE started the construction of ion beam irradiation facilities to promote a new project ''Advanced Radiation Technology Study using Ion Beams (ART project)''. The ART project is intended to push forward R and D on materials for space and nuclear fusion reactors, biotechnology and new functional materials using ion beams. Two ion accelerators (an AVF cyclotron and Tandem type accelerator) are now under construction and expected to be operational in the summer of 1991. Two other accelerators (a van de Graaff accelerator and ion beam implanter) are scheduled to be installed in 1993. In this report, the present R and D activities using gamma rays and electron beams are first summarized, and the future programme using ion beams is described. (author)

[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.)