Effect of SEBS on water treeing behaviors of cross-linked polyethylene
We investigated the effect of an aromatic polymer, styrene-(co-ethylene-butadiene)-styrene (SEBS), on water tree resistance of cross-linked polyethylene (XLPE). The XLPE/SEBS samples were characterized by means of gel content determination, different scanning calorimetry (DSC), scanning electron microscopy (SEM) and the accelerated water treeing experiment. Our results clearly indicated that the samples with SEBS showed improved water tree resistance in comparison to blank samples. It was also found that the blends had excellent dielectric property form the viewpoint of practical application.
Space charge and electrical conduction in Maleic Anhydride-grafted polyethylene
The space charge behavior such as charge distribution and electrical conduction of maleic anhydride grafted LDPE (LDPE-g- MAH) was investigated. Heterocharge was found in LDPE and it decreased with increasing MAH graft ratio in LDPEg- MAH. Conduction currents also decreased with increasing MAH graft ratio. The relationship between the space charge behavior and the electrical conduction characteristics in LDPEg- MAH is discussed.
Joint strength of aluminum ultrasonic soldered under liquidus temperature of Sn–Zn hypereutectic solder
Abstract In order to obtain high-strength aluminum joints, ultrasonic soldering of 1070 aluminum was conducted under liquidus temperature of Sn–Zn hypereutectic solder. A device for ultrasonic soldering was assembled, which propagated ultrasonic vibrations in a direction perpendicular to joining surfaces. This device joined 1070-Al using quasi-melting Sn–Zn hypereutectic solder without using any artificial spacers. The strength of the solder joints was evaluated by tensile tests. The optimum joining conditions were determined, and the effects of solder compositions and soldering temperature on the joint strength and the solder layer thickness were examined. In this ultrasonic soldering process, the highest tensile strength was obtained for the solder joints fabricated at 220 °C for the Sn–23Zn and Sn–40Zn solder compositions. The joint strength was equivalent to that of 1070-Al heat treated at 220 °C. The sound joints were obtained at 300 °C using Sn–82Zn solder, the liquid phase volume fraction of which was theoretically only 0.24. The present work also revealed that the thickness of retained solder layer in the joint after ultrasonic soldering could be estimated. Accordingly, ultrasonic soldering under the liquidus temperature of Sn–Zn hypereutectic solder could be a spacer-free soldering method to obtain high-strength aluminum joints.