Space-charge distributions in plate and coaxial cable samples of various polyethylene (PE) materials such as high density polyethylene, linear low density polyethylene, low density polyethylene, and cross-linking polyethylene under dc voltage are systematically investigated by the pulsed electro-acoustic method. The chemical structure and morphology of the sample materials are studied. The formation mechanism of space charge and the relations among space charge, chemical structure, and morphology are discussed. Our research results show that the distribution characteristics of space charge in various PE materials can be attributed to their chemical structure and morphology.

The space charge characteristics in cross-linking polyethylene (LPE) are investigated under various electrical stresses from dc to power frequency. The pulsed electro-acoustic method is improved to meet the needs of measurement under ac voltages. The frequency and phase angle dependences of the space charge are studied by means of phase-locking and frequency-converting techniques. Test results show that space charge can develop and accumulate in LPE under an ultralow frequency voltage. The critical frequency of the applied ac voltage is less than 0.02 Hz. The mechanism of the formation of space charge in LPE under an ac voltage is discussed through degassing of a sample in vacuum.

Momentum transfer cross section of xenon is deduced from experimental electron drift velocity data over the energy range from 0.02 to 10 eV by using an algorithm based on a Boltzmann equation method. The result shows that the Ramsauer-Townsend minimum is located at an electron energy of 0.7 eV with a magnitude of 9*10-17 cm2. It is found that the present momentum transfer cross section is in excellent agreement with the experimental data points of Register et al. (1986) and that the calculated diffusion coefficient (parallel direction to the electric field) from the deduced cross section agrees very well with the measurements of Hashimoto and Nakamura (1990) for E/N above 0.07 Td. The fractional difference between the calculated electron drift velocity and the experimental one is suppressed within 1.2% at E/N below 0.1 Td and within 3% at E/N above 0.1 Td. Above an electron energy of 8.32 eV, inelastic collision cross sections are necessary for the deduction of the momentum transfer cross section. Therefore, the total excitation cross section of Hayashi (1983) and the ionization cross section of Krishnakumar and Srivastava (1988) are used to deduce the momentum transfer cross section over a range of high electron energies. As a result, the peak of the deduced momentum transfer cross section is located at an electron energy of 5 eV with a magnitude of 3*10-15 cm2.

Mainly from the temperature dependence of transitions in dynamic modulus, loss tangent, and dielectric loss, associated with microbrownian motions of main chains, it was concluded that blends of NR and BR are microheterogeneous and those of SBR and BR are almost microhomogeneous. Furthermore, even SBR/BR blends tended to be heterogeneous if the styrene content in SBR was increased. On the other hand, unvulcanized SBR/BR blends have been reported to be heterogeneous from observation of phase contrast micrographs. To investigate this vulcanization effect further, measurements of temperature dependence of dynamic modulus and tan δ of unvulcanized blends were compared with those of vulcanized blends.

The Rolling Contour Optimization Theory (RCOT) can lead to improved steering, fuel efficiency, riding comfort, and braking performance of tires relative to those of conventional shape. The conventional shape has been guided by natural equilibrium profiles, while the RCOT technology shape is guided by that of the tire in motion. This reduces useless distortions caused by running the tire under load. The RCOT design focuses on the distribution of belt and sidewall tension in the tire. Controlling tension in the belt and carcass area while the tire is in motion was the key to creating this new tire shape.