Abstract
This paper describes the effect, on fusion strength, of design factors of electrofusion (EF) joints, which are new-type fusion joints for polyethylene gas pipes.
A comprehensive evaluation method for EF joint integrity has been developed. First, fusion interface temperature and welding voltage and current were continuously measured while block specimens were being fused. Then, wire movement was observed and the width of the molten layers was measured with a polarzing microscope.
A determination of the fusion mechanism of EF joints is attempted, and the influence of various design factors on fusion strength is discussed. The relationships between the fusion joint strength and input energy or interface temperature when wire arrangement, conditions of welding current and voltage, and wire material were varied, were clarified using block specimens.
Wire temperature during application of welding current was measured. The thermal degradation of polyethylene resin in the vicinity of the wires by FT-IR and GPC analysis was chemically examined.
