Radiation-induced polymerization of ethylene in a pilot plant. I. Bulk process

Radiation-induced bulk polymerization of ethylene was carried out with use of a pilot plant with a 10 liter reactor at pressures of 225–400 kg/cm², temperatures of 30–95°C, ethylene feed rates of 5–28 kg/hr, and dose rate of 3.8 × 10⁵ rad/hr. Characteristics of the process are mild polymerization conditions and capability of producing medium density polyethylene in powder form. The spacetime yield and molecular weight of polymer were in the range of 3.5 to 13.1 g/liter hr and 2.2 × 10⁴ to 14 × 10⁴, respectively. The space-time yield increased with mean residence time and 2.4 powders of pressure, and decreased with temperature. Molecular weight changed similarly with the reaction conditions. These results were consistent with those of the bench plant experiment and the scale effect was small. Polymer deposit to the reactor wall limited a period of continuous operation of the plant. The amount of deposited polymer was increased with the square of reaction time. The rate of polymer deposit was proportional to polymer concentration and to the cube of pressure. The polymer deposit cannot be solved in the bulk process.     

Energy distributions of field emitted electrons from a multi-wall carbon nanotube

Field emission energy distributions of electrons from one of the six pentagons located at the end of a multi-wall carbon nanotube have been measured by means of a high-resolution cylindrical energy analyzer. In a clean pentagon, the sub-peak was obtained at about 500 meV below the main peak, exhibiting a shift with increasing applied voltage. For electrons emitted from an adsorbate onto the pentagon, no fine structure was observed in the spectra. The broadening of the leading edge was also observed for both clean and adsorbed pentagon, indicating the field penetration into the nanotube due to its semimetallic nature. The full-width at half-maximum was 280 meV at the applied voltage of 660 V and increased linearly with applied voltage.