Abstract
It is well known that the temperature for plastic welding is higher than the glass transition temperature (Tg) in order to make the plastic soften and melt. However, we found the conditions under which some engineering plastics, such as polyamide66, polycarbonate and polyphenylene-ether, can be welded at less than Tg using a Langevin transducer equipped with half-wave-length step horn. The temperatures on the interface of welding by ‘cold welding’ were strongly dependent on the entanglement density of the plastics. In addition to the relatively low temperature during welding, the tensile strength of the welding part was larger than that of the matrix region. Fillers and rubber particles which were blended in the engineering plastics were observed to be oriented and removed from the welding regions, respectively. It suggested that the strong ultrasonic wave force moved the polymer chains even at the lower temperature. The mechanism and long-range movement of the polymer chain will be discussed.
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