PE100 water supply pipe >> PE100 water supply pipe PE100 water supply pipe PE100 water supply pipe, hot melt connection 1) Determination of temperature The best welding temperature for butt welding of polyethylene pipe is 200 ~ 230 ° C, the general manufacturer determines 210 ±10 ° C; is the processing temperature of polyethylene material, above the viscous flow transition temperature of the material, only under this condition, the polyethylene produces a molten flow, and the macromolecules of the polymer can be interdiffused to form a entanglement, which gives the largest Strength and high quality welding results; practice has shown that temperatures below 180 ° C, even if the heating time is long, can not achieve good quality welding results. If the temperature is too high, it is possible to activate the C bond in the molecular chain to react with oxygen to degrade the material, and the polyethylene material will be destroyed by oxidation. Volatile substances and gases are precipitated, the structure of the material changes, unsaturated hydrocarbons are formed, and impurities are formed, thereby deteriorating the quality of the weld. 2) Determination of time Determination of heating time: 10 × wall thickness (mm) seconds after the welding end face is flat. The length of the heating time determines the quality of the weld; whether the temperature can be uniformly transmitted to the weld surface and a certain depth, and the optimum welding temperature is maintained during the conversion phase. The optimum time for the end face to melt is increased as the area to be heated increases. More importantly, the energy propagated by convection and radiation decreases as the thickness of the tube wall increases. The unevenness of the end face of the pipe causes uneven heat transfer, entraps air, creates pores, and ultimately affects the quality of welding. Therefore, it needs to be closely matched with the pressure, apply a certain pressure while heating, flatten the welding surface, and promote plasticization. The ideal weld surface is heat transferred and then depressurized. The determination of the switching time is as short as possible within 10 seconds, the end face cooling is very fast, and the slow docking speed directly affects the welding quality. Determination of cooling time: see Table 1; 1.15 ~ 1.33 × wall thickness (mm) minutes. The thermal conductivity of the polymer material is poor, only a few tenths of the metal, the cooling rate is correspondingly slow, and it needs to be crystallized and shrunk during the cooling time. Therefore, it takes a sufficient time to drop to the crystallization temperature for sufficient grain growth. , eliminate internal stress, and cool under a certain pressure to avoid shrinkage holes on the welding end face.
