This paper uses terahertz (THz) spectroscopy for the first time as a simple method for estimating the molecular weight of a polymer across a very wide range. The viscosity average molecular weight (Mv) was measured and estimated as the molecular weight. Currently, to measure the Mv, a sample is dissolved in a solvent then measured its inherent viscosity. However, this procedure is complicated and time-consuming in practice. Additionally, as the molecular weight increases, the measurement accuracy decreases if Mv of a sample is above 3 million. Therefore, a new simple method is desired. A linear high-density polyethylene sample with an Mv range of 0.1 to 7.4 million was used. THz absorbance spectra of the samples were measured from 50 to 600 cm^-1 (1.5 to 18 THz) then the multivariable analysis technique was applied. Consequently, a very high correlation coefficient (R2 ≈ 1) between the estimated and the measured Mv values were obtained across the range of the samples. This method is essential and suitable for industrial applications.

In 2008 the International Electrotechnical Committee (IEC) offered an ideal contact current waveform as the IEC specified waveform, while there have never been new requirements based on it for the calibration waveform. In this paper, a calculation method is proposed to quantitatively evaluate to what extent the contact discharge waveform from an ESD generator deviates from the IEC specified waveform. The energy ratio of the difference waveform between the contact discharge waveform and the IEC specified waveform to the IEC specified waveform energy is used as an index of waveform quality, and the relationship is shown between the waveform quality and waveform parameters of the standard requirement adding "60% time width of first peak" and "falling depth", not in the requirement but newly introduced. The energy ratios are calculated for the measured contact discharge currents from different eight models of ESD generators and the measured air discharge currents from an ESD generator in a hot and humid environment, which were conducted in our previous studies. The results show that even if the contact discharge waveforms from the ESD generators meet all the IEC requirements, the energy ratio increases according to the generated ringing after the first peak and the resulting waveform quality degrades, but the ringing tends to be reduced and the waveform quality is improved when the ESD generators provide the time width of 60%t peak and falling depth closer to those of the IEC specified waveform. For the air-discharge waveforms that are not subject to the calibration standard, the energy ratios of the waveforms that meet all the IEC requirements are smaller than those of the contact discharge waveforms from the same type of the ESD generator, and the energy ratios of the waveforms that do not meet the first peak requirement are comparable to those of the contact discharge waveforms from the ESD generators. In the air discharge waveform, as with the contact discharges, it is confirmed that the wider the 60% time width of the first peak and the shallower the falling depth, the lower the energy ratio and the better the waveform quality. Future work is to clarify the mechanism how come the time width of 60% peak and falling depth improve the waveform quality of contact discharge and air discharge currents from the ESD generators.

In this paper, an accumulation of space charge in insulating materials and its effect on the discharge inception voltage were investigated by measuring the space charge distribution formed in the materials by applying a dc voltage to it through an air gap. In previous studies, the space charge accumulations in insulating materials were observed by applying the dc voltage to them through contacted electrodes. However, the voltage is applied to the material through the air gap in the actual usage of some insulating materials for motor windings. Therefore, we conducted the measurement of the space charge distribution in a sample with an air gap. The results showed that as space charge accumulates inside the insulating material, the voltage applied to the air gap increases, and the discharge inception voltage decreases.

As charge injection from metal into dielectric polymer causes degradation and breakdown of electronic and power devices, the band alignment at the metal/polymer interface should be revealed. To investigate the dominant factors of the band alignment at the metal/polymer interface, we carried out a combined experimental and first-principles computational study. We examined Au/polypropylene (PP) interface and Au/polyimide (PI) interface. PP and PI were chosen as a model system for nonpolar and polar polymers, respectively. The results imply that the band alignment can be determined under the assumption that vacuum levels of metal and polymer match at the interface regardless of the dipole moment of polymers.